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MSR COMPONENT REPLACEMENTS USING REMOTE CUTTING AND <_.’ WELDING TECHNIQUES r,

,I*

Peter P. Holm

This report was prepared as an account of work sponsored by the United States Government. Neither the United States nor the United States Atomic Energy Commission, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness or usefulness of any information, apparatus, product or process disclosed, or represents that i t s use would not infringe privately owned rights.

ORNL- TM- 3939

C o n t r a c t No.

W-7405-eng- 26

R e a c t o r Division

HSR COMPONENT REPLACEMENTS USING REMOTE CUTTING AND WELDING TECHNIQUES

P e t e r P. Holz

December 1972

OAK RIDGE NATIONAL LABORATORY O a r Ridge; Teniessee operated by

37830

UNION CARBIDE CORPORATION for the U.S. ATOMIC ENERGY COMMISSION NOTICE This report was prepared as an account of work sponsored by the United States Government. Neither the United States nor the United States Atomic Energy Commissron, nor any o f their employees, nor any of their conlractors, subcontractors, or their employees, makes any warranty, express o r implied, or assumes any legal liability or responsibility for the accuracy, completeness o r usefulness of any information, apparatus, product or process disclosed, o r represents t h a t its use would not infringe privately owned rights.

_._

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iii

CONTEXTS

.............................. 1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . 2 . CONCLUSIONS AND SUMMAIIY . . . . . . . . . . . . . . . . . . . . .

Page .

ABSTRACT

STATUS OF THE TEC3l!OLOCN 3.1

3.2

...................... 3.1.1 Ligh-Ling Frovisions f o r Maintenance . . . . . . . . . In-Cell Viewing Apparatus . . . . . . . . . . . . . . . . . Cell Illmiriation

3.2.1 3.2.2

3.3

3.4 3.5

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

Direct Viewing Through Lead Glass o r ZincBromide Wimdows

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

Optical Equipment: and Fiber Optics Closed Circuit

3.2.4

Special Irlspections

7 7 7 7 7

Mirrors. Periscopes.

.................. Television . . . . . . . . . . . . . .

3.2.3

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

................... 3.3.1 L i f t i n g Devices . . . . . . . . . . . . . . . . . . . 3.3.2 Miscellaneous Long-Handled Tools . . . . . . . . . . 3.3.3 Portable Eetaining Brackets . . . . . . . . . . . . . 3.3.4 Thermocou-@e and Electrical Connector Tools . . . . . Tool and Equipment Conveyance Means . . . . . . . . . . . . Pipe Cutting Equipment . . . . . . . . . . . . . . . . . . . 3.5.1 Pipe Cutters . . . . . . . . . . . . . . . . . . . . 3.5.2 S e a l Weld Cutters . . . . . . . . . . . . . . . . . . In-Cell Handling Tools

................ Conveyance Means f o r Use Within t h e C e l l . . .

8 9

10 10

10 11 11

11 12 12 20

3.6

Equipment f o r Pipe Spreading

3.7

Carriers and

3.8

Carriers f o r Use (Outside t h e C e l l

3.9

In-Cell Preparations for Equipment R e i n s t a l l a t i o n

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

.....

................ Conveyance of Components to Reinstallation Location . . . . Pipe Alignment Technology . . . . . . . . . . . . . . . . . Weld Preparation and Tack Welding of Pipe Joints . . . . . Closure Welding . . . . . . . . . . . . . . . . . . . . . .

3.10 In-Cell Cleanliness Control

3.11

3.12 3.13

3.14

................... 3.14.2 Seal Welding . . . . . . . . . . . . . . . . . . . Inspection and Acceptance Tests . . . . . . . . . . . . . .

3.14.1 Pipe Welding

3.15

27 31

34 34

APPENDIX A Calculations f o r Anticipated Maximum Delections and Restoration Forces for Cutting INOR-8 Piping Material

......

APPENDIX B 1) Proposal for Development of a Split-Bearing-Sleeve Carriage for Remote Maintenance Applications in Nuclear Reactor Systems

4.9

................... Manufacturers Information on Split-Roller Bearings . . . . .

REFERENCES

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

ILLUSTRATIONS

Page .

............ 5 ORNL Cutter o r Machining Head Module . . . . . . . . . . . . 13 ORNL O r b i t a l Cutting Equipment . . . . . . . . . . . . . . . 14 S e a l P l a t e Welds . . . . . . . . . . . . . . . . . . . . . . 21 Sandwich Seal Weld . . . . . . . . . . . . . . . . . . . . . 22 Canopy Weld Schemes . . . . . . . . . . . . . . . . . . . . . 23 S e a l Lip Closures . . . . . . . . . . . . . . . . . . . . . . 24 Component Pipe Stub Weld J o i n t Positioner Arrangement . . . . 29 Pipe Alignment J:ig f o r Line Cutting and Welding . . . . . . . 29 ORNL O r b i t a l Welding System . . . . . . . . . . . . . . . . . 35 F i g . 11. Equipment Hook.Up, ORNL Weld System . . . . . . . . . . . . . 36 F i g . 12 . Conceptual Diaphragm o r Sandwich Seal Weld with ORNL Weld Head Supported from a Motorized Carousel Linkage . . . . 38 F i g . 13. Flanged Vessel Seal Weld Closure Scheme f o r O r b i t a l System I n s e r t s . . . . . . . . . . . . . . . . . . . 39 F i g . 14. Conceptual Design . . . . . . . . . . . . . . . . . . . . . . 41 . 1. Fig. 2. F i g . 3. Fig . 4 . Fig . 5. Fig. 6. F i g . 7. F i g . 8. Fig. 9. F i g . 10. Fig

Typical Replacenient J o i n t Location

........

Table 1

Expected Life of Cutter Blades

. . . . . . . . . . . . . . . 16

vii MSR COMPONENT REPLACEMENTS USING REMOTE CUTTING A!7D WELDING TECHNIQUES

P. P. Holz ABSTRACT

I n molten s a l t I-eactor systems t h e maintenance of components i n highr a d i a t i o n zones w i l l be accomplished by using remotely operated tools. System components, such a:; pumps, heat exchangers, and valves w i l l be exchanged by c u t t i n g t h e in:l.et and o u t l e t pipe connections, replacing t h e component, and welding t h e pipe by remote means. Remote maintenance requires s p e c i a l equipment f o r viewing and c l o s e inspection of equipment arid systems i n s i d e t h e c e l l t o determine what i s wrong; it a l s o requii-es s y e c i a l apparatus t o convey tools t o t h e place where work i s t o be performed. The main steps i n remote maintenance procedures w i l l be severing t h e pipe and other connections, spreading t h e pipe ends t o provide clearance f o r removing t h e component, conveying t h e component from i t s l o c a t i o n i n s i d e t h e c e l l i n t o a shielded c a r r i e r , and t r a n s p o r t i n g t h e c a r r i e r outside. ReinstaLling a new component t o replace t h e one removed w i l l involve t h e s t e p s of maintaining cleanliness control, conveying t h e replacement equipment, t o its c e l l location, realigning t h e component and t h e pipe ends f o r reassembly, tack welding t o hold components i n place during f i n a l closure welding, and then performing t h e inspection and acceptance checks t o assure that, t h e r e p a i r s have met q u a l i t y and r e l i a b i l i t y standards. S e a l weld c u t t i n g and rewelding may be required f o r some v e s s e l enclosures. Overall system maintenance planning t o precede f u t u r e l a r g e s c a l e molten s a l t breeder r e a c t o r const;ruction by industry i s envisioned a s a four-stage evolut i a :

1) Technology study

consideration of remote maintenance requirements i n conceptual design

mockups

component tests under simulated r e a c t o r conditions

Simulation

General engineering r e a c t o r p r o j e c t mockups

test

4 ) Small demonstration r e a c t o r

- tests

i n reactor system mockups

t e s t s under a c t u a l r e a c t o r conditions.

Accordingly, t h i s r e p o r t i s intended t o serve a s a u s e f u l program outl i n e guide. The r e p o r t describes i n d e t a i l how we intend t o perform remote maintenance within t h e sevlwe i n - c e l l r a d i a t i o n and temperature environments. It a l s o describes t h e current s t a t u s of t h e technology required t o perform each remote maintenance task, giving s p e c i a l emphasis t o t h e f'unctions we need t o p e r f e c t on a f i r s t order p r i o r i t y : remote cutting, welding, and positioning device development. Additional development programs a r e recommended t o provide a l l o f t h e needed remote-control devices t o demonstrate complete maintenance procedures f o r removing and replacing a l l types of components i n t h e high-radiation, high-temperature zones within t h e r e a c t o r

viii shielding. The " s t a t e of t h e a r t " f o r many of t h e functional t a s k s such a s viewing, l i g h t i n g , component and equipment movement and t r a n s f e r i s already adequate f o r remote c o n t r o l operations, and hence w i l l not require s p e c i a l e f f o r t s a t t h i s time.

1.0 INTRODUCTION After r e a c t o r operations a t high-power l e v e l s have b u i l t up t h e radiat i o n l e v e l s i n t h e shielded c e l l s containing t h e nuclear system components, t h e problems of mairitenarice and r e p a i r become more d i f f i c u l t and more i m portant. No r e a c t o r i s 2-mmune t o t h e s e problems. The need f o r remote t o o l ing and apparatus t o cut, bevel, and weld piping i n high-radiation l e v e l zones i s of utmost i.mport;ance f o r t h e replacement of r e a c t o r components t h a t have f a i l e d i n service. Exact specif ica.t ions to cover a n t i c i p a t e d temperatures and r a d i a t i o n and contamination l e v e l s i n t h e molten-salt r e a c t o r c e l l a t t h e time of a maintenance shutdom. a r e not as y e t available, but t e n t a t i v e estimates a r e given i n R. W. McClung's report on "Remote Inspection of Welded Joints.''' "Anticipated temperatures i n t h e r e a c t o r c e l l range from 1000 t o 1200째F. However, l o c a l i z e d cooling f o r both welding and inspection can probablgr b r i n g temperatures down t o t h e range 200 t o 600째F and possib1;y even t o 200 t o 400째F. The a n t i c i p a t e d l e v e l of radiation3' i n t h e r e a c t o r c e l l t e n days a f t e r t h e system i s shut down and drained i s expected t o be approximately lo5 R / h r . The dominant r a d i a t i o n w i l l b e gamma rays from r e l a t i v e l y noble f i s s i o n products deposited on t h e metal surfaces 0.f t h e heat exchanger tubes and on t h e g r a p h i t e i n t h e core vessel. The area of highest dose r a t e (calculated t o be l.d& X lo5 R/hr) i s a t t h e midplane immediately adjacent t o a heat exchanger. Values i n other portions of t h e c e l l may be 25 t o 30$ of t h e maximum. Most o f t h e r a d i a t i o n w i l l have photon energies of 0.8 MeV and below." The elevated c e l l temperatures and r a d i a t i o n l e v e l s eliminate any p o s s i b i l i t y of personnel access i n t o t h e c e l l f o r any d i r e c t work whatever on molten s a l t breeder r e a c t o r maintenance. It w i l l be e s s e n t i a l t h a t a l l work be done remotely. It i s planned t o replace a component by severing i t s pipe connections, rebeveling t h e ends of t h e i n - c e l l piping, aligning t h e beveled ends with t h o s e of t h e replacement, and rewelding t h e component i n t o t h e system, a l l by t h e use of remote-cont 1-01equipment. Adequate viewing, inspection, pipe spreading, and pipe :3ligmiient equipment must also be a v a i l a b l e and demons t r a t e d t o b e operable by remote c o n t r o l t o support t h e b a s i c operations of remote c u t t i n g and rewelding.

Best estimates now i n d i c a t e t h a t Hastelloy, Inconels, o r s p e c i a l 300 s e r i e s s t a i n l e s s s t e e l alloys, w i l l be used f o r a l l t h e salt-containing pipe and component materials f o r molten s a l t breeder reactors. Pipe s i z e s a r e expected t o range from 1 t o 20 inches and pipe w a l l thicknesses from 1/4 t o 1 inch. Cylindrical diameters f o r t h e heat exchangers and core v e s s e l w i l l be i n t h e order of 5 f e e t and 30 f e e t respectively. The p r i mary system metal s e l e c t i o n s add a number of r e s t r i c t i o n s t o common repair t o o l and l u b r i c a n t m a t e r i a l selections. No aluminum or other low-melting alloys, and no sulfw-beasr.ing o i l s can be used where they might possibly

contact Hastelloy N, because t h e s e materials may r e a c t t o cause a l o s s of desired Hastelloy N properties. Similarly, f o r s t a i n l e s s s t e e l s , chlorine-free materials must be used. Semi-remote maintenance i s t h e preferred and s a f e s t approach because

it reduces personnel 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 undertaking nuclear r e p a i r operations. However, t h e a b i l i t y t o perform maintenance by remote c o n t r o l r e q u i r e s t h a t t h e r e a c t o r system be designed t o provide access t o a l l components, t o allow f o r conveyance of t o o l s and equipment within t h e c e l l areas, and t o provide a l s o f o r t h e storage of contaminated r e p a i r t o o l s and r e l a t e d equipment when they a r e not i n use. The r e a c t o r designers, s t r e s s analysts, and r e a c t o r maintenance engineers must confer during a l l design stages t o be sure t h a t clearances a r e adequate f o r maintenance access and equipment replacement and t h a t t h e layout of pipe-runs and components, with provisions f o r support and expansion, represents t h e optimum compromise between maintenance needs and nuclear materials inventory i n t h e system.

It i s recognized t h a t providing f o r remote-control removal and replacement of a l l components of a r e a c t o r system would be p r o h i b i t i v e l y expensive. I n practice, therefore, t h e degree of ease provided f o r remote maintenance must depend upon t h e a n t i c i p a t e d frequency of maintenance f o r each component. Pumps, ( p a r t i c u l a r l y t h e r o t a r y pump elements, t h e j e t pumps used f o r f i l l i n g t h e s a l t system, and t h e j e t pumps used i n conjunction with t h e gas separators), valves, heat exchanger bundles, samplers, and o t h e r items may f a i l o r need maintenance more frequently than, say, t h e r e a c t o r vessel, which i s designed f o r a 30-year maintenance-free l i f e . A higher a n t i c i p a t e d frequency of maintenance could j u s t i f y r a t h e r elaborate remote-control devices t o speed up and make more r e l i a b l e t h e operations of r e p a i r or replacement. There is, however, a degree of uncertainty i n p r e d i c t i n g t h e l o c a t i o n s a t which one should be prepared t o make r e p a i r s by remote control. To r e duce t h e r i s k of having t h e r e a c t o r system shut down a long time f o r r e p a i r and maintenance, general purpose devices should be readied a t t h e outset t o handle unexpected r e p a i r operations i n v i r t u a l l y a l l l o c a t i o n s with minimum delay. The codes f o r in-service inspection of nuclear r e a c t o r systems recognize t h e problem of examining r a d i o a c t i v e areas where human access i s impossible and suggest t h a t it w i l l be necessary t o devise and develop methods f o r t h e inspection of vessels, pipe, and equipment t o detect flaws by remote means. There i s a general need f o r remote handling, positioning, cutting, and welding equipment with which t o r e p a i r t h e flaws disclosed. One could conceivably adapt t h e inspection equipment f o r applicat i o n with r e p a i r work.

It can be seen from t h e above t h a t replacement and c e r t a i n in-place r e p a i r s of r a d i o a c t i v e components involve t h e c a p a b i l i t y t o perform a number of sequential s t e p s o r functions many of which a r e e s s e n t i a l l y t h e same f o r most components. The equipment t o perform t h e s e functions can be developed generally, independent of t h e s p e c i f i c d e t a i l s of a p a r t i c u l a r r e a c t o r design, i f t h e r e a c t o r design i s developed with adequate a t t e n t i o n t o t h e requirements of remote maintenance and of t h e remotely controlled

equipment. If, i n some c w e s , t h e provisions f o r t h e performance of a p a r t i c u l a r function r e s t r i c t s t h e designer too much, a modified piece of equipment may have t o be developed concurrent with t h e r e a c t o r design phase. It i s recommended, tlnerefore, t h a t maintenance development f o r each of t h e four stages of evolution proceed along t h e following general pattern: I.

Technology study

1. Prepare a general survey of maintenance needs of a r e a c t o r system based on a general design concept.

11.

During t h e concepi:,ual design stage, plan how t h e maintenance of each of t h e radios.ctive components of a r e a c t o r system w i l l be performed.

From t h e remote ma.intenance plans, determine t h e functions needed and s e l e c t f o r study those functions f o r which t h e r e i s l i t t l e o r no previous experience.

Conduct s t u d i e s t o i d e n t i e r e s t r i c t i o n s which each function may place on t h e r e a c t o r design. Work with t h e r e a c t o r designer t o provide for maintenance operations i n t h e design of t h e r e a c t o r system equipment arrangement

Simulation t e s t mockups

1. Proceed with t h e development of equipment to perform t h e various functions and, with t h e demonstration i n a mockup designed t o simul a t e f e a t u r e s of t,he r e a c t o r system. A l t e r t h e d e t a i l s of t h e equipment design m d t h e r e a c t o r design a s required t o minimize inconvenience, increase s a f e t y and r e l i a b i l i t y , reduce cost, or provide f o r other considerations which may be s i g n i f i c a n t .

111. General engineering r e a c t o r project mockups

1. Prepare f o r , and c a r r y out t h e demonstration of t h e remote maintenance plan, including a l l of t h e functions, i n a r e a c t o r mockup. Perfect t h e d e t a i l e d procedures and check l i s t s . 2.

Acquire and t e s t a l l of t h e equipment needed f o r maintenance of t h e a c t u a l r e a c t o r system.

IV. Small demonstration r e a c t o r Use a s much of t h e maintenance equipment a s i s necessary during t h e r e a c t o r system construction phase t o assure t h a t t h e r e have been no changes i n t h e design which would compromise t h e maintenance plan. We have already provein t h e remote c u t t i n g and welding operations on pipe t o be f e a s i b l e with adequate piping supports f o r cutting, and with near precision pipe end realignment f o r welding. Limited s t u d i e s made on how to support and r e a l i g n i n - c e l l r e a c t o r piping revealed many new problem areas and u n c e r t a i n t i e s , and pointed out urgent needs f o r developmental

4 experimentation before one can proceed t o develop apparatus, equipment, and techniques f o r t h i s work. We, therefore, recommend t h a t t h e next s t e p be a more thorough technology study along with mockup t e s t s t o e s t a b l i s h pipe springback allowances and pipe realignment tolerance requirements. Cutting and welding machinery can t h e r e a f t e r be adapted t o meet t h e best pipe support and positioning c r i t e r i a we a r e a b l e t o establish. We suggest a new review of automated commercial pipe c u t t i n g and welding equipment f o r t h a t time. The i n d u s t r i a l development of such machinery i s presently proceeding a t a f a s t pace; therefore, automated c u t t i n g and welding equipment should become r e a d i l y a v a i l a b l e from commercial sources f o r adaptions f o r our work with r e a c t o r maintenance tasks. I n t h i s report we have used t h e reference design f o r t h e s i n g l e f l u i d molten-salt breeder r e a c t o r =to determine t h e need f o r t h e component

replacement c a p a b i l i t y and have developed a remote maintenance plan for t h e replacement of t y p i c a l componentso The plan i s generally based on t h e ORNL maintenance technology employing an o r b i t a l c a r r i a g e which clamps onto a pipe t o propel t h e c u t t i n g andlor welding heads around t h e circumference of a pipe, while a programmer-controller automatically controls t h e operations involved i n pipe cutting, beveling, and welding. For the c u t t i n g and welding o f f l a n g e s e a l s or s e a l s of other types, we plan t o u t i l i z e t h e same or s i m i l a r equipment, except f o r t h e c a r r i a g e and c a r r i a g e drive. Many s e a l closure designs a r e available; t h e report i l l u s t r a t e s and discusses t h e maintainability of s e v e r a l t y p i c a l conf i g u r a t i o n s . The "Status of t h e Technology" s e c t i o n describes t h e sequent i a l s t e p s or functions which a r e needed t o carry out a maintenance plan and discusses b r i e f l y t h e s t a t u s of equipment and operating experience f o r each of t h e functions. The f u t u r e development requirements f o r r e mote maintenance equipment a r e described including some cost estimates and suggested p r i o r i t i e s . This report includes recommendations from our pipe alignment studies i n Appendix A, and suggests piping arrangements f o r simplified maintenance, Figure 1 i l l u s t r a t e s t h e recommended mounting of components f o r ease of replacement. The l o c a t i o n f o r t h e replacement j o i n t can be predesignated and supports provided so t h a t t h e pipe spreading and realignment requ-frements can be handled i n g r e a t l y simplif i e d fashion using standard threaded, hydraulic or pneumatic jacking equipment. Section 3,12.1.1 o f t h e "Experience S t a t u s Pipe Alignment Schemes" and Appendix B, "Proposal f o r t h e Development of a Split-BearingSleeve Carriage f o r Remote Maintenance Applications i n Nuclear Reactor Systems, I' both discuss t h e highly important subject of equipment and pipe alignment i n more d e t a i l and suggest development experfmentat ion with sleeves t o s i m p l i m remote maintenance operations, a t l e a s t fcr t h e smaller pipe s i z e s .

This report does not include d e t a i l e d recommendations f o r t h e development of s p e c i a l materials for construction f o r t h e maintenance equipment t o meet t h e contemplated high temperature and high r a d i a t i o n s e r v i c e requirements. A study should be performed t o determine t h e maximum temperature and r a d i a t i o n i n t e n s i t y t o be expected within t h e r e a c t o r c e l l s and t o estimate t h e a d d i t i o n a l research and development needed t o s e l e c t and t e s t materials t h a t w i l l stand up under t h e s e conditions.

ALIGNWNT Fig. 1.

kQLIIPMHT NOT S H O W

S p i c a 1 Replacement J o i n t Location

6 2.0

CONCLUSIONS AND SUMMAHY

For t h e sake of completeness, we have included i n t h e report a descript i o n of t h e equipment and technology f o r performing a l l of t h e functions needed f o r t h e replacement of a component. Many of these, such a s l i g h t i n g , viewing, and component and maintenance equipment movement r e f l e c t t h e b e n e f i t of extensive experience gained during t h e operation of t h e HRT, E R E , and other r e a c t o r projects. We b e l i e v e t h a t they a r e adequately understood and r e q u i r e e s s e n t i a l l y no development study before a r e a c t o r grade item could be designed. There a r e other functions such a s c a r r i a g e o r b i t propulsion, pipe c u t t i n g and welding, which have received only l i m i t e d evaluation f o r possible application t o molten s a l t r e a c t o r s i n connection with our work on t h e o r b i t a l pipe welding system with programmed automated cutting, beveling, and welding accessories. 239 25 These s t u d i e s l e d t o t h e development of an automated pipe welding system which i s now being used by t h e Tennessee Valley Authority i n t h e i r Browns Ferry fluclear Plant construction, and which has served a s a prototype and p a t t e r n f o r t h e u n i t s t o be used i n t h e Fast Flux Test F a c i l i t y a t Hanford. The development of an i n d u s t r i a l c a p a b i l i t y f o r t h e production of t h e automated welder increases our confidence t h a t t h e equipment, a f t e r modification f o r t h e environment and f o r t h e remote operation, w i l l perform t h e functions needed f o r r e a c t o r component replacement. However, t h e r e a r e some aspects o f t h e modifications needed t o permit remote operation for which f u r t h e r study would help i n optimizing t h e equipment design. We would reevaluate t h e automated welding equipment which has become a v a i l a b l e commercially s i n c e t h e s t a r t of our e a r l i e r welding program, choose t h e one which best s u i t s our needs, modify a s necessary, and t e s t it under conditions simulating some of those expected i n a r e a c t o r system. We would expect t h a t t h e b a s i c equipment for development and t e s t i n g would be b u i l t from standard l i n e materials and t h a t s u b s t i t u t e materials would not be needed a t t h i s time. The urgent function for which p h a s I s t u d i e s and phase I1 s:;nulation would be h e l p f u l t o t h e e a r l y phases of a r e a c t o r p r o j e c t i s t h a t of pipe and component alignment i n preparation f o r welding. We a r e proposing t h a t where possible t h e pipe be made f l e x i b l e enough t o permit t h e necessary displacement needed f o r proper alignment. Some preliminary estimates described i n Appendix "A" i n d i c a t e t h a t f o r most pipe s i z e s t h i s would be a p r a c t i c a l approach. For t h e very l a r g e pipes, or f o r cases where t h e pipe length does not permit much f l e x i b i l i t y , we a r e proposing t h a t a short s e c t i o n of pipe be t a i l o r e d t o f i t between t h e misaligned pipe ends and t h a t it be welded i n place with t h e remote welder. Our s t u d i e s have 'indicated t h a t t h e approach i s f e a s i b l e , but we would l i k e t o gain some experience i n applying t h e w e l d e r t o such s i t u a t i o n s . A proposal f o r developing a gear-driven split-bearing-sleeve c a r r i a g e f o r possible maintenance applications i s included i n Appendix B. This more r i g i d c a r r i a g e would gain a d d i t i o n a l torque c a p a b i l i t y f o r pipe c u t t i n g and beveling work, would be more r e a d i l y adaptable f o r i n t e r n a l pipe cleaning applications, and hopefully, would a l s o simplify solutions t o alignment problems for small pipe s i z e s by serving t o minimize t h e displacement of pipe ends a f t e r being cut. The clamping o f t h e c a r r i a g e might be enough t o hold t h e displacement t-. l i m i t s within t o l e r a n c e ranges acceptable f o r rewelding.

7 McClungl has describ'ed t h e development necessary to provide equipment f o r performance of t h e inspection function and much of t h i s w i l l be accomplished during thle program f o r t h e in-service inspections o f r e a c t o r vessels. We b e l i e v e t h a t t h e necessary t r a n s p o r t function needed f o r moving t h e inspection equipment along t h e pipe welds can be obtained with t h e weld carriages. However, t h e influence of t h f s inspection function on t h e b a s i c c a r r i a g e design should be evaluated before f i n a l c a r r i a g e design s e l e c t i o n s a r e made. In t h e future, during phase 111, t h e general engineering r e a c t o r project mockups, when it i s time t o t e s t t h e molten s a l t r e a c t o r system designs using semblance of t h e more complicated systems and components, it would be a g r e a t sdvanbage to be a b l e t o perform remote maintenance t e s t s on t h e mockups. This w i l l help to assure t h a t t h e r e a c t o r system components i n t h e f i n a l design a r e capable of being maintained. The s a t i s f a c t o r y performance :If remote-handling devices, cleanliness control, and operating techniques can a l s o be proved i n mockup t e s t s , giving increased confidence i n t h e i r r e l i a b i l i t y and providing t r a i n i n g i n maintenance techniquI3s th:rt w i l l someday reduce downtime. 3.0

3TATUS OF

3.1 3.1.1

Cell Illuminat ion

Lighting Provision:: f o r Maintenance 3.1.1.1

Experience. In t h e HRE, t h e HRT, aid t h e E R E , i n - c e l l l i g h t i n g proved adequate f o r r e p a i r purposes. 2 9 3 9 5 ' F I n t e g r a l Pi,;ghts on t h e underside of a portable s h i e l d provided su:oplemental illumination when required. The l i g h t s incli,ided dimmer controls, placed e x t e r n a l t o t h e c e l l , to provide contrast and shadow e f f e c t s . Portable, suspended l i g h t s were used as required to help d i s t i n -

guish :;pecietl ob3 e c t s

3.1.1.2

Future -.DeveLopment Requirements Updat e t h e l i g h t i n g equipment t o be sure t h a t s e l e c t i o n s represent, t h e b e s t c u r r e n t l y a v a i l a b l e commercial equipment. Permanent inc e l l wiring and l i g h t i n g , i f used, should consistr of materials to, withstand c e l l r a d i a t i o n exposure l e v e l s of up t o t h e oi-der of 10llR and ambient c e l l temperatures o f about 1_200"F,and up t o 1500째F f o r short periods.

3.2 3.2.1

THE TECHNOIOGY

:h-Cell Viewing Apparatus

Direct Viewing Through Lead Glass or Zinc-Bromide Windows 3.2.1.1

Current; Concepts. Direct viewing i s u s u a l l y adequate for unobstructed s t r a i g h t line-of-sight and general area observati.ons. For r e a c t o r maintenance operations it, w i l l be necessa.ry t c ) provide gamma-ray shielding. Commercially

8 marketed lead-glass s h i e l d plugs and zinc-bromide windows a r e commonly used and a r e generally s a t i s f a c t o r y f o r vision, illumination and shielding. Shield effectiveness i s gene r a l l y proportional t o density. Density values f o r major r e a c t o r shielding materials a r e a s follows: Concrete

density about 2.2

Iron

Aluminum

Lead

Lead Glass

Zinc-Bromide Solution

7.8

2.7

11.3

6.2

2.5

Hence lead g l a s s s h i e l d plugs have approximately 8% of t h e gamma shielding value of iron, and zinc-bromide windows provide approximately 10% b e t t e r shielding than concrete.

3.2.2

3.2.1.2

Experience. ORNL and others, including a l l hot c e l l operators, have had considerable experience with lead g l a s s and zinc-bromide f o r shielded viewing applications. Theoretical design information i s r e a d i l y available7 and a c t u a l s e l e c t i o n d e t a i l s a r e l i s t e d i n t h e design and operations r e p o r t s f o r various nuclear i n s t a l l a t i o n s . 6 j

3.2.1.3

Future Development Requirements.

Optical Equipment: 3.2.2.1

None

Mirrors, Periscopes, and Fiber Optics

Definition. The use of mirrors t o a s s i s t d i r e c t viewing has proven h e l p f u l f o r many remote observations. Simple -&ilt-Li;KGges can be operated i n conj%ctlon with long handled t o o l s t o provide s u f f i c i e n t manipulations f o r adequately aligning t h e mirror f o r viewing. Commercially a v a i l a b l e periscopes, omniscopes, telescopes and f i b e r o p t i c s equipment can be obtained t o meet a l l s o r t s of needs i n nominal r a d i a t i o n and high-temperature environments, and have been used e f f e c t i v e l y i n r e a c t o r r e p a i r and i n hot c e l l work applications.

3.2.2.2

Experience. - ORNL has varied experience with o p t i c a l equipment i n numerous applications. The "blanket mirror viewing device" and viewing scopes used i n conjunction with HRT core hole plugging operations2'9 op$J.cal t o o l i n g devices and and t h e periscope used i n periscopes used i n t h e MSRE6'8' examiriatioris of t h e Boiling Nixflear Superheater Power S t a t i o n (BONUS) a t Rincon, Puerto Rico a r e examples of apparatus used i n some of ORNL's remote viewing experiences. A report on nuclear v e s s e l r e p a i r s a t Savannah River12 l i s t s some of DuPont's o p t i c a l t o o l i n g experiences.

3.2.2.3

Future Development Requirements. t i v e l y new science with p o t e n t i a l

3.2.2.4

Cost Estimate. A quarter-manyear e f f o r t should be scheduled f o r t h e f i r s t phase o f a maintenance development program t o i n v e s t i g a t e o p t i c a l viewing means and t o provide recommendat i o n s and e,stimates for subsequent f e a s i b i l i t y t e s t i n g and mockup studies.

3.2 3

Fiber o p t i c s i s a r e l a f o r obswvations i n 2r2;s where access l i m i t a t i o n s and/or obstructions prevent t h e use of morel conventional viewing equipment, We recommend a l i t e r a t u r e search i n t o nuclear applications of t h e technology. All 3 p t i c a l equipment must meet t h e i n - c e l l environmental conditions expected t o p r e v a i l a t t h e time of r e p a i r , and must be t e s t e d under actual, o r simulated conditions. Insulation, shielding, or cooling development may be necessary f o r scine of t h e equipment.

Experience, - Many advances have been made i n t e l e v i s i o n technology f o r nuclear applications during t h e past few

Closed Circuit Television

3.2.3.1

years General E l e c t r i c Company, Westinghouse, and others r o u t i n e l y u s e TV f o r in-service and s p e c i a l inspections of r e a c t o r s . 1 2 7 1 3 9 1 4 Closed c i r c u i t TV performance evaluations a r e allso a v a i l a b l e from i n - c e l l surveillance and from hot c e l l users.L5916 ORNL has a l s o used t e l e v i s i o n f o r observi n g reisctor r e p a i r and surveillance of t h e HRT and MSRE reactom. 17 9 1 e

3.2.3.2

Future Development Requirements. The TV camera and wiring must b e a b l e t o withstand t h e i n - c e l l temperature and radiat i o n f i e l d . Insulation, shielding, or cooling system development may be necessary.

10 3.2.3.3

3.2.4

Cost Estimate. It i s recommended t h a t a quarter manyear e f f o r t and $10,000 equipment money be provided f o r Phase I of a maintenance development program t o procure r a d i a t i o n and temperature r e s i s t a n t TV equipment, and t o update design c r i t e r i a , performance s p e c i f i c a t i o n s and cost estimates f o r subsequent development work.

Special Inspections 3.2.4.1

Experience and Future Development Requirements. Refer t o t h e report by R. W. McClung, Remote Inspection of Welded J o i n t s , ORPJL-TM-3561, September 1971.

3.3 3.3.1

3.3.2

In-Cell Handling Tools

L i f t i n g Devices

3.3.1.1

Concept and Experience. Oak Ridge National Laboratory's standard practive has been to build cradle-type l i f t i n g devices f o r a l l r e a c t o r system components a t t h e time of t h e components' i n i t i a l i n s t a l l a t i o n i n t h e c e l l ; and t h i s has g r e a t l y simplified t h e subsequent remote handling. 6'19 It i s necessary, however, to b u i l d t h e f i x t u r e s with f e a t u r e s t h a t f a c i l i t a t e t h e use of remote "slip-on" guides or hooki n s e r t rings f o r handling. Experience has shown a l s o t h a t where possible, programs f o r crane movements should be f o r mulated and documented while t h e plant i s being b u i l t .

3.3.1.2

Future Development Requirements. All i n - c e l l handling t o o l s and l i f t i n g f i x t u r e s a r e u s u a l l y o f all-metal construction of materials compatible with t h e Hastelloy N primary system material, and of simple designs employing mechanical linkages. The t o o l s and f i x t u r e s , therefore, have l i t t l e or no dependence upon i n - c e l l environmental conditions during maintenance periods, with t h e exception of metal expansion when exposed to t h e elevated temperature i n t h e c e l l . L i t t l e time and e f f o r t w i l l be required t o adapt tools of e a r l i e r designs f o r f u t u r e applications. Specific f i x t u r e s and tools, however, must be proof t e s t e d , and operating procedures must be established and documented e i t h e r during t h e construction of t h e reactor, or i n f i l l - s c a l e mockup t e s t s .

3.3.1.3

Cost Estimates. An engineering e f f o r t of about 1 1/2 manyears f o r design and development of handling t o o l s w i l l be required, plus $20,000 f o r materials and prototype equipment.

Miscellaneous Long-Handled Tools 3.3.2.1

Concept and Experience. Tools i n t h i s category include simple, long-handled u t i l i t y hooks and rods f o r i n - c e l l uses t o i n s t a l l , o r remove, insulation, heaters, e t c . The

11 t o o l s a r e aI.so used t o a s s i s t pickup and t r a n s f e r operations; typical. too;. d e s i ns and operations a r e documented f o r HRT r e p a i r work. 6,20,%

3.3.2.2 3.3.3

3.3.4

Future Development Required. None s p e c i f i c a l l y ; t o o l s w i l l be developed along with t h e components they w i l l serve.

Portable Retaining Brackets

3.3.3.1

Concept and Experience. Reactor c e l l roof blocks and c e l l s i d e s shoulc! contain hooks and shelves upon which t o hang o r s e t porta’ble brackets f o r t h e temporary parking of m i s cellaneous m a l l i n - c e l l items, such a s i n s u l a t i o n jackets, heaters, etc., and r e p a i r t o o l s . Portable brackets resembling cases fc:r milk b o t t l e s were used for HRT and MSRE c e l l work.

3.3.3.2

Future Development Required. None s p e c i f i c a l l y ; brackets w i l l be developed along with t h e components they w i l l support.

Thermocouple and E l e c t r i c a l Connector Tools

3.3.4.1

Concept and Experience. Simple, long- handled, s c i s sor- a c t ion t o o l s were designed for HRE and MSRE i n - c e l l thermocouple maintensnce. The base of t h e thermocouple t o o l accommodates t h e male and female halves of a couple. The t o o l ’ s actuator i s used t o open or close t h e s c i s s o r linkage t o e i t h e r make or break t h e coupling. Similar t o o l s a r e a l s o available f o r push-pull type e l e c t r i c a l connector assembly and disassembly. Wrenches w i t t i long handles a r e a v a i l a b l e f o r use with multiplepin connectors for instruments and controls. The wrench i s used t o engai:e and t u r n t h e connector’s screw coupling. A s c i s s o r motim actuator, b u i l t i n t o t h e wrench t o o l , i s employed -LO alj-gn and make o r break t h e coupling halves. Thermocouple tools, e l e c t r i c a l connector t o o l s and o t h e r ORNL h a n d l ing equipment items a r e described i n t h e ORNL Remote Maint enance Cat a:l.ogue.

3.3.4.2

Future Development Required. stitutions.

3.4 3.4.1.1

--Tool and

None, except f o r m a t e r i a l sub-

Equipment Conveyance Means

Concept and Experience. It i s assumed t h a t t h e portable s h i e l d maintenance technology developed f o r t h e HRE and t h e MSRE w i l l be applied with molten s a l t breeder reactors.” C e l l conditions w i l l determine t h e need f o r a i r locks, e t c . , however, t h e b a s i c scheme, proven i n p r i o r operation of t h e experimental reactors, w i l l be t o u t i l i z e portable s h i e l d s of l e a d or s t e e l and t o arrange t h i s m e t a l l i c shielding t o p r o t e c t t h e operator from r a d i a t i o n a f t e r access holes have The portable s h i e l d been opened on t o p of t h e c e l l blocks.

12 w i l l a l s o provide t h e operator with a shielded platform f o r loading t o o l s i n t o t h e c e l l . Loading holes w i l l be located within a c i r c u l a r t u r n t a b l e i n s e r t within t h e portable s h i e l d platform t o permit t h e t o o l s and/or f i x t u r e s t o be located and centered over t h e work area a s required. The underside of t h e s h i e l d will a l s o include hooks and bars t o provide temporary hanger supports f o r maintenance t o o l s and mobile equipment o r components items. The platform of t h e portable s h i e l d w i l l again a l s o be comprised of two separate sections t o allow t o t a l access f o r t h e t r a n s f e r of l a r g e equipment items i n t o t h e c e l l through t h e portable s h i e l d ' s platform frame opening. The r e a c t o r building would be temporarily evacuated f o r t h i s type of maintenance operation. The t r a n s f e r s of l a r g e equipment items e n t a i l closed c i r c u i t TV operat i o n s and a zinc-bromide viewing window from a d i s t a n t spec i a l l y shielded c o n t r o l room.

3.4.1.2

Future Development Required. The portable maintenance shield approach must be incorporated i n t o t h e o r i g i n a l c e l l and c e l l roof block layout design. Mockup t r i a l s w i l l be required t o e s t a b l i s h operating i n s t r u c t i o n s and guides f o r maintenance. Costs f o r t h i s e f f o r t a r e undetermined at present.

3.5

3.5.1

Pipe Cutting Equipment

Pipe Cutters

3.5.1.1

In 1968 and 1969 ORNL developed and t e s t e d proExperience. totype u n i t s of t h e automated, o r b i t a l pipe c u t t i n g and welding machinery as p a r t of a f e a s i b i l i t y study f o r t h e MSR maintenance program. 2 3 The machining head (see Fig. 2 ) was able t o cut pipe, t r i m t h e ends square, and prepare end bevels on schedule 40 s t a i n l e s s s t e e l pipes i n s i z e s up t o 6 inches i n diameter with r e l a t i v e l y l i t t l e d i f f i c u l t y . However, problems arose i n c u t t i n g Inconel because of i t s work-hardening tendencies, and more d i f f i c u l t i e s a r e expected f o r work on pipe s i z e s l a r g e r than 6 in. as t h e c u t t i n g operations were slow, c u t t e r feed r a t e s were minimal, and c u t t e r s dulled r a p i d l y and required frequent replacement. A l l ORNL machining t e s t s were performed on h o r i z o n t a l piping. Figure 3 i l l u s t r a t e s a c u t t i n g operation on 6 in. pipe. S l i t t i n g saws and double bevel c u t t e r s tracked t r u e within approximately 0.003 in. Single bevel c u t t e r s tend t o walk out of, and away from t h e cut, e s p e c i a l l y on t h e harder Inconel pipe. The c u t t e r drive motor power and speed control c a p a b i l i t i e s appeared adequate. Observations indicated, however, t h a t t h e carriage drive i s 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 capa b i l i t y . We observed r o l l e r slippage on t h e pipe and frequently t r i p p e d t h e carriage drive r o l l e r c i r c u i t breaker protection. Cutter feed and c a r r i a g e t r a v e l speed adjustment changes, however, restored operations. The c a r r i a g e and machining head withstood loading and vibrations caused by t h e m i l l i n g c u t t e r s ,

Fig. 2.

O W L Cutter or Machi

Fig. 3.

ORNL Orbital Cutting Equipnent

but only with proper t r a v e l speed and t o o l feed s e l e c t i o n . Improvements;, however, a r e required to provide a stronger and more p o s i t i v e c u t t e r depth c o n t r o l and to provide more s t a b l e longitu.dina1. adjustments. A s p l i t - b e a r i n g sleeve c a r r i a g e concept development i s proposed (see 2 . 5 . 1 . 2 ) which could provide means for a more r i g i d c u t t i n g assembly which could s t i l l be remotely i n s t a l l e d and operated f o r i n - c e l l pipe c u t t i n g needs. Otherwise, improved locking clamps a r e desired i n conj u n c t i c n w i t h t h e present c a r r i a g e for prevention of longi t u d i n a l an6 r a d i a l c u t t e r s h i f t s . Pipe c o l l a r clamps a r e required f o r pipe c u t t i n g operations where t h e pipe slopes i n excess of 5 degrees from horizontal. We have cut with high-speed and Circoloy 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 alloyed tool s t e e l appeared t o s t a y sharper longer, - possibly by a s much a s a f a c t o r of one and a h a l f . Tests with carbide c u t t e r blades showed an even longer blade l i f e . Carbide t o o l s , however, a r e b r i t t l e , and we d i d break some blades, probably a s a r e s u l t of blade c h a t t e r . E f f i c i e n t c u t t i n g r e q u i r e s t h e t h i c k e s t p o s s i b l e c h i p per c u t t i n g toot:n, but t h i s may have to be compromised considerably t o obtain reasonable c u t t e r l i f e and proper surface f i n i s h . Thi,; i s p a r t i c u l a r l y t r u e i n t h e case of highn i c k e l stee1,s where t h e base m a t e r i a l tends to work-harden with t h e r e s u l t t h a t c h i p removal. i s inadequate or incomp l e t e . Resu:Lts from Inconel machining experiments 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 relieved t o 19rovide ample clearance f o r c h i p f a i l o E t . Allowi n g chips t o f a l l out f r e e l y w i l l . minimize t h e Inconel work hardening caused by trapped chips. 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 during c u t t i n g , Off-the-shelf commercial c u t t e r s used appeared t o cut with 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 , and imprcved c u t t i n g w a s noted where c u t t e r s were reground l c c a l l y t o p r e c i s i m s p e c i f i c a t i o n . Almost 75% tooth engagement can be a t t a i n e d . The impwtance of proper t o o l t r a v e l and c u t t e r speed adjustments, e s p e c i a l l y f o r c u t t i n g Inconel materials, cannot be minimized. Available machine shop machining data do not app.Ly t o t h e o r b i t a l c u t t i n g assembly because our equipment does not; have t h e d r i v i n g power of shop machines. Aiso, dry macliining i s s p e c i f i e d for nuclear r - Z c . 2 ; i ; r syztem 1" tenance because coolants a r e e i t h e r hazardous or might contaminate t h e nuclear system. Therefore t h e tool t r a v e l , c u t t i n g speeds, and t o o l feed r a t e s must be s e v e r a l magnitudes lower than usual shop p r a c t i c e . I -

Table I shows t h e number of inches of cut a blade can be expected to make before it must be resharpened. The t a b l e a l s o shows how deep t h e blade would cut i n t r a v e l i n g t h e indicated numbm of inches around a 6-in.-diam pipe, taking a 30 m i l or a l.2 m i l cut, a s indicated.

Table 1. Expected L i f e of Cutter Blades ~~

Des c r i p t i o n

Blade Lifetime In Stainless S t e e l

I n Inconel ~

~~~~

~~~

70 t o 80 ft/min 3 1/4 in./min .001 i n .

Saw Tooth Speed Carriage Speed Feed Per Tooth

Inches of cut, average depth 30 mils. inches

50 ft/min 1 in./min .0005 i n .

Total Depth of cut, 6-inch pipe wall. 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 high speed s t e e l

530

3/ 4

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

800

1 1/8

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 high speed s t e e l

430

5/8

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 Circoloy a l l o p

650

70" included double angle m i l l 2 3/4 i n . d i a . , 20 t e e t h , 1 / 2 i n . wide high-speed s t e e l

470

Inches of cut, average depth 1 2 mils. inches

T o t a l Depth of cut, 6- inch pipe wall. inches.

n 730

7/16

7/ 8

600

11/32

11/16

420

1/4

*Trade name for C i r c u l a r Tool 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 of h i g h carbon, medium chrome, high vanadium, high t u n g s t e n and medium c o b a l t composition.

17 WE? selected c u t t i n g speeds between 70 and 80 surface fpm for c u t t i n g s t a i n l e s s s t e e l materials, and chose 50 fpm for Inconel i n order t o achieve reasonable c u t t e r l i f e . These c:utting speeds correspond t o approximately 100 and 62.5 revolut;ions/min f o r t h e 3-in. -diam a l l o y s t e e l s l i t t i n g saws. Feed per t o o t h selections compatible with t o o l strength and t o o l r i g i d i t y were 0.001 in. for s t a i n l e s s s t e e l work and 0.005 in. for Inconel with 3 1/4 and 1 in./min ( t r a v e r s i n g s u r f a c e ) blade t r a v e l r a t e s . Our feed per t o o t h r a t e s a r e low when conipared t o r a t e s i n standard machine shop work, but a r e s t i l l c r e d i t a b l e considering our small-sized and low-powered e uipment. Our c u t t e r motor c o n s i s t s essent i a l l y of a 1 3 hp e l e c t r i c d r i l l . The depths of cut depend on a v a i l a b l e hp and c u t t e r shapes, and on t h e sharpness of t h e c u t t e r s , a s they i n t u r n a f f e c t t h e power required a t t h e c u t t e r motor spindle. We repeatedly cut 0.030 in. deep i n t o s t a i n l e s s s t e e l , and 0.015 in. i n t o Inconel.

A l l of our machining operations with t h e ORNL o r b i t a l equipment must be accomplished i n t h e standard "milling up'' mode of operation where t h e c u t t e r t o o t h i n contact with t h e pipe i s moving i n t h e same d i r e c t i o n as t h e carriage. We l a c k r i g i d i t , y f o r reverse, o r "climb m i l l " cutting. Our c a r r i a g e ' s t o r s i o n bar clamping a c t i o n on t h e carriage r o l l e r does not give enough f r i c t i o n contact f o r climb cutting. Oak Rid.ge National Laboratory a l s o has experience with t h e Trav-L-C'utter pipe saw and Guillotine pipe saws manufact u r e d by t h e E. H. Wachs Company of Wheeling, I l l i n o i s , and with pipe c u t t i n g and beveling machines of t h e H & M Pipe Beveling Machine Company of Tulsa, Oklahoma. The Wachs equipment i s a v a i l a b l e with a i r o r e l e c t r i c drives i n horsepower r a t i n g s equivalent t o machine shop saws. H & M equipment i s e l e c t r i c a l l y driven; t h e i r c u t t e r s a r e

furnished with e i t h e r pneumatic or e l e c t r i c a l drives. One of t h e prime objectives of t h e Fast Flux Test Facil i t y (FFTF) a t Hanford i s t o perform nuclear f u e l s t e s t i n g f o r t h e Liquid Metal Fast Breeder Reactor ( W B R ) program. The t e s t f a c i l i t y must have t h e c a p a b i l i t y t o i n s t a l l and remove f i e 1 assemblies by remotely controlled equipment. A s i z e a b l e program i s underway a t t h e Hanford Engineering Development Laboratory (HEDL) t o develop and t e s t equipment with which t o cut and weld t h e open- and closed-loop r e a c t o r t o p closures f o r removal and r e i n s t a l l a t i o n of experimental t e s t assemblies. 2 4 ORNL i s monitoring t h e i r development of cutting, welding, and r e l a t e d equipment f o r a p p l i c a t i o n t o r e l a t i v e l y small (6.72-in. mean diameter) pipe. They a r e t e s t i n g t h e i r equipment i n a mock-up a t 500째F. Their material and equipment s e l e c t i m s a r e intended t o withstand lo5 R/hr gamma r a d i a t i o n exposures.

1% 3.5.1.2

Future Development Required. Cell layout and a v a i l a b l e o r b i t clearance around pipes f o r t h e sawing and beveling equipment w i l l be important f a c t o r s i n determining t h e s e l e c t i o n of machinery f o r remote maintenance and r e p a i r operations. The ORNL equipment described i s compact and lightweight. Our carriage-cutter head working u n i t i s designed t o be remotely clamped around a pipe and i s about 4 in. t h i c k i n r a d i a l dimension, and 1 0 1/2 in. long. The technology for i t s application t o cut and/or bevel pipes remotely by automated programmed controls i s established. Our compact equipment, however, i s limited i n power f o r both t h e t o o l t r a v e l propulsion and t h e t o o l feed. Subsequent sections of t h i s report and Appendix "B" discuss an a l t e r n a t e carriage design using a s p l i t - b e a r i n g sleeve. The s p l i t - s l e e v e c a r r i a g e i s supported by a s e t of split-bearings on each end. A separate motor gear drive, mounted t o t h e pipe, couples t o a s p l i t - g e a r which i s permanently attached t o one of t h e sleeve's end bearings and drives t h e sleeve around t h e pipe. This a l t e r n a t e design o f f e r s considerably more r i g i d and uniform c a r r i a g e propulsion than i s a v a i l a b l e from t h e f l e x i b l e , horseshoeshaped ORNL carriages. Rigid carriages a r e d e s i r a b l e for pipe c u t t i n g service; c u t t e r t o o l vibrations, or t o o l c h a t t e r a r e minimized, and c u t t e r s h i f t tendencies a r e eliminated. A strong p o s s i b i l i t y e x i s t s , however, t h a t pipe ends w i l l tend t o spring apart r a d i a l l y (and a x i a l l y ) when cut. The magnitude o f t h i s s h i f t tendency w i l l be determined by a c t u a l process system layout and piping supports. It w i l l be most pronounced with short pipe runs, and i n t h e l a r g e r pipe s i z e s . We, therefore, a n t i c i p a t e t h a t t h e s p l i t - b e a r i n g sleeve carriage design may be l i m i t e d t o cutt i n g applications on t h e smaller pipe s i z e s , say, up t o through 6- or %-inch pipes. Beyond t h e s e s i z e s strong poss i b i l i t i e s p r e v a i l t h a t sleeve end bearings cannot withstand t h e f o r c e s r e s u l t i n g from t h e spring-action when t h e pipe i s cut, and t h e bearings may be deformed or crushed. These carriages would a l s o r e q u i r e a minimum of 1 0 inches pipe clearance, a s contrasted t o t h e 4-inch r a d i a l clearance requirement f o r basic ORNL carriages. Split-sleeve carriage r i g i d i t y o f f e r s advantages f o r remotely operated pipe c u t t i n g and pipe end beveling operat i o n s , plus t h e p o s s i b i l i t y of mounting and supporting cutt e r s or brushes t o such carriages for i n t e r n a l pipe cleaning Also, t h e s e carriages could probably needs. (See 2.9.1.2). be used f o r maintaining pipe alignment during pipe c u t t i n g operations. (See Appendix "B" ). These p o t e n t i a l b e n e f i t s seem t o outweight t h e aforementioned disadvantages and suggest t h a t a development program would be j u s t i f i e d t o establ i s h f e a s i b i l i t y and l i m i t a t i o n s .

19 The Wach's equipment has ample power, but t h e equipment i s considerably l a r g e r and heavier (by a f a c t o r of 10 p l u s ) ; it requires s u b s t a n t i a l o r b i t clearance. The outside dimensions f o r a Wach's Trav-L-Cutter a r e 24 3 / 4 X 11 1 / 2 X 20 in., a s compared t o 9 X 4 X 1 0 1 / 2 in. f o r t h e ORNL o r b i t a l equipment. Guil:l.otin saws do not require o r b i t clearance. They u s u a l l y f i t a space i n t h e order of 6 in. beyond each pipe side, with t h e i r operating mechanism i n a fixed plane extending up t o 3 1/2 pipe diameters on one s i d e f o r a width of about 6 inclies along t h e pipe. Guillotine saws can be u t i l ized only t o sever o r s t r a i g h t cut pipes; they cannot make bevel cuts.

3.5.1.3

Cost Estimat;es. No work has been done t o adapt commercial sawing machj-nery f o r remote i n s t a l l a t i o n . An equipment design, development, f a b r i c a t i o n and checkout program i s estimated t o require about 1 3 / 4 manyears of e f f o r t plus about $24,000 f o r materials, f a b r i c a t i o n , t e s t samples, and mockups. The cost excludes prototype machinery a c q u i s i t i o n c o s t s of about $3800 f o r a Trav-L-Cutter and about $1200 f o r a Guillotine saw with up t o %in. pipe sawing capacity. There Ere a number of manufacturers who market pipe c u t t i n g and beveling machines and l a t h e s f o r pipe-end preparations. The machines a r e normally used by pipe f a b r i c a t o r s and ksy l a r g e construction companies t o prebevel pipe ends f o r cocstruction welding. Typical machinery c o n s i s t s of c i r c u l a r gear tracks, o r horseshoe-shaped gear tracks, t o be i n s t a l l e d over pipes, with t h e t r a c k u t i l i z e d t o o r b i t e i t h e r a t o r c h o r an end m i l l f o r c u t t i n g and/or beveling. ORNL has ex-gerience i n using an H & M "Pipe-End-Prep Lathe" t r a c k t o handle 14 t o 20 in. pipes. H & M equipment has p o t e n t i a l fo:r conversion t o remote operation. It i s definit e l y adequate f o r flame-cut and bevel preparations, but lacks a properly fimctioning p r e c i s i o n "out-of-round"

s l i d e attach-

ment t o accurately monitor and gauge t h e out of roundness prevailing i n commercial pipes so t h a t compensating t o o l p o s i t i o n changes can be made. The w r i t e r believes t h a t H & M type equipment o f f e r s c e r t a i n merits f o r consideration. Equipme.nt dimensions, weight, and o r b i t clearances a r e i n between t h e dimensions l i s t e d f o r ORNL and Wachs' equipment. If t h e H & M equipment i s t o be used f o r r e a c t o r work, individual t r a c k s should be selected f o r each pipe size. The frame-tracks f o r multiple pipe s i z e application l a c k some r i g i d i t y , and may o f f e r t o o l a r g e an envelope when used on t h e sma:L1 end of t h e i r pipe capacity range. It i s estimated t h a t , i f performed i n conjunction with t h e previously proposed work f o r developing remotely operated saws, t h e development of a wo:rkable H & M t r a c k t o handle a representative 12 in. ]?ipe cut and bevel preparation would require 3/4 manyear and $85C10. Additional c o s t s f o r H & M equipment items would b e i n -:he order of $2500.

A note of caution i s repeated: labor, material, and machinery costs quoted previously a r e based on standard c u t t i n g p r a c t i c e with environmental temperature service l i m i t e d t o possibly a s high a s 300"F, and r a d i a t i o n l e v e l s It may be necessary t o develop subup t o about l o 4 R / h r . s t i t u t e materials t o meet t h e contemplated high-temperature and high-radiation service requirements. A l l costs f o r such development and f o r s u b s t i t u t e materials of construction w i l l be additive. A study should be performed f i r s t t o determine t h e l i m i t i n g c e l l conditions so a s t o determine t h e additiona l research and development needs. 3.5.2

Seal Weld Cutters 3.5.2.1

Experience. There a r e a number of schemes f o r s e a l welding, including Diaphragm and Seal P l a t e Weld schemes, Fig. 4; Sandwich S e a l Weld schemes, Fig. 5 ; Canopy Weld schemes, Fig. 6; and Seal Lip Closures, Fig. 7. The welded s e a l s shown i n t h e i l l u s t r a t i o n s a r e types f o r which standard cutt i n g equipment can be adapted t o work by remote control. More d e t a i l e d discussions a r e given i n Section 2.14.4, "Seal Weld Closure Welding. " Various m i l l i n g and/or grinding means a r e normally used with conventional hand t o o l i n g t o sever t h e s e a l s . To t h e best of t h e w r i t e r ' s knowledge, with t h e exception of mounting portable grinders t o extension handles t o l o c a t e t h e t o o l operator away from any d i r e c t r a d i a t i o n beams, and/or t o permit t h e i n s t a l l a t i o n of portable l e a d shielding between t h e work and t h e operator, Oak Ridge National Laboratory, t o date, has had no experience i n t o t a l l y remote c u t t i n g of s e a l welds.

3.5.2.2

Future Development Required. Specific t o o l , t o o l support, and t o o l manipulation devices w i l l vary for each of t h e types of s e a l weld l i s t e d . Oak Ridge National Laboratory has assembled a f i l e of s e a l weld c u t t e r t o o l i n g s e l e c t i o n s based on published maintenance information and on observat i o n s of naval shipboard practices. The f i l e includes information on grinders and grinding wheels, pipe c u t t e r s and c u t t e r b i t s , saws and blades, pipe-end prep machines and t o o l s , pipe centering and pipe expansion devices. No time or cost estimate can be prepared p r i o r t o s e l e c t i n g t h e s e a l j o i n t or j o i n t designs. The development e f f o r t f o r t h e j o i n t c u t t e r should be performed i n conjunction with reweld machinery t r i a l s . It i s recommended t h a t t h e designers s e l e c t t e n t a t i v e s e a l weld conf i g u r a t i o n s now and thereby permit t h e developer t o proceed with a f e a s i b i l i t y study t h a t could include t o o l i n g design, purchase, adaption, and t e s t s . Test r e s u l t s should influence and provide d i r e c t i o n t o t h e f i n a l MSBR s e a l design.

ORNL DWG 73-2389

Fig. 4.

S e a l P l a t e Welds

ORPJL DWG 73-2391

,,'

Fig. 6. Canopy Weld Schemes

ORNL DWG 73-2392

SPhC\hL +.--

Fig. 7. Seal L i p Closures

25 W

3.5.2.3

Cost Estimates. It i s estimated t h a t a budget of t h r e e mans years z G $ c ; 0 , 0 0 0 could e s t a b l i s h worthwhile gui?!,l f ~ 3 for preliminary seal-cut and seal-reweld f e a s i b i l i t y evaluation. (Note: Item 2.14.2, "Closure Welding - Seal Welds" development costs a r e included with t h i s estimate. ) The cost estimate caution l i s t i n g s t a t e d previously a l s o appl ie s her e. 3.6

3.6.1.1

EauiDment f o r PiDe SDreading

Concept; and Limited Experience. After c u t t i n g t h e pipes on each s i d e of a component one must spread them apart t o permit t h e i-eady removal of t h e component. Depending on loop layout:, it may a l s o be necessary t o jack up one o r t h e other of t h e pipe ends adjacent t o t h e cut t o eliminate binding f o r t h e remainder of a cut. For remote operational needs it i s planned t o u t i l i z e t h e s p e c i a l pipe alignment machinery discussed i n Section 2.12, "Pipe Aligning Technology" t o a l s o serve t h e pi-pe spreading needs, a t l e a s t f o r t h e smaller pipe sizes. WE! have l i m i t e d experience i n resolving pipe r e s t r a i n i n g problems associated with pipe s l i t t i n g operation. S p l i t saw c u t t e r hench t e s t s showed t h e importance of s e l e c t i n g t h e proper pipe support l o c a t i o n r e l a t i v e t o t h e o r b i t i n g p l a t form. Care must be taken t o permit f r e e movement of t h e cut piece, and t;o prevent t h e binding of t h i s piece against t h e saw. Slit-saw c u t t e r materials a r e b r i t t l e ; our t e s t t r i a l s showed t h a t it i s possible t o crack and break a r e s t r a i n e d saw blade.

3.6.1.2

3.7

Future Development Required. Aligning Technology".

Refer t o item 2.12,

"Pipe

Carriers a.nd Convevance Means f o r Use Within t h e Cell

3.7.1.1

Experience. Carrier technology from ORNL and other ins t a l l a t i o n s i s a v a i l a b l e s o t h a t s p e c i a l i s t s i n c a r r i e r des i g n can meet whatever requirements a r e established by t h e f i n a l des igrl of system component s

3.7.1.2

Future Development Required.

3.8

None anticipated.

Carriers f o r Use Outside t h e Cell

3.8.1.1

Experience. Carrier technology from ORNL and other i n s t a l l a t i o n s i s a v a i l a b l e so t h a t s p e c i a l i s t s i n c a r r i e r design can meet whatever requirements a r e encountered.

3.8.1.2

Future Devehpment Required.

None anticipated.

3.9

In-Cell Preparations for Equipment Reinstallation

3.9.1.1 Definitions and Experience. Final preweld pipe-end joint preparations include kerf and/or chip removal from the open pipe joint, removal of salt including salt traces clinging to the pipe wall and the installation of a suitable purge block plug into the pipe near the open joint. One must also establish acceptable environmental, off-gas airlock and ventilation conditions for the cell. A l l cutting chips from mechanical sawing, kerf from plasma flame cutting, and salt residue on interior pipe walls adjacent to the cut joint, must be totally removed from the pipe prior to installing purge blocks or making a facsimilie in preparation for final pipe rewelding. Provisions must be made and incorporated with air locks and ventilation systems, t o permit the cell off-gas system to safely handle purge and welding gases from subsequent pipe rewelding operations. ORNL has had considerable experience for some of the categories from operational maintenance experiences with homogeneous reactors and the MSRE. 5â&#x20AC;&#x2122;6â&#x20AC;&#x2122;23 Additional information is also available from the remote top closure evaluation work of the FFTF at Hanford, Washington. 2 4 3.9.1.2

Future Development Required. A study should be started early in a reactor project and should combine the efforts of the reactor designers and maintenance personnel to assure that the piping system layout provides adequate clearances for maintenance equipment and for the introduction of replacement components. The group should discuss all phases of the repair and reinstallation requirements. Special tools and other requirements that become apparent from the discussions (such as a pipe wall scraper for removing traces of salt from pipe interior) should be listed and categorized. Where possible, new tooling requirements should be combined with existing tooling, or at least with the masts and manipulators of existing long-handled tools.

3.9.1.3

Cost Estimates. It is estimated that 1 1/4 manyears and $18,000 will be required to perform the supplemental work, including the cleanliness control work discussed in Section 2.10 below.

3.10 In-Cell Cleanliness Control 3.10.1.1

Definitions and Experience. In-cell cleanliness control includes all the precautionary measures t o assure that all prewelding cleanliness requirements of the ASME Code and RDT Standards are met and maintained throughout the welding operation. Wiping joints with acetone solvent and lintfree rags before welding, proper filing of defects observed between passes, and brushing of all weld bea.ds, etc. are terms of cleanliness control that have been found t o be necessary. 259 269 27

27 W

3.10.1.2

Future Devel.opment Required. Cleanliness control development requirements and associated costs a r e included with t h e l i s t ing of item 2.9 above.

Experience. - Carrier t a i n e d from ORNL and

3.11 Conveyance of Components t o R e i n s t a l l a t i o n Location 3.11.1.1

3.11.1.2

and conveyance technology can be obother i n s t a l l a t i o n s f o r d i r e c t applicat i o n t c remote maintenance problems.

Future Development Required.

3.12

3.12.1.1

None anticipated.

Pipe Alignment Technology

Concept and Experience. There i s only limited p r a c t i c a l experience with t h e use of remote control equipment t o spread t h e ends of pipe a f t e r cutting, t o p o s i t i o n new components i n proper alignment, and t o hold them i n p o s i t i o n during welding. Most of t h e a v a i l a b l e r e a c t o r maintenance experience documentation r e f e r s t o underwater maintenance, with e i t h e r t h e c e l l o r t h e (component p a r t i a l l y flooded. Molten S a l t Breeder Reactor (MSER) maintenance must be performed under dry contit i o n s . The limited dry experience t h a t i s a v a i l a b l e i s primarily from work i n t h e MSRE mockup and i n t h e MSRE c e l l where s p e c i a l l y mounted screw-jacks were i n s t a l l e d i n conjunction with f r e e z e flanges i n t h e primary pipe system t o spread o r close t h e flanges. Instructions f o r pipe alignment were developed a s a p a r t of t h e extensive Westinghouse Pennsylvania Power and Light Company study f o r t h e Pennsylvania Advanced Reactor Program (PAR)28 o f t h e l a t e 1950's. The PAR was planned 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 pressurized l;o 1000 psi. The designers recognized t h a t a c i r c u l a t i n g f u e l would increase 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 t h a t completely remote maintenance w o u l d be mandatory.

The remote c o n t r o l devices and pro-

cedures planned f o r use on t h e PAR system a r e described i n t h e fol.lowing paragraphs. The primary coolant systems of t h e PAR consisted of closed :Loops, each with but one point fixed. Hence, posit i o n e r s to r e a l i g n t h e pipe f o r welding were not required t o apply bending moments t o t h e piping and only simple radia l and a x i a l motions were needed t o g r i p t h e pipe and t o a l i g n t h e pipe ends. PAR loop piping was expected t o encounte r thermal cycles which would introduce s t r e s s e s t h a t would cause t h e pipe ends t o spring from t h e i r o r i g i n a l p o s i t i o n when t h e pipe was cut. The PAR design c r i t e r i a regulated primary pipe s t r e s s e s t o l i m i t pipe expansions so t h a t no point of t h e piping would move i n excess of 1/2 inch during t h e f l e x u r e from hot t o cold position. Their r e a c t o r vessel, because of i t s weight and hanger design, had t h e completely fixed position. A l l other components and t h e piping were

28 f r e e t o move about t h e r e a c t o r i n a horizontal plane. Because of t h i s f l e x i b i l i t y , only r e l a t i v e l y simple positioner devices were required t o properly hold piping f o r severance operations and t o r e a l i g n t h e replacement piping p r i o r t o welding. Narrow clamping band u n i t s on each side of t h e cut points included jaws t o firmly g r i p t h e pipe. The cutt i n g and welding equipment could move r a d i a l l y and a x i a l l y f o r realignment and mounting. Cut points were preselected on horizontal pipe runs t o f u r t h e r reduce bending moment requirements f o r t h e replacement piping. The PAR primary system (16-in. p i p e ) positioner design assumed that t h e maximum loads t o be imposed on t h e pipe, i n e i t h e r t h e r a d i a l or t h e a x i a l direction, would be 15 tons and t h a t a 1-in. a x i a l movement of t h e pipe t o provide clearance would be adequate f o r removal of t h e components. Replacement components contained nozzle configurations i d e n t i c a l with t h e removed component. Crane access was chosen t o p o s i t i o n new components within 1 in. of t h e f i n a l i n - c e l l location. A l l a x i a l and r a d i a l loads were transmitted t o permanently i n s t a l l e d struct u r e s . These supports were designed not t o d e f l e c t under t h e calculated loads required for pipe manipulations. During t h e removal of a component, i d e n t i c a l p o s i t i o n e r s w o u l d be l o w e r e d over t h e piping onto t h e r i g i d s t e e l s t r u c t u r e s on each s i d e of t h e cut point. After t h e positioners were locked t o t h e supports, t h e i r self-contained hydraulic systems were t o provide a l l t h e forces required t o r e s t r a i n or a l i g n t h e piping. F i n a l alignment was t o be accomplished t o within 1/32 in. The termination of t h e PAR p r o j e c t precluded complete t e s t i n g of t h e maintenance schemes t o show t h a t they would accomplish a l l t h e r e s t r a i n i n g and pipe aligning manipulat i o n s required f o r proper c u t t i n g and rewelding work s e t ups. The project, however, d i d conduct equipment t e s t s t o e s t a b l i s h remote maintenance f e a s i b i l i t y and t o provide valuable guidelines f o r f u r t h e r studies. Among t h e problems t h a t remained when t h e PAR work had discontinued was t h e f a c t t h a t t h e maintenance equipment and t h e positioning equipment components were bulky and complex. Many positioners were required t o handle t h e numerous pipe sizes, and each demanded a g r e a t deal of c e l l room. Although O m ' s approach t o positioning w i l l generally follow PAR guidelines, we plan t o use g r e a t l y simplified apparatus. For example, piping w i l l generally be cut a t component stub nozzles. The positioner support t h e r e f o r e can be incorporated t o t h e component's s t r u c t u r e o r framing a t considerable space savings. Pipe d e f l e c t i o n movements can be minimized. Figure 8 exemplifies a possible arrangement.

29 ORNL DWG 73-2393

Fig. 4.

Component Pipe Stub Weld J o i n t P o s i t i o n e r Arrangement

Fig. 9.

Pipe Alignment J i g f o r Line Cutting and Welding

Component ( A ) and t y p i c a l connecting pipes ( B ) and (c) Preselected cut-point a r e commonly supported by framing ( D ) area ( E ) has accurately machined ( t o b e t t e r than normal m i l l dimensional tolerances ) piping, precision indexed t o component reference l i n e s . A permanent pipe clamping f i x t u r e (F) i s both adjustable and removable. The f i x t u r e includes a centered r i n g groove t o accomodate a r i n g welded t o t h e pipe. The i n t e g r a l pipe r i n g permits t h e f i x t u r e t o s h i f t a x i a l l y during loop heatup expansion and cooldown contraction to minimize t h e introduction of bending moments and s t r e s s e s t o t h e pipe. The mating surfaces of t h e pipe clamp f i x t u r e w i l l contain a n t i g a l l spray coatings. A t y p i c a l component replacement operation i s presently envisioned a s follows:

1. Mount t h e " o r b i t a l vehicle" c a r r i a g e over area ( E ) . I n s e r t an inspection module. Verify t h a t clamp ( F ) i s secured over pipe ( B ) . Apply module's inspection gear t o properly index t h e carriage a t t h e preselected cut-plane; lock carriage drive t o pipe. 2. I n s t a l l a catch pan and a vacuum cleaner system f o r "hot chip" control. I n s t a l l a c u t t e r module i n exchange f o r t h e inspection module. Test indexing - proceed t o cut. 3 . Transfer equipment t o pipe l i n e ( C ) ; repeat operat i o n s 1 and 2.

4. Detach component (A) from i t s support, a t t a c h a l i f t i n g f i x t u r e . Use crane for removal. 5. Enter replacement component (A' ). I t s pipe stub has been previously machined t o template indexing data. Component ( A ' ) i s bagged, except for stub pipe weld ends, and lowered i n place. B o l t component (A' ) t o supports. Attempt t o match stubs and piping. If stub ends a r e too long, matchmark pipe, remove component, remachine. If stubs a r e t o o short, obtain wax impressions for machining a spool piece i n s e r t . F i t as required t o a t t a i n j o i n t alighment. Adjust t h e permanent pipe clamp f i x t u r e (F) i f required, but only f o r small displacements t o avoid excessive s t r a i n s . We plan t o use s p e c i a l custom-built spool i n s e r t s t o connect pipes f o r rewelding i n places where it i s otherwise impossible t o a t t a i n s a t i s f a c t o r y pipe-end alignment f o r rewelding. Many components contain multiple pipe connections. Depending on t h e respective azimuth l o c a t i o n s of t h e pipe stubs on t h e replacement component, equipment maintenance procedures t o be developed i n t h e mockup w i l l more than l i k e l y require spool piece connectors f o r t h e makeup of some of t h e s e l i n e s . The spool piece scheme avoids t h e p r e s t r e s s i n g of pipes f o r f i t u p on t h e f i n a l l i n e attachments of multiple l i n e s .

31 6 . Rei-nstall " o r b i t a l vehicle" carriage with t h e inCheck t h e f i n a l alignspection module i n s e r t over pipe (B). ment of t h e pipes and a l i g n t h e carriage. Clamp and lock c a r r i a g e drive t o pipe. Swap t o c u t t e r module, m i l l t h e adjoinfng pi.pe ends t o get t h e precision needed. Remove t h e c u t t e r module, clean t h e prepared j o i n t ; then i n s t a l l t h e weld module. Tack or stagger weld matched pipe ends t o avoid d i s t o r t i o n . Perform s i m i l a r work on pipe l i n e ( C ) . Finally, fin.ish weld both j o i n t s .

7. Remove r e p a i r equipment. Adjust t h e supports and t i g h t e n b o l t s . Whenever a pipe section or component i s r e moved a f t e r having been i n service, r e s i d u a l s t r e s s e s can e x i s t j.n t h e piping and w i l l appear a s forces and moments upon c u t t i n g t h e pipe. The forces and moments w i l l be present even though t h e piping may have been i n s t a l l e d i n i t i a l l y i n a s t r e s s - f r e e condition. Stresses can be caused by d i f ferences between t h e ambient temperature a t which t h e piping was i n s t a l l e d and t h a t which e x i s t s during maintenance operat i o n , k~ythermal cycling i n system operation, by changes due t o y i e l d i n g a t high-temperature operation (creep), or by changes of configureation caused by welding, or by s h i f t i n g of pipe support hangers, supports, o r s t r u c t u r e s . The suggested scheme f o r c u t t i n g only i n t h e v i c i n i t y of t h e component nozzle stubs and f o r using common-component pipe r e s t r a i n t clamp supports l o c a t e s pipe cut points adjacent t o r i g i d components and tends t o reduce r a d i a l pipe movements and pipe bending moments. The scheme thereby minimizes problems with replacement components. The scheme a l s o compens a t e s f o r a x i a l pipe s h i f t s by l e t t i n g t h e pipe clamp f i x t u r e s h i f t f r e e l y with t h e pipe's axis. Appendix A l i s t s calculated maximum pipe s h i f t s t o be a n t i c i p a t e d i n c u t t i n g of pipe i n a maintenance operation on a t y p i c a l r i g h t angle bend pipe-line i n s t a l l a t i o n . The i l l u s t r a t i o n s selected represent " i d e a l " balanced symmetrical layouts; i n p r a c t i c e p i p i n g

systems w i l l more than l i k e l y be f a r more complex. The def l e c t i o n and r e s t o r a t i o n f o r c e figures, however, i l l u s t r a t e t h e magnitude of t h e problem, and t h e problems dependence upon pipe s i z e and lengths of pipe runs. The longer t h e p i p e ' s length, t h e g r e a t e r i t s deflection, or shrinkage upon c u t t i n g , - but t h e r e s t o r a t i o n f o r c e requirements decrease with increased pipe lengths t o reduce t h e o v e r a l l problem of jockeying pipes about t o a l i g n an old i n - c e l l pipe end with t h e pipe stub of a newly i n s t a l l e d component. Smaller diameter pipes a r e l e s s r i g i d , hence considerably l e s s f o r c e i s required to move t h e smaller l i n e s within t h e c e l l . Accordingly, t h e i d e a l c e l l pipe layout,from a maintenance standpoint, c o n s i s t s of long runs of small diameter balanced geometry pipe l i n e s . We a l s o note n e g l i g i b l e angular pipe deflections f o r t h e proposed pipe supports affixed t o a common base with t h e respective components; t h e magnitude of t h e angular deflection, or r o t a t i o n , upon c u t t i n g t h e pipes i s not s u f f i c i e n t t o cause problems of matchup f o r butted ends for re-welding i f t h e pipe ends a r e squared t o usual tolerances.

Reactor designers cannot predict a l l possible trouble areas, or it may not be p r a c t i c a l t o provide pipe stub posit i o n e r s a t every location where they might be needed. Therefore, a portable pipe alignment j i g f o r l i n e c u t t i n g and welding, such as shown i n Fig. 9, w i l l be needed t o provide f o r pipe maintenance anywhere within t h e system. The cablesupported positioner assembly could swing i n t o place over t h e pipe t o be cut. Then, two hydraulic cylinders, housed withi n t h e j i g ' s t o p cover, would be energized t o extend a s e t of contoured shoes t o firmly g r i p t h e pipe and press it i n t o t h e alignment j i g and r e e s t a b l i s h r a d i a l alignment. Matching corner-cable s l i n g s a r e i n tension to balance t h e applied hold-down forces, Narrow clamps designed t o g r i p t h e pipe firmly should be i n s t a l l e d butted up to each s i d e of t h e j i g ' s shoes to minimize pipe bending moment s t r e s s e s when t h e pipe i s cut.

3.12.1.2

Future Development Requirements. We should e s t a b l i s h which vessels a r e t o be replaced, which ones to be repaired i n place, and which components of vessels a r e t o be removed f o r r e p a i r or replacement. Expected pipe f l e x i b i l i t y needs should be estimated f o r comparison, and f o r t h e v e s s e l s t h a t a r e t o be replaced it must be determined how pipe s i z e s , wall thickness, length and method of attachment t o t h e v e s s e l w i l l influence t h e f l e x i b i l i t y . A t i g h t l y coupled arrangement such a s t h a t proposed f o r t h e MSBR's*' does not permit much f l e x i b i l i t y and it may t h e r e f o r e become necessary t o r e s o r t t o t h e use of t a i l o r e d spool pieces f o r short l a r g e diameter pipe runs. Where t h e l a r g e coolant s a l t piping could have long runs, t h e r e may be enough f l e x i b i l i t y a v a i l a b l e t o permit some maintenance pipe alignment, however, even : e r e pipe i n t h e 20 inch pipe range i s not e a s i l y bent. The smaller service l i n e s ( 6 and 8 inches diameter) could be made f l e x i b l e enough t o permit r e l a t i v e l y easy alignment a f t e r t h e v e s s e l i s i n s t a l l e d and t h e l a r g e r l i n e s welded together. The references t o t h e PAR imply t h a t t h e l a r g e s t vessel, or t h e r e a c t o r vessel, would be fixed and t h a t t h e other components would then be adjusted t o it f o r alignment. The a c t u a l supports, r o t a t i o n s , and t i l t s of t h e s e "other components'' remain t h e major problems t o be resolved, along with t h e problems of properly holding t h e pipes for f i n a l alignment before welding. The designer-maintenance study group (see itme 2.9, "In-Cell Preparations f o r Equipment Reinstallation'! ) should analyze a l l i n - c e l l pipe systems for a n t i c i p a t e d pipe d e f l e c t i o n s h i f t s and movements when t h e pipes a r e severed during component replacement maintenance operations. Their analyses should determine t h e equipment and pipe support types needed, t h e locations of t h e cut planes, and t h e space needed f o r pressure cylinder i n s e r t i o n t o move t h e pipe ends as required. Alternatively, a study should be sponsored t o i n v e s t i g a t e possible merits of u t i l i z i n g commercially a v a i l a b l e s p l i t bearing sleeves t o r e t a i n pipe alignment f o r c u t t i n g and to

33 reestal3lish alignment f o r preweld and weld-tacking assembly, a s d e t a i l e d i n Appendix B. There may be a pipe s i z e r e s t r i c t i o n f o r an e f f e c t i v e range where s p l i t - b e a r i n g sleeves perm i t a highly simplified approach t o pipe alignment maintenanse needs. An investigatory program should s t a r t e a r l y i n t h e reacto:r pro;ject. S p l i t bearing sleeve maintenance, even i f p r a c t i c a b l e only f o r t h e smaller pipe sizes, would permit s u b s t a n t i a l o v e r a l l cost savings. 3.12.1.3

3.13 3.13.1.1

Cost Estimates. A f e a s i b i l i t y study on a selected small pipe s i z e of 3-in. sched 40 s t a i n l e s s s t e e l pipe, o r of 3-in. 40 1ncone:L pipe, f o r s p l i t - b e a r i n g sleeve maintenance would ent a i l about 3/4 manyears and approximately $15,000. A Phase I1 extension t o determine range l i m i t a t i o n s f o r t h e scheme should be a program of approximately l i k e magnitude. Costs of Phase 111: f i n a l checkouts including more complex alignment apparatus f o r t h e l a r g e r pipe s i z e s a r e indeterminate a t t h i s time. Work f o r t h i s phase should be combined with f u l l - s c a l e mockup schemes of a c t u a l component i n s t a l l a t i o n s , which would e n t a i l considerable manpower, material, equipment, and r e l a t e d costs. Weld Preparation and Tack Welding of Pipe J o i n t s Conce t; and Experience. A t present it i s proposed t o use d 3 e d " weld metal r i n g s t h a t a r e i n t e g r a l l y attached t o t h e pipe s t u b s of t h e replacement component, o r t o t h e r e placement pipe. 2 3 A "buttered" r i n g i s prepared by depositi n g weld metal around t h e pipe stub i n t e r i o r and then machining t h e deposit t o a washer shape. The i n t e g r a l weld metal r i n g i s : shaped and spaced t o simulate a Kelloggitype rectanbular r i n g consumable i n s e r t . The f i n a l machining of t h e washer i s t o be made t o match t h e mating i n - c e l l pipe end by using templates made from wax impressions. The washer shaped pipe end o f f e r s t h e a d d i t i o n a l advantage o f having a f a i r l y

r i g i d end configuration capable of withstanding moderate abuse during pipe handling operations. The f i n a l pipe alignment positioning, however, i s c r i t i c a l . The prepared end shape of t h e i n - c e l l pipe s e c t i o n c o n s i s t s of a nominal 1/16-inch root f a c e and a bevel angle. This rootface i s comparatively flimsy; hence vulnerable t o nicking o r deformation with bumping o r other improper pipe handling. It i s desirable t o attempt t o contact t h e j o i n t f a c e only i n a butted plane. It may become necessary t o temporarily p r o t e c t t h e i n - c e l l pipe-joint ends with bumper s h i e l d s u n t i l a replacement component (with i t s i n t e g r a l pipe stub ends) i s lowered t o f i n a l elevation. The i n t e g r a l r i n g and stub w i l l be t a c k welded t o t h e i n - c e l l pipe using t h e automated o r b i t a l pipe welding equipment as soon a s proper alignment i s obtained. All aligning machinery mu,st remain energized f o r t h e tacking operations t o clamp and r e s t r a i n t h e pipe sections and thereby firmly seat

34 t h e pipe ends. S u f f i c i e n t tacks must be placed t o avoid t h e breaking of tacks a f t e r r e s t r a i n t removal, or during rootpass welding. Preliminary f e a s i b i l i t y t r i a l s seem t o indic a t e t h a t t h e above procedure can be made t o work properly. 23'25 3.13.1.2

Future Development Requirements. To be discussed under Sect i o n 2.14.1, "Closure Welding - Pipe Welding". 3.14

3.14.1

Closure Welding

Pipe Welding

3.14.1.1

Ex erience. The ORNL automated welding f e a s i b i l i t y study a* follow-up report on f i r t h e r weld development with t h e ORNL system,25 and a report on automated o r b i t a l welding with r e c e n t l y a v a i l a b l e commercial equipment systems, 2 6 a s well a s an ORNL film on Automated Welding,27 a l l describe automated o r b i t a l welding operations i n considerable d e t a i l . Some consideration was given t o adapting t h e o r i g i n a l ORNL equipment f o r remote application, however, e s s e n t i a l l y no proper scale demonstrations were attempted, and t h i s s t i l l remains t o be done. It i s now a l s o important t o monitor t h e progress of t h e newly a v a i l a b l e commercial automated Five companies s t a r t e d marketo r b i t a l welding systems. 25'26 ing such equipment i n 1972. The AEC i s planning t o use such machinery extensively f o r t h e pipe system construction of LMFBR f a c i l i t i e s . It may become appropriate t o conduct f'uture maintenance welding experimentation with t h e s e commercial systems t o u t i l i z e trained, knowledgable operators and q u a l i f i e d welding and inspecting procedures. The ORNL automated equipment c o n s i s t s of an " o r b i t a l " c a r r i a g e t h a t clamps onto a pipe and propels t h e welding apparatus around t h e circumference of t h e pipe. The carriage accommodates interchangeable heads f o r c u t t i n g pipe o r f o r making tungsten inert-gas-arc welds. There i s an automatic welding programmer-controller t h a t constantly maintains a l l conditions necessary t o produce high q u a l i t y welds. There i s a l s o a hand operated pendant u n i t t o provide a l t e r n a t i v e s t a r t and stop controls. To begin automated welding, an appropriate procedure i s dialed i n t o t h e programmer-controller, a button i s pushed, and t h e machine takes over t o produce t h e weld and then shuts i t s e l f off. A recorder coupled t o t h e system i s used t o record t h e major welding parameters including current, a r c voltage, carriage speed, wire feed r a t e , and s t a r t and stop. Figures 10 and 11 show t h e welding system.

3.14.1.2

Future Development Requirements. Automated welding i s now operational f o r d i r e c t pipe welding i n construction applicat i o n s . 2 6 Commercial equipment systems a r e now marketed below $40,000 t o automatically butt-weld pipes from 3 t o 36 in. diameter and f o r wall thicknesses of 3/16 t o 1 1/2 in. The

PHOTO Y-106815

Fig. 10.

ORNL O r b i t a l Welding System

!x-ranpl_hce

ORNL DWG73-2395

,u"

I 4 i

Fig.

11.

Equipment Hook-Up, ORNLWeld System-

37 machines 0rbj.t t h e pipe f o r welding. Welds produced meet ASME and RDT Code Standards f o r nuclear-quality gas-tungstena r c welding of pipe. The commerical machines for t h e present must be manually mounted on pipes, and operator understanding and judgment a r e required f o r t h e setups. The ORNL o r b i t a l c a r r i z g e and automated welding equipment can be i n s t a l l e d remotely and operated from a remote s t a t i o n .

3.14.1.3

Cost Ektimates. There i s a cho:ice of custom building individu a l ORNL type systems one a t a time a t roughly 1 1/2 t o 2 times t h e costs of t h e commercial mass produced systems, or of attempting t o dhvise means and procedures t o adapt and conv e r t t h e commercial machinery t o remote control applications. Since most nuclear piping systems w i l l probably be b u i l t with automated welding equipment by t h e l a t e 1970's, it i s recommended t h a t t h e commercially a v a i l a b l e equipment be adapted f o r remote c o n t r o l operation. It i s estimated t h a t two manyears of e f f o r t plus $40,000 f o r supporting services and materials w i l l be required i n addition t o purchase of a commercially a v a i l a b l e automated welding system, estimated t o cost $38,000. The note of caution, however, must be repeated. A s with t h e pipe c u t t i n g and beveling equipment, a l l present materials of construction f o r e i t h e r t h e ORTXL o r t h e commercial welder w i l l -not withstand environmental- temperatures i n excess of 300째F and ma;y not hold up f o r an acceptable l i f e i n r a d i a t i o n f i e l d s of 10 R/hr. A program must t h e r e f o r e be sponsored t o deve1o.p s u b s t i t u t e materials, t o conduct f i r n a c e t e s t s , and t h e r e a f t e r , t o b u i l d prototype weld heads f o r t o t a l weld system checkout i n s u i t a b l e high-temperature t e s t c e l l s . E s t i mating cost:; for t h i s work would be premature and w i l l be develo,ped when environmental conditions a r e s e t more firmly, and a f t e r t h e establishment of t h e remote handling c a p a b i l i t y f o r coinmercrial w e l d e r s .

3.14.2

Seal Welding

3.14.2.1

Description. Seal weld closures were i l l u s t r a t e d and d i s cussed i n Section 2.5.2. W e expect t h a t t h e welding head used i n O m , experiments, o r a commercial head of equivalent design,, could be adapted t o follow t h e c i r c u l a r path of t h e s e a l perimeter by a t t a c h i n g t h e head t o t h e end of a j i b boom, which i s centered on t h e v e s s e l flange, a s shown i n Fig. 12. Adaptive controls w i l l be used t o properly l o c a t e t h e t o r c h and t o a d j u s t t h e torch-tungsten positioning f o r minor geomet,rical contour i r r e g u l a r i t i e s and/or minor f i t u p inconsistencies of mating s e a l members. For s e a l welds on t h e s i d e of t h e vessel, it i s possible t o support t h e same type weld head from a c a r r i a g e t o r i d e a r a i l t r a c k about t h e perimeter of a vessel, as i l l u s t r a t e d i n Fig. 13. We have completed a concept study f o r a crawler-carriage t o

For CUPllINOt Use s i r or e l e c M c cuttftq tools, e;l.snders, plasma torch, &/or

gouging torch

Fig. 12. Conceptual Diaphragm or Sandwich Seal Weld with ORNL Weld Head Supported from a Motorized Carousel Linkage

Fig. 13.

Flanged Vessel Seal Weld Closure Scheme f o r Orbital System I n s e r t s

r i d e a s e t of s e a l l i p s a s shown i n Fig. 14* The f i n a l design f o r s e a l weld closures w i l l govern t h e s e l e c t i o n of t h e type of c a r r i a g e t o be used with a weld head Ghich i s common t o other systems.

3.14.2.2

Future Development Required. New types of carriages and weld-head propulsion schemes a r e needed f o r s e a l weld app l i c a t i o n s . Presently a v a i l a b l e weld heads from t h e commercial systems can perform t h e h e l i a r c s e a l welds required and t h e heads need only t o be adapted f o r remote control and automated s e a l welding operation. It i s reasonable t o assume t h a t t h e weld heads developed f o r pipe welding could be used interchangeable i n t h e s e a l welder.

3.14.2.3

Cost Estimates. Approximately t h r e e manyears and $40,000 should be budgeted i f t h i s work can be performed i n conjunct i o n with recommended item 2.5.2, "Seal Weld Cutters" development. The s p e c i a l high-temperature and high-radiation equipment s t i p u l a t i o n s l i s t e d under item 2.14*1, "Closure Welding - Pipe Welding" again a l s o apply f o r s e a l welding equipment.

3.15 3.15.1.1

Inspection and Acceptance Tests

Concept and Experience. The technology of remote inspection and acceptance t e s t i n g by means of t h e more conventional penetrant checks, radiography and sonic inspection i s described i n t h e report "Remote Inspection of Welded Joints", ORNL-TM-3561, September 1971, by R. W. McClung. In addition, it now appears t h a t it may be possible t o evaluate t h e data recorded as t h e weld i s being made and from t h e data t o It i s determine t h e likelihood of a flaw i n each weld pass. known, from experience, t h a t excessive a r c voltage and low current w i l l cause lack of weld penetration; low a r c voltage and high current, o r low wire feed and high weld current w i l l cause melt-through; high wire feed and low weld current w i l l b a l l t h e bead; inconsistent carriage t r a v e l and hence, uneven weld speeds w i l l r e s u l t i n uneven bead depth and contour; etc. The Recorder shown with t h e welding system i n Figures 10 and 11 charts welding current, a r c voltage, c a r r i a g e speed and wire feed r a t e . The charted record can be compared t o previously prepared acceptable standards. If a l l p l o t s f a l l within predetermined allowable band-widths, t h i s i s evidence of a good weld. Simultaneously incurred i r r e g u l a r i t i e s t o any two of t h e charted f'unctions should cause concern. (Single p l o t deviations u s u a l l y i n d i c a t e instrument Calibration, o r s i g n a l noise f l u c t u a t i o n s . ) Usually, a c a r e f u l v i s u a l inspection, with t h e c h a r t ' s time s c a l e used t o calc u l a t e t h e s p e c i f i c l o c a t i o n of t h e suspected flaw, w i l l confirm a weld defect. It i s hoped t h a t t h e Code w r i t e r s and t h e inspection agencies w i l l amend t h e i r present inspection p o l i c i e s t o permit t h e s u b s t i t u t i o n of information

zlo i 4 : ffi 0

42 from recorder charts f o r those Code requirements t h a t cannot be established with r e l i a b i l i t y by remote means.

3.15.1.2

Future Development Required. Recommendations f o r f i t u r e development work on remot e inspect ion and acceptance t e s t s a r e contained i n McClung' s report on "Remote Inspection of Welded Joints"

43 APPENDIX A CALCULATIONS FOR fYNTICIPATED MAXlMuM DEFLECTIONS

AND RESTORATION FORCES FOR CUTTING INOR-8 PIPING MATERIAL In considering t h e problems of remote maintenance on molten s a l t r e a c t o r systems, we have been concerned about how pipe ends might move or spring apart a f t e r a cut i s made t o remove some component which i s t o be replaced. The weight of components and of t h e pipe i t s e l f w i l l impose s t r e s s e s a s w i l l thermal expansion o r thermal cycling a f t e r t h e system was i n s t a l l e d . One can a n t i c i p a t e t h a t t h e pipe ends w i l l surely s h i f t o r d e f l e c t a f t e r a cut has been made. To be a b l e t o r e a l i g n t h e pipe and hold it i n p o s i t i o n f o r rewelding w i l l require some s o r t of clamping mechanism which w i l l have t o be designed t o overcome t h e f o r c e s exerted on t h e pipes. Force w i l l a l s o be required t o r e s t o r e t h e cut pipe t o i t s o r i g i n a l p o s i t i o n p r i o r t o realigning and rewelding t h e replacement component i n t o t h e system. Two pipe layouts have been analyzed t o obtain an approximation of t h e magnitude of t h e problem. The cases a r e somewhat simplified and idealized t o permit ready analysis, but t h e calculated d e f l e c t i o n values should nevertheless be reasonable approximations. In any event, with standard supports and braces f x - t h e components of t h e system, t h e calculated s t r e s s e s on runs of pipe a r e such a s t o cause t h e cut ends t o d e f l e c t about an inch o r less, not a s much a s a f o o t o r so. This information i s important i n determining what s o r t of equipment w i l l be needed for aligning and holding pipes t o be rewelded. The cases t h a t were analyzed were s e l e c t e d t o i l l u s t r a t e t h e e f f e c t s of pipe length and pipe diameter on t h e magnitude of t h e d e f l e c t i o n when a cut i s made. The calculations of t h e amount of d e f l e c t i o n and t h e forces required t o r e s t o r e t h e def l e c t e d pipe t o i t s o r i g i n a l p o s i t i o n i n d i c a t e values t h a t we can l i v e with,provided t h a t we use proper f o r e s i g h t i n e s t a b l i s h i n g t h e system design t o meet reasonable requirements f o r f u t u r e maintenance. Calculat ions

For a molten salt; r e a c t o r system operating near 1300째F over a threeyear period, we have calcul.ated t h e maximum d e f l e c t i o n of pipe ends a f t e r c u t t i n g and calculated t h e f o r c e s required t o r e s t o r e t h e pipe ends t o t h e i r o r i g i n a l position. These c a l c u l a t i o n s a r e based on t h e assumption t h a t t h e system piping was o r i g i n a l l y i n s t a l l e d so t h a t s t r e s s e s were within those established by t h e c r i t e r i a of Code Case 1315. The following paragraphs and i l l u s t r a t i o n s describe t h e calculations t h a t were performed and show t h e r e s u l t s t h a t were obtained. Given : 1. Maximum permissible creep r a t e : Code allowable ma.ximum = 1% i n 100,000 hrs = .26$ in 3 years

44 2.

Assume: a)

t h e uniform creep r a t e conservatively w i l l not exceed 50% max. Select a uniform creep r a t e of .13% ( t h i s represents 1/7 of t h e maximum thermal expansion). N

t h e r e i s no s t r e s s i n t h e pipe a t assembly.

Calculat e : a)

Pipe S h i f t s vs. Pipe Lengths f o r

1) A t y p i c a l piping arrangement; both ends of t h e pipe run a r e f i x e d ; no permanent pipe end support guides a t cut point. 2)

A t y p i c a l piping arrangement; both ends of t h e pipe run a r e fixed; t h e fixed pipe end supports include a common fixed base with guides on each s i d e of t h e pipe cut t o r e s t r a i n t h e pipe being cut.

The magnitude of t h e r e s t o r a t i o n f o r c e t o be applied t o t h e cut pipe ( f i r s t case) t o r e t u r n t h e pipe t o i t s precut location.

1) Force vs. Pipe Length 2)

Force vs. Pipe Size

CASE WITHOUT GUIDES PIPE SHIFTS VS. PIPE LENGTHS

before cooldown

I f

a f t e r cut

--_

-u3

cp = angular s h i f t a t cut & = l i n e a r s h i f t a t cut-horizontal Ay = l i n e a r s h i f t a t cut-vertical

plane

& = t o t a l linear shift 1 = p a r t i a l pipe length*

= 0 f o r piping arrangement shown = 0.0013 ( A

& = 0.0013 (2

30)

+ 30)

& = & Az = PIPE LE1\TGTH* 5' + 2'6" = 7'6"

10' 15'

20'

+ 2'6" + 2'6" + 2'6"

W 24- &T2

LINEN? PIPE SHIFTS AT CUT &, & = 0.117"

AZ = 0.17"

= 12'6"

b, & = 0.195"

Az = 0.28"

= 17'6"

b, & = 0.273"

AZ = 0.38"

= 22'6"

b, Ay = 0.351"

= 0.50''

*Pipe lengths were s e l e c t e d t o correspond t o lengths used f o r t h e Case With Support Guides where t h e +2'6" i s t h e d i s t a n c e between f i x e d end supports, with t h e pipe c u t made 6" from t h e r e a r support f i x t u r e .

46 CASE WITH SUPPORT GUIDES P I P E S H I F T S VS. P I P E LENGTHS

before cooldown

cp = angular s h i f t a t cut

& = l i n e a r s h i f t a t cut, v e r t i c a l plane &x = l i n e a r s h i f t a t cut, horizontal plane fjy = r e s u l t a n t s h i f t , a f t e r cut, Y-plane

R #-

p a r t i a l pipe length*

GUIDE

T= sin-1 Ax = hx'

for pipe arrangement shown

+ [ ( a + 24) -

+ 24)

cos

cpl

Where &x' i s Ax for case without guides.

= 0.0013 ( 3 0

+ A)

cp = sin-' &x = 0.0013 ( 3 0

[: P I P E LENGTH*

term z O

+ R) +

.*. &x

+ 24 -

= .0013 (30

+ 24 + R)

cos cp]

ANGULAR AND LINEAR P I P E S H I F T S cp & 6Y 0 0.117" 0.117" 0" -4'

2'6" = 7 ' 6 "

+ 2'6" 15' + 2'6'' 20' + 2'6" 10'

= 12'6,"

0" -4'

0.195"

0.195''

= 17'6"

0" -4'

0.273"

= 22'6"

0" -4'

0.351"

47 RESTORATION FORCE VS. PIPE SIZE

Ay = l i n e a r l i n e slnift W = force t o restore E = modulus o f e l a s t i c i t y

= p a r t i a l pipe length* 1 = moment of i n e r t i a

,----.

-1/3WR3

E1 -3EI&

6" Sched. 80 Pipe (. 432 w a l l )

20" Sched. 80 Pipe (1.031 w a l l )

Force W t o r e s t o r e :

A 2599.07 A

40.49

+ 2'6"

W (pounds)

7'6"

20'

+ 2'6'' = + 2'6" =

8.405

61.440

20" Sched. 80 Pipe W (pounds)

760

49,000

250

16,200

17'6"

125

8,000

22' 6"

4,750

10' + 2'6" = 12'6"

15'

(W i s t h e f o r c e required t o r e t u r n t h e pipe i t s precut position. )

6" Sched. 80 Pipe PIPE LENGTH

AND LENGTH

49 APPENDIX B PROPOSAL FOR D!WELOPMENT OF A SPLIT-BEARING-SLEEVE CARRIAGE FOR REMOTE MAD!?TENANCE APPLICATIONS I N NUCLEAR REACTOR SYSTEMS We recommend t h e buil-ding and t e s t i n g of a more r i g i d gear-driven c a r r i a g e t o supplement our present f l e x i b l e horseshoe-shaped f r i c t i o n r o l l e r - d r i v e carriage. The gear-driven c a r r i a g e could be used t o advantage f o r increased torque capacity remote c u t t i n g and beveling work, f o r highest t r a c k i n g accuracy needs, and f o r i n t e r n a l pipe cleaning app l i c a t i o n s . The s u b s t i t u t e c a r r i a g e c o n s i s t s of a s p l i t sleeve which i s supported by s p l i t r o l l e r bearings on each end. A motorized s p l i t - g e a r t r a c k i s attached t o one of t h e end bearings t o o r b i t t h e sleeve about t h e pipe. The s p l i t - s l e e v e c a r r i a g e might a l s o provide a simplified s o l u t i o n t o pipe alignment problems. It i s recommended t h a t a determination be made t o e s t a b l i s h how much i n i t i a l pipe displacement can be withstood by a sleeve supported on s p l i t bearings. This w i l l show whether t h e s p l i t bearing-sleeve can be used f o r remote maintenance pipe c u t t i n g needs f o r some of t h e r e a c t o r s e r v i c e pipe l i n e s . A t e s t program i s suggested to a s c e r t a i n f e a s i b i l i t y , t o seek t h e pipe s i z e l i m i t s f o r which s p l i t - b e a r i n g s a r e capable of t r a n s n i t t i r i g moments, and t o compare t h e non-conventional approach t o more commonly accepted alignment technology based on r e s t r a i n t s attached to loose pipe ends. Maintenance opeyations with split-bearing-sleeve equipment a r e examplif i e d below:

Sk. 1

-&-

Determine where to cut pipe r e l a t i v e t o t h e replacement componentDs p r e f a b r i c a t e d end stu.b ( d i s t a n c e x'); l o c a t e and a t t a c h s p l i t bearing B* t o pipe accordingly ( d i s t a n c e x); bearing B includes a preassembled s p l i t f r o n t bushing guide. (The s p l i t bearings might include a s o f t m a t e r i a l or knurled bushing sleeve t o f i t i n s i d e t h e inner r a c e f o r b e t t e r attachment to t h e pipe and t o make allowance f o r probably out-of-roundness of t h e pipe. Otherwise, one must consider two separate f u n c t i o n a l devices, one t o f i r m l y clamp t h e pipe and one t o c e n t e r t h e bearing on t h e pipe. The l a t t e r could be i n form of on attachment to t h e pipe clamp.) *Stocked Split-Roller-Bearings a r e commercially a v a i l a b l e from t h e Cooper S p l i t Roller Bearing Corporation, Pittsburgh, Pa., and from other bearing manufacturers on s p e c i a l Drder.

50 2.

Sk. 2

I n s e r t t h e lower half of bearing A with a s p l i t gear s e c t o r attached t o t h e bearing f r o n t face i n t o a l o c a t i n g cradle. Position t h e cradle about bearing B. Next, place t h e t o p h a l f of bearing A, with i t s t o p gear section preattached, t o mate t o i t s lower h a l f . Now permanently i n s t a l l bearing-gear assembly A t o t h e pipe. Remove t h e l o c a t i n g cradle.

Sk. 3

I n s t a l l a cradled motor assembly ahead of gear-bearing assembly A. Check t h e adjustment of t h e cradle during t i g h t e n i n g t o ensure f r e e rotat i o n of t h e bearing. I n s t a l l t h e s p l i t sleeve. Test d r i v e t h e sleeved assembly. The s p l i t sleeve contains a l a r g e c a v i t y t o f i t a c u t t e r head module with i t s sawblade,or t h e weld head module with i t s torch. It could a l s o include hosed pressurization, or vacuum exhaust, f o r chip d i s posal o r accumulation. I n s t a l l t h e c u t t e r head and connect t h e o r b i t a l system's power and c o n t r o l cables t o t h e drive gear motor and t h e module insert. (It i s possible t o e a s i l y adapt t h e balance of ORNL's automated o r b i t a l weld-cut system f o r t h i s application. )

51 rr,

Sk. 4

ELEVATION VIEW

I Typical External Heater

Let us assume we have cut through t h e pipe t o remove t h e replacement component and t h a t t h e bearing supported maintenance sleeve assembly i s s t i l l attached. It i s q u i t e l i k e l y t h a t a s h i f t w i l l occur i n t h e piping upon severing each l i n e . This s h i f t would be most pronounced f o r t h e f r e e end of t h e permanent pipe a s t h e component i s u s u a l l y anchored and i t s short stubpipe l o c a t e s t o t h e anchor support. With t h e pipe s h i f t , t h e sleeve may now be placed i n s t r a i n ; i n f a c t , it i s doubtful t h a t t h e sleeve would then be r o t a t a b l e . S t r a i n gauges attached a x i a l l y t o t h e sleeve's e x t e r i o r would be used t o i n d i c a t e t h e magnitude and t h e d i r e c t i o n of pipe s h i f t . Heat could be applied t o t h e permanent piping i n selected locations t o permit s t r e s s - r e l i e v i n g . The building crane could be u t i l i z e d f o r d i r e c t up p u l l , o r i n combination with s l i n g s , pulleys, etc. f o r required pipe movements i n other planes. Eventually, sleeve r o t a t i o n could then be reestablished and f i n a l p r e c i s i o n pipe s h i f t adjustments could then be made likewise a f t e r i n s e r t i n g and observing d i a l gauges attached t o sleeve bosses on each s i d e o'f t h e pipe c u t - l i n e f o r guidance. We could t r a n s f e r pipe s t r e s s concentrations away from t h e pipe cut l o c a t i o n and thereby r e a l i g n t h e pipe ends formed by t h e cut t o assure near concentric pipe alignment f o r t h e stub end of t h e replacement component. The ensleeved s t r e s s - r e l i e f approach which a l i g n s pipe ends p r i o r t o component removal should e s t a b l i s h useable pipe alignment f o r subsequent reassembly. Dangers from banging i n t o (and u p s e t t i n g ) f r a g i l e weld j o i n t contours on t h e pipe ends a r e minimized where t h e pipe f i t u p i s established p r i o r t o removing one of t h e pipe j o i n t members and subsequent re-entry i s with an i d e n t i c a l pipe. The maintenance sleeve i s dissambled from t h e j o i n t p r i o r t o component removal. We would r e s o r t t;o more conventional pipe realigning means i f a sleeve and/or i t s bea:rings a r e permanently damaged a s a r e s u l t of excessive pipe moment f o r c e a c t i o n upon severing t h e pipe.

52 5.

End Preparations and I n t e r n a l Pipe Cleaning

Sk. 5

V M

9a .ak

The regular maintenance sleeve and t h e component, including i t s pipe stub with end bearing 'B', have been removed. Attach an a l t e r n a t e s p l i t sleeve t o t h e remaining bearing ' A ' gear-motordrive while it i s s t i l l i n s t a l l e d near t h e end of t h e permanent i n - c e l l pipe. The a l t e r n a t e sleeve includes i n t e r n a l wideThis sleeve can be b u i l t t o accombearing i n s e r t s i n l o c a t i o n ' C ' . modate t h e ORNL machining head module for preparing a beveled pipe end. As t h i s sleeve i s self-propelled, it may a l s o include provisions for a t t a c h i n g t h e equipment needed for a l l i n t e r n a l pipe cleaning.

53 6.

Reassembly

Sk. 6

(Upper)

Reassembly problems d i f f e r f o r various components and depend upon a v a i l a b l e a x i a l room f o r entry of t h e component with i t s pipe s t u b ( s ) . A guided e n t r y u t i l i z i n g t h e 'B'-bearing tapered sleeve-guide i s pref e r r e d i f space i s available. The s p l i t 'B'-bearing-guide-sleeve combination i s preassembled on t h e replacement component's stub-pipe end while t h e component i s out of t h e c e l l . The s p l i t maintenance sleeve would be r e i n s t a l l e d over the 'A'-bearing p r i o r t o i n s t a l l i n g t h e r e placement component. The component would be f i r s t lowered t o a f i n a l elevation support platform and then scooted i n t o place while guiding t h e pipe stub i n t o t h e funnel end of t h e sleeve. The sleeve would guide t h e pipe stub i n t o i t s proper l o c a t i o n r e l a t i v e t o t h e i n - c e l l pipe

ion clearance

-__

-- -

Sk. 6 (Lower)

For t h e case of only v e r t i c a l access f o r a replacement component, pipe ends would have t o be butted. The cradle assembly scheme described with Sk. 2 would apply.

After assembly of t h e component by e i t h e r scheme, t h e rewelding of t h e pipe ends would be accomplished with t h e weld head module i n s t a l l e d i n t o t h e sleeve cavity.

55 REFERENCE INFORMATION

I OP HALF HOUSING

HALF OUTER RACE

-- HALF CAGE WITH ROLLERS CAGE JOINT “U” CLIPS L__

_-__--’

HALF INNER RACE

--.

1 ,. “+I . -l.-,a

___TWO HALF CLAMPING RINGS

____------- HALF INNER RACE

-d

-----% ~,

/ -

___--.------------------

TWO HALF CLAMPING R i H G j HALF CAGE WITH ROLLERS

CAGE JOINT “U” CLIPS HALF OUTER RACE HALF SEAL BOTTOM HALF HOUSING

PEDESTAL BASE

REFERENCE INFORMATION

PROCEDURE I

Loosen holding b o l t s and remove top h o l f of pedestal and top h o l f of hauzin;. i i i t out r o i i e r c i s a m b l y cnd inner race. Withdraw

cn:rriige

spring steel "U" c l i p s on opposite sides of roller ossombly. Ssporoto halves of rolI*r assembly and put t o one r i d e l o y on c l a m place of pope,. R e m o , s the lour bolts h o l d i n g the clamping collors around the i*i.cr rote mmk* a w e to keep t h e mating halvos of clomplng collrrrs t o j a t h r r . S s p o m t e the halves of the inner race and wmsh thoroughly w i t h

gooJ :leaning solvent and dry w i t h l i n t - f r e e w i p i n g moterial 01 let stond u n t i l completely dry. 1. the same mannmr, c1.m and dry the clamping both halves of the r o l l e r oss.mbly and the outer r o c * . I t i s not n - c e i s o r y 12 remova the outer roc, from the cartridge housing t o claon it. (If e v e . n e c t s s o r y t o remove the outer race, first make sur0 thot all rid. co!lil;s,

Toke h o l f LI r o l l e r assembly, graas. we11 e l l over i f beoring i s t o bo lubricated by grsas., and then ploce on inner rmce and slid. rrrovnd u n t i l i t i s s i t t i n g on the bottom hmlf outer race, w i t h the ends of the cog. flush w i t h the housing j o i n t face.

n i p p i n g - s c r e w s and holding b a c k - s c r e w s whsrs f i t t e d era removed.)

For n o r m a l stmody load sarvic.. the shaft must be of nominal s i z o w i t h i n th. limits of plus 0.000" to minus 0.002", and c y l i n d r i c a l l y true. Clean ond l i g h t l y o i l th- area of the shmft t o receive the inner race and place the t w o halves of the inner rase i n the prop., a x i a l location. T a p the holrss of the inner race u n t i l secure and snug on the shaft. N E V E R H I T T H E R A C E WITH A HAMMER OR OTHER HARD M E T A L L I C TOOL. USE WOOD OR PLASTIC MALLET. There should be a s l i g h t gop o t both a n d l of the h.1v.s of the inner race. Put clamping collars i n place, moking sure they f i t snugly ogoinst the r a c e shouldor. c l a m p i n g

Rsmovo locking pins (2) from soch aluminum t r i p l e lobyrinth r e a l and place sa01 around shaft i n corwct position w i t h r s l o t i o n t o cartridg. groove, and reinsert locking pins. T h e seals, w h m correctly ossembl.d, w l l l g r l p the shaft firmly and r.voIvo w i t h i t but w i l l permit a x l a l m e w men? of the s h o h w h m n.c.asary.

Remove iocking orrmgmment, o l l o r i n g s h a f t t e r e s t .v.nly

in the

baoring.

c e l ! o r i o i n t should overlap the race j o i n t by obout Vi'' t o on E x ponsion Typ. Bearing.. The omount of ovstlap i s oxtremmly important for the fitted clamping c o l l a r of fixed t i p innor races. It w i l l b. noted thar.

Greos. the remaining h a l f r o l l e r ossembly oII over ( w i t h f o i r l y heavy c o o t ) and ploce over exposod part of innev I O C O . R-plase spring "U" c l i p s by l i g h t l y topping into recess.i i n rollet pockets, thus l o c k i n g tho

i s nn air01 on t h i s collar which must coincide w i t h the morkod race ioint. This e n s u r e s the alignment of th. shouldorr of the inner race. Us. locking worhorr under the heods of the clamping collar bolts, ond r t n r t t o tightel, tnom, but before f i n a l tightening of bolts, check a x i a l location of inner rote to mako SUI* i t i s i n th. correct position on the s h a f t so that i t w i l l ba central w i t h the r e s t of the u n i t w h m oss.mb1.d. In cases where o x i o l expansion has to be handled, the inn., roc. i s offsot so that s ( t c r f u l l expansion of the s h d t hos taken ploce, the races and r o l l i n g elements w i l l 011 be central w i t h on. another. A l s o check t o mak. sur* th-t the t w o h o l r e s o f the inner race aro NOT TOUCHING soch other, m d thot the s l i g h t gap i s approximately a q v o l on both sides. The gap i s pu,poroly b u i l t i n t o tho bsoring, and shovld thoro bo N O qap, the s h o h i s vdn'.rsizo w h i c h w i l l rorult in unsatisfactory pwformonco. If the shaft i s within the required limits, the propor omount of gap i s automoticolly present when the clamping collors are f i n a l l y tightnned. Now f i n i s h tig'itening of clomping E O I I O V bolts, using D pioc. of pip. on tho socket w:.nch t o c a k e sure they nro cbrolutmly tight. S s o Torque T o b l s on p,>gs 12. A l l f ~ v rb o l t s should be pullod up evenly when tightening th. i ~ n race ~ r on the shaft. In the sx,pnsion typ. unit, check both clamping rings t o si* t i o t they ore hord against th. race shoulder a l l around. I n rke C O J I of the fixad unit, check the and clomping collar t D make sure i t is hard o y i n i t the shoulder 011 around.

halves of the roller assembly together.

Grms. w i t h the required omount, the inside of top h a l f of cartridge w i t h h o l f out.* r a c e i n position. Make sure the i o i n t s of th. cartridge housing, both t o p end bottom halves, o r e absolutely c h o n beforn apply ing greoss. Place top h a l f of coltridge i n t o p o s i t i o n over oss.mb1.d bearing end sools moking sure thmt j o i n t s match the bottwn half. Us. locking washers on bolts ond tighten up evenly 011 four b o l t s in cortridg-. Moks sura end f o c s r of cartridge are f l u s h when com?let.ly tightend.

Apply a c w t i n g of o i l on the spherical s e a t of the t a p h o l f of the pedestol ond place i n position, but d o not tight." u p bolts.

I f possible,

turn shaft

s l o w l y t w o or three times

t o permit the

cortridg. t o f i n d i t s own olignment so that the logding of the roller. i s evenly distributsd. I f t h i s i s not pessibls, make s u r i tho? cartridge fn:as ore obsolutcly square w i t h the shaft.

1 b i g h t e n up top h a l f of unit. G l r e b o w i n g threa or four shots w i t h c)

P l r c s bottom h a l f of ped.=tal i n position and l i g h t l y o i l the 3 p h . r i c i l scot for tho cortvidge. T h s position of th. bottom h o l f of cartridge w i l l determine on w h i c h sid. of p i l l o w block the greoro f i t t i n g w i l l bo for lubrication. Toke car= t o locat. bottom h o l f of cortridg. s o thot greaa. f i t t i n g i s eosily o c c e s r i b l o . I f th. bearing i s t o be lubricotod by grease, opply the required quontity i n s i d e of the lower h a l f o f the cartridge w i t h the h a l f outer roce i n position and then ploce i n the bottom h o l f of the pedestal. Jnck u p the shaft rlightl; i f t h i s hos not olreody beon don..

S h o u l d further d e t o i l s

required regarding fitting

grease gun t o f i l l the graos. passages s o t h a t noxt time th. b r o r i n g i s gr.0s.d you w i l l b. SUI. that graos. i s g-tting t o the r o l l i n g p a r t s . Use discration when graoslng, according to s p e d and duty. 00 not o v e r f i l l w l t h gnar., otherwise a "Hot B e a r i n g " may result.

O i l Lubricotion. Follow o b o r e instructions except substitute lubri c a t l n g o i l for gr.0~0. O i l level i n bottom h a l f o f cartridge should b. o s outlined under O I L L U B R I C A T I O N on p g . 13.

and lubrication of

t h e becring, pleose contecr

COOPER S P L I T R O L L E R B E A R I N G CORPORATION

1725 Wa.hinglon Road, Pittsburgh, Pennrylvonia 15241

REFERENCES 1. R. W. McClung, Remote Inspection of Welded J o i n t s , ORNL-TM-3561 (September 1971T.

J. S. Culver, Viewing Equipment f o r Use i n t h e HRT Core and Blanket Vessels, OIWL-rn36 (March 1960).

I n t e r n a l Memo, P. P. Holz t o I. Spiewak, "Dry Maintenance F a c i l i t y f o r t h e HRT", Oc-tober 11, 1960.

I n t e r n a l Memo, J. P. J a r v i s t o S. E. Beall, "Use of t h e Dry Maintenance F a c i l i t y f o r HRT Maintenance", May 17, 1962.

5. P. P. Holz, "Remote Maintenance Through Portable Shields", ANS Winter Meeting, Pittsbui?gh, Pa., November 1966, (complete paper a v a i l a b l e from author). 6.

R. Blumberg and E. C. Hise, MSRE Design and Operations Report - P a r t X - Maintenance Equipment and Procedures, ORNL-TM-910 (June 1968).

Theodore Rockwell 111, Reactor Shielding Design Manual, Naval Reactors Branch, Division of Reactor Development, USAEC, Chapter 6, TID-7004 (March 1956).

R. C. Robertson, MSRE Design and Operations Report, P a r t I, Descript i o n of Reactor Design 9ORNL-TM-728 (January 1965).

I n t e r n a l Memo, B. D. Draper and E. C. Hise t o Distribution, "Remote Maintenance Procedures Report", November 26, 1959.

lo.

I n t e r n a l Memo, A. A. Abbatiello t o Distribution, "Optical Tooling f o r t h e MSRE", June 4, 1962.

11.

Correspondence, E'. P. Holz t o Distribution, "Trip Report t o BONUS, (Boiling Nuclear Superheater Power S t a t i o n ) , Rincon, Puerto Rico, September 25, 1967 t o October 13, 1967','.

12.

J. P. Maloney, e t a l , Repair of a Nuclear Reactor Vessel, DP-1199, Dupont Savannah River Laboratory (June 1969).

13.

D. S. Ritchie, -.e t a 1 "Remote Controlled Viewing f o r t h e Dragon React or Main Pres sur e Ves sell: Atomic Energy E s t ablishment Winf r i t h , England, Dragon Froject Report 228, October 1963.

14.

R. N. Duncan and D. L. Richardson, F i n a l Report on BONUS Reactor Boiler Fuel Element InsDection. October 5 ' t o 12. 1967. ReDort APED5392 (Class I ) , Nuclear Energy Division, General E l e c t r i c Company, - _ San Jose, California, November 1967.

15. Conceptual Design of a Surveillance and In-Service Inspection System f o r t h e Reactor Vessel Fast Flux Test F a c i l i t y , Phase B Report, Chapter 3, Southwest Research I n s t i t u t e , San Antonia, Texas, Dec. 31, 1969, (report prepared f o r t h e P a c i f i c Northwest Laboratory by t h e B a t t e l l e Memorial I n s t i t u t e ) .

16.

Conceptual Design of a Surveillance and In-Service Inspection System

for t h e Primary Piping and Components, Fast Flux Test F a c i l i t y , Chapter 3, Phase C Report, Southwest Research I n s t i t u t e , San Antonia, Texas, January 16, 1970, (report prepared f o r t h e P a c i f i c Northwest Laboratory, B a t t e l l e Memorial I n s t i t u t e ) . 17.

I n t e r n a l Memo, P. P. Holz t o Distribution, "Miniature TV Camera Manipulator", ( f o r HRT viewing), November 26, 1959.

18.

R. L. Moore, Closed Circuit Television Viewing i n Maintenance of Radioactive Systems a t ORNL, ORNL-TM-2032 (November 1, 1967), (paper a l s o presented t o t h e ANS Winter Meeting, Pittsburgh, Pa., Nov. 1966).

19.

M. W. Rosenthal, e t a l , The Development S t a t u s of Molten-Salt Breeder Reactors, ORNL-4812, Chapter 1 2 (August 1972).

20.

I n t e r n a l Memo, P. P. Holz t o Distribution, "Some Miscellaneous Maintenance Tools Used t o Manipulate Loose Objects i n t h e HRT Core", Nov. 17, 1959.

21.

I n t e r n a l Memo, P. P. Holz t o Distribution, "Additional Miscellaneous Maintenance Tools Used i n t h e HRT Core", September 26, 1960.

22.

"ORNL Remote Maintenance Tool Catalogue No. 58", June 1960. (Compilat i o n of t o o l s and procedures by t h e Mechanical Department, Engineering and Mechanical Division. )

23.

P. P. Holz, F e a s i b i l i t y Study of Remote Cutting and Welding for Nuclear Plant Maintenance, ORNL-TM-2712 (November 1969).

24.

R. F. Gilmore, Open- and Closed-Loop Closure Remote Cutting and Welding Evaluation, B a t t e l l e Northwest Laboratory Report BNWL-1303 (UC-38), May 1970.

25.

P. P. Holz, The ORNL Automated O r b i t a l Pipe Welding Systems, ORNL4830

I -

- qm---*=--

26.

G. M. Goodwin and P. P. Holz, Automated O r b i t a l Welding of Type 304 S t a i n l e s s S t e e l Pipe with t h e Astro-Arc System, O m - T M Report ( d r a f t i s s u e d i s t r i b u t e d for comments J u l y 1972. )

27.

"Automated Welding", Film a v a i l a b l e from t h e ORNL Film Library, 1971.

28.

Pennsylvania Advanced Reactor Project - Layout and Maintenance, WCAP 1104 and 1105, Vol. IV, P a r t s 1 and 2, Westinghouse E l e c t r i c Corp. and Pennsylvania Power and Light Company, March 1959, ChaFters 3, 4, and 5 (chapter 4.2 for Alignment Discussions).

29.

Molten-Salt Reactor Program Semiannual Progress Report f o r Period Ending Feb. 28, 1969, ORNL-4396, Chapter 5-MSBR Design (Aug. 1969).

30.

J. R. Tallackson, p r i v a t e communication t o R. W. McClung, Jan. 29, 1971.