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ORNL-TM 2712

C o n t r a c t No. W-7405-eng-26

Reactor Division

FEASIBILITY STUDY OF REIIilOTE CTJTTING AND WELDING FOR NUCiXAR PLANT MAINTENANCE P e t e r P. Holz -

c 8

NOVEMBER 1969

OAK RIDGE NATIONAL LABORATORY O a k R i d g e , Tennessee operated by UNION CARBIDE CORPORATION f o r the U . S . ATOMIC ENERGY COMMISSION

L E G A L NOTICE-

fii

CONTENTS Page

............................ ACK,NOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . . . . .

ABSTRACT

SECTION A

.................... 1.1 Introduction . . . . . . . . . . . . . . . . . . . . . 1.2 Approaches to Maintenance . . . . . . . . . . . . . . . 1.2.1 Some Examples of Maintenance Methods . . . . . . 1.3 Remote Maintenance Considerations. . . . . . . . . . . 1.3.1 Equipment Location for Maintenance . . . . . . . 1.3.2 Mechanical Joint Considerations . . . . . . . . 1.3.3 Welded Joint Closure Considerations . . . . . . 2. HISTORY OF RBIOTE WELDING . . . . . . . . . . . . . . . . . 2.1 Background . . . . . . . . . . . . . . . . . . . . . . 2.2 The Pennsylvania Advanced Reactor Program. . . . . . . 2.3 The Atomics International Program . . . . . . . . . . . . 2.4 State of the Art Survey . . . . . . . . . . . . . . . 2.5 Survey Findings. . . . . . . . . . . . . . . . . . . . 2.6 Continued Need f o r Remote Welding Development . . . . . 3. THE SELECTION OF A SYSTEM TO BE DEVELOPED FOR REMOTEMAINPENANCE ..................... 3.1 "Orbital-Vehicle" System Advantages . . . . . . . . . . 3.2 Future System Expansion and Modification Plans . . . . 3.2.1 Development of Additional Modules . . . . . . . 3.2.2 Alternate Carriage for Seal-Weld Capability . . 1

MAINTENANCE PHILOSOPHY

3.2.3

Development of Special Features for Nuclear System Applications

3 3

4 5 6 6 6 7 10 10

10 11

13 15

15 15 15

..........

PRESENT PROGRAM STATUS .

.................. General . . . . . . . . . . . . . . . . . . . . . . . .

1.7

4.1 4.2 ORNL's Prototype Automated Remote Cutting and Welding System for 6 and 8-in. Pipes . . . . .

SECTION B

4.2.1

4.2.2

.... Carriage . . . . . . . . . . . . . . . . . . . . Universal Machining Head . . . . . . . . . . . .

17 18

........... 4 . 2 . 4 Welding Programmer and C o n t r o l U n i t . . . . 4.2.5 Power Supply . . . . . . . . . . . . . . . . 4.2.6 Equipment M o d i f i c a t i o n s f o r Remote Work . . 5 . MACHINING SJYJDIES . . . . . . . . . . . . . . . . . . . . . 4.2.3

U n i v e r s a l Welding Head

. . . .

5 . 1 General . 5.2

5.3 j.4

5.5

....................... Equipment E v a l u a t i o n . . . . . . . . . . . . . . . . . Tooling . . . . . . . . . . . . . . . . . . . . . . . . Machining Feeds and Speeds . . . . . . . . . . . . . .

Machining Techniques for S l i t t i n g and Beveling Pipes; Pipe End P r e p a r a t i o n Requirements f o r Welding

..... 6 . WELDINGSTUDIES . . . . . . . . . . . . . . . . . . . . . . 6.1 General . . . . . . . . . . . . . . . . . . . . . . . . 6 . 2 Preweld J o i n t Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.3

J o i n t Fitup Tolerance

6.4 6.5 6.6 6.7 6.8

................... Electrode Configuration . . . . . . . . . . . . . . . . Automatic Arc Voltage C o n t r o l . . . . . . . . . . . . . Pre-Weld P o s i t i o n i n g . . . . . . . . . . . . . . . . . Root Pass . . . . . . . . . . . . . . . . . . . . . . . Fillpasses. . . . . . . . . . . . . . . . . . . . . . . Repair Weldirig . . . . . . . . . . . . . . . . . . . .

6.9 6.10

I n e r t Shield G a s

7 . SPECIAL ORBITAL EQUIPMENT MAINTENANCE mQUIREMFNTS. . 7.1 Carriage . . . . . . . . . . . . . . . . . . . . . .

7.2

. . . . 7.1.1 Drive R o l l e r s . . . . . . . . . . . . . . . . . 7.1.2 I d l e r s . . . . . . . . . . . . . . . . . . . . . E l e c t r i c a l Items . . . . . . . . . . . . . . . . . . .

7.3 M i l l i n g Head 7.4 Welding Head 7.5 General . . .

..................... ..................... .....................

18 25

25 28 28 28

30 30 31 33 34 34 40 40 40 41 41 4.2

43 43

44 b4

44 44

44 44 45

SECTION C

8 . PROGRAM PROPOSAL:

DZVELOPBENT OF RENOTE CUTPING. WELDING AND INSPECTION EQUIPKENT FOR REACTOR SYSTEM MAINTENANCE .

8.1

O v e r a l l Requirexents f o r Remote Cut/Weld Maintenance

. .

46 46

8.2 A Long-Range, Three-phase Development Program for

. . . . . . . . . . 8-2.1 Phase I, The General Program. . . . . . . 8.2.2 Phase 11, The Pipe Joint Program. . . . . 8.2.3 Phase 111, The Vessel Closure Program . . Pipe and Vessel Maintenance.

. . . .

47 47 48 48

1 U

FEASIBILITY STUDY OF REMOTE CUTTING AND WELDING FOR NUCLEAR PLANT MAINTENANCE P e t e r P . Holz

ABSTRACT When r e a c t o r s and r e l a t e d systems r e q u i r e maintenance and r e p a i r s on h i g h l y r a d i o a c t i v e components, t h e r e i s an important need f o r remotely c o n t r o l l e d equipment t o remove and r e p l a c e p a r t s of t h e n u c l e a r systems. Remote c u t t i n g and welding can be v a l u a b l e t e c h n i q u e s f o r component r e p l a c e ment as w e l l as f o r s e a l i n g f l a n g e s and v e s s e l c l o s u r e s . Welding o f f e r s very a t t r a c t i v e advantages: j o i n t s can b e made l e a k t i g h t , j o i n t c o n f i g u r a t i o n s r e q u i r e l e s s c e l l space t h a n f l a n g e d j o i n t s ; and t h e l o c a t i o n s of j o i n t s can be changed comparatively e a s i l y , i f n e c e s s a r y . I n s e e k i n g equipment which could b e adapted t o remotely c o n t r o l l e d o p e r a t i o n f o r r e a c t o r maintenance, ORNL s e l e c t e d t h e A i r Force " o r b i t a l v e h i c l e " cut-and-weld system as c u r r e n t l y b e i n g most promising f o r f u r t h e r development t o meet n u c l e a r system r e q u i r e m e n t s . The concept of an o r b i t a l v e h i c l e equipment system f o r automated p i p e work o r i g i n a t e d i n 1964 a t t h e Rocket P r o p u l s i o n Laboratory of t h e A i r Force Systems Command a t Edwards A i r Force Base. The development of t h i s system w a s performed i n c o n j u n c t i o n w i t h North American Rockwell Corporation, Los Angeles D i v i s i o n , who designed, b u i l t and t e s t e d i n i t i a l models. ORNL h a s s t a r t e d t o modify and adapt t h e o r b i t a l d e s i g n f o r completely remote work applications. The o r b i t a l system i n c l u d e s a c a r r i a g e , i n t e r c h a n g e a b l e modules f o r machining or t u n g s t e n - a r c welding, a w e l d programmer, and a c o n v e n t i o n a l power s u p p l y . The working u n i t i s q u i t e compact, about 4 i n . t h i c k i n r a d i a l dimension x 10 1/2 i n . long, designed t o b e clamped around a p i p e .

To d a t e , w e have completed t h e d e t a i l e d drawings f o r f a b r i c a t i o n of t h e p r o t o t y p e o r b i t a l system and have procured a l l t h e components f o r i n i t i a l non-nuclear t e s t s of t h e equipment. We have demonstrated t h e f o l l o w i n g o p e r a t i o n s by remote c o n t r o l methods t h a t were g e n e r a l l y s a t i s f a c t o r y : clamping of t h e c a r r i a g e on t h e p i p e , c u t t i n g and b e v e l i n g w i t h one o r b i t a l head, changing heads, and performing f i l l e r p a s s welding o p e r a t i o n s . We n s t e d t h a t n e a r l y p e r f e c t p i p e j o i n t p r e p a r a t i o n and alignment were r e q u i r e d t o a c h i e v e a c c e p t a b l e r o o t p a s s welding without t h e a d d i t i o n of weld i n s e r t s . These requirements were t h e most d i f f i c u l t t o meet w i t h t h e o r b i t a l equipment, and r o o t p a s s welding gave t h e most t r o u b l e . However, an a l t e r n a t e method of r o o t p a s s

2 welding gave good r e s u l t s when j o i n i n g s u r f a c e s were machined t o provide e x t r a metal on one i n s i d e p i p e edge and were g i v e n a f u s i o n welding without f i l l e r wire on t h e r o o t p a s s . These weldments showed f u l l p e n e t r a t i o n and e x c e l l e n t , even bead shape a l l t h e way around t h e p i p e . I n a l l c a s e s , t h e subsequent f i l l e r p a s s e s were made e a s i l y and were of good q u a l i t y . S i n c e welding v a r i a b l e s such as t r a v e l speed, c u r r e n t , wire f e e d r a t e , a r c v o l t a g e , and a r c c o n t r o l v o l t a g e a l l a f f e c t weld q u a l i t y , it was observed d u r i n g t h e t e s t s t h a t weld d e f e c t s could o f t e n be d e t e c t e d as t h e y occurred by n o t i n g t h e p i p s on r e c o r d e r c h a r t t r a c e s . The r e p o r t d e s c r i b e s f a c t o r s involved i n r a d i o a c t i v e system maintenance, summarizes some p r e v i o u s work on remote maintenance development, and e x p l a i n s how t h e automated o r b i t a l c u t t i n g and welding machinery system may overcome problems t h a t have been encountered i n n u c l e a r r e p a i r work. P r o g r e s s of t h e f e a s i b i l i t y study t o d a t e i s summarized, i n c l u d i n g d e s c r i p t i o n s of t h e p r o t o t y p e equipment and t h e r e s u l t s of machining and welding t e s t s . The r e p o r t d e s c r i b e s a d d i t i o n a l requirements f o r development t o p r o v i d e f u l l y remote o p e r a t i o n s and c o n t r o l s and proposes a long range program f o r development of a complete remote maintenance system f o r r a d i o a c t i v e system equipment replacement by c u t t i n g and welding.

ACKNOWLEDGMENTS The a u t h o r acknowledges w i t h thanks t h e e x c e l l e n t c o o p e r a t i o n and a s s i s t a n c e of t h e Permanent Tube J o i n t Technology S e c t i o n of t h e A i r Force Rocket P r o p u l s i o n Laboratory, A i r Force Systems Command, Edwards, C a l i f o r n i a . The p r o j e c t e n g i n e e r , Captain John L. Feldman, USM', alia h i s s t a f f , p a r t i c u l a r l y M r . Edward H . S t e i n and L t . A l b e r t B . Spencer, USAF, a l l have done an o u t s t a n d i n g j o b i n supplying r e q u e s t e d t e c h n i c a l information and d a t a . C . Bruce Deering of t h e A E C ' s Oak Ridge Operations S i t e O f f i c e provided l i a i s o n between AEC and t h e A i r Force. Carl M. Smith, J r . , gave i n v a l u a b l e day t o day a s s i s t a n c e with equipment d e s i g n , development, shakedown and checkout, and W i l l i a m A . B i r d and Robert L . Moore gave important h e l p with t r o u b l e - s h o o t i n g and r e f i n i n g of t h e e l e c t r o n i c s and i n s t r u m e n t a t i o n . E . L . Armstrong, W. I?. C a r t w r i g h t , T . Ray Housley, Dunlap S c o t t , G . M. S l a u g h t e r , I r v i n g Spiewak, T . K . Walters, and L . C . W i l l i a m s provided v a l u a b l e guidance and s u p p o r t . S p e c i a l t h a n k s a l s o t o W . E . Thompson f o r h i s a s s i s t a n c e i n e d i t i n g t h i s r e p o r t , and t o o t h e r s , u n l i s t e d f o r b r e v i t y , who c o n t r i b u t e d i n many ways.

3 SECTION A 1. MAINTENANCE PHILOSOPHY 1.1 I n t r o d u c t i o n

I n t h e d e s i g n , development, and t e s t i n g of molten s a l t r e a c t o r s a t t h e Oak Ridge N a t i o n a l Laboratory, t h e need f o r remote welding equipment was encountered. However, t h e development of r e a c t o r d e s i g n s which i n c l u d e p r o v i s i o n s f o r maintenance by remote welding l o g i c a l l y r e q u i r e s t h a t a welding p r o c e s s b e proven feasible b e f o r e t h e d e s i g n s t u d i e s are completed. S i m i l a r l y , t h e c a p a b i l i t y f o r remote welding must be f u l l y developed b e f o r e a l a r g e r e a c t o r i s designed on t h e b a s i s of maintenance methods which r e q u i r e remote welding. The p o t e n t i a l of remote welding f o r s a v i n g t i m e i n r e p l a c i n g r e a c t o r system components and f o r producing more r e l i a b l e j o i n t s and seals was recognized, and f e a s i b i l i t y s t u d i e s of remote welding were s t a r t e d as p a r t of t h e Molten S a l t R e a c t o r Program. From d i s c u s s i o n s of remote maintenance w i t h t h e d e s i g n e r s , b u i l d e r s , and o p e r a t o r s of o t h e r r e a c t o r s , it h a s become c l e a r t h a t t h e s p e c i a l welding equipment and t e c h n i q u e s t h a t have been d e v i s e d on many o c c a s i o n s for s p e c i f i c r e p a i r or replacement j o b s are n o t g e n e r a l l y a p p l i c a b l e . There i s s t r o n g i n t e r e s t i n a p o r t a b l e , remotely c o n t r o l l e d welding system t h a t would b e g e n e r a l l y a p p l i c a b l e i n r e a c t o r maintenance and r e p a i r work. A r e l i a b l e , automated system t o produce h i g h - q u a l i t y welds, even without remote c o n t r o l s , would b e welcomed b y t h e r e a c t o r b u i l d e r s , who r e p o r t c o n s i d e r a b l e d i f f i c u l t y i n o b t a i n i n g q u a l i f i e d welders and i n a c h i e v i n g a c c e p t a b l e weld q u a l i t y on f i e l d work a t t h e c o n s t r u c t i o n s i t e . U s e of automated systmes f o r c o n s t r u c t i o n welding would a l s o g i v e c o n f i dence and e x p e r i e n c e which would h e l p t h e a p p l i c a t i o n of remotely c o n t r o l l e d u n i t s i n maintenance and r e p a i r work. The problems of maintenance and r e p a i r on r e a c t o r systems a f t e r o p e r a t i o n h a s b u i l t up t h e r a d i a t i o n l e v e l s are important and widespread-no r e a c t o r i s immune. The need f o r remote welding equipment has been recognized b y r e a c t o r d e s i g n e r s , b u i l d e r s and o p e r a t o r s ; b u t , t o d a t e t h e r e i s no remote welder t h a t can b e used for g e n e r a l p i p e and seal welding a p p l i c a t i o n s , a l t h o u g h s p e c i a l purpose d e v i c e s have been employed f o r some r e a c t o r maintenance j o b s . Automatic welding equipment i s b e i n g used t o d a y f o r many a p p l i c a t i o n s . Some of t h e a u t o m a t i c welding methods and equipment seem w e l l s u i t e d t o development f o r remote welding. I n p a r t i c u l a r , a n a u t o mated pipe-welding a p p a r a t u s developed b y North American A v i a t i o n f o r t h e A i r Force showed promise f o r remote c o n t r o l a p p l i c a t i o n s i n n u c l e a r r e a c t o r systems. I n a l l r e a c t o r systems maintenance must be performed b y some method whenever t h e need arises. If it could be accomplished w i t h r e l i a b i l i t y a t r e a s o n a b l e c o s t , completely remote maintenance would be p r e f e r r e d , because, it reduces p e r s o n n e l r a d i a t i o n exposures and s i m p l i f i e s t h e problems of decontamination p r i o r t o u n d e r t a k i n g t h e maintenance operat i o n s . Remote welding o f f e r s g r e a t promise f o r g e n e r a l a p p l i c a t i o n i n

t h a t almost any p a r t of a r e a c t o r system which might f a i l can be c u t ou'; arid r e p l a c e d i f equipment i s a v a i l a b l e f o r remote c u t t i n g and rewelding. With f i r s t - o f - a - k i n d r e a c t o r s , it i s n e c e s s a r y t o t e s t t h e d e s i g n s u s i n g mock-ups of t h e more complicated systems and components. I f , a t t h i s stage, t h e a b i l i t y t o perform remote mainteriance can b e t e s t e d on t h e mock-ups, t h e f i n a l d e s i g n can be demonstrated t o be f u n c t i o n a l l y sound and c a p a b l e of b e i n g maintained. The s a t i s f a c t o r y performance of remote h a n d l i n g d e v i c e s and t e c h n i q u e s can be proved i n mock-up t e s t s , g i v i n g i n c r e a s e d confidence i n t h e i r r e l i a b i l i t y and p r o v i d i n g t r a i n i n g i n maintenance t e c h n i q u e s which w i l l reduce downtime.

It i s recognized t h a t provisioris f o r remote c o n t r o l removal and r e placement of a l l components of a r e a c t o r system would b e p r o h i b i t i v e l y expensive. I n p r a c t i c e , t h e r e f o r e , t h e degree of e a s e provided t o accomp l i s h remote maintenance depends upon t h e a n t i c i p a t e d frequency of maint e n a n c e on each component. A r e a c t o r v e s e l designed f o r a 30-year maintenance-free l i f e w i l l h o p e f u l l y r e q u i r e no remote maintenance equipment. Pumps, v a l v e s , c o l d t r a p s arid o t h e r items which f a i l or need maint e n a n c e more f r e q u e n t l y may j u s t i f y r a t h e r e l a b o r a t e remote c o n t r o l d e v i c e s t o speed up and make more reliable t h e o p e r a t i o n s of maintenance and replacement. If p o r t a b l e remote welding equipment can be proved workable, even a l r e a d y - b u i l t r e a c t o r s not designed f o r remote maintenance may r e c e i v e many of t h e b e n e f i t s . I n October 1968, a d r a f t of t h e "Code f'or I n s e r v i c e I n s p e c t i o n of Nuclear Reactor Coolant Systeins" was developed under t h e s p o n s o r s h i p of t h e American S o c i e t y o f Mechanical S n g i n e e r s arid t h e AEC. The Committee which prepared t h e d r a f t of t h e Code n a t e d t h a t " r e c o g n i t i o n w a s g i v e n t o t h e problems of examining r a d i o a c t i v e areas where human a c c e s s i s i m p o s s i b l e , and p r o v i s i o n s are i n c o r p o r a t e d i n t h e Code f o r t h e examination of such areas by remote means which a r e n o t y e t f u l l y developed." The Code c l e a r l y shows t h a t welds a r e considered t o be of prime importance amont t h e areas r e q u i r i n g i n s p e c t i o n . The g e n e r a l need f o r remote c u t t i n g and welding equipment which can r e p a i r f l a w s d i s c l o s e d by t h e i n s p e c t i o n s i s given emphasis by t h e c r i t e r i a speLled o u t i n t h e Code. 1.2

Approaches t o Maintenance

Components which f ' a i l e d or developed t r o u b l e a f t e r r a d i o a c t i v i t y l e v e l s had b u i l t up have been r e p a i r e d i n many r e a c t o r s . The methods employed i n :flaking r e p a i r s have i n v a r i a b l y been make-shift i n terms of equipment, t e c h n i q u e s acd procedures because s t a n d a r d equipment f o r r e mote maintenance i s n o t a v a i l a b l e . There seem t o have been two g e n e r a l approaches t o r e a c t o r system maintenance: Where p o s s i b l e , floodirig w i t h water h a s been used t o provide r a d i a t i o n s h i e l d i n g while s t i l l a l l o w h g v i s i b i l i t y and m o b i l i t y . I n o t h e r c a s e s p o r t a b l e o r temporary s h i e l d s , u s u a l l y l e a d , have been employed t o p r o t e c t workers who must e n t e r r a d i a t i o n f i e l d s . The methods have been combined a t times.

5 W

1.2.1

Some Examples of Maintenance Methods

The Gas-Cooled Reactor Experiment i n Idaho w a s flooded w i t h water and r e p a i r e d by d i v e r s working underwater t o b r e a k and remake f l a n g e j o i n t s i n r e p l a c i n g s e c t i o n s of two c o o l i n g water l i n e s . Two d i v e r s worked 112 hours i n making t h e r e p a i r s . No welding was involved. R a d i a t i o n exposures were about 400 t o 600 m r f o r t h e workers' b o d i e s and about 50% more f o r t h e i r hands. 1 D i v e r s were a l s o used i n making r e p a i r s t o t h e c o r e s u p p o r t p l a t e and t h e f u e l channels of t h e Big Rock P o i n t b o i l i n g water r e a c t o r . T h i s work involved b o l t i n g p i e c e s i n p l a c e and n o t welding. Later, r e p a i r work on t h e t h e r m a l s h i e l d of t h e same r e a c t o r was performed underwater w i t h long-handled t o o l s and t e l e v i s i o n viewing. A t t h i s t i m e , t h e r a d i a t i o n l e v e l s had i n c r e a s e d , d u r i n g a d d i t i o n a l r e a c t o r o p e r a t i o n , t o t h e p o i n t where t h e u s e of d i v e r s a g a i n could n o t be c o n s i d e r e d . The underwater maintenance o p e r a t i o n s involved some machining work and included seal welding of a l l n u t s and keepers.a'" The D r e s d e n - l b o i l i n g water r e a c t o r experienced a number of c r a c k s i n welds which were r e p a i r e d by d i r e c t work from behind a l e a d s h i e l d w i t h a l e a d p i p e t o p r o t e c t t h e w o r k e r ' s hand and arm. By having j u s t a small h o l e i n t h e l e a d p i p e t o a l l o w movement of t h e welding head, workers were p r o t e c t e d as much as p o s s i b l e d u r i n g t h e i r working t i m e i n s i d e t h e r a d i a t i o n zone. Even so, more t h a n 50 welders had t o be c a l l e d upon so t h a t no p e r s o n would have t o work i n t h e r a d i a t i o n f i e l d l o n g enough t o r e c e i v e an overexposure t o r a d i a t i ~ n . ~ ' ~ On t h e BONUS b o i l i n g water, n u c l e a r s u p e r h e a t r e a c t o r , O a k Ridge s u p p l i e d a welder t o work on t h e s u p e r h e a t e r steam p i p i n g . With some water s h i e l d i n g and a l e a d box f o r t h e worker, welds were made d i r e c t l y on t h e t u b e s . 6 The b o i l i n g water r e a c t o r of t h e Oyster Creek Nuclear Power P l a n t w a s found t o have c r a c k s i n f i e l d w e l d s on t h e t u b e s f o r t h e c o n t r o l rod d r i v e s .7 F o r t u n a t e l y t h e c r a c k s w e r e discovered b e f o r e t h e r e a c t o r had been o p e r a t e d . N e v e r t h e l e s s a one-year d e l a y r e s u l t e d from t h e t i m e req u i r e d t o diagnose t h e problem and i t s e x t e n t and t o p r e p a r e t o make t h e n e c e s s a r y r e p a i r s , even though remote c o n t r o l o p e r a t i o n s were n o t necessary. Similar c r a c k s have been found, a l s o b e f c r e o p e r a t i o n s s t a r t e d , i n t h e b o i l i n g water r e a c t o r s f o r t h e Nine-Mile P o i n t Power P l a n t of Niagara Mohawk and t h e Tarapur Nuclear Power S t a t i o n i n I n d i a . Had t h e s e c r a c k s n o t been d i s c o v e r e d b e f o r e o p e r a t i o n s s t a r t e d , t h e j o b of f i x i n g them would have involved long shut-downs.

For work on t h e c a l a n d r i a of t h e Sodium G r a p h i t e Reactor, Atomics I n t e r n a t i o n a l developed a remotely c o n t r o l l e d c u t t i n g and welding system. Bench t e s t s were promising f o r s p e c i a l i z e d welding on t h e SGR c a l a n d r i a , which t h e remote welder was s p e c i f i c a l l y designed t o f i t ; however, t h e r e a c t o r p r o j e c t w a s t e r m i n a t e d and t h e equipment w a s never used i n a radiation f i e l d

A remote welder w a s r e n t e d from Atomics I n t e r n a t i o n a l t o make weld r e p a i r s on t h e t u b e - t o - t u b e s h e e t welds of t h e steam g e n e r a t o r of t h e Fermi sodium-cooled, fast r e a c t o r . T h i s machine w a s used t o make 1200 w e l d s , t a k i n g 45 s e e p e r

The Dounreay F a s t Reactor developed a s m a l l l e a k i n a sodium c o o l a n t o u t l e t p i p e n e a r t h e r e a c t o r v e s s e l . The r e a c t o r w a s down f o r one y e a r t o l o c a t e and r e p a i r t h e leak.'' The c u t t i n g of t h e l e a k i n g s e c t i o n was done d i r e c t l y u s i n g a l e a d s h i e l d , b u t a s p e c i a l remote welding gadget w a s designed and b u i l t f o r rewelding t h e p i p e . 1 2 , 1 3 Welders r e c e i v e d t h e i r t h r e e months' r a d i a t i o n exposure l i m i t i n s i x h o u r s ' working t i m e . Problems were encountered i n o b t a i n i n g s k i l l e d welders t o do t h e j o b . The H a l l a m sodium-graphite r e a c t o r used an automated remotely cont r o l l e d welder i n s i d e a h o t c e l l t o s e a l weld t h e c o n t a i n e r s f o r s p e n t f u e l e l e m e n t s . Manipulators are used t o o p e r a t e t h e remote welding apparatus.1 4

1 . 3 Remote Maintenance C o n s i d e r a t i o n s I n g e n e r a l , r a d i o a c t i v e r e a c t o r system components are i n t e r c o n n e c t e d with l a r g e p i p e s which must b e disconnected and r e j o i n e d when components are r e p l a c e d . Also l a r g e v e s s e l a c c e s s openings must b e opened for Lns p e c t i o n and replacement of i n t e r n a l s arid t h e n r e s e a l e d . Flanges w i t h mechanical seals and remote welding are two p o s s i b l e methods of r e j o i n i n g p i p e o r c l o s i n g v e s s e l openings. Some o f t h e c o n s i d e r a t i o n s which a f f e c t t h e c h o i c e of t h e appraach are given below. More d e t a i l e d d i s c u s s i o n s on weld j o i n t maintenance are included i n S e c t i o n B.

1.3.1 Equipment Location f o r Maintenance TO b e b e s t s u i t e d f o r remote maintenance, r e a c t o r components and p i p i n g should be p h y s i c a l l y l o c a t e d s o as t o p e r m i t a c c e s s from above f o r removal and replacement o p e r a t i o n s . T h i s , however, imposes r a t h e r s e v e r e r e s t r i c t i o n s on l a y o u t s i n c e it v i r t u a l l y e l i m i n a t e s s t a c k i n g of equipment w i t h i n a c e l l . T h e r e f o r e , i f c e l l space s a v i n g s from s t a c k i n g of components a r e t o b e achieved, c o n s i d e r a t i o n must be g i v e n t g t h e p r e d i c t e d frequency of'rnaintenance an any s p e c i f i c assembly of p i F i n g arid components s o t h a t t h e most f r e q u e n t l y worked-on assemblies w i l l be placed i n t h e most r e a d i l y a c c e s s i b l e l o c a t i o n s . The d e s i g n e r t h u s p r o v i d e s u n r e s t r i c t e d overhead a c c e s s on a f i r s t p r i o r i t y basis f o r t h e components needing maintenance on a r e g u l a r l y scheduled basis, and t h e n p r o v i d e s a c c e s s f o r a n t i c i p a t e d " t r o u b l e area" work. When t h i s has been done: remote methods can b e employed most e f f e c t i v e l y t o reduce t h e c o s t and i n c r e a s e t h e r e l i a b i l i t y of maintenance o p e r a t i o n s .

1 . 3 . 2 Mechanical J o i n t C o n s i d e r a t i o n s a.

A l l r e a c t o r system j o i n t s must b e l e a k - t i g h t t o p r e v e n t t h e o u t l e a k a g e o f c o o l a n t and r a d i o a c t i v i t y or t h e i n - l e a k a g e of e x t e r n a l g a s e s which might contaminate t h e contained f l u i d . Furthermore, some of t h e r e a c t o r c o o l a n t s become v e r y c o r r o s i v e

7 Y

when exposed t o atmospheric oxygen or m o i s t u r e . An i n e r t gas b u f f e r between t h e gas or l i q u i d i n t h e p i p e s and t h e atmosphere i s sometimes employed, a t s l i g h t l y h i g h e r p r e s s u r e , t o a s s u r e that mechanical j o i n t s a r e e f f e c t i v e l y l e a k t i g h t . Since t h i s seal i s s o important f o r t h e i n t e g r i t y of t h e system, t h e equipment which m a i n t a i n s t h e o v e r p r e s s u r e must be e x t r a r e l i a b l e . b.

Any mechanical seal r e q u i r e s l a r g e f o r c e s t o keep t h e s e a l i n g s u r f a c e s i n c o n t a c t d u r i n g a l l e x c u r s i o n s of system temperat u r e and p r e s s u r e . A s a n example, t h e s o l i d m e t a l s e a l s which use r i n g s i n grooves r e q u i r e a c e r t a i n minimum f o r c e t o maint a i n t h e seal. A d d i t i o n a l s t r e n g t h i s needed t o r e s i s t t h e axial and bending s t r e s s e s t r a n s m i t t e d through t h e p i p e . There are a c c e p t a b l e clamping and b o l t i n g methods f o r p r o v i d i n g t h i s s t r e n g t h where t h e j o i n t i s not s u b j e c t e d t o l a r g e t h e r m a l stresses which deform t h e r i n g s e a l , or t o h i g h t e m p e r a t u r e s which m i g h t a n n e a l t h e clamps. Unfortunately, t h e h i g h e r t e m p e r a t u r e s (1000 t o 1500째F) o f advanced r e a c t o r systems make s a t i s f a c t o r y b o l t i n g o r clamping a d i f f i c u l t problem.

I n h i g h - r a d i a t i o n f i e l d s , t h e f l a n g e d j o i n t s must be o p e r a t e d and maintained by remote means. There a r e problems of o p e r a t i n g b o l t s o r bulky clamps by remote c o n t r o l , of removing t h e component without damaging t h e j o i n t , i n s p e c t i n g and c l e a n i n g t h e p r e c i s i o n seal s u r f a c e s , i n s t a l l i n g t h e p o l i s h e d r i n g undamaged, i n s t a l l i n g t h e new component, a l i g n i n g t h e j o i n t , remaking t h e clamp, and l e a k checking t h e seal. Some of t h e s e problems would b e encountered i n remote welding, a l s o . When a mechanical j o i n t l e a k s , t h e maintenance crew has a choice of r e p a i r by t i g h t e n i n g t h e j o i n t o r by r e p l a c i n g t h e r i n g with one p l a t e d w i t h a s o f t metal such as g o l d .

For replacement by welding or by f l a n g e d connections, a l l j o i n t s connecting t h e component i n t o t h e system must be i n proper a l i g n m e n t b e f o r e b o l t i n g o r clamping. Warpage d u r i n g t h e t h e r m a l c y c l i n g t h a t occurs i n any p l a n t may r e q u i r e awkward placement of t h e j o i n t and a complicated i n s t a l l a t i o n sequence as t h e new component i s brought i n t o t h e f i n a l p o s i t i o n . The changes i n p r e v i o u s l y e s t a b l i s h e d l o c a t i o n s w i l l r e q u i r e c a r e f u l measurement by remote means t o determine t h e e x a c t l o c a t i o n of t h e i n c e l l j o i n t s o t h a t adjustments can b e made t o a l i g n t h e new component. A mechanical j o i n t does n o t permit much margin f o r e r r o r i n alignment and f i t t i n g a f t e r t h e component i s i n t h e c e l l , wherea:, with a welded j o i n t , i n - c e l l machining of mating s u r f a c e s could b e used t o c o r r e c t c e r t a i n misalignments.

Welded J o i n t Closure Considerat i o n s

a. W

I n j o i n i n g p i p e s , welding can b e used e i t h e r t o provide a f u l l s t r e n g t h , f u l l p e n e t r a t i o n welded j o i n t , or t o provide a s e a l around a gasketed f l a n g e j o i n t . Most f u l l - s t r e n g t h weld c l o s u r e s r e q u i r e m u l t i - p a s s welds which are d i f f i c u l t t o make.

Yet t h e s e all-welded j o i n t s , t o be l e a k t i g h t , must be metall u r g i c a l l y sound. J o i n t alignment, purge gas, weld a r c , and weld metal f e e d v a r i a b l e s w i l l a f f e c t bead shapes and weld q u a l i t y . These v a r i a b l e s a r e d i s c u s s e d i n more d e t a i l i n Section B. b.

Numerous problems t h a t are a s s o c i a t e d w i t h t h e i n s p e c t i o n of welds are n o t encountered 3r a r e less s e v e r e w i t h f l a n g e d j o i n t s . It i s an accepted f a c t t h a t welds must be thoroughly and p r o p e r l y i n s p e c t e d t o a s s u r e j o i n t i n t e g r i t y . Nuclear p l a n t weld q u a l i t y r e q u i r e n e n t s exceed t h e s p e c i f i c a t i o n s for c o n v e n t i o n a l steam power p l a n t s . Weld i n s p e c t i o n t e c h n i q u e s must work i n h i g h r a d i a t i o n backgrounds which make normal radiogrzphy i m p o s s i b l e . I n s p e c t i o n equipment m a n i p u l a t i o n s must b e c o n t r o l l a b l e from remote l o c a t i o n s and viewing i s p o s s i b l e o n l y by i r i d i r e c t means. I n s p e c t i n g w i t h magnetic f i e l d s , or charged p a r t i c l e beams, g e n e r a l l y i s u n s u i t a b l e t o n u c l e a r p l a n t m a t e r i a l s and/or c o n d i t i o n s . U l t r a s o n i c i n s p e c t i o n has shown promise, although much more must b e done t o a d a p t u l t r a s o n i c t e c h n i q u e s t o remote work. The P a c i f i c N o r t h w e s t Laboratory has proposed an ultrasonic i n s p e c t i o n development program f o r t h e FFTF. Another u l t r a s o n i c i n s p e c t i o n development program i s b e i n g sponsored by iridustry through t h e Edison E l e c t r i c I n s t i t u t e , arid i s beirig conducted under s u b c o n t r a c t a t t h e S x t h w e s t Research I n s t i t u t e , Hous:on,

Texas. 1 5 c.

Preweld j o i n t p r e p a r a t i o n r e q u i r e d f o r remote welding i n v o l v e s a c c u r a t e , a x i a l l y square p r e c u t t i n g of t h e j o i n t , matching o f t h e r e s p e c t i v e i n s i d e and (outside d i a m e t e r s a l o n g w i t h p r e c i s i o n alignment of t h e p i g e s t u b t o b e welded, arid p o s s i b l e r e b e v e l i n g t o o b t a i n a c c e p t a b l e alignment of mating j o i n t members. It i s i m p e r a t i v e t h a t a thorough c l e a n i n g of t h e p i p e i n t e r i o r a t t h e j o i i i t area precede a l l work, and t h a t utmost c a r e b e t a k e n t o c o x p l e t e l y remove a l l weld p r e p a r a t i o n c u t t i n g s which might damage pumps, v a l v e s , e t c . , i f allowed t o remain i n t h e system and c i r c u l a t e with t h e f l u i d . Wire b r s h i n g and s o l v e n t c l e a n i n g may a l s o be r e q u i r e d t o p r e p a r e t h e w e l d area.

R e p a i r s t o f a u l t y reweld j o i n t s a r e e q u a l l y d i f f i c u l t . The p r e v i o u s l y d e s c r i b e d i n s p e c t i o n and c l e a n i n g requirements a p p l y t o rewelding a l s o . WFERENCES

1. Divers Repair GCRE Vessel, Nucleonics, p . 78, May 1961. 2.

J . I . Riesland and E . A . Gustafson (GE San J o s e ) , Work Performed on F u e l Channels and t h e Core Support P l a t e a t Big Rock P o i n t Nuclear Power P l a n t , Conference on Reactor Operating Experience, J u l y 28-29, 1965, Supplement t o Vol. 8, T r a n s a c t i o n s of t h e American Nuclear S o c i e t y , 1965.

9 v

L. M. Hausler Modifications Conference on Supplement t o

and R. L . Hauter (Consumers Power), In-Vessel of I r r a d i a t e d Reactor I n t e r n a l s a t Big Rock P o i n t , Reactor Operating Experience, J u l y 28-29, 1965, Vol. 8, T r a n s a c t i o n s of t h e American Nuclear S o c i e t y ,

1965

4. R .

H . Holyoak (Commonwealth Edison) The 1967 In-Service I n s p e c t i o n of Dresden 1 Nuclear Power P l a n t , T r a n s a c t i o n s of t h e American Nuclear S o c i e t y , V o l . 10, p . 635, November 1967.

C l i f f o r d Z i t e k , P e r s o n a l communication d u r i n g a v i s i t t o ORNL, l9@.

E v e r e t t Rogers (Oak Ridge Y-12 P l a n t ) P e r s o n a l communication; Rogers d i d t h e welding f o r t h e BONUS r e p a i r s , 1968.

United S t a t e s Atomic Energy Commission Licensing Docket No. 50-219, Amendment 35, F i n a l Report on Reactor Vessel Repair Program, March

1968.

L . Newcomb, C a l a n d r i a Remote Maintenance Tool Development, Atomics I n t e r n a t i o n a l Report NAA-SR-11202, A p r i l 1966.

9. J . F . McCarthy, Compilation of Current T e c h n i c a l Experience a t t h e E n r i c o Fermi Atomic Power P l a n t , Monthly Report No. 7 t o t h e U . S. Atomic Energy Commission, February 1967. 10.

L. T . Bogarty, Modular Steam Generator F a b r i c a t i o n , Atomics I n t e r n a t i o n a l Report NAA-SR-11739,

February

1966.

11. Dounreay Developments: Good p r o g r e s s on PFR; DFR i s back a t f u l l power, Nuclear Engineering, p . 633, August 1968. 12.

Memo t o Myron B. Kratzer, A s s i s t a n t General Manager I n t e r n a t i o n a l A c t i v i t i e s , U . S. AEC, from Carl R. Malmstrom, AEC S c i e n t i f i c Rep r e s e n t a t i v e , U. s. Embassy, London, England; T r i p Report t o Dounreay, February 20,

1968.

13. R. R . Matthews and K. J. Henry, Dounreay Experimental Reactor Establishment, TRG Report 1854R, Nuclear Engineering, Vol. 13, No. 149, pp. 840-844, October 1968.

14.

S. Berger e t a l . , S i x Element I r r a d i a t e d Fuel Shipping Cask, Atomics I n t e r n a t i o n a l Report NAA-SR-12547, Appendix 10, pages 310-319, November 1967.

15.

Grady Whitman, Welding Research Council, P r e s s u r e Vessel Research Committee, P e r s o n a l communication, September 1968.

10 2.

HISTORY OF REMOTE WELDING 2.1

Background

Attempts t o develop automated remote welding systems f o r use i n n u c l e a r work have been pursued, of'f and on, f o r more t h a n t e n y e a r s . Most of t h e e f f o r t s , i n c l u d i n g some at ORNL, were on a s m a l l s c a l e . Limited f i n d i n g s from t h e e a r l i e s t remote welding work formed t h e background f o r t h e Pennsylvania Advanced Reactor (PAR) maintenance welding development program. 2.2

The Pennsylvania Advanced Reactor Program

The Pennsylvania Advanced Reactor (PAR) w a s planned i n t h e mid

1950's t o use a c i r c u l a t i n g aqueous s l u r r y f u e l p r e s s u r i z e d t o 1000 p s i . The h i g h - p r e s s u r e system r e q u i r e d e x t r a c a r e i n f a b r i c a t i o n t o a v o i d l e a k s and a l s o placed a premium on b e i n g able t o r e p a i r l e a k s t h a t developed. It w a s recognized t h a t c i r c u l a t i n g f u e l would i n c r e a s e t h e r a d i a t i o n l e v e l s i n t h e r e a c t o r system areas and would make com@ e t e l y remote maintenance a n e c e s s i t y . I n p l a n n i n g t h e PAR,16 Westinghouse s p e c i f i e d remote welding as t h e mandatory method f'or performing maintenance on t h e r e a c t o r p l a n t . Alkhough c e r t a i n phases of t h e development program were completed, t h e PAR p r o j e c t w a s t e r m i n a t e d b e f o r e t h e remote welding t e c h n i q u e s were e v e r demonstrated i n a n o p e r a t i n g r e a c t o r system. A t u b e - p l u g g i n g procedure had been devised t o use remote welding i n m a i n t a i n i n g t h e system g e n e r a t o r ; t h e p l u g w a s t:, b e i n s e r t e d i n t o t h e t u b e and welded t o t h e t u b e s h e e t . A f l a n g e on t h e p l u g provided t h e m e t a l f o r t h e weld and a l s o covered t h e l e a k p a t h between t h e t u b e and t u b e s h e e t . The t u n g s t e n - a r c welding p r o c e s s w a s s e l e c t e d by t h e PAR group f o r remotely b u t t welding j o i n t s i n t h e f i x e d p i p i n g . To s i m p l i f y equipment, it w a s decided t h a t each remote welding head would be designed t o f i t no more t h a n two p i p e s i z e s . A c o n t r a c t had been n e g o t i a t e d w i t h a man'if a c t u r e r of welding equipment t o improve an e x i s t i n g machine t o permit continuous r o t a t i o n welding with 100 p e r c e n t a r c t i m e , with a u t o m a t i c and complete c o n t r o l , and w i t h completely dependable weld q u a l i t y . A p r o t o t y p e model of t h e machine w i t h f u l l y automatic c o n t r o l s showed promise i n bench t e s t s , b u t it w a s n o t equipped f o r remote work. Also, t h e machine needed f u r t h e r development t o b e s u f f i c i e n t l y r e l i a b l e f o r remote maintenance work.

2 . 3 The Atomics I n 5 e r n a t iorial Program During t h e 1960k, Atomics I n t e r n a t i o n a l , now a D i v i s i o n of North American Rockwell Corporation, developed and p e r f e c t e d a number of a u t o mated welding systems. Some were remotely c o n t r o l l e d f o r work i n conn e c t i o n w i t h A E C ' s sodium-cooled r e a c t o r s ; o t h e r s were automated, bu'; n o t remotely c o n t r o l l e d , f o r space program requirements and for t h e shop f a b r i c a t i o n of h e a t exchangers and t u b i n g systems f o r c i v i l i a r i power r e a c t o r s . While much of t h e i r work w a s c o n c e n t r a t e d on p m d u c t i o n

welding o p e r a t i o n s i n shop f a b r i c a t i o n , A I a l s o developed advanced remote welding technology f o r s p e c i f i c a p p l i c a t i o n s , such as i n t e r n a l tube welding f o r steam g e n e r a t o r f a b r i c a t i o n , deep-hole welding f o r work on t h e c a l a n d r i a of t h e sodium-graphite r e a c t o r , and s e a l welding t h e c o n t a i n e r s f o r n u c l e a r f u e l canning. I n t e r n a l welding equipment makes t u b e - t o - t u b e - s h e e t welds and a l s o t u b e - t o - t u b e welds, with t h e welding head l o c a t e d i n s i d e t h e t u b e . A I ' S a u t o m a t i c a l l y programmed system was developed f o r f a b r i c a t i o n of hightemperature, h i g h - p r e s s u r e modular steam g e n e r a t o r j o i n t s f o r t h e Sodium Component T e s t I n s t a l l a t i o n . It d i d not o p e r a t e by remote control.'' Deep-hole welding equipment w a s developed as a n e x t e n s i o n of i n t e r n a l welding technology t o permit remote removal and replacement of p r o c e s s t u b e and a s s o c i a t e d g r a p h i t e l o g assemblies from t h e Sodium G r a p h i t e Reactor C a l a n d r i a Core. Blind c u t t i n g and T I G rewelding were accomplished by remote c o n t r o l equipment r e a c h i n g as f a r as 40 f t through a b i n . inside-diameter tube. 8 The seal welding of s p e n t f u e l i n c a n s w a s performed i n a manipul a t o r c e l l at Hallam. 14

2.4

S t a t e of t h e A r t Survey

Seeking i n f o r m a t i o n on remote maintenance equipment and t e c h n i q u e s t h a t might b e a p p l i c a b l e t o molten s a l t r e a c t o r s , ORNL conducted a survey e a r l y i n 1968 t o determine t h e s t a t e of t h e a r t . Emphasis w a s placed on remote welding, which was considered t o be of g r e a t e s t i n t e r e s t f o r molten s a l t r e a c t o r systems. S p e c i f i c i n q u i r i e s were made about a l l development and a p p l i c a t i o n s of remotely o p e r a t e d , automated equipment f o r r e a c t o r system maintenance and r e p a i r s . Equipment and t e c h n i q u e s f o r c u t t i n g b e v e l i n g , welding and t e s t i n g weld q u a l i t y were p a r t i c u l a r l y sought o u t . i 7 We s p e c i f i c a l l y looked f o r a u t i l i t y machine t h a t would do c u t t i n g , b e v e l i n g and welding w i t h one s e t up.

2.5

Survey F i n d i n g s

The survey d i s c l o s e d a f e w s p e c i a l l y designed, automated welding assemblies which were remotely c o n t r o l l e d by m a n i p u l a t o r s . Argonne N a t i o n a l Laboratory has performed welding on t h e complex e x p e r i m e n t a l equipment i n s i d e a h o t c e l l i n t h i s way; a t H a l l a m , Nebraska, Atomics I n t e r n a t i o n a l h a s a m a n i p u l a t o r c e l l equipped f o r making s e a l welds on c o n t a i n e r s f o r s p e n t f u e l elements; A e r o j e t Corporation a t Azusa, C a l i f o r n i a , used a similar s e t u p f o r canning r a d i o i s o t o p e s o u r c e s . The E l e c t r i c Boat Company at Groton, Connecticut, and t h e Liquid Carbonics Company of Chicago, b o t h D i v i s i o n s o f General Dynamics, developed an automated welding system â&#x201A;Źor use on shop f a b r i c a t i o n work, without remote c o n t r o l s . I n t h e p r o d u c t i o n of components f o r submarines, welding i s b e i n g done i n c r e a s i n g l y by t h e automated welding systems (TIG, w i t h weld i n s e r t s f o r r o o t p a s s ) . The Nav claims t i m e and d o l l a r s a v i n g s a l o n g w i t h s u p e r i o r weld q u a l i t y . Y7 It was p o i n t e d out by a number of t h e people interviewed t h a t , a t

12 p r e s e n t , no one markets automated welding machinery f o r f i e l d use, a l t h o u g h t h e r e are many a p p l i c a t i o n s where automated equipment would be most v a l u a b l e . The f o l l o w i n g comments from Mr. Richard H . Freyburg, A s s i s t a n t Manager of Operations f o r Consolidated Edison Company of New York, p o i n t o u t some of t h e r e a s o n s why r e a c t o r b u i l d e r s have keen i n t e r e s t i n automated welding equipment, even without remote c o n t r o l s : " I n d u s t r y can n o t t a k e t r a i n e d n u c l e a r welders from s i t e t o s i t e f o r r e a c t o r c o n s t r u c t i o n because union r e s t r i c t i o n s u s u a l l y permit only one company welder f o r every 12 welders s u p p l i e d by t h e l o c a l union. The t r a i n i n g program f o r n u c l e a r welders i s t e d i o u s ; we're lucky t o g e t 60% of t h e new men q u a l i f i e d . Many of t h o s e p a s s i n g t h e n u c l e a r welding q u a l i f i c a t i o n t e s t s are not w e l l s u i t e d f o r c o n s t r u c t i o n work i n o t h e r r e s p e c t s . If we had r e l i a b l e , r e l a t i v e l y simple, automated machinery f o r b e v e l i n g and welding, we could t r a i n w e l d e r s faster t o o p e r a t e t h e automated equipment and t h e q u a l i t y of t h e welds would be b e t t e r , with fewer r e j e c t i o n s . I n f a c t , automated b e v e l i n g and welding machines, on construction, could b e worked around t h e c l o c k . We could even a f f o r d t o p u t on an e x t r a man t o permitcoflee b r e a k s f o r t h e o p e r a t o r s and s t i l l b e w e l l ahead. Furthermore, i f o u r people g a i n confidence i n t h e automated machinery d u r i n g c o n s t r u c t i o n of t h e r e a c t o r , t h e y w i l l b e g l a d t o pay t h e p r i c e l a t e r f o r a more expensive, remotely operated machine f o r r e a c t o r maintenance work. My most u r g e n t need i s f o r a r e l i a b l e , automated welder t h a t reduces r e j e c t i o n s on c o n s t r u c t i o n f i e l d work. I11 8 Maintenance and a s s o c i a t e d program and c o n t r o l equipment f o r a u t o mated welding have not y e t been s i n p l i f i e d and made rugged t o t h e p o i n t where such systems economically c h a l l e n g e manual welding f o r f i e l d work. Our survey, however, r e v e a l e d two automated systems which, w i t h modif i c a t i o n s , might be u s e f u l f o r remote n u c l e a r work. One i s a n " o r b i t a l v e h i c l e combination c u t , b e v e l , weld c a r r i a g e concept" developed and t e s t e d by North American A v i a t i o n , Lss Angeles, a D i v i s i o n of North American Rockwell Corporation, under A i r Force C o n t r a c t ; t h e o t h e r i s 8 combination of e i t h e r Wachs ( E . H . Wachs Company, Wheeling, I l l i n o i s ) or F e i n ( P r e s c o t t Tool Company, West Boylston, M a s s a c h u s e t t s ) p i p e c u t t e r s f o r c u t t i n g , p l u s s p e c i a l l y automated Dyna-Surge APW S e r i e s Systems (Liquid Carbonic D i v i s i o n , General Dynamics Corporation, Chicago, I l l i n o i s ) f o r welding. The Dyna-Surge system technology o r i g i n a t e d a t t h e E l e c t r i c Boat D i v i s i o n of t h e General Dynamics Corporation and w a s 1 ~ s e dfor t h e i r p r o d u c t i o n welding i n submarine work. Dyna-Surge weld head a s s e m b l i e s employ a s t a t i o n a r y c y l i n d r i c a l t r a c k , clamped around t h e p i p e , with a geared r o t a t i n g p a r t on which t h e e l e c t r o d e h o l d e r i s mounted. Torch support and t r a v e l components are similar t o equipment marketedby AB ASEA SVETSMASKINER, t h e Stockholm, Sweden manufacturer t'cr s p e c i a l European automated weld machinery, o r by Clarke, Chapman & Co., L t d . of England. Wachs and F e i n p i p e c u t t e r s a r e commongly used 5.n coal mining o p e r a t i o n s , i n f a b r i c a t i n g g a s p l a n t equipment, i n

marine s a l v a g e work, and i n production pre-weld p i p e end shaping. A s t i l l e x p e r i m e n t a l automatic welding machine f o r l a r g e s i z e overland t r a n s m i s s i o n p i p i n g only i s .being b u i l t by CRC-CROSE, I n c . of Houston, Texas, and i s now b e i n g t r i e d o u t i n a f u l l s c a l e f i e l d t e s t on a C o a s t a l S t a t e s G a s Producing Company p i p e l i n e i n t h e Southwest .19

2.6

Continued Need f o r Remote Welding Development

There were two f u l l - f l e d g e d remote welding development programs p r i m a r i l y a s s o c i a t e d with r e a c t o r p r o j e c t s , t h e PAR and t h e SGR, which were d i s c o n t i n u e d b e f o r e remote welding equipment w a s f u l l y developed. Other d e v i c e s f o r remote welding have been b u i l t and used t o perform s p e c i f i c j o b s i n making r e p a i r s t o r e a c t o r systems.

For a number of y e a r s , ORNL h a s used an automated, remotely c o n t r o l l e d welding a p p a r a t u s i n s i d e a h o t c e l l t o s e a l r a d i o i s o t o p e source c o n t a i n e r s . I n t h i s case t h e c o n t a i n e r s are s m a l l , t h e j o b i s r e p e t i t i v e , and t h e remote welding equipment does n o t have t o b e moved about w i t h i n t h e c e l l . I n g e n e r a l p r a c t i c e , r e a c t o r f u e l elements a r e seal welded i n t h i n - w a l l e d c o n t a i n e r s b e f o r e b e i n g placed i n t h e s h i e l d e d c a r r i e r when t h e y are t o b e shipped o f f s i t e . T h i s seal weld i s u s u a l l y made by remotely c o n t r o l l e d equipment i n a h o t c e l l . Other remote welding o p e r a t i o n s have been performed a t v a r i o u s t i m e s and p l a c e s using equipment s p e c i a l l y adapted f o r t h e s p e c i f i c job. The state of t h e a r t seems t o be t h a t automated welding equipment has been developed t o a p o i n t where it i s p o s s i b l e t o a d a p t comm e r c i a l l y a v a i l a b l e equipment t o t h e performance of s p e c i f i c and, t o remote welding j o b s . d a t e , f a i r l y simple

Although automated welding i s b e i n g used i n c r e a s i n g l y i n shops f o r a v a r i e t y of a p p l i c a t i o n s , t h e r e a r e no p r e s e n t a p p l i c a t i o n s of automated welding t o n u c l e a r r e a c t o r system components b e i n g welded i n t h e f i e l d . I n t h e shop production of components f o r t h e n u c l e a r power systems of submarines, automated welding i s b e i n g i n c r e a s i n g l y used. Weld i n s e r t r i n g s a r e used t o f u s i o n weld Naval. j o i n t r o o t p a s s e s . The N a v y r e p o r t s s a v i n g s i n t i m e and c o s t ovdr manual welding, and claims s u p e r i o r weld q u a l i t y , a l s o . Needs f o r remote welding equipment have become more widespread and a c t u a l a p p l i c a t i o n s of equipment f o r performing s p e c i f i c remote welding j o b s have become more numerous. To d a t e , however, no one has p e r f e c t e d a g e n e r a l l y u s e f u l remote welding system, It i s i n s t r u c t i v e t o c o n s i d e r why t h e equipment h a s n o t been developed t o d a t e , even though a t t e m p t s have been made, and t o e v a l u a t e t h e p r o s p e c t s f o r s u c c e s s i f a n o t h e r a t t e m p t i s made. The f o l l o w i n g f a c t o r s seem important:

1. Limited funding f o r c e d p r e v i o u s d e v e l o p e r s t o r e s o r t t o crude c o n t r o l and programming equipment and t o l i m i t t h e i r mechanical d e s i g n s t o o v e r s i m p l i f i e d hardware items.

Welding and programmed c o n t r o l a p p a r a t u s of t h e p a s t lacked pulsed-arc and a r c l e n g t h r e g u l a t i o n , i n t e g r a t e d d i g i t a l f u n c t i o n a l c o n t r o l s and s o l i d s t a t e d e v i c e s f o r i n s t a n t response a c t u a t i o n . Today ' s remote c o n t r o l c a p a b i l i t i e s are much more s o p h i s t i c a t e d and a d a p t a b l e t o meeting welding quality specifications.

3. M i n i a t u r i z e d components and automated welding hardware were n o t a v a i l a b l e for a p p l i c a t i o n i n t h e p r e v i o u s l y attempted remote welding systems. Welding equipment systems t h a t have been developed r e c e n t l y for t h e N a t i o n a l A e r o n a u t i c s and Space A d m i n i s t r a t i o n and for advanced a i r c r a f t a p p l i c a t i o n s are much s u p e r i o r t o t h o s e t h a t were a v a i l a b l e i n t h e e a r l i e r a t t e m p t s t o a d a p t equipment for remotely c o n t r o l l e d welding operations. REFERENCES

Vol. N , Peansylvania Advanced Reactor P r o j e c t , Layout and Maintenance, P a r t s 1 and 2, WCAP 1104 and 1105; Westinghouse E l e c t r i c Corporation and Pennsylvania Fower and Light Company, March 1959.

Memo from P. P. Holz t o D i s t r i b u t i o n , A P r e l i m i n a r y Survey of Remote C u t t i n g and Welding Techniques Under Development i n t h e United S t a t e s , MSR-68-44, February 20, 1968. Richard H . Freyburg, A s s i s t a n t Manager of Operations, Consolidated Edison Company of N e w York, P e r s o n a l communication by telephone, October 1, 1968.

Wall S t r e e t J o u r n a l , J u l y graph 5 .

8-69 i s s u e , Page

23, Column

4, Para-

3. THE SELECTION OF A SYSTEM TO BE DEVELOPED FOR REMOTE MAINTENANCE 3.1

"Orbital-Vehicle" System Advantages

The A i r F o r c e ' s o r b i t a l v e h i c l e machinery developed by North American-Rockwell f o r p i p e j o i n t - r e p l a c e m e n t maintenance o f f e r s a number of advantages f o r c u t t i n g and rewelding n u c l e a r p i p i n g . A s i n g l e , compact c a r r i a g e p r o p e l s i n t e r c h a n g e a b l e heads f o r c u t t i n g o r welding. T h i s s i n g l e s e t u p f o r a l l phases of r e p a i r work s i m p l i f i e s t h e indexing on t h e s p o t t o be c u t and welded and a s s u r e s r e p e t i t i v e p r e c i s i o n t o o l alignment. Equipment s e t u p time s a v i n g s a l s o r e s u l t , e s p e c i a l l y where weldment r e p a i r s might b e r e q u i r e d . The t u n g s t e n i n e r t gas (TIG) welding p r o c e s s which had been used by t h e A i r Force i n t h e i r work w i t h o r b i t a l machinery w a s a l s o chosen f o r i n i t i a l t e s t s a t ORNL because it o f f e r s most promise of meeting n u c l e a r weld requirements. T h i s p r o c e s s has s e v e r a l i n h e r e n t c h a r a c t e r i s t i c s t h a t are e s p e c i a l l y s u i t a b l e f o r remote f i x e d - p o s i t i o n welding. TIG welding i s a low i n e r t i a p r o c e s s and i s r e l a t i v e l y slow, which makes it much easier t o c o n t r o l and monitor f o r h i g h i n t e g r i t y welds. The amount of molten metal a t any time i s r e l a t i v e l y s m a l l , c r e a t i n g a q u i c k - f r e e z i n g puddle with s u f f i c i e n t s u r f a c e t e n s i o n t o c o u n t e r a c t g r a v i t y . The p r o c e s s t h u s works e q u a l l y w e l l whether t h e weld i s going u p - h i l l , down-hill o r h o r i z o n t a l l y . The a r c l e n g t h of t h e non-consumable e l e c t r o d e can be maintained more e a s i l y t h a n t h a t o f a consumable e l e c t r o d e . There i s no f l u x or s l a g a s s o c i a t e d w i t h t h e process t o r e q u i r e s p e c i a l i n t e r p a s s cleaning, although brushing t o remove t h e l i g h t oxide f i l m i s d e s i r a b l e . F i l l e r wire i s f e d d i r e c t l y i n t o t h e weld puddle. The metal does n o t have t o b e t r a n s f e r r e d i n t o a molten state a c r o s s an e l e c t r i c a r c , an o p e r a t i o n t h a t sometimes r e s u l t s i n s p a t t e r and uneven bead f o r m a t i o n s . A system w i t h i n t e g r a l wire f e e d h a s t h e c a p a b i l i t y t o complete a weld of t h i c k e r s e c t i o n t h a n can be made by autogenous welding. It a l s o i s more l i k e l y t o provide s a t i s f a c t o r y c r a c k - f r e e weld metal of good composition, g r a i n s i z e and p o r o s i t y . T I G equipment c a n b e made compact and p o r t a b l e . 3.2

F u t u r e System Expansion and M o d i f i c a t i o n P l a n s

The o v e r a l l development program f o r an automated c u t -and-weld r e a c t o r maintenance system i s d i v i d e d i n t o two p a r t s ; a system f e a s i b i l i t y s t u d y and development phase, and f u t u r e system expansions and m o d i f i c a t i o n s a l o n g t h e l i n e s d e s c r i b e d below.

3.2.1

Development of A d d i t i o n a l Modules

The a b i l i t y t o change modules on t h e o r b i t a l v e h i c l e c a r r i a g e s u g g e s t s t h a t development and a p p l i c a t i o n of a d d i t i o n a l , i n t e r c h a n g e a b l e modular i n s e r t packages might b e t h e easiest way of accomplishing a d d i t i o n a l f u n c t i o n s . S i n c e welding o p e r a t i o n s r e q u i r e s t r i c t c l e a n l i n e s s c o n t r o l and it i s important t o keep c h i p s and d i r t out of t h e p r o c e s s system, a clean-up module or attachment may b e needed. Welding

16 r e q u i r e s t h a t oxide and dye p e n e t r a n t t e s t films b e removed from bead s u r f a c e s b e f o r e making a d d i t i o n a l weld f i l l e r p a s s e s . A modular head could b e developed t o a p p l y s o l v e n t c l e a n e r s and t o d r i v e a r o t a r y w i r e b r u s h f o r p h y s i c a l l y c l e a n i n g t h e w e l d . We p l a n t o a l s o develop a d d i t i o n a l modular heads f o r a welding i n s p e c t i o n package, complete w i t h TV camera, d i a l i n d i c a t o r s , p e n e t r a n t i n s p e c t i o n d e v i c e s , e t c . 3.2.2

A l t e r n a t e C a r r i a g e f o r Seal-Weld C a p a b i l i t y

P r e s e n t machinery i s designed f o r work on p i p i n g only, w i t h t h e c a p a b i l i t y of p r e p a r i n g j o i n t s f o r b u t t - w e l d i n g , and of performing t h e welds. I n v e s t i g a t i o n s have been s t a r t e d t o determine whether t h e e x i s t i n g modules a l o n g with t h e programmer can b e used f o r s e a l welding a p p l i c a t i o n s . Such a system may i n c l u d e a s u b s t i t u t e c a r r i a g e t o "walk" about a s e t of indexed mating contoured seal l i p s . Motor p r o p u l s i o n equipment for t h i s a l t e r n a t e s e a l - j o i n t c a r r i a g e should be compatible w i t h t h e o r b i t a l v e h i c l e c a r r i a g e d r i v e so t h a t it can be o p e r a t e d w i t h t h e same c o n t r o l s and i n s t r u m e n t a t i o n . An a l t e r n a t e approach under c o n s i d e r a t i o n for v e s s e l seal-weld c l o s u r e s i s based on a free-swinging c a r r i a g e o p e r a t e d from a r a d i u s l i n k a g e a t t h e c e n t e r l i n e of t h e opening. 3.2.3

Development of S p e c i a l F e a t u r e s f o r Nuclear System A p p l i c a t i o n s

A number of a d d i t i o n a l d e s i g n m o d i f i c a t i o n s w i l l b e n e c e s s a r y i n a d a p t i n g t h e p r e s e n t A i r Force machinery t o p r o v i d e b e t t e r i n s t a l l a t i o n and o p e r a t i o n c a p a b i l i t i e s f o r n u c l e a r a p p l i c a t i o n s . These m o d i f i c a t i o n s w i l l i n v o l v e changes t o p o s i t i o n i n g and h a n d l i n g a t t a c h m e n t s s o t h a t a l l of t h e equipment can be i n s t a l l e d and operated from any a v a i l a b l e overhead a c c e s s . The A i r Force d e s i g n was modified somewhat b e f o r e b e i n g used t o f a b r i c a t e a p r o t o t y p e u n i t f o r t h e ORNL f e a s i b i l i t y s t u d i e s . The ORNL p r o t o t y p e , l i k e t h e A i r Force equipment, u t i l i z e s readily-machinable, l i g h t - w e i g h t materials, g e n e r a l l y aluminum. Reactor maintenance a p p l i c a t i o n s w i l l r e q u i r e equipment which i s rugged, i s a b l e t o b e decontamin a t e d and r e p a i r e d , i f n e c e s s a r y , while b e i n g k e p t i n s i d e a h o t c e l l , and i s r e s i s t a n t t o r a d i a t i o n an6 h i g h t e m p e r a t u r e s . It should b e p o s s i b l e t o i n c o r p o r a t e materials and t o develop d e s i g n m o d i f i c a t i o n s which w i l l a d a p t t h e system t o n u c l e a r work w i t h o u t r e d u c i n g t h e proven e f f e c t i v e n e s s of t h e o v e r a l l system d e s i g n o r o p e r a t i o n s . For i n i t i a l t e s t s with t h e p r o t o t y p e , s i g n i f i c a n t s a v i n g s i n t i m e and money were achieved by u s i n g u n i t s t h a t i n c o r p o r a t e s t a n d a r d i n d u s t r i a l components and m a t e r i a l s . T h i s approach w i l l be continued t h r o u g h most o f t h e development program. The more c o s t l y u n i t s , i n c o r p o r a t i n g s p e c i a l m a t e r i a l s f o r ease of decontamination and f o r r e s i s t a n c e t o r a d i a t i o i t arid t o h i g h t e m p e r a t u r e s , w i l l only be b u i l t a f t e r p r e s e n t t e s t s have shown complete s u i t a b i l i t y and performance of t h e d e s i g n . For f u t u r e machinery systems we contemplate r e l o c a t i n g some e l e c t r o n i c c o n t r o l components from t h e i r p r e s e n t module s t a t i o n s t o t h e programmer, and p o s s i b l y r e p l a c i n g some of t h e e l e c t r i c a l s e n s i n g and c o n t r o l equipment i n t h e module with f l u i d i c systems t o minimize r a d i a t i o n damage problems.

SECTION B

PRESENT PROGRAM STATUS

4.1

General

ORNL r e p r e s e n t a t i v e s v i s i t e d t h e North American A v i a t i o n Los Angeles, C a l i f o r n i a D i v i s i o n o f North American Rockwell Corporation and t h e Rocket P r o p u l s i o n Laboratory, U.S. A i r Force Systems Command, Edwards A i r Force Base, C a l i f o r n i a d u r i n g March 1968. A t t h a t t i m e North American Rockwell, as A i r Force c o n t r a c t o r , had a l r e a d y f a b r i c a t e d two p r o t o t y p e o r b i t a l v e h i c l e machines f o r c u t t i n g and welding 1- t o 3 - i n . and 3- t o 6 - i n . diameter t u b i n g . Performance t e s t i n g had j u s t been started. Designs had a l s o been completed b y NAR f o r u n i t s t o handle l a r g e r diameter pipes; 6- t o 9 - i n . , 9- t o 12-in., and 12t o 16-in. Arrangements were made f o r t h e Atomic Energy Commission t o r e c e i v e A i r Force c o n t r a c t o r d e s i g n data. Design drawings f o r t h e 6- t o 9 - i n . diameter o r b i t a l v e h i c l e machinery were s u p p l i e d t o t h e AEC d u r i n g A p r i l and M a y 1968. The Commission, i n t u r n , r e l a y e d t h e i n f o r m a t i o n t o ORNL. A f t e r d e t a i l e d review, ORNL redesigned equipment t o i n c l u d e p r o v i s i o n s f o r remote i n s t a l l a t i o n and o p e r a t i o n c a p a b i l i t i e s , and prepared d e t a i l e d drawings and s p e c i f i c a t i o n s f o r t h e commercial purchase of mechanical assemblies. F a b r i c a t i o n of t h e p r o t o t y p e u n i t f o r t e s t i n g at ORNL began i n August 1968 and was completed d u r i n g February 1969. To save time and i n i t i a l c o s t s , arrangements were made t o borrow a s p a r e A i r Force programmer t o c o n t r o l t h e o p e r a t i o n of t h e equipment f o r a l i m i t e d e v a l u a t i o n p e r i o d . A replacement prog r a m e r i s b e i n g f a b r i c a t e d by ORNL and w i l l be completed by September

1969 The i n i t i a l ORNL development e f f o r t s started i n March

1969 and

were d i r e c t e d toward e s t a b l i s h i n g t h e f e a s i b i l i t y of using remotely

o p e r a t e d machinery that w i l l c u t , b e v e l , and e i t h e r seal or s t r e n g t h weld j o i n t s and p i p i n g f o r n u c l e a r a p p l i c a t i o n s . I n i t i a l c u t t i n g and welding s t u d i e s and t e s t s c l o s e l y followed c u r r e n t USAF r o c k e t system welding technology developments. D e t a i l e d d i s c u s s i o n s on e a r l y development f i n d i n g s a t ORNL are r e p o r t e d on i n t h e f o l l o w i n g c h a p t e r s on p i p e machining and welding s t u d i e s . The development work t o date shows t h a t it i s feasible t o use automated o r b i t a l machinery f o r remote c u t t i n g and welding.

4.2

ORNL's P r o t o t y p e Automated Remote C u t t i n g and Welding System f o r 6 and 8 - i n . P i p e s

The A i r Force h a s o r b i t a l c a r r i a g e s f o r t h e f o l l o w i n g o u t s i d e d i a m e t e r ranges; 3 t o 6 i n . , 6 t o 9 i n . , 9 t o 12 i n . , and 12 t o 16 i n . W e s e l e c t e d t h e 6- t o 9 - i n . c a r r i a g e f o r work w i t h 6- and 8 - i n . p i p e s . A l l l i s t e d c a r r i a g e s u s e t h e same i n t e r c h a n g e a b l e machining and welding heads.

18 The automated remote c u t t i n g and welding machinery package i n c l u d e s t h e f o l l o w i n g components shown i n F i g . 1, 2, and 3: c a r r i a g e , machining head, welding head, weld p r o g r a m e r , and welding power s u p p l y . The f u n c t i o n s performed by t h e s e components and b r i e f equipment summations are d e s c r i b e d i n t h e f o l l o w i n g p a r a g r a p h s . 4.2.1

Carriage

The c a r r i a g e p r o v i d e s a r i g i d , stable p l a t f o r m on which t h e machining head and t h e welding head can b e mounted, indexed, and o p e r a t e d . F i g u r e 4 shows t h e c a r r i a g e w i t h t h e welding head. The c a r r i a g e s u p p l i e s a d r i v e mechanism t o r o t a t e t h e p l a t f o r m around t h e p i p e circumference a t p r e s e t , r e p r o d u c i b l e speeds, w i t h c o n t r o l s t o m a i n t a i n t h e p l a t f o r m s u r f a c e a t a c o n s t a n t d i s t a n c e from t h e p i p e s u r f a c e s o t h a t t h e m i l l i n g c u t t e r depth and a r c l e n g t h c o n t r o l s w i l l perform p r o p e r l y . The p l a t f o r m w i l l m a i n t a i n i t s l a t e r a l p o s i t i o n w i t h r e s p e c t t o t h e p i p e j o i n t while r o t a t i n g about t h e p i p e , s o t h a t when modules are changed from c u t t i n g , b e v e l i n g and welding, t h e a l i g n ment w i l l a l r e a d y b e c o r r e c t . The c a r r i a g e geared a c t u a t o r arm a s s e m b l i e s clamp s e c u r e l y t o t h e p i p e ; i t s d r i v e r o l l e r s are loaded by s p e c i a l t o r s i o n bars t o m a i n t a i n c o n t r o l l e d r o l l e r clamping p r e s s u r e and t o compensate f o r p i p e o v a l t y w i t h i n commercial. s p e c i f i c a t i o n s . C a r r i a g e d e s i g n p e r m i t s a l l l i s t e d t a s k s t o b e accomplished w i t h i n a 4 1/2-in. r a d i a l clearance. The c a r r i a g e s t r u c t u r e c o n s i s t s of two s i d e p i e c e s which p r o v i d e a p l a t f o r m f o r t h e welding and machining heads, and two end s u p p o r t s . These s u p p o r t s c o n t a i n t h e water, i n e r t gas and e l e c t r i c a l power conn e c t i o n s and switches; t h e f r o n t s u p p o r t a l s o c o n t a i n s t h e clamping d e v i c e , namely worn g e a r s which p o s i t i o n t h e i d l e r o l l e r s through a s l i d e r c r a n k l i n k a g e . The c a r r i a g e r o t a t e s v i a a d i r e c t d r i v e system from motors mounted a t t h e two hinge p o i n t s of t h e a c t u a t i n g arms w i t h i n t h e r o l l e r s . The v u l c a n i z e d h i g h t e m p e r a t u r e , a b r a s i o n r e s i s t a n t viton coating provides t h e necessary r o l l e r t r a c t i o n . 4.2.2

U n i v e r s a l Machining Head

The machining head shown i n F i g . 5, can b e mounted on t h e c a r r i a g e t o c u t p i p e o r t u b i n g , m i l l t h e t u b e ends square, and b e v e l t h e edges t o t h e d e s i r e d c o n f i g u r a t i o n f o r welding. The machining head i n c l u d e s an o u t e r housing, a T r i a c , speed-regulated, 1/4-hp a i r - c o o l e d e l e c t r i c d r i v e motor of t h e t y p e produced f o r hand d r i l l s , p l u s t h e d r i v e motor housing and c u t t e r a s s e m b l i e s . Two-axis manual c u t t e r adjustment i s a v a i l a b l e . S e v e r a l t y p e s of c u t t e r b l a d e s can be i n s t a l l e d as needed. 4.2.3

U n i v e r s a l Welding Head

The welding head, F i g . 6, can b e mounted on t h e c a r r i a g e i n p l a c e of t h e machining head a f t e r t h e c u t t i n g and. b e v e l i n g o p e r a t i o n s have been completed. The welding head i s designed w i t h ad j u s t a b l e v e r t i c a l and h o r i z o n t a l s l i d e s t o l o c a t e t h e e l e c t r o d e a c c u r a t e l y w i t h r e s p e c t t o t h e c u t and beveled edges of t h e weld j o i n t . F i l l e r wire w i l l be

-.*

bl i

Fig.

6. Universal Welding Head.

25 W

f e d a u t o m a t i c a l l y a t t h e d e s i r e d r a t e t o t h e weld j o i n t from a s p o o l which s t o r e s enough wire f o r m u l t i p l e f i l l e r weld p a s s e s . The welding head w i l l p r o v i d e an i n e r t welding gas t o t h e t o r c h cup, w i l l p r o v i d e power and c o o l i n g water flow t o t h e t o r c h head, and w i l l o s c i l l a t e t h e welding e l e c t r o d e a c r o s s t h e seam. It w i l l a l s o p r o v i d e i n t e g r a l s w i t c h e s f o r t e s t o p e r a t i n g t h e wire f e e d jog, t h e o s c i l l a t o r , and i n e r t gas flow. 4.2.4

Welding Programmer and C o n t r o l U n i t

A pendant-housed s t a r t - s t o p c o n t r o l u n i t and t h e console-welding programmer c o n t a i n t h e measurement r e c o r d e r s and c o n t r o l d e v i c e s t h a t p r o v i d e f o r automated welding. The programmer,shown i n F i g s . 7 and 8, i s designed t o c o n t r o l and/or sequence each of t h e f o l l o w i n g weld v a r i a b l e s or f u n c t i o n s ; welding c u r r e n t v s . t i m e , maximum welding c u r r e n t , welding c u r r e n t p u l s e amperes and p u l s e t i m e , c u r r e n t upslope t i m e , weld t i m e , c u r r e n t downslope t i m e , welding v o l t a g e , welding t o o l speed and s t a r t and s t o p t i m e , w i r e f e e d speed and s t a r t and s t o p time, a r c v o l t a g e c o n t r o l v o l t a g e , and o s c i l l a t o r f r e q u e n c y . The welding c u r r e n t and t h e c a r r i a g e ( t o o l ) d r i v e c i r c u i t s are r e s p e c t i v e l y s e r v o - c o n t r o l l e d . The w i r e feed r a t e can b e a d j u s t e d t o m a i n t a i n c o n s t a n t e l e c t r o d e / w e l d puddle d i s t a n c e s by u s i n g a feedback system t o monitor t h e a r c v o l t a g e and compare it t o a p r e s e t , p r e determined v a l u e , and, as r e q u i r e d , g e n e r a t e a c o r r e c t i o n s i g n a l . Changes i n t h e a r c gap are r e f l e c t e d as changes i n a r c v o l t a g e and t h e s e changes g e n e r a t e a c o r r e c t i o n s i g n a l which changes t h e f i l l e r w i r e speed t o b u i l d up o r t o d e c r e a s e t h e weld puddle t o m a i n t a i n a p r e s e t a r c gap. The wire f e e d system a l s o i n c l u d e s a t r a n s i s t o r i z e d motor c o n t r o l s e r v o system t o q u a n t i t a t i v e l y r e g u l a t e f i l l e r d e p o s i t s i n response t o a tachometer feedback s i g n a l . P i p e o v a l t y c o r r e c t i o n s a r e r e g u l a t e d by a mechanical cam d e v i c e which r i d e s t h e p i p e and s p r i n g l o a d s t h e weld head w i t h i n t h e c a r r i a g e t o t e n d t o m a i n t a i n a constant tool/workpiece spacing. Lighted b u t t o n s are provided f o r f u n c t i o n i n d i c a t i o n and/or s e l e c t i o n . I n d i c a t i n g meters a r e i n c o r p o r a t e d f o r t o o l and wire f e e d speed, a r c v o l t a g e , and weld c u r r e n t . The u n i t i s designed t o p r o v i d e s i g n a l s which c a n b e used w i t h commercially-available r e c o r d e r s t o p r o v i d e permanent r e c o r d s . A t p r e s e n t w e u s e a m u l t i - c h a n n e l Sanborri 150 Recorder. The A i r Force programmer, F i g . 7 a l s o i n c l u d e s p r o v i s i o n s f o r punched c a r d i n p u t t o p r o v i d e a u t o m a t i c c a p a b i l i t y f o r program s e t u p . T h i s f e a t u r e i s e s p e c i a l l y d e s i r a b l e f o r p r o d u c t i o n work. For t h e t i m e being, however, p r i m a r i l y f o r economy r e a s o n s , we are n o t u s i n g punch c a r d t e c h n i q u e s i n our replacement programmer. 4.2.5

Power Supply

Most c o m m e r c i a l l y - a v a i l a b l e welding power supply u n i t s are compatible w i t h t h e programmer c o n t r o l c i r c u i t r y and can b e employed as power s o u r c e s . We u t i l i z e a L i n c o l n Model T I G 300/300 welder w i t h minor c i r c u i t m o d i f i c a t i o n s . I n d u c t i v e t r a n s i e n t s u p r e s s o r s and a t r a n s i s t o r i z e d r e a c t o r

k" k

28 c o n t r o l a m p l i f i e r shown i n F i g . 9 have been added t o t h e w e l d e r s ' r e a c t o r c o n t r o l c i r c u i t s . Welder c o n t r o l s f o r g a s and water s o l e n o i d v a l v e r e l a y s are t r a n s f e r r e d t o t h e programmer. 4.2.6

Equipment M o d i f i c a t i o n s f o r Remote Work

ORNL's 6- t o 9 - i n . - d i a m e t e r c a r r i a g e and t h e welding and m i l l i n g i n s e r t heads i n c o r p o r a t e a number of changes and m o d i f i c a t i o n s t o similar A i r Force equipment. Our machinery i n c l u d e s a c t u a t o r s , l i f t i n g and p o s i t i o n i n g l u g s designed f o r remote t o o l i n g and h a n d l i n g . We have a l s o e l i m i n a t e d from t h e o r i g i n a l A i r Force weld head two d i s c o n n e c t s i n t h e welding power supply l i n e and t h e water and g a s l i n e s . Our c a b l e s a r e i n t e g r a l . with t h e t o r c h and r o u t e d i r e c t l y from t h e t o r c h h o l d e r through a grommet-' i n s e r t i n t h e ad jacerit c a r r i a g e f r o n t p a n e l . S t r a y RF c u r r e n t s and p o t e n t i a l water l e a k s a r e e l i m i n a t e d . Our d i r e c t l y coupled t o r c h a l s o p e r m i t s completely independent weld head ( i n , o r out of c e l l ) checkout and replacement. The s e p a r a t e power and c o n t r o l l e a d s a t o p p o s i t e ends of t h e c a r r i a g e work w e l l i n remote i n s t a l l a t i o n . Separated c o r d s do n o t t a n g l e while r o t a t i n g t h e c a r r i a g e t o loop c a b l e s p r i o r t o c u t t i n g o r welding, o r d u r i n g a c t u a l work o p e r a t i o n s . We have a l s o added a Lossy-Line Absorptive F i l t e r RF Suppressor t o p r o v i d e i n c r e a s e d p r o t e c t i o n of w i r i n g and components c o n n e c t i n g t o t h e e l e c t r o d e . Our w i r e f e e d e r e x i t t r o u g h i s oxide coated t o e l i m i n a t e a r c i n g and f u s i n g . I t s t r o u g h p i v o t d e v i c e i s a l t e r e d t o permit more f l e x i b i l i t y and t o p r o v i d e a l o c k - i n f e a t u r e t o c e n t e r t r a c k i n g . A s i m i l a r h o r i z o n t a l t r a v e l l o c k i n g d e v i c e w a s added t o t h e c u t t e r head t o p r e v e n t l a t e r a l c a r r i a g e motion while c u t t i n g . Our c u t t e r t o o l f e e d a c t u a t o r includes r a t c h e t depth set c o n t r o l .

MACHINING STUDIES

5 . 1 General Considerable t i m e was s p e n t t o check and g e n e r a l l y confirm A i r Force machining d a t a and t o develop c u t t i n g and m i l l i n g t e c h n i q u e s f o r s t a i n l e s s s t e e l and I n c o n e l p i p i n g . We noted t h a t c u t t i n g c r i t e r i a a p p l i c a b l e f o r 300 s e r i e s s t a i n l e s s s t e e l p i p e s do n o t a p p l y f o r I n c o n e l work. A v a i l a b l e I n c o n e l p i p e w a s chosen t o approach H a s t e l l o y N material c h a r a c t e r i s t i c s . We were a b l e t o p r e p a r e beveled p i p e j o i n t s . C u t t e r t r i a l s s t a r t e d i n l a t e February 1969. Major performance t e s t s h e l d d u r i n g March and A p r i l included saw t r a c k i n g s t u d i e s and runout d e t e r m i n a t i o n s and machining s t u d i e s on ( i n o r d e r ) 304 s t a i n l e s s s t e e l , 347 s t a i n l e s s s t e e l and I n c o n e l p i p i n g . We t e s t e d 1/16 i n . and 3/32 i n . t h i c k high speed s t e e l and C i r c o l o y a l l o y s l i t t i n g saws and h i g h speed s t e e l s i n g l e and double b e v e l c u t t e r s . We v a r i e d c u t t e r speeds, c u t t e r f e e d s , and c a r r i a g e t r a v e l rates t o determine programmed o p e r a t i n g combinations f o r a c c e p t a b l e t o o l performance and p i p e s u r f a c e f i n i s h . T e s t e f f o r t s a l s o served t o e v a l u a t e our equipment, and t o develop a c c e p t a b l e machining t e c h n i q u e s f o r b o t h s l i t t i n g and b e v e l i n g p i p e t o p r e p a r e d e s i r e d p i p e end c o n f i g u r a t i o n s f o r welding. We noted p a r t i c u l a r l y t h a t p i p e w a l l t h i c k n e s s v a r i a t i o n s , even w i t h i n t h e allowed

31 k

code l i m i t s f o r commercial p i p i n g , g r e a t l y complicate t h e j o i n t machining requirements f o r dependable weld j o i n t g e o m e t r i e s . 5.2

Equipment E v a l u a t i o n

The machining head a p p e a r s t o have c a p a b i l i t y t o c u t p i p e , t r i m ends square, and t o p r e p a r e end b e v e l s . L i t t l e d i f f i c u l t y i s encountered i n machining s t a i n l e s s materials; problems, however, arise i n c u t t i n g I n c o n e l because of i t s work-hardening t e n d e n c i e s . A l l ORNL machining t e s t s were performed on h o r i z o n t a l p i p i n g . S l i t t i n g saws and double b e v e l c u t t e r s t r a c k t r u e w i t h i n approx. .OO3 i n . S i n g l e b e v e l c u t t e r s t e n d t o walk o u t o f , and away from t h e c u t , e s p e c i a l l y on t h e h a r d e r I n c o n e l p i p e . C u t t e r d r i v e motor power and speed c o n t r o l c a p a b i l i t i e s appear a d e q u a t e . The c a r r i a g e and machining head w i l l w i t h s t a n d l o a d i n g and v i b r a t i o n s caused by t h e m i l l i n g c u t t e r s w i t h p r o p e r t r a v e l speed and t o o l f e e d s e l e c t i o n . Improvements, however, a r e x q u i r e d t o p r o v i d e a s t r o n g e r and more p o s i t i v e c u t t e r d e p t h c o n t r o l and t o g i v e more stable l o n g i t u d i n a l a d j u s t m e n t s . A r a t c h e t - c o n t r o l l e d worm g e a r d e p t h c o n t r o l i s contemp l a t e d f o r more p r e c i s e f e e d c a p a b i l i t y . A l o c k i n g clamp a l r e a d y i n s t a l l e d t o t h e l o n g i t u d i n a l adjustment a p p e a r s t o a d e q u a t e l y p r e v e n t axial c u t t e r s h i f t s .

The c u t t e r d r i v e motor and i t s speed r e d u c t i o n g e a r t r a i n work w e l l . We have observed no s i g n s of motor o v e r h e a t i n g d u r i n g performance t e s t s , even d u r i n g s e v e r e m i l l i n g o p e r a t i o n s . The 110 V ac motor i s r a t e d a t about 5 anps; 2.5-amp r e a d i n g s were t h e h i g h e s t noted i n t e s t o p e r a t i o n s . Motor speed c o n t r o l appears adequate, f o r speeds r a n g i n g from about 30 rpm t o about 120 r p n . Observations t o d a t e i n d i c a t e t h e c a r r i a g e d r i v e may be t h e l i m i t i n g f a c t o r on c u t t i n g c a p a b i l i t y . We have observed r o l l e r s l i p p a g e on t h e p i p e , and a t t i m e s have t r i p p e d t h e d r i v e r o l l e r c i r c u i t b r e a k e r p r o t e c t i o n . Cutter f e e d and c a r r i a g e speed adjustment changes, however, r e s t o r e d o p e r a t i o n s . During a r e c e n t maintenance p e r i o d t o r e v u l c a n i z e t h e r o l l e r v i t o n f r i c t i o n s u r f a c e s w e found a broken s h e a r p i n on one of t h e two c a r r i a g e d r i v e r s . We do n o t know when t h i s p i n sheared, o r f o r how long we may have o p e r a t e d w i t h b u t a s i n g l e c a r r i a g e d r i v e r o l l e r . (The o t h e r motor operated s a t i s f a c t o r i l y , b u t slipped within i t s concentric c a n n i s t e r housing. A v a i l a b l e i n d i c a t o r s i g n a l s r e g i s t e r e d p r o p e r d u a l motor o p e r a t i o n b u t n o t t h e e f f e c t of t h e sheared p i n . ) T h e r e f o r e , w e are u n c e r t a i n how much t h e c u t t i n g performance may be l i m i t e d by t h e c a r r i a g e d r i v e system. However, w e were a b l e t o make t h e machine work even w i t h only one motor a c t u a l l y d r i v i n g i t s r o l l e r .

5.3 Tooling We have c u t w i t h high speed s t e e l and C i r c o l o y a l l o y s l i t t i n g saws and m i l l i n g c u t t e r s . The a l l o y e d t o o l t e e t h a p p e a r t o s t a y s h a r p e r l o n g e r , p o s s i b l y by as much as a f a c t o r of one and a h a l f . E a r l y r e s u l t s from I n c o n e l machining e x p e r i m e n t a t i o n i n d i c a t e t h a t t h e c u t t i n g edges of a l l c u t t e r t e e t h must be generously r e l i e v e d t o

provide ample c l e a r a n c e f o r c h i p f a l l o u t . Free f a l l i n g c h i p s minimize work hardening t e n d e n c i e s f o r I n c o n e l p i p e . It i s a l s o q u i t e important t h a t a l l t e e t h of a c u t t e r engage t h e work d u r i n g t h e c u t t i n g . O f f t h e s h e l f commercial c u t t e r s used t o d a t e appear t o c u t w i t h u s u a l l y only about a f o u r t h of t h e i r t e e t h . Improved c u t t i n g w a s noted when c u t t e r s were regound l o c a l l y t o p r e c i s i o n s p e c i f i c a t i o n s ; almost s e v e n t y - f i v e p e r c e n t t o o t h engagement can b e a t t a i n e d . We f u r t h e r noted t t z import a n c e of t o o l t r a v e l and c u t t e r speed a d j u s t m e n t s f o r I n c o n e l p i p e work. A v a i l a b l e machine shop machining d a t a do n o t a p p l y t o t h e o r b i t a l c u t t i n g assembly because it does n o t have t h e d r i v i n g power of shop machines. Also, d r y machining i s s p e c i f i e d f o r n u c l e a r system maintenance because c o o l a n t s might contaminate t h e n u c l e a r system. T h e r e f o r e t h e t o o l t r a v e l , c u t t i n g speeds and t o o l f e e d rates must b e much lower t h a n u s u a 1 shop p r a c t i c e . The t a b l e on t h e f o l l o w i n g page shows t h e number of i n c h e s of c u t a b l a d e can b e expected t o make b e f o r e it must be resharpened. The t a b l e a l s o shows how deep t h e b l a d e would c u t i n t r a v e l i n g t h e i n d i c a t e d number of i n c h e s around a 6 - i n . - d i a m e t e r p i p e , t a k i n g a 30-mil or a 12-mil c u t , as i n d i c a t e d . The s h o r t c u t t e r l i f e experienced i n t e s t o p e r a t i o n s means t h a t b l a d e s w i l l have t o b e r e p l a c e d f r e q u e n t l y . We p l a n t o t e s t c a r b i d e c u t t e r b l a d e s i n hopes t h a t t h e y w i l l last l o n g e r .

5 . 4 Machining Feeds and Speeds E f f i c i e n t cutting requires t h e thickest possible chip per c u t t i n g t o o t h , b u t may have t o be compromised somewhat t o o b t a i n r e a s o n a b l e c u t t e r l i f e and p r o p e r s u r f a c e f i n i s h . T h i s i s p a r t i c u l a r l y t r u e i n t h e c a s e of h i g h - n i c k e l s t e e l s where t h e base material t e n d s t o work harden w i t h t h e r e s u l t t h a t c h i p removal i s inadequate or incomplete. We s e l e c t e d A i r Force recommended c u t t i n g speeds between 70 and 80 s u r f a c e f e e t p e r minute f o r s t a i n l e s s s t e e l s and chose 50 f e e t p e r

minute f o r I n c o n e l i n o r d e r t o a c h i e v e r e a s o n a b l e c u t t e r l i f e . The c u t t i n g speeds correspond t o approximately 100 and 62.5 r e v o l u t i o n s p e r minute f o r o u r 3 i n c h d i a m e t e r a l l o y s t e e l s l i t t i n g saws. T e s t v e r i f i e d f e e d p e r t o o t h s e l e c t i o n s compatible w i t h t o o l s t r e n g t h and r i g i d i t y were .001 i n . f o r s t a i n l e s s work, and about .0005 i n . f o r I n c o n e l . We chose r e s p e c t i v e t r a v e l speeds of 3 1/4 in./min. and 1 in./min. f o r t h e 32 t o o t h saws based- on t h e formula FEED p e r TOUCH ( m i l s ) =

TRAVERSING SPEED ( i n . / m i n . ) No. TEE?TH CUTTER x SPEED (rpm)

Our f e e d p e r t o o t h rates are low when compared t o rates i n s t a n d a r d machine shop work, b u t are s t i l l c r e d i t a b l e c o n s i d e r i n g our small s i z e d arid low powered equipment. The d e p t h s of c u t depend on a v a i l a b l e h o r s e power and c u t t e r shapes, and on t h e s h a r p n e s s of t h e c u t t e r s , as t h e y i n t u r n a f f e c t t h e power r e q u i r e d a t t h e c u t t e r motor s p i n d l e . We rep e a t e d l y c u t .O3O i n . deep i n t o s t a i n l e s s , and . O l 5 i n . i n t o I n c o n e l . W e a n t i c i p a t e deeper c u t t i n g c a p a b i l i t y w i t h t h e " a l l c a r b i d e c u t t e r s " now on o r d e r .

T a b l e 1. Expected Life of C u t t e r Blades ~

De s c r i p t i o n

In Inconel

70 t o 80 f't/min 3 1/4 in./min

50 f t / m i n 1 in./min .OOO5 i n .

.001 i n . I n c h e s of' c u t , average d e p t h j 0 u1Lls. inches

1/16-in. - t h i c k s l i t t i n g saw, 3 i n . d i a . , 32 t e e t h h i g h speed s t e e l

Blade L i f e t i m e

I n Stainless Steel Saw Tooth Speed C a r r i a g e Speed Feed P e r Tooth

T a t a l Depth of c u t , 6-inch pipe w a l l . inches

I n c h e s of c u t , average d e p t h 12 m i l s . inches

T o t a l Depth of c u t , 6-inch pipe w a l l . inches.

5 30

314

Circoloy alloy*

800

I 1/8

3/32-in. - t h i c k s l i t t i n g s a w , 3 i n . d i a . , 32 t e e t h h i g h speed s t e e l

430

5/8

Circoloy a l l o y - %

650

7/8

600

11/32

70" i n c l u d e d double a n g l e m i l l 2 3/4 i n . d i a . , 20 t e e t h , 1/2 i n . wide h i g h speed s t e e l

470

11/16

420

1/4

1/16-in. - t h i c k s l i t t i n g saw,

3 i n . d i a . , 32 t e e t h

730

3/32-in. - t h i c k s l i t t i n g saw,

3 i n . d i a . , 32 t e e t h

Trade name f o r C i r c u l a r T o o l Company (Providence, R.I.) s p e c i a l high-speed s t e e l a l l o y e d b l a d e s o f h i g h carbon, medium chrome, h i g h vanadium, high t u n g s t e n and medium c o b a l t composition.

33 v

5.5

Machining Techniques f o r S l i t t i n g and Beveling Pipes; Pipe End P r e p a r a t i o n Requirements f o r Welding

An important feature d e s i r e d f o r p i p e weld j o i n t s i s a p e r f e c t match f o r a d j o i n i n g pipe ends. P i p e i n s i d e walls must a l i g n and must be c o n c e n t r i c . R e g a r d l e s s of t h e geometry of a s e l e c t e d j o i n t , whether it i s V-bevel, J-bevel, or b u t t , p r e c i s i o n f i t u p and mating g e o m e t r i c a l c o n c e n t r i c i t y w i l l be r e q u i r e d , a l o n g w i t h square-cut ends and a uniform gap, o r complete c o n t a c t , of t h e j o i n t ends. ASME Materials S p e c i f i c a t i o n s , S e c t i o n Two, B o i l e r Code f o r P i p i n g permit v a r i o u s d i a m e t r i c a l and w a l l t h i c k n e s s dimensional v a r i a t i o n s . S e c t i o n SB 167 f o r Nickel-Chrome A l l o y Pipe, as an example, p e r m i t s an a l l o w a b l e e c c e n t r i c i t y of p i p e i n s i d e and o u t s i d e d i a m e t e r up t o t e n p e r c e n t of t h e nominal w a l l t h i c k n e s s . Comparable SA 106 S t e e l Pipe Specs a l l o w f o r 12 1/2 p e r c e n t t h i c k n e s s v a r i a t i o n s below nominal p i p e w a l l t h i c k n e s s . Diameters f o r l a r g e p i p i n g may v a r y as much as 1/8 i n . A l l commercial p i p e i s governed by t h e s e s p e c i f i c a t i o n s . Our e x p e r i e n c e i n d i c a t e s t h a t p i p i n g dimensions v a r y at least as much as, or s l i g h t l y more t h a n t h e a l l o w a b l e t o l e r a n c e s .

F i g u r e 10 i l l u s t r a t e s problems encountered when we c u t commercial p i p i n g f o r a J - b e v e l weld j o i n t w i t h our o r b i t a l equipment. The c a r r i a g e r o l l e r s r i d e t h e p i p e o u t s i d e s u r f a c e , which t h e n becomes t h e r e f e r e n c e s u r f a c e f o r t h e c u t t e r . For s i m p l i c i t y , F i g . 10 shows t h e end view e c c e n t r i c i t y about only one c e n t e r l i n e . I n p r a c t i c e , one e n c o u n t e r s e c c e n t r i c i t i e s i n s e v e r a l p l a n e s . The two e l e v a t i o n s shown r e p r e s e n t matched and mismatched j o i n t a l i g n m e n t . Mismatching d e s t r o y s mating i n s i d e d i a m e t e r s u r f a c e c o n t a c t and p r o h i b i t s p r o p e r r o o t p a s s weld p e n e t r a t i o n . To a c h i e v e matched and a l i g n e d j o i n t s u r f a c e s r e q u i r e s s e n s o r s and c o n t r o l s which w i l l p r o p e r l y r e g u l a t e t h e r o o t p a s s weld v a r i a b l e s (weld c u r r e n t , -speed, - w i r e f e e d , and - a r c v o l t a g e ) t o a d d u s t f o r v a r i a t i o n s of t h e j o i n t . To d a t e we have no s e n s i n g means which w i l l a u t o m a t i c a l l y a d j u s t t h e programmed weld v a r i a b l e s f o r nonuniform geometries of the weld joint. F i g u r e 11 i l l u s t r a t e s how a remedial c u t can be t a k e n t o approach uniform w a l l t h i c k n e s s f o r p i p e weld j o i n t s . T h i s r e q u i r e s t h a t t h e o p e r a t o r o b t a i n a c c u r a t e dimensional i n f o r m a t i o n from h i s i n i t i a l s l i c i n g cut so t h a t he can p r o p e r l y p o s i t i o n and feed t h e c u t t e r f o r subsequent machining. A wax impression of t h e p i p e end c o n t o u r could b e used f o r remote work a p p l i c a t i o n s . If t h e p i p e i s contaminated and t h e n c o n t a m i n a t e s t h e impression device, d u p l i c a t e non-contaminated r e p l i c a s can be made i n h o t c e l l s o r g l o v e boxes v i a a r e c a s t p l a s t e r of p a r i s p r o c e s s . T h i s t e c h n i q u e of remote r e p l i c a t i o n h a s been used s u c c e s s f u l l y i n working w i t h v e r y h i g h l y r a d i o a c t i v e m a t e r i a l s .

F i g u r e 12 shows one way o f f i e l d matching a p i p e end w i t h a p i p e s t u b p r e v i o u s l y welded o n t o a replacement component. For r e a c t o r maintenance, replacement items such as pumps, h e a t exchangers, e t c . , are a l l j i g p r e f a b r i c a t e d . A b l a n k end s t u b of s l i g h t l y h e a v i e r s c h e d u l e pipe, t o g a i n a s m a l l e r i n s i d e d i a m e t e r for subsequent f i t u p machining, could be f i e l d ground t o a n i m p r e s s i o n r e p l i c a of t h e p i p e end.

34 A machining t e c h n i q u e has been developed f o r remotely p r e p a r i n g J - b e v e l p i p e ends f o r welding. F i g u r e 13 s c h e m a t i c a l l y r e p r e s e n t s a n i n - c e l l maintenance c u t t i n g procedure which t e n d s t o compensate f o r t h e v a r i a t i o n s i n p i p e w a l l t h i c k n e s s which, under t h e ASME Code, can be as much as 12 1/25.

1. Step 1: Make a l i g h t c u t around t h e p i p e with a t h i c k s l i t t i n g s a w and i n s p e c t for t r u e t o o l t r a c k i n g . Continue s l i t t i n g t o t h e predetermined d e p t h which w i l l l e a v e a land s u r f a c e f o r t h e r o o t weld. 2.

S t e p 2: On t h e c u t t e r s h a f t , mount a hardened s t e e l t h r u s t washer and a s i n g l e - a n g l e m i l l i n g c u t t e r so t h a t t h e washer w i l l r i d e i n t h e s l i t made by t h e saw and w i l l guide t h e bevel cutter.

S t e p 3: A f t e r making t h e b e v e l c u t , i n s e r t a t h i n s l i t t i n g sawblade and c u t through t h e w a l l .

4. Make

a w a x impression of t h e c u t j o i n t .

Make a p l a s t e r of

paris non-contaminated r e p l i c a .

Machine t o a c o n s t a n t land w a l l t h i c k n e s s a t t h e j o i n t by c u t t i n g metal from segments of t h e land s u r f a c e where measurements of t h e r e p l i c a i n d i c a t e it i s t o o t h i c k .

6 . Make a second r e p l i c a t i o n of t h e j o i n t f o r u s e i n o u t - o f c e l l machining on t h e s t u b end of a replacement component t o make it f i t t h e p i p e i n s i d e t h e c e l l .

Use i n f o r m a t i o n from t h e r e p l i c a t o s e t programmer weld c u r r e n t c u r v e s s o t h a t t h e y w i l l compensate for v a r i a t i o n s i n t h e arc gap caused by out-of-roundness o r by t h e machining t o g i v e c o n s t a n t land w a l l t h i c k n e s s .

A l l of o u r machining o p e r a t i o n s must b e accomplished i n t h e s t a n d a r d " m i l l i n g up" mode of o p e r a t i o n where t h e c u t t e r t o o t h i n c o n t a c t w i t h t h e p i p e i s moving i n t h e same d i r e c t i o n as t h e c a r r i a g e . We l a c k r i g i d i t y f o r r e v e r s e , or "climb m i l l " c u t t i n g . Our t o r s i o n bar clamping a c t i o n on t h e c a r r i a g e r o l l e r does n o t g i v e enough f r i c t i o n c o n t a c t f o r climb c u t t i n g .

WELDING STUDIES

6.1

General

O r b i t a l T I G welding o p e r a t i o n s on p i p e r e q u i r e p r e c i s e w e l d j o i n t machining t o o b t a i n c o n c e n t r i c p i p e i n s i d e d i a m e t e r s and matched p i p e w a l l t h i c k n e s s e s as w e l l as n e a r - p e r f e c t alignment of t h e r e s p e c t i v e t.wo j o i n t members. F a i l u r e t o meet t h e s e requirements r e s u l t s i n r o o t welds t h a t are undercut, l a c k f u l l p e n e t r a t i o n , or t h a t have t o o much p e n e t r a t i o n , r e s u l t i n g i n e x c e s s i v e convexity. F i l l - p a s s weld c r i t e r i a

ORNL DWG. 69-11837

w ul

END

\/WV

STrCTiON

MATCHED ALIGNMENT Fig.

10.

Orbital

Cutter

(Riding

Pipe

O.D.).

Typical

"As Cut"

Pipe

Joints.

ORIlL DWG. 69-11838

ZORRECTIVE CUT

---- - 7

W ch

Fig.

I\AODlFIED SECTION ___...

END VIEW

MODIFIED 11.

Orbital

Cutter

(Tiding

Pipe

O.D.).

Corrective

Joint

Cutting

Plan.

ORNL DWG. 69-11839

Fig.

12.

Modified

Final

Joint

Preparation.

ORNL DWG. 69-11840

STEP3

Fig.

13.

Pipe

Joint

- Machining

Sequence.

39 V

do n o t a p p e a r t o be q u i t e s o c r i t i c a l , though we note a dependence of s u c c e s s i v e welds on p r i o r weld p a s s e s . It i s q u i t e simple t o l a y good f i l l e r s o v e r good r o o t welds, or over good p r i o r f i l l e r welds. It i s d i f f i c u l t t o perform r e m e d i a l t a s k s over poor s u b s t r a t e s . All t h e s e o b s e r v a t i o n s a r e based upon o u r r e c e n t work, which h a s g e n e r a l l y i n volved extra-heavy 6 - i n . -diameter, 347 s t a i n l e s s s t e e l p i p e prepared w i t h V- o r J - b e v e l j o i n t s , and always f i t t e d up without j o i n t gap, and w i t h o u t weld i n s e r t s . Remote work on n u c l e a r systems cannot u s e gap j o i n t s o r t h e common weld i n s e r t r i n g s . T e s t o p e r a t i o n s w i t h t h e o r b i t a l welding equipment were started d u r i n g late February 1969. The f i r s t t e s t s c o n s i s t e d of simply p l a c i n g weld beads around t h e e x t e r i o r s u r f a c e of t h e p i p e . Subseq u e n t l y , V- and J - b e v e l p i p e - j o i n t r o o t and f i l l e r p a s s weld t e s t s were t r i e d . We had hoped t h a t a c c e p t a b l e r o o t p a s s weldments could be o b t a i n e d without having t o do t h e p r e c i s i o n machining t h a t i s r e q u i r e d f o r c l o s e alignment and f i t t i n g of mating s u r f a c e s . However, t h e t e s t welds showed t h a t p r e p a r i n g t h e s u r f a c e s f o r p r e c i s i o n matching and alignment i s important i n a c h i e v i n g q u a l i t y welds. Because it i s time consuming and d i f f i c u l t t o do p r e c i s i o n machining by remote c o n t r o l , we p l a n t o experiment w i t h j o i n t s i n which one p r e a p p l i e s weldwire f i l l e r metal t o one of t h e two j o i n t ends p r i o r t o p l a c i n g t h e p i p e i n s i d e t h e c e l l . T h i s t y p e of j o i n t p r e p a r a t i o n p e r m i t s p l a i n f u s i o n r o o t p a s s welding, and r e q u i r e s no o t h e r f i l l e r w i r e a d d i t i o n s . It should a l s o g r e a t l y reduce t h e r e q u i r e ments f o r p r e c i s i o n j o i n t matching and alignment. S e v e r a l h i g h l y s u c c e s s f u l r o o t p a s s welds have j u s t been performed by a similar method i n which t h e p i p e ends were machined t o i n c l u d e an i n t e g r a l f l a t washer on one of t h e two mating J - j o i n t s e c t i o n s . T h i s washer p e r m i t t e d t h e r o o t p a s s weld t o b e a s i n g l e f u s i o n weld which, i n t h e tests e x h i b i t e d e x c e l l e n t bead shape and f u l l weld p e n e t r a t i o n . A t t h e moment w e s t i l l l a c k e s s e n t i a l i n f o r m a t i o n t o s u i t a b l y program t h e p i p e r o o t p a s s weld ( w i t h f i l l e r wire a d d i t i o n ) f o r p i p e s i n t h e h o r i z o n t a l p l a n e . We have found no e a s y s o l u t i o n t o t h e problem of s e n s i n g t h e weld puddle b e h a v i o r as it relates t o c o n s i s t e n t f u l l weld p e n e t r a t i o n . Such a s e n s i n g c a p a b i l i t y would permit a u t o m a t i c c o n t r o l and would make it p o s s i b l e t o do remote welding w i t h f a r l e s s c r i t i c a l s p e c i f i c a t i o n s f o r p r i o r j o i n t p r e p a r a t i o n . W e have, however, r e c e n t l y coupled a Sanborn 150 Recorder t o our weld programmer t o s t u d y simultaneous d a t a p r i n t o u t s of t h e i n t e r - r e l a t e d weld f u n c t i o n s (weld t r a v e l speed, - w i r e feed r a t e , - a r c v o l t a g e , and - a r c current, e have j u s t begun t o l e a r n how t o s e l e c t and voltage control). W i n t r o d u c e p r o p e r weld programs f o r c o n t r o l l e d h i g h q u a l i t y welding. There a p p e a r s t o b e an e x c e l l e n t chance t h a t we w i l l soon be able t o develop j o i n t p r e p a r a t i o n , f i t u p , and weld c r i t e r i a f o r c o n s i s t e n t r e a c t o r q u a l i t y welding.

We observed manual TIG welding o p e r a t i o n s i n an a t t e m p t t o s t u d y j u s t how a welder a c t u a l l y m a n i p u l a t e s h i s feed wire r e l a t i v e t o h i s weld puddle. S l i g h t p u l s i n g of t h e wire advance motions were noted,

40 w i t h speed adjustments t o m a i n t a i n t h e wire a t t h e weld p u d d l e ' s lower edge. For t h e p r e s e n t we l a c k b u i l t - i n programmer w i r e f e e d p u l s e c a p a b i l i t y . We do, however, have t h e c a p a b i l i t y f o r weld c u r r e n t p u l s i n g w i t h up t o 50 amperes peak t o peak p u l s e amplitudes a t either o r 60 p u l s e s p e r minute. However, t h e s e p u l s e s do n o t g i v e t h e puddle s t a b i l i t y observed i n manual welding. An improvised method of wire f e e d p u l s i n g was t e s t e d m d appeared t o g i v e improved puddle s t a b i l i t y , b e t t e r a r c t i e - i n t o t h e j o i n t w a l l s , and uniform bead p e r i p h e r y . A Wavetek wave f u n c t i o n g e n e r a t o r provided 3 c y c l e s p e r second p u l s i n g w i t h 50% on and o f f times. A d d i t i o n a l t r i a l s w i l l b e scheduled with r e f i n e d c i r c u i t r y .

6.2 Preweld J o i n t Cleaning S t o r e d metals w i l l form e x t e r n a l oxide c o a t i n g s . These oxides are r e f r a c t o r y . Excess power ( w e l d c u r r e n t ) i s r e q u i r e d t o o b t a i n i n i t i a l weld p e n e t r a t i o n when m e t a l s u r f a c e s are oxide coated, and t h i s o f t e n r e s u l t s i n weld p o r o s i t y due t o h y d r a t i o n of t h e o x i d e . Once p e n e t r a t i o n has been achieved, new problems a r i s e . One e n c o u n t e r s d i f f i c u l t i e s w i t h weld puddle c o n t r o l , e s p e c i a l l y i n o r n e a r overhead weld positions. Weld d e p o s i t s are uneven w i t h b a l l i n g t e n d e n c i e s and void i n c l u s i o n s . Foutine c l e a n i n g procedures of s t a i n l e s s s t e e l w i r e b r z s h i n g t80 c u t o x i d e c o a t i n g s and wiping w i t h s o l v e n t t o remove s u r f a c e d i r t and g r e s s e t r a c e s a r e n e c e s s a r y f o r a l l welds w i t h t h e p r e s e n t o r b i t a l equipment. A d d i t i o n a l draw f i l i n g , o r g r i n d i n g , may be r e q u i r e d f o r f i l l e r p a s s e s t o renove s h a r p notches or p r o t z u s i o n s t o o b t a i n smooth, blenaed surfaces.

6.3 J o i n t F i t u p T o l e r a n c e J o i n t mismatch h a s a l r e a d y beeii l i s t e d as a cause f o r poor r o o t p a s s welds i n h o r i z o n t a l p i p e l i n e s . Mismatch i s most c r i t i c a l i n t h e overhead o r 6 o ' c l o c k p i p e p o s i t i o n . Here a s l i g h t mismatch of a d j a c e n t i n n e r d i a m e t e r p i p e j c i r , t l i p s , commonly r e f e r r e d t o as mating land s u r f a c e s , c a u s e s t h e weld t o p u l l o u t , o r suck back m e t a l due t o g r a v i t y c o n d i t i o n s . We concluded t h a t it w i l l b e n e c e s s a r y t o match p i p e bottom q u a d r a n t s most p r e c i s e l y f o r b e s t weld r e s u l t s , s i n c e m i s f i t c o n d i t i o n s can b e t o l e r a t e d t o a g r e a t e r degree i n t h e t o p quadrant s u r f a c e s . Pipe j o i n t mating s u r f a c e s should p r e f e r a b l y make p h y s i c a l c o n t a c t on f i t u p f o r r a d i o a c t i v e system remote maintenance welding. Purge g a s l o s s e s are minimized with c o n t a c t i n g s u r f a c e s , and f i l l e r metal a d d i t i o n s are reduced, a l s o .

6.4 I n e r t S h i e l d

Gas

There i s a d i f f e r e n c e i n i o n i z a t i o n p o t e n t i a l of i n e r t g a s e s which a f f e c t t h e h e a t i n p u t t o t h e weld zone. H e l i u m r e q u i r e s o n l y about 60% of t h e welding c u r r e n t r e q u i r e d f o r a n e q u i v a l e n t weld w i t h argon s h i e l d g a s . D i f f e r e n t arc plasma shapes r e s u l t . Argon s p r e a d s t h e welding h e a t ; helium c o n c e n t r a t e s h e a t . A i r Force ' e x p e r i m e n t a t i o n i n d i c a t e d

41 t h a t wide welding. have a l s o gas purge

argon plasmas g i v e b e s t r e s u l t s f o r work w i t h s t a i n l e s s A l l ORNL work h a s been done w i t h argon s h i e l d i n g g a s . We used argon g a s t o purge p i p e i n t e r i o r s , u s u a l l y w i t h a 20 c f h flow.

6.5 E l e c t r o d e C o n f i g u r a t i o n A i r Force e x p e r i m e n t a t i o n i n d i c a t e d t h a t b e t t e r welds can b e o b t a i n e d by t a p e r i n g t h e t o r c h e l e c t r o d e t u n g s t e n t o a 60" included a n g l e . E l e c t r o d e c o n f i g u r a t i o n i n f l u e n c e s t h e a r c spread p a t t e r n . The tendency of an arc t o spread t o an a d j a c e n t area c a u s e s t h e weld nugget t o f u s e o n l y i n t e r m i t t e n t l y t o t h e j o i n t s i d e w a l l s , r e s u l t i n g i n l a c k of f u s i o n and an uneven, knotty-rope a p p e a r i n g s u r f a c e on t h e weld bead. It i s p r a c t i c a l l y impossible t o l a y subsequent a c c e p t a b l e f i l l p a s s e s over such d e f e c t i v e s u r f a c e s ; one must r e s o r t t o c o r r e c t i v e i n t e r p a s s machining and b l e n d i n g p r i o r t o proceeding w i t h f u r t h e r welding. We t e n t a t i v e l y s t a n d a r d i z e d on a 60" included e l e c t r o d e a n g l e f o r o u r s t a i n l e s s welding work.

6.6 Automatic Arc Voltage C o n t r o l It i s n e c e s s a r y t o c o n t r o l b o t h t h e t o r c h - t o - p i p e d i s t a n c e and t h e t o r c h e l e c t r o d e - t o - w e l d puddle d i s t a n c e t o m a i n t a i n a c o n s t a n t a r c l e n g t h and a c k t a n t a r c v o l t a g e w i t h a s e l e c t e d i n e r t welding g a s . The o r b i t a l system weld head i s s p r i n g loaded w i t h i n t h e c a r r i a g e . A cam f o l l o w e r r i d e s t h e p i p e ' s p e r i m e t e r and a c t u a t e s a s p r i n g t o p e r p e n d i c u l a r l y v a r y t h e weld head t o work-piece s p a c i n g and c o n t i n u o u s l y compensate f o r o v a l t y o r l o c a l f l a t s p o t s i n t h e p i p i n g . North American Rockwell a l s o devised an e l e c t r o n i c a r c v o l t a g e c o n t r o l (AVC) system t o m a i n t a i n c o n s t a n t electrode-to-weld puddle s p a c i n g . The A i r Force programmer b u i l t by Rockweel i n c l u d e s a feedback system which monitors t h e a r c v o l t a g e , compares it t o a predetermined v a l u e , and, as r e q u i r e d , g e n e r a t e s a c o r r e c t i o n s i g n a l t o a d j u s t t h e w i r e f e e d rate. The AVC s y s t e m t h u s actually senses o r observes changes i n t h e arc gap as changes i n a r c v o l t a g e t o i n c r e a s e o r d e c r e a s e t h e f i l l e r wire speed t o d e p o s i t l a r g e r or smaller weld puddles t o m a i n t a i n p r e s e t gap. The a n g l e of t h e t i p of t h e e l e c t r o d e d e t e r m i n e s where t h e a r c w i l l i n i t i a t e . A r c emission can occur from any s p o t of t h e heated e l e c t r o d e ' s t a p e r e d e m i t t i n g s u r f a c e . Weld bead shape can b e somewhat v a r i e d by changing e l e c t r o d e t i p a n g l e s . P r e c i s i o n , c a u t i o n and c a r e are r e q u i r e d even w i t h AVC r e g u l a t i o n t o c o n f i n e t h e arc emission d i r e c t i o n t o keep from bumping i n t o p i p e j o i n t s i d e w a l l s or weld puddles. A d d i t i o n a l p r e c a u t i o n s are n e c e s s a r y t o p r e v e n t contacting t h e electrode with t h e f i l l e r w i r e during the overlap p o r t i o n o f t h e weld. The w i r e f e e d motor c u t o f f p o i n t must b e programmed t o s t o p i n t h e i n i t i a l downslope p o r t i o n of t h e weld c u r r e n t .

6.7

Pre-Weld P o s i t i o n i n g

P i p e ends t o be j o i n e d by welding must b e r i g i d l y h e l d i n p o s i t t o r i d u r i n g welding t o p r e v e n t weld heat-induced p i p e movement a t t h e joint due t o expansion and c o n t r a c t i o n f o r c e s . P i p e s may be clamped o r f u s i o n t a c k welded p r i o r t o t h e r o o t p a s s .

We p l a n t o use mechanical clamps f o r remote maintenance welding, as machine t a c k welding p r e s e n t s a d d i t i o n a l problems: after t a c k i n g , p i p e j o i n t groove s u r f a c e s of t h e t a c k must be machined t o a t h i n , blended buildup; s u r f a c e s must t h e n b e w i r e brushed and s o l v e n t cleaned; machine t a c k welding must a l s o be confined t o t h e upper h a l f of t h e pipe t o p r e v e n t u n d e r c u t t i n g a t t h e end of t h e tackweld.

6.8 Root Pass The i d e a l root-weld p a s s r e q u i r e s t h e s h o r t e s t p o s s i b l e a r c l e n g t h without " s t i c k i n g " and w i t h a d d i t i o n s of as much f i l l e r wire as p o s s i b l e for c r a c k s e n s i t i v e metals. For p i p e i n h o r i z o n t a l r u n s weld p a s s e s should s t a r t i n t h e overhead p o r t i o n of a j o i n t t o take utmost advantage of t h e c h i l l i n g e f f e c t s of c o l d p i p e s . P i p e j o i n t l a n d s should i d e a l l y b e uniform i n t h i c k n e s s and i n width. The a n g l e f o r wire e n t r y and t h e e x i t l o c a t i o n of t h e wire f e e d e r guide t u b e r e l a t i v e t o t h e weld puddle are c r i t i c a l . Experimentation t o d a t e has f o l l o w e d o t h e l i s t e d A i r Force recommended s e t t i n g s ; For s t a i n l e s s s t e e l welding:

Root P a s s Arc Length = 1/16 i n . F i l l e r Wire Rate, approx. 10 i n . / m i n . with .045-in. w i r e

Tool Drive ( c a r r i a g e ) T r a v e l Speed, approx . 4 in./min. Pipe J o i n t Lands, approx. 1/16 i n . high

1/16 i n . wide x

Wire Feeder E n t r y Angle 25 t o 30" above t h e tangent point with pipe surface, 1/4 i n . away from t h e e l e c t r o d e , w i t h t h e wire dragging t h e groove d i r e c t l y below t h e e l e c t r o d e . AVC s e t a t 8 1 / 2 t o 9 v o l t s w i t h argon purge g a s S t a r t P o s i t i o n approx. Some i n d i c a t i o n s of r o o t p a s s weld programmer v o l t m e t e r and wire f e e d rate i n d i c a t e any v a r i a t i o n s i n a r c l e n g t h . t i n g t h e pipe j o i n t i f voltage readings

9 o'clock

q u a l i t y can b e observed from meter r e a d i n g s . Both meters The weld bead i s n o t p e n e t r a hold s t e a d y b u t w i r e f e e d

43 rates r e g i s t e r o n l y below s e l e c t e d rates. Usually a small i n c r e a s e i n welding c u r r e n t w i l l remedy t h i s s i t u a t i o n . If, however, t h e w i r e f e e d e r motor b u i l d s up t o t h e s e t rate, and v o l t a g e c o n t i n u e s t o climb, poor welding a l s o r e s u l t s , and t h e c y c l e should be stopped a t once. The problem w i l l u s u a l l y b e an e x c e s s i v e j o i i i t gap f o r m a t i o n w i t h t o o much pushthrough i n t h e upper q u a d r a n t s of t h e p i p e , f i l l e r w i r e bound up w i t h i n t h e wire f e e d e r d r i v e and not f e e d i n g i n t o t h e weld, or excessive puddle f l u i d i t y i n p i p e v e r t i c a l p o s i t i o n s c a u s i n g puddle flow away from t h e e l e c t r o d e t i p .

6.9 F i l l P a s s e s S a t i s f a c t o r y weld f i l l p a s s e s do n o t appear t o p r e s e n t g r e a t problems. The second weld p a s s , or f i r s t f i l l pass, r e q u i r e s some s p e c i a l c a r e t o p r o p e r l y add f i l l e r w i r e and o b t a i n weld b u i l d u p without a f f e c t i n g t h e r o o t p a s s drop-through. Heat i n p u t s e l e c t i o n s f o r t h i s and subsequent p a s s e s r e q u i r e o n l y f u s i o n t o t h e p r e v i o u s p a s s and t o t h e j o i n t s i d e w a l l s . O s c i l l a t i o n of t h e weld t o r c h assists t o assure f u s i o n i n t o t h e s i d e w a l l . Current p u l s i n g t e n d s t o m a i n t a i n a stable weld puddle. Few programmer i n p u t changes are r e q u i r e d f o r i n i t i a l f i l l p a s s e s , e x c e p t t o add t o r c h o s c i l l a t i o n and t o h a l v e t h e w i r e f e e d e r e x i t t o p i p e s u r f a c e e n t r y a n g l e . F i n a l f i l l p a s s e s can be made w i t h i n c r e a s e d weld power, wider o s c i l l a t i o n , and faster w i r e f e e d s . An 11 o ' c l o c k f i r s t f i l l e r p a s s start p o s i t i o n g e n e r a l l y h e l p s t o b a l a n c e p a r t i a l d i s t o r t i o n of t h e p i p e c r e a t e d by t h e r o o t p a s s .

6.10 R e p a i r Welding The o r b i t a l welding system can a l s o b e employed t o r e p a i r some weld d e f e c t s . Two common d e f e c t s are i n t e r m i t t e n t l a c k of f u s i o n a l o n g t h e s i d e w a l l s of a j o i n t , and cold, b a l l e d , r o p e y - l i k e d e p o s i t s a l o n g a weld j o i n t s i d e w a l l . R e s u l t a n t d e f e c t i v e s u r f a c e s t h e n p r e v e n t subsequent weld p a s s p u d d l e s f r o m w e t t i n g and f l o w i n g smoothly.

Weld beads e x h i b i t areas of l a c k of f u s i o n and v o i d i n c l u s i o n s . P l a c i n g t h e e l e c t r o d e j u s t ahead of t h e p o o r l y fused area and manually s t a r t i n g a new weld p a s s w i t h o u t f i l l e r w i r e a d d i t i o n s o r o s c i l l a t i o n w i l l g e n e r a l l y remelt ana f u s e t h e weld. P i n h o l e s can a l s o be r e p a i r e d i n a similar manner with t h e t o r c h l o c a t e d d i r e c t l y over t h e p i n h o l e p r i o r t o a delayed e l e c t r o d e " s t a r t - f i r e . " A procedure t o f i l l l o c a l weld areas which have been p u r p o s e l y ground o u t t o remove weld d e f e c t s i s t o p l a c e t h e c a r r i a g e about 1/2 i n . i n f r o n t of t h e area t o be f i l l e d , set a s h o r t arc gap of 1/32 i n . , and i n i t i a t e a weld c y c l e . The AVC wire f e e d c o n t r o l w i l l start t o add w i r e as soon as t h e arc gap i n c r e a s e s once t h e c a r r i a g e t r a v e r s e s t h e r e c e s s e d area. The w i r e f e e d e r motor w i l l a g a i n s h u t o f f on t h e f a r s i d e of t h e depressed area t o permit manual weld downsloping.

44 7.

SPECIAL ORBITAL EQUIPMFIIJT MAINTENANCE R.?ZQUIREMFNTS

Orbital equipment used f o r maintenance of r e a c t o r systems may become contaminated. I n such c a s e s , r e p a i r s t o t h e o r b i t a l equipment, or component replacement o p e r a t i o n s may have t o be performed i n s h i e l d e d h o t c e l l s . Viton-rubber-coated r o l l e r s u r f a c e s may r e q u i r e p e r i o d i c i n t e r c h a n g e ; motors, c u t t e r s , t o r c h e s , e t c . , may have t o be r e p l a c e d . Equipment maintenance procedures are l i s t e d f o r major equipment i n - c e l l components which might b e s u b j e c t e d t o contamination. Work e x p e r i e n c e t o d a t e s u g g e s t s a number of m o d i f i c a t i o n s which could be made t o t h e o r b i t a l equipment t o p r o v i d e b e t t e r a c c e s s f o r r e p a i r s t o be performed by remote c o n t r o l i n s i d e a h o t c e l l and t o reduce t h e time r e q u i r e d f o r maintenance of t h e o r b i t a l equipment. The changes i n d i c a t e d on t h e b a s i s of e x p e r i e n c e t o d a t e are d e s c r i b e d i n t h e f o l l o w i n g p a r a graphs.

7.1 C a r r i a g e 7.1.1 Drive R o l l e r s

7.1.2

Idlers

Minor changes t o t h e wire t r o u g h of each c a r r i a g e a r m and p r o v i s i o n s f o r an e x t e r n a l l y a c c e s s i b l e , f l a t , Winchester t y p e connector i n r e s p e c t i v e motor c i r c u i t s would permit f a s t e r i n t e r c h a n g e f o r s p a r e r o l l e r a s s e m b l i e s . The removal of two r o l l e r end p l u g s and two r o l l e r end cap screws and opening t h e e l e c t r i c a l c o n n e c t o r frees the drivers.

I d l e r replacement p r e s e n t l y r e q u i r e s t h e somewhat t e d i o u s disassembly of e l e c t r i c a l c o n n e c t o r s , t h e c a r r i a g e rear frame and s i d e w a l l s , and t h e l i n k p i n s . For maintenance t o b e performed i n s i d e a h o t c e l l some s i m p l i f i c a t i o n s a r e p o s s i b l e , e s p e c i a l l y w i t h use of modified r i g h t a n g l e e l e c t r i c a l c o n n e c t o r replacements. We recommend j i g g e d holddown d e v i c e s f o r a l l hot c e l l i d l e r interchange operations t o m a i n t a i n t h e h i g h l y c r i t i c a l c e n t e r l i n e alignment of t h e jackscrews Fjith t h e t o r s i o n b a r g e a r and t h e t o r q u e a:r:n scar.

'7.2

!3 l.ectrica1. Iterris

Access i s avaiLabLe Yor a l l component e l e c t r i c a l w i r i n g and a c c e s s o r y items by simply removing cover p l a t e s . More e x t e n s i v e u s e of m i n i a t u r e c o n n e c t o r s might be d e s i r a b l e f o r e l e c t r i c a l system p a r t s which might r e q u i r e maintenance d u r i n g developmental t e s t p e r i o d s .

7.3 M i l l i n g Head Hot c e l l j i g s w i l l be r e q u i r e d t o s u p p o r t t h e m i l l i n g head f o r c u t t e r replacement. The c u t t e r i s r e p l a c e d by removing t h e b o l t h o l d i n g it t o t h e o u t p u t s h a f t . Washers a r e employed t o hold t h e cutter tightly

45 v

Improvements a r e necessary f o r more p r e c i s e d e p t h of c u t a d j u s t ments and f o r t h e h o r i z o n t a l c u t t e r placement adjustment. P r e c i s i o n worm g e a r replacements a r e contemplated f o r e x i s t i n g m i t e r g e a r s . We a l s o p l a n t o add an a i r l i n e connection through t h e r e a r c a r r i a g e p a n e l t o modify c u t t e r motor f o r c e d c o o l i n g and t o keep c h i p s generated d u r i n g c u t t i n g from e n t e r i n g g e a r d r i v e s , t h e motor, and t h e p o s i t i o n i n g adjustments.

No problems a r e expected f o r r o u t i n e c u t t e r motor s e r v i c i n g i n v o l v i n g b a c k p l a t e , c o n t r o l p a n e l and c u t t e r removal. Motor b r u s h e s c a n b e r e p l a c e d by simply moving t h e motor p a r t i a l l y o u t of t h e housing. The g e a r t r a i n connecting t h e motor t o t h e output s h a f t i s s e r v i c a b l e by disassembling t h e motor c a n i s t e r .

For o u r next model, c u t t e r motor speed c o n t r o l c i r c u i t r y w i l l be e l i m i n a t e d from t h e head and t r a n s f e r r e d t o t h e programmer.

7.4 Welding Head P e r i o d i c c l e a n i n g of t h e weld head i s important t o prevent highfrequency a r c i n g . The weld head i s disassembled by f i r s t removing t h e w i r e f e e d s p o o l . The t o r c h , o s c i l l a t o r , and wire f e e d mechanism s l i d e o f f t h e v e r t i c a l guide as a u n i t after t h e removal of t h e v e r t i c a l adjustment knob. The common mounting b l o c k i s removed by unscrewing t h e h o r i z o n t a l guide p i n s and t h e s e t s c r e w on t h e h o r i z o n t a l a d j u s t ment s h a f t . The wire f e e d i s disconnected from t h e t o r c h and o s c i l l a t o r by removing two screws. The feed p r e s s u r e - a d j u s t i n g screw should be removed t o i n s p e c t b e a r i n g r a c e s between r o t a t i n g d i s k s . S p e c i a l , simple remote t o o l i n g w i l l be r e q u i r e d t o r e p l a c e threaded t o r c h assemblies, o r t o i n t e r c h a n g e e l e c t r o d e s .

Jigs a r e recommended t o support t h e weld head f o r h o t c e l l maintenance work. We p l a n weld head d e s i g n change improvements f o r o u r next model's o s c i l l a t o r adjustment cam t o t h e l i d l a t c h device, and t o t h e h o r i z o n t a l and v e r t i c a l t o r c h movement g e a r t r a i n s . P r e s e n t i t e m s do n o t work w e l l with remote t o o l i n g . We a l s o p l a n t o t r a n s f e r t h e p r e s e n t "touchdown" l i g h t , which i n d i c a t e s e l e c t r o d e c o n t a c t w i t h t h e work on s e t u p , from t h e welding head t o t h e programmer.

7.5 General I n t h e f u t u r e w e a l s o hope t o i n c o r p o r a t e b r i g h t e r d i r e c t i o n a l l i g h t i n g f o r b o t h t h e m i l l i n g and weld heads, t o p o s s i b l y e n l a r g e t h e viewport openings, and t o a l t e r t h e f r o n t p a n e l of t h e c a r r i a g e t o p e r m i t improved viewing f o r h o t c e l l and o p e r a t i o n a l s e t u p s and p o s s i b l y f o r monitoring use i n a c t u a l r e a c t o r r e p a i r u s e .

We are a l s o i n v e s t i g a t i n g f l u i d i c s e n s i n g and c o n t r o l d e v i c e s f o r remotely s e t t i n g and c o n t r o l l i n g o s c i l l a t o r o p e r a t i o n . T h i s would reduce c o s t s , g a i n r e l i a b i l i t y , improve weld head r i g i d i t y and compactness and e l i m i n a t e maintenance time requirements t o p l a c e long handled t o o l s i n t o t h e c e l l t o a l t e r t h e p r e s e n t e l e c t r o - m e c h a n i c a l o s c i l l a t o r ' s amplitude s e t t i n g s r e q u i r e d f o r s u c c e s s i v e f i l l p a s s e s .

46 SECTION C

PROGRAM PROPOSAL: DEVELOPMENT OF REMOTE CUTTING, WELDING AND INSPECTION EQUIPMENT FOR REACTOR SYSTEM MAINTENANCE

8.1 O v e r a l l Requirements f o r Remote Cut/Weld Maintenance The q u e s t i o n of how maintenance w i l l be accomplished i s one which must b e answered a t t h e t i m e a r e a c t o r system i s b e i n g designed i n o r d e r t h a t a p p r o p r i a t e p r o v i s i o n s f o r maintenance w i l l be included i n t h e d e s i g n . 'Iln c o n s i d e r i n g t h e d e s i g n of a Molten S a l t Breeder Reactor, ORNL h a s explored t h e r e p o r t e d e x p e r i e n c e i n t h e whole f i e l d of r e a c t o r maintenance problems and methods of making r e p a i r s . The advantages of welded j o i n t s i n n u c l e a r s y s t e m s a r e g e n e r a l l y recognized, b u t t h e r e i s no s u i t a b l e equipment f o r performing remote c u t t i n g and welding o p e r a t i o n s i n t h e ways r e a c t o r system maintenance would r e q u i r e . However, t h e r e are some new t y p e s of equipment which show promise f o r r a d i o a c t i v e system a p p l i c a t i o n s a f t e r f u r t h e r development of remote c o n t r o l s and o t h e r s p e c i a l f e a t u r e s f o r work i n h i g h r a d i a t i o n areas. The o r b i t a l c u t t i n g and welding equipment developed f o r t h e A i r Force and adapted for remote h a n d l i n g and o p e r a t i o n by ORNL demonstrated good performance i n t e s t s of a p r o t o t y p e u n i t , and t h u s gave support t o t h e formation of a new philosophy f o r m a i n t a i n i n g p i p i n g systems and v e s s e l c l o s u r e s i n r a d i o a c t i v e systems. The new maintenance philosophy i s t o r e l y on t h e use of remote c u t t i n g and welding equipment t o remove from t h e n u c l e a r system any component which f a i l s and t o i n s t a l l a replacement. T h i s p r o v i d e s a g r e a t d e a l more f l e x i b i l i t y and r e l i a b i l i t y t h a n a p i p i n g system i n which f l a n g e d j o i n t s must b e opened and r e s e a l e d by remote c o n t r o l . Remote c u t t i n g and welding would provide f o r a l l maintenance on t h e p i p i n g system and on seal welding t h e f l a n g e d openings i n v e s s e l s . For maintenance of t h e e l e c t r i c a l , i n s t r u m e n t a t i o n and o t h e r systems, long-handled t o o l s or s p e c i a l remote c o n t r o l d e v i c e s would be used i n t h e manner a l r e a d y demonstrated i n t h e MSN and o t h e r r e a c t o r s . The o r b i t a l equipment w i l l r e q u i r e f u r t h e r m o d i f i c a t i o n s and a d d i t i o n s t o meet t h e s p e c i a l needs of remote maintenance o p e r a t i o n s on p i p e s and v e s s e l s , s o t h a t , f o r example, t h e equipment can b e p o s i t i o n e d a t t h e work s i t e by remote c o n t r o l , without b e i n g a b l e t o see d i r e c t l y what i s b e i n g done. The A i r Force c u t t i n g and welding equipment h a s semi-remote c o n t r o l s f o r t h e c u t t i n g and welding operat i m s and t h e s e w i l l r e q u i r e a d d i t i o n a l s p e c i a l f e a t u r e s f o r f u l l y remote c o n t r o l .

Work on r a d i o a c t i v e systems n o t o n l y r e q u i r e s remote c o n t r o l s f o r a l l o p e r a t i o n s , b u t a l s o r e q u i r e s t h a t t h e maintenance equipment be f a b r i c a t e d of materials t h a t r e s i s t t h e damaging e f f e c t s of r a d i a t i o n and w i t h s t a n d h i g h t e m p e r a t u r e s and t h e c o r r o s i v e a c t i o n of decontamination chemicals. The performance of remote maintenance

47 V

o p e r a t i o n s w i l l r e q u i r e s p e c i a l attachments for viewing, measuring, and s e n s i n g from a s h i e l d e d work area and f o r performing i n s p e c t i o n o p e r a t i o n s by remote c o n t r o l . T h i s w i l l n e c e s s i t a t e t h e development of h i g h l y s p e c i a l i z e d a p p a r a t u s p l u s new t e c h n i q u e s and procedures f o r examination, measurement and i n s p e c t i o n . Remotely c o n t r o l l e d methods for a c c u r a t e l y p o s i t i o n i n g and a l i g n i n g l a r g e p i p e s must b e developed i n o r d e r t o b e a b l e t o do high q u a l i t y welding on p i p e j o i n t s . There are many i n t e r r e l a t e d and d i f f i c u l t problems f o r which s o l u t i o n s are n o t now a v a i l a b l e . The development programs d e s c r i b e d below are proposed t o provide t h e needed equipment and t e c h n i q u e s f o r remotely c o n t r o l l e d , automated c u t t i n g and welding on h i g h l y r a d i o a c t i v e p i p i n g and components of n u c l e a r systems. The remote maintenance equipment development program w i l l f i r s t be concerned w i t h completion of t h e t e s t i n g and e v a l u a t i o n of t h e A i r Force o r b i t a l equipment with s p e c i a l emphasis on improved c u t t i n g c a p a b i l i t y f o r extra hard m a t e r i a l s such as a l l o y s w i t h h i g h n i c k e l c o n t e n t , and t h e development of p r o p e r t e c h n i q u e s f o r a c c e p t a b l e r o o t p a s s welding. S u c c e s s f u l completion of t h e t e s t i n g and e v a l u a t i o n program should g i v e a s s u r a n c e t h a t t h e b r o a d e r , long range development program c a n produce a f u l l y automated and remotely c o n t r o l l e d system which w i l l meet t h e r i g i d q u a l i t y requirements f o r maintenance on n u c l e a r systems. 8.2

A Long-Range, Three-phase Development Program for Pipe and V e s s e l M a i n t e nanc e

The l o n g range program encompasses t h r e e phases: g e n e r a l i n v e s t i g a t i o n s of welding requirements and remotely c o n t r o l l e d equipment f o r welding, a n extended p i p e - j o i n t program, and a v e s s e l c l o s u r e program. It i s proposed t h a t t h e s t u d y of g e n e r a l remote welding problems and t h e development of equipment t o handle t h e s p e c i f i c problems of r e a c t o r p i p e j o i n t s and v e s s e l c l o s u r e s should b e pursued c o n c u r r e n t l y . Remote welding equipment m o d i f i c a t i o n s can be developed, s t u d i e d , and t e s t e d a t t h e same time g e n e r a l s t u d i e s are i n p r o g r e s s , w i t h r e f i n e ments from t h e g e n e r a l s t u d i e s b e i n g added as t h e y become a v a i l a b l e . 8.2.1

Phase I. The General Proaram

Major i n v e s t i g a t i o n s u n d e r t h e g e n e r a l program are t h e b a s i c s t u d i e s of f a c t o r s t h a t determine t h e q u a l i t y of welded j o i n t s i n v a r i o u s metals, t h e s t u d i e s of d i f f e r e n t welding t e c h n i q u e s and c o n t r o l s needed t o assure t h a t weld q u a l i t y c r i t e r i a are m e t , t h e d e t e r m i n a t i o n of materials and components t h a t w i l l w i t h s t a n d t h e e f f e c t s of r a d i a t i o n , t e m p e r a t u r e , and of chemical decontamination t r e a t m e n t s , t h e improvement of welding c o n t r o l s and programming appar a t u s , t h e development of equipment and t e c h n i q u e s for r e m o t e - c o n t r o l alignment of components, and t h e d e t e r m i n a t i o n of environmental and c l e a n l i n e s s c r i t e r i a . For t h e a p p l i e d phase of t h e g e n e r a l program, mockup work i s planned t o e v a l u a t e v a r i o u s new or modified t y p e s of equipment and remote c o n t r o l s , e s p e c i a l l y t h e p i p e p o s i t i o n i n g and movement schemes designed t o a c h i e v e a c c e p t a b l e p i p e j o i n t alignment p r i o r t o welding.

It i s a l s o recommended t h a t t h e welding m e t a l l u r g y of i r r a d i a t e d materials b e i n v e s t i g a t e d . It i s important t o know whether n e u t r o n i r r a d i a t e d p i p e metal shows r a d i a t i o n e f f e c t s which w i l l a f f e c t welding and whether minute c r a c k i n g w i l l occur i n h e a t - a f f e c t e d weld zones. A t p r e s e n t , o n l y l i m i t e d data are a v a i l a b l e from t e s t s conducted a t ORNL.20 Attempts t o weld small c o r r o s i o n samples removed from t h e MSRE gave e f f e c t i v e welds i n only 70% of t h e cases;a1 however, f u r t h e r t e s t i n g i n d i c a t e d t h a t b e t t e r c l e a n i n g of t h e metal s u r f a c e s t o remove s a l t r e s i d u e s p r i o r t o welding would s o l v e t h e problem. Test specimens should b e obtained from a c t u a l i r r a d i a t e d s e c t i o n s of r e a c t o r p i p e i n which t h e combined e f f e c t s of neutron i r r a d i a t i o n and t h e r m a l c y c l i n g are p r e s e n t . The Navy, h a s i n f o r m a l l y expressed i n t e r e s t i n s t u d y i n g t h e welds i n h i g h l y i r r a d i a t e d s e c t i o n s of n u c l e a r submarine p i p e systems. Valuable d a t a and maintenance e x p e r i e n c e might b e o b t a i n e d , i n c o o p e r a t i o n w i t h t h e N a v y , by u s i n g t h e remotely c o n t r o l l e d c u t t i n g and welding equipment t o c u t out and r e p l a c e t e s t s e c t i o n s of t h e s h i p board n u c l e a r system p i p i n g s o t h a t t h e removed s e c t i o n s could be s u b j e c t e d t o d e t a i l e d study of t h e old welds and of new welds made on t h e i r r a d i a t e d metal. 8.2.2

Phase 11, The Pipe J o i n t Program

The c o n t i n u a t i o n of t h e p i p e j o i n t program w i l l r e q u i r e development, and t e s t i n g of p r o t o t y p e c a r r i a g e s f o r t h e l a r g e r p i p e s i z e s , d e s i g n , development, and t e s t i n g of second g e n e r a t i o n c u t t i n g and welding heads, and t h e e s t a b l i s h m e n t of s p e c i f i c t e c h n i q u e s , methods and equipment f o r c u t t i n g and welding v a r i o u s metals. It i s also planned t o u s e t h e f i n d i n g s of t h e environmental s t u d y and t h e materials and components study, c a r r i e d out under t h e g e n e r a l program t o upgrade t h e materials and components of t h e p i p e j o i n t maintenance machinery t o w i t h s t a n d t h e e f f e c t s of r a d i a t i o n , temperature, and of decontamination t r e a t m e n t s i n actual nuclear applications.

8.2.3

Phase 111, The Vessel Closure Program

A d u a l approach i s suggested f o r t h e development of equipment f o r c u t t i n g and welding of seals on t h e manhole-type openings i n l a r g e v e s s e l s i n r e a c t o r systems. The i n i t i a l c u t t i n g , b e v e l i n g and welding work w i l l b e performed u s i n g v a r i o u s commercially a v a i l a b l e components adapted f o r remote c o n t r o l . Performance a p p r a i s a l s from t h e s e t e s t s w i l l permit t h e development of m o d i f i c a t i o n s t o overcome t h e problems t h a t are encountered and a f t e r f u r t h e r t e s t s , t h e f i n a l component s p e c i f i c a t i o n s w i l l b e e s t a b l i s h e d f o r i n d u s t r y t o supply complete equipment systems f o r f u r t h e r t e s t i n g on v e s s e l c l o s u r e maintenance. Another p a r t of t h e program w i l l b e concerned with a p p l i c a t i o n of o r b i t a l v e h i c l e machinery t o t h e s p e c i a l problem of seal welding on l i p s i n s t a l l e d around manhole c o v e r s . The p i p e welding development program w i l l determine t h e a p p l i c a b i l i t y of t h e modular i n s e r t carriage scheme f o r remote maintenance work. A f t e r o b t a i n i n g s a t i s f a c t o r y p e r formance on p i p e welds, t h e welding equipment could b e mounted on s p e c i a l c a r r i a g e s designed t o s u i t t h e manhole cover g e o m e t r i e s . These c a r r i a g e s should u t i l i z e t h e same c u t , b e v e l , weld and i n s p e c t i o n

49 i n s e r t s and o p e r a t e from t h e same programmer as t h e p i p e welder. Great time s a v i n g s and s i z e a b l e d o l l a r s a v i n g s can r e s u l t from a p p l y i n g such a system d i r e c t l y t o seal welding. Spare p a r t problems and invent o r i e s are a l s o minimized. The f i n a l procurement o f t h e components s e l e c t e d t o s u i t t h e needs of a n u c l e a r environment w i l l i n c o r p o r a t e t h e most promising a p p a r a t u s , materials and components i n d i c a t e d by t h e development and t e s t i n g a c t i v i t i e s .

20.

Molten S a l t Program Semiannual Report f o r t h e Period ending February 28, 1966, ORNL Report No. 0rn-3936, p . 117, 1966.

21. Molten S a l t Reactor Experiment Monthly Report f o r August 1968, ORNL Report No. MSR-68-123, p . 19, 1968.

51 Internal Distribution

1-3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

13* 14. 15 16. 17

18.

19 20. 21. 22.

23 * 24. 25 * 26. 27 * 28.

29 30 31 32. 33 34

35 *

36. 37 * 38 39 * 40. 41. 42. 43 44. 45. 46. 47 48. 49.

MSRP D i r e c t o r ' s O f f i c e R. K. A d a m s G. M. Adamson J . L. Anderson R . F . Apple E . L. Armstrong, Y - 1 2 D . L. Aubuchon C . F. Baes J . M. B a k e r P . S. Baker S. J . B a l l C . E . Bamberger C . J . Barton H . F. Bauman S. E . B e a l l R. L. Beatty M. J . B e l l M . Bender C . E. B e t t i s E . S. B e t t i s D. S. B i l l i n g t o n W . A - Bird R . E . Blanco F. F . Blankenship R . Blumberg A . L. Boch E . G. Bohlmann C . J . Borkowski G . E. Boyd J. Braunstein M. A. Bredig E . J . Breeding R. B. Briggs H. R. B r o n s t e i n J R Buchanan C . A. Burchsted D. A. Canonico W. F. Cartwright, Y - 1 2 J. M. Chandler C . J. C l a f f e y F. H. Clark W. R . Cobb H. E. Cochran C . W. C o l l i n s E. L. Compere K. V. Cook W. H. Cook J . W. Cooke L. T . Corbin

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52. 53 54 * 55 56 * 57 58. 59 * 60. 61. 62. 63 * 64. 65. 66. 67. 68. 69. 70. 71 72 73 * 74 * 75 * 76. 77 * 78. 79

W. B . C o t t r e l l B. COX J . L. Crowley F. L. Culler D. R . Cuneo J . E . Cunningham J . M. Dale D. G . Davis R . J . DeBakker C . B. Deering, AEC-OSR J . H. DeVan S. J . D i t t o H . G. Duggan A . S. Dworkin I . T . Dudley W . P. E a t h e r l y D . E l i a s , AEC-Washington R . J . Emmert J . R. Engel E . P. E p l e r W. K. Ergen R . M. Farnham J . C . Feeman, Y - 1 2 D . E . Ferguson L. M. F e r r i s B. Fleischer M. H . Fontana A . P. F r a a s 80. E . A . F r a n c o - F e r r e i r a , Y - 1 2 81. J . K. Franzreb 82. H . A . Friedman 83. D . N . Fry 84. J . H . Frye 85. R. M. F u l l e r 86. W. K . Furlong 87. C . H. Gabbard 88. W . R . G a l l 89. R . B . G a l l a h e r 90 * J . H. Gibbons 91 * J . M. Googin, Y-12 92 W. R . Grimes 93 A . G. G r i n d e l l 94 * R . W. Gunkel 95 * R . H. Guymon 96. J. P. Hammond 97 * B. A . Hannaford 98. P . H. Harley 99 * W . 0. Harms 100. C . S. H a r r i l l

52 101. 102.

103. 104. 105. 106. 107. 108.

P. T. R. P. D. J. J. M.

109. E . 110. H . 111. D .

112-131.

132. 133-134. 135 * 136, 13'7. 138. 1-39*

P. R. T. T. W. H. H. G.

140. W . 1i.l.

142. P . 143. 3 . 1b4.

135. M. P-6. 0 . 147. C .

1M. T .

L49 *

H. 1-50. F . 151. J . 152 * S . 1-53 0 . 15h. R . 155 T . 156. J . 157 C .

158. J . 159. C . 160. W . 161. P. 162. R. 163. A . 164.

165. 166. 167. 168. 169. 170.

171.

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N . Haubenreich E . Haynes E . Helms G. Herndon N . Hess R . Hightower W. H i l l R. H i l l C . Hise W . Hoffman K . Holmes P . Holz W. Horton R . Housley L. Hudsoii R . Huntley Inouye F . Jackson R. Jascey, Y-12 H . Jcrdan I . Kaplan R. Kasten J . Ked1 T . Kelley J . Kelly A . Kelly R . Kennedy W. K e r l i n T . Kerr Kertesz J . Keyes S . Kirslis H . Klepper B . Korsneyer S . Kress W . Krewscn E . Lamb A . Lane G . Lawson J . Leonard S . Lee B . Lindauer P. Litman L . Long L. Lotts I . Lundin N . Lyon L . Macklin G . MacPherson E . MacPherson H . Mauney

172. 173 174. 1.75 176. 177 * 178. 1-79 180. 181. 182.

1-83. 184.

185. 186. 187. 188. 189. 190. 191. 192.

1-93 194. 195 * 196. 197 198. 1-99* 200. 201. 202.

203. 201.

205. 206

207-216. 217. 218.

219. 220. 221. 222.

223-227. 228.

229. 230. 231 * 232. 233 * 234. 235 '

R . W . McClung H . E . McCoy H . C . McCurdy D . L . McElroy C . K. McGlothlan J . R . McGuffey H . A . McLain L . E . McNeese J . R . McWherter H . J . Metz A . S. Meyer E. C. Miller R . L . Moore G . Morris D . C . Morrison J C Moyers H. A . N e l m s E . L . Nicholson L. C . Oakes W . R . Osborn L. F . P a r s l y P. P a t r i a r c a A . M. P e r r y T . W. Pickel H . B. P i p e r J . L . Redford M. Richardson R . C . Robertson J . N . Robinson W . C . Robinson R . G . Ross J . Roth T . H . Row H . C . Savage W . F. S c h a f f e r Dunlap S c o t t J . L. Scott H . E . Seagren J . H. Shaffer L . J . Shersky M. D . Silverman M. J . Skinner G . M. S l a u g h t e r A . N . Smith C. M . Smith, J r . F . J . Smith G. P. Smith 0. L . Smith P . G. Smith I . Spiewak R. C. Steffy

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53 v

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240.

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H. S t o n e r , Y-12 A . Strehlow R. Tallackson H. Taylor Terry E . Thoma E. Thompson B. Trauger E . Unger K . Walters M. Watson S. Watson L. Watts F. Weaver H . Webster M. Weinberg R . Weir W. West E. Whatley

255. 256. 257. 258. 259 260. 261. 262. 263. 264. 265. 266. 267. 268-269. 270-271. 272-274 275 * 276-277 -

J . C . White G. D. Whitman R. P. Wichner L. C . W i l l i a m s C. H . Wodtke L. V . Wilson M . M . Yarosh W. J . Yaggi, Y - 1 2 Gale Young H. C . Young J . P. Young E . L . Youngblood F. C . Zapp C e n t r a l Research L i b r a r y Document Reference S e c t i o n Laboratory Records Laboratory Records (LRD-RC) Nuclear S a f e t y Information Center

External Distribution

278. 279

280-281. 282.

283-284. 285. 286. 287. 288. 289-298. 299- 300. 301-302. 303-304. 305 - 306. 307-321 -

D . F. Cope, AEC-OSR A. K. C. T.

Giambusso, AEC-Washington 0. Laughon, AEC-OSR L . Matthews, AEC-OSR W . McIntosh, AEC-Washington H. M. Roth, AEC-OR0 M . Shaw, AEC-DRDT W. L. Smalley, AEC-OR0 D . S . Zachry, Jr., AEC-OR0 AFRPL (RPRPD/Capt. F . M. Cassidy) Capt. F. M. Cassidy, USAF, AFRPL, Edwards Am E . E . S t e i n , AFRPL, Edwards AFB Capt. J . L . Feldman, ASD, ASNJD-10, W r i g h t P a t t e r s o n AFE3 L t . A . B . Spencer, ASD, ASWD-20, Wright P a t t e r s o n AFB D i v i s i o n of T e c h n i c a l Information Extension (DTIE)