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OAK RIDGE NATIONAL LABORATORY operated by UNION CARBIDE CORPORATION for t h e
NUCLEAR DIVISION
U.S. ATOMIC ENERGY COMMISSION ORNL - TM-
3763
.
ESTIMATED BEHAVIOR OF TITANIUM IN MSBR CHEMICAL PROCESSING SYSTEMS L. M. Ferris
NaTlCL This document contains information of a preliminory noture and was prepared primarily for internal use a t the Oak Ridge National Laboratory. It i s subject to revision or correction and therefore does not represent a finot report.
UTMN W THIS DOCUMENT is UULIMITUI
.
..- . ,
I
-
.
*’.
I
6
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.
ORTJL- TM-3 763
C o n t r a c t No. W-7405-eng-26
CHEMICAL TECHNOLOGY D I V I S - I O N C h e m i c a l D e v e l o p m e n t Section B
ESTIMATED BEHAVIOR OF TITANIUM I N MSBR CHEMICAL PROCESSING SYSTEMS
Lo M, F e r r i s NOTICE
A P R I L 1972
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, cornpleteness or usefulness of any information, apparatus, product or process disclosed, or represents that its use would not infringe privately owned rights.
OAK RIDGE NATIONAL LABORATORY O a k Ridge, T e n n e s s e e 37830 operated by UNION CARBIDE CORPORATION for the U.S, ATOMIC ENERGY COMMISSION
iii CONTEN'IS Page Introduction p p . . . 0 . UD. F i . 0 . . . o . 0 c 0 0 . . U . . . ., . E . 0 2. Thermodynamic Treatment Hastelloy 30 Leaching of Titanium from Titanium-Modified FuelSalt ., + I v a e I' LI o q i G G 5 ,. .* .* of 4, Estimated Behavior of Titanium During Fluorination 1.
5. 6. 7. a, 9.
. 0 0 . m. . o . . e D into MSBR v e .* c = MSBR
4
(I 5 e 6 . 9 , 13 Acknowledgments , Q E o e o 1 c v . 0 . e n e a i( D . . e . c . 13 References p C.O cI *..* ,.+ y Y.,.l 7..0 u *.a 0 14 FuelSalt n d ( L 0 o 0 r o c D ..E s =, . ..* o . . e D Behavior of Titanium in Reductive Extraction Processing . 5 = Estimated Behavior of Titanium During Hydrofluorination . .- + Behavior of Titanium in Oxide Precipitation Processes 0 o s o
1
ESTIMATED BEHAVIOR OF TITANIUM IN MSBR CHEMICAL PROCESSING SYSTEMS Li, M, Ferris
ABSTRACT Available thermodynamic information was used to estimate the behavior of titanium in a fluorination--reductive extraction flowsheet for processing MSBR fuel salt. It was first shown that titanium is likely to be leached from a titaniummodified Hastelloy N containment vessel into a LiF-BeF2TnF4-UF4 fuel salt at 600"~.The primary reaction would probably be 3 m4(d) + Ti(&,stelloyl= TiFz(d) + 3 uF3(d]a The estimates showed that, during f uorina ion, TiF3 wou d be oxidized to TiF4. A large fraction of the TiF4 would be expected to volatilize during fluorination, Any titanium not volatilized by fluorination would be present in the salt that enters the reductive extraction step. Experimental data confirmed the prediction that titanium would be practically quantitatively extracted from the salt in this step. It was also shown that titanium can be transferred from a bismuth phase to a salt phase by oxidation with gaseous HF, and that HF is not a sufficiently strong oxidant to convert TiF3 to TiF4. KEY WORDS:
"MSBR, *Processing, "Modified Hastelloy N, *Titanium, fused salts, fluorination, reductive extraction process,
1. INTRODUCTION Hastelloy N (68% Ni--l@
Mo--fi Cr--5% Fe) was used' for the con-
tainment vessel and other metallic components in the Molten-Salt Reactor Experiment (MSRE). to 2 w t
%
However, use of a modified Hastelloy containing up
titanlum is being considered' for molten-salt breeder reactors
(MSBRS) since an alloy of this type is expected to be more resistant to radiation embrittlement than Hastelloy N,
In the event that a suttable
alloy is developed, it is of interest to know what extent titanium will be leached from the alloy into the molten salt and, if the extent of
2
l e a c h i n g i s s i g n i f i c a n t , how t i t a n i u m w i l l behave i n an MSBR chemical p r o c e s s i n g system.
The p r e s e n t r e f e r e n c e flowsheet2*
f o r chemically
p r o c e s s i n g an MSBR involves, f i r s t , f l u o r i n a t i n g t h e s a l t t o remove uranium as
uF6 and, then, c o n t a c t i n g t h e r e s u l t a n t s a l t wi'ch l i q u i d
bismuth c o n t a i n i n g about 0 002 mole f r a c t i o n each of l i t h i u m and thorium t o remove p r o t a c t i n i u m by r e d u c t i v e e x t r a c t i o n .
The rare e a r t h s remain
i n t h e s a l t during t h e s e p r o c e s s s t e p s and a r e removed i n a subsequent
metal t r a n s f e r p r o c e s s
Protactinium and o t h e r elements e x t r a c t e d i n t o
bismuth w i l l subsequently be t r a n s f e r r e d t o a s a l t phase by hydrof l u o r i n a t i o n o f t h e bismuth i n t h e presence of t h e s a l t .
The purpose
of t h i s r e p o r t i s t o estimate t h e behavior of t i t a n i u m both i n t h e r e a c t o r system and i n t h e v a r i o u s chemical p r o c e s s i n g s t e p s .
The es-
timates, which were made using t h e g e n e r a l thermodynamic t r e a t m e n t developed by B a e ~ ,could ~ be compared, i n some cases, d i r e c t l y w i t h experimental r e s u l t s . 2.
THERdODYNAMIC TREATMENT
&es4 h a s summarized a l a r g e amount of e q u i l i b r i u m d a t a i n v o l v i n g molten LiF-BeF2 s o l u t i o n s i n terms of s t a n d a r d h a l f - c e l l p o t e n t i a l s f o r which + e- = F - ( d ) + l / 2 H (g> E" i s d e f i n e d as zero a t a l l temperatures; ( g ) and ( d ) denote gaseous
m'
( E " ) referred t o t h e r e a c t i o n HF
and d i s s o l v e d s p e c i e s , r e s p e c t i v e l y .
The s t a n d a r d s t a t e f o r most s o l u t e s
i s t h e h y p o t h e t i c a l unit mole f r a c t i o n i d e a l s o l u t i o n i n LiF-BeF2
33.3 mole $ ) + The exceptions a r e LiF, BeF2, Be2+,
+ L i , and
(66.7-
F-; t h e
a c t i v i t y of each o f t h e s e s p e c i e s i s d e f i n e d as u n i t y i n t h e r e f e r e n c e
s a l t composition.
With LiF-BeF2
(66.7-33.3 mole %) as t h e s t a n d a r d
s t a t e , t h e a c t i v i t y c o e f f i c i e n t s f o r s o l u t e s a r e u n i t y , whereas YL~= F '*5 and yBeF2 =
3:
The p o t e n t i a l f o r a complete r e a c t i o n i s o b t a i n e d by a l g e b r a i c a l l y adding t h e n e c e s s a r y h a l f - c e l l r e a c t i o n p o t e n t i a l s .
For example, a t
600째C t h e e q u i l i b r i u m o f pure c r y s t a l l i n e chromium metal w i t h U4+ d i s solved i n LiF-BeF (66.7-33.3mole %) can be expressed as t h e a l g e b r a i c 2 sum of t h e two h a l f - c e l l r e a c t i o n s :
3
The standard free energy change for reaction (3) is:
A G O
-ZFE" = ( - 2 . 3 ~ ~log ) K
=
,
in which z is the number of' faradays, F is the Faraday constant, R is the gas constant, T is the absolute temperature, and K is the equilibrium For our purposes, we will assume that E" values (and K's derived
constant.
from them) are the same in LiF-BeF2-ThF4 (72-16-12mole %), the composition of the MSBR carrier salt, as they are in LiF-BeF2 (66,7-33.3mole %)
All
estimates included in this report were made at 600"~. The electrochemical behavior of titanium species in molten fluoride salts has been studied voltammetrically by Manning.' Manning'
From this work,
estimates the following at 6 0 0 " ~ :
Ti3'
+ 3/2 Ni
Ti4+
+
(e)
1/2
+
=
Ti
3/2 Ni2+
=
Ti3+ + 1/2 Ni2+
, *
E"
=
-1.8 ? 0.1 V
(5)
;
E"
=
0.2 10.05 V
(6)
;
E"
=
0,368 V
;
E"
=
-1.43 -t 0.1 V
Combining Eq, (5) with 3 / 2 Ni2+
+ 3
e-
=
3/2 Ni
(e>
yields Ti3+
+ 3
e- =
Ti
(4
.
(8)
4 Similarly, from Eqs. (6) and (7) we obtain: Ti3+
Use of Eqs.
=
Ti4+
-
+ e
;
E"
=
-0,568f O,O5 V
.
(9)
(8) and ( 9 ) , along with values of E" for other appropriate
half-cell reactions, allows estimation of the behavior of titanium in
8
molten-salt reactor system and in the associated chemical processing plant.
3. LMCHING OF TITANIUM FROM TITANIUM-MODIFIED HASTZLLOY INTO MSBR FUEL SALT The question of whether titanium will be leached from a modified Hastelloy into an MSBR fuel salt at a significant rate is a difficult one to answer since the overall rate of leaching would depend both on the rate a t which titanium diffuses to the surface of the a l l o y and on the
4+ is
oxidizing power of the saltr Of the species present in the salt, U the most likely oxidant for titanium.
The reaction would probably be: E"
for which log K
=
=
0.286 10.1 V
,
4-941 1.7, since the reaction producing Ti4+, given
below, is thermodynamically much less favorable: Ti
(4+ 4 U4+
=
4 U3+ + Ti4+
;
E"
=
-0.282 1 0.15 V
e
(11)
-6,5 f 3. Comparison of the E" for reaction (10) with that of reaction (3) confirms earlier predictions" The value of log K for reaction (11) is
that titanium would be much more reactive than chromium to oxidants in the fuel salt.
Despite the fact that the thermodynamic driving force
for the leaching of titanium from a modified Hastelloy N is much greater than that for the leaching of chromium, it is nearly impossible to estimate the thermodynamic activity of titanium at the surface of the alloy. Not only will the concentration of titanium in the bulk alloy be less than one-third of that of chromium (about 2% vs 7%) but also the diffusion coefficient for titanium in Hastelloy N is about a factor of 10 lower
t h a n t h a t f o r chromium,,7
Thus, t h e t i t a n i u m a c t i v i t y a t t h e H a s t e l l o y
s u r f a c e a t a given t i m e should be considerably lower t h a n t h e chromium activfty.
Only d i r e c t experimentation can show whether t h e a c t i v i t y i s
low enough t o o f f s e t t h e l a r g e d r i v i n g f o r c e r e p r e s e n t e d by t h e 3'
for
r e a c t i o n (10). An experimental study conducted s e v e r a l y e a r s ago by DeVan and provided evidence t h a t t i t a n i u m might be leached from H a s t e l l o y N
Evans'
a t a h i g h e r r a t e than chromium,
Mo c o n t a i n i n g up t o 8 w t
%
I n t h e i r s t u d i e s , c a s t a l l o y s of N i - - l %
of an a d d i t i v e were made i n t o t u b i n g from
which thermal convection loops were f a b r i c a t e d t o NaF-LiF-KF-UF4
(11,2-45.3-41.0-2.5
These l o o p s were exposed
mole %) f o r 500 and 1000 h r .
The
hot-zone temperature of each loop w a s 815"c, and t h e cold-zone temperature
was 6 5 0 " ~ . A f t e r each t e s t , t h e s a l t w a s chemically analyzed f o r t h e additive.
The c o r r o s i o n s u s c e p t i b i l i t i e s ( i o e,
t h e a d d i t i v e s i n c r e a s e d i n t h e following o r d e r :
t h e amount l e a c h e d ) of i r o n < niobium <
vanadium < chromium < t u n g s t e n < t i t a n i u m < aluminum.
With t h e excep-
t i o n of t u n g s t e n and niobium, t h e s u s c e p t i b i l i t i e s i n c r e a s e d i n t h e same o r d e r as d i d t h e thermodynamic s t a b i l i t i e s of t h e f l u o r i d e compounds of t h e r e s p e c t i v e elements,
It i s s i g n i f i c a n t t o n o t e t h a t t h e r a t e of
l e a c h i n g w a s much h i g h e r d u r i n g t h e 500-hr p e r i o d t h a n during t h e 1000-hr period.
This r e s u l t s u g g e s t s t h a t n e a r l y s t e a d y - s t a t e c o n d i t i o n s were
e s t a b l i s h e d w i t h i n t h e f i r s t 500 h r ,
4,
ESTIMATED BEHAVIOR OF TITANIUM DURING FLUORINATION OF MSBR FUEL SALT
I n t h i s and t h e ensuing s e c t i o n s , it will be assumed t h a t t i t a n i u m i s p r e s e n t i n measurable c o n c e n t r a t i o n s i n MSBR f u e l s a l t t h a t e n t e r s
t h e chemical p r o c e s s i n g p l a n t ,
A s noted i n S e c t , 1, t h e f i r s t chemical
p r o c e s s i n g s t e p i s f l u o r i n a t i o n of t h e s a l t t o remove uranium as UF6. F l u o r i n a t i o n should r e s u l t i n t h e q u a n t i t a t i v e o x i d a t i o n of Ti3+ t o T i
9
E o = 2-30 zk 0.1 V
4+
:
6
for which log K
=
13 .t 1. Reaction (12) can also be written as:
Since the boiling point of TiF4 is only about 284"C,'
it is probable that
a significant fraction of the titanium would be removed from the salt as TiF during fluorination and would accompany evolved UF6 to the fuel
4
reconstitution step. An example of the inherent tendency of TiF4 to volatilize from fluoride melts is provided by the experience of Manning
et a1.I'
They found that, after K2TiF6 was added to molten LiF-NaF-KF
or LiF-BeF2-ZrF4 solutions at 55OoC, TiF4 volatilized from the melt and condensed on cooler parts of the system,
5.
BEHAVIOR OF TITANIUM IN REDUCTIVE EXTRACTION PROCESSING
Any titanium not removed during fluorination will be present in the salt that enters the reductive extraction step2'
for protactinium isolation.
In this step, the salt is contacted with a liquid bismuth stream containing about 0,002 mole fraction each of lithium and thorium, Protactinium, residual uranium from the fluorination step, zirconium, and some of the noble-metal fission products are transferred to the bismuth phase in this step. The extraction into liquid bismuth of a solute MF,,
present in l o w
concentration in molten LiF-containing salts, can be expressed as the general reaction: MFn(d)
+
Li (Bi)
= M(Bi)
+
n LiF
(a) '
in which (d) and (Bi) denote the salt and bismuth phases, respectively, This reaction is the sum of the half-reactions
ne ne- = M +
nLi=nLi +ne-
7
'v
The s t a n d a r d p o t e n t i a l f o r r e a c t i o n p o t e n t i a l s f o r r e a c t i o n s (15) and
(14), i . e .
(16), i s
t h e a l g e b r a i c sum of t h e
r e l a t e d t o t h e equilibrium
c o n s t a n t as f o l l o w s : n M "LiF
a
K =
n
= e
(nFE" /RT)
all a MFn L i
,
i n which a i s a c t i v i t y and t h e o t h e r symbols a r e as d e f i n e d p r e v i o u s l y . By l e t t i n g a
Ny (where N i s mole f r a c t i o n and y i s an a c t i v i t y co-
=
e f f i c i e n t ) and by d e f i n i n g t h e d i s t r i b u t i o n c o e f f i c i e n t f o r a given
DM =
element as
NM/Nm
n
, it
was shown by F e r r i s "
that
With LiF-BeF2 (66.7-33.3 mole %) as t h e s a l t phase, k e s 4 d e f i n e d yLiF
1.5 and ym
n
log
=
=
Thus,
1.
(nFE0/2.3RT)
=
+ n l o g yLi - n l o g ( 1 . 5 ) - l o g yM
;
(19)
o r , at O'OO"C,
log
4
=
n(5.773)Eo
-
0.176n
+
n l o g yLi
-
l o g yM
(20)
I n o r d e r to c a l c u l a t e l o g KM f o r a given element, we obviously need
values of t h e a c t i v i t y c o e f f i c i e n t s yLi and 7, t h a t are r e f e r r e d to t h e pure metals as t h e s t a n d a r d s t a t e , i n a d d i t i o n t o t h e a p p r o p r i a t e E" values.
Values of E" f o r a l a r g e number of s o l u t e s are a v a i l a b l e from
B a e ~ ;t h~o s e f o r titanium s p e c i e s were e s t i m a t e d by Manning.'
Values of
yLi and yM f o r s e v e r a l s o l u t e s were t a k e n from t h e l i t e r a t u r e and were summarized by F e r r i s et a1.l'
These v a l u e s of y ~ and i yM a r e f o r v e r y
d i l u t e s o l u t i o n s o f M i n l i q u i d bismuth.
No information on t h e a c t i v i t y
coefficient of titanium in liquid bismuth could be found in the literature. Thus we will assume that yTi is equal to yZr. Workers at Brookhaven National Laboratory obtained13 yZr = 0.012 at 700째C. If we assume that the excess E chemical potential pZr = (2.3RT) log yzr does not change throughout the temperature range 60O-70O0C, we can calculate log yzr
=
log Y T = ~ -2.1
*1
at 600"c. From the above sources, we obtain E" = 1.224 f 0.1 V at 600"c for the reaction
1
and, using Eq. (20), estimate log K ~ i 3 += 10.4 f 2 with LiF-BeF2 (66.7-
33.3 mole %) as the salt phase. Table 1 compares this value and the values for other selected solutes with values obtained experimentally using LiFBeF2-ThF4 (72-16-12 mole %) as the salt phase.
The values of log KZr and
1
log Ku are those measured earlier by Ferris et a1.,14 whereas the value 1
of log K T ~ was determined in the course of the present work.
Note that
the values of log Ki obtained for LiF-BeF2-ThF4 (72-16-12 mole % ) are
.
somewhat higher than those calculated for LiF-BeF2 (66.7-33.3mole %)
1
Table 1. Comparison of Values of log KM Calculated for LiF-BeF2 (66.7-33.3 mole 4) with Those Determined Experimentally at 600"c for LiF-BeF2-ThF4 (72-16-12mole %) log KM log YM
E"
0)
Calculated for LiF-BeF2 (66.7-33.3 mole %)
Measured with LiF-BeFz-ThF4 (72-16-12mole %)
M
n
Li
1
-4.13
Zr
4
-2.1
1.226
13.2
1
14.7 f 0.3
U Ti
3 3
-3.87
1.143
11.1 f 0.2
-2.1
1.224
10.7 f 1 10.4 f 2
-
-
-
13.6 f 0.4
I
9 1
The experiment to determine the value of log KTi was conducted using the general procedure outlined previously. l4
This experiment was initiated
by simultaneously hydrofluorinating, in a molybdenum crucible, LiF-BeF2ThF4-CsF (71.7-15.9-12-0.4 mole
5 ) and bismuth containing dissolved titanium.
This treatment resulted not only in the transfer of the titanium to the salt phase but also in the removal of oxide from the system. With the system at 600째c, thorium was added in increments to effect the reductive extraction of titanium from the salt into the bismuth phase.
At least 24
hr was allowed for equilibration after each thorium addition before filtered samples of the respective phases were removed for analysis.
The salt and
metal samples were analyzed for titanium by a colorimetric method; the lithium concentration in the metal phase was determined by flame photometry. Data from this experiment are summarized in Table 2,
and a plot of log
D T ~ vs log DLi is shown in Fig. 1. The scatter in data points precludes determination of the value of n.
However, thermodynamic considerations
(Sect. 6) strongly indicate that n should be 3 (and not log Kii3+ point.
=
4).
The value of
13.6 f 0,4 is the mean of the values calculated from each data
This value is somewhat higher than the estimated value (Table 1);
however, the agreement is good, considering the uncertainties in the thermodynamic quantities used.
Furthermore, the experimentally determined
value of log K$i3+ is consistent with the results of an earlier experiment by Moulton et a1.,15 which indicated that log K;i3+
should be greater than
1
log Ku3+. In their experiment, it was found that titanium dissolved in bismuth did not effect detectable reduction of either U3+ or Pa4+ from LiF-BeF2-ThF4 (72-16-12 mole %) at
600 to 7'00째C.
During the chemical processing of MSBR fuel salt, it appears certain that titanium, if present in the salt entering the reductive extraction step, will be quantitatively extracted into the bismuth stream along with protactinium and other easily reduced species.
6* ESTIMATED BEHAVIOR OF TITANIUM DURING HYDROFLUORINATION In the reference MSBR chemical processing method,2 9
the bismuth
phase from the reductive extraction step used to isolate protactinium would be treated with an HF-H2 mixture in the presence of a salt phase
10
Table 2. Distribution Coefficients and Values of log K.;li3+ Obtained at 600"c from Measurements of the Equilibrium Distribution of Titanium Between Molten LiF-BeFz-ThF4-CsF (71.7-15.9-12-0.4 mole %) and L i q u i d Bismuth Solutions f
5 Sample
lo6 NLi
10 DLi
DTi
log KTi3f
3 6 7 8 9
8.73 16.0 18.7 16*6 27.4
1.218
10
20.8
13.3 13.6 13.6 13.9 13.4 13.8
11
20.5 33.7 65.0 28.3
0.038 0.435 0 695 1.06 1..31 1.76 2-33 3.88 5.94 1507
12
13
14
2.226
2.604 2.310 3.822 2.898 2* 856
4.704 9.072 3.948
9
14.0
13.6 12,9
14.4
11
ORNL
D W G 72-3210
;
I .(
0.
0
0.0 I
I
2
3
4 5 IO' D L ~
6
7 8910
Fig. 1, Equil.ibrium Distribution of Titani.um Between Molten LiF-BeFZ-ThF4-CsF ( 71 7-15 .9-12-0.4mole % ) and Liquid Bismuth Solutions at 600"~.
12
to oxidize protactinium and other elements present in order to effect their dissolution in the salt phase.
-c-
Since titanium could be one of the
elements initially present in the bismuth phase, its behavior during hydrofluorination is of interest. The reaction of primary interest is:
3 m(g) + Ti(c)
=
3/2 H2(g)
+
;
TiF3(d)
E"
=
1.43
,
f 0.1 V
(22)
for which log K = 25 2 2 at 600째C. Despite the fact that the activity coefficient for titanium in liquid bismuth is of the order of
thermo-
dynamic considerationsledus to expect titanium to be easily hydrofluorinated from a bismuth phase into a molten fluoride salt phase.
This expectation
was confirmed (at least under one set of conditions) in the initial phase
of the experiment described in Sect. 5. In this experiment, bismuth and LiF-BeFz-ThF4-CsF (71.7-15.9-12-0.4 mole %), contained in a molybdenum crucible, were simultaneously hydrofluorinated at 600"c to remove oxides from the system, After sparging with purified argon, sufficient titanium metal was added to give a titanium concentration of 2500 wt ppm in the bismuth phase.
Analysis of a sample of this phase confirmed that all the
titanium was dissolved in the bismuth.
The two-phase system was then
sparged at 6 0 0 " ~ for about 20 hr with HF-H2 (50-50 mole % ) *
Analyses of
the respective phases showed that all of the titanium had been transferred
to the salt phase during the hydrofluorination period. Gaseous HF does not appear to be a sufficiently strong oxidant to convert Ti3+ to Ti4+; consequently, hydrofluorination of a bismuth-salt system should leave the titanium in the salt as TiF
3'
This conclusion
is based on the following estimate at 600"~; Ti3+
+ HF(g)
for which log K
=
=
1/2 H2(g)
-3.3
k
0.3.
+
Ti4+
+ F-
EO
=
-0.59
0.05
v
Since the activity coefficients for the
solutes are defined as unity, the expression for the equilibrium constant for reaction (23) will give:
Expressing the partial pressures in atmospheres, we find that, even with 4+ nearlypureHF as the gas phase, the equilibrium concentration of Ti is extremely low as compared with the Ti3+ concentration:
1
0,0004
10
0 002
100
OtO05
a
7. BEHAVIOR OF TITANIUM IN OXIDE PRECIPITATION PROCESSES Oxide precipitation is being studied as an alternative to fluorination-reductive extraction for isolating protactinium and subsequently removing uranium from MSBR fuel salt.16 Pa2o5;17
9
18
Protactinium would be precipitated as consequently, the salt would have to be treated with an oxidant
such as HF to convert Pa4+ to Pa5+ prior to the precipitation step. As shown in Sect. 6, HF is not a sufficiently strong oxidant to convert Ti3+ to Ti4+ No information could be found in the literature on the behavior
.
of Ti3'
in molten fluoride salts containing dissolved oxide.
Experimental
work would be required to determine this behavior.
Some information on the apparent solubility of T i 0 2 in fluoride melts is available.
Mailen''
had indications that Ti02 was less soluble than
U02 in LiF-BeF2-ThF4 (72-16-12mole %) at 600"c. Similarly, Bamberger and BaesZ0 equilibrated Ti02 with LiF-BeF2-ThF4 (72-16-12 mole %) at 600"c, The equilibrium titanium concentration in the salt was about
40 w t
ppm,
which is lower than the solubility of U02 in this salt.
8. ACKNOWLEDGMENTS The author thanks J. F. Land for conducting the experimental portion of this work.
Analyses were provided by the group of W, R. Laing, ORNL
Analytical Chemistry Division,
14
9. REFERENCES 21. Appl. Technol. 8(2),
1-76(1970). 2. L, E. McNeese, MSR Program Semiann. Frogr. Rept. Feb. 28, 1971,
1. H. E. McCc
ORm-4676, p. 234.
3- W. L. Carter, E, L. Nicholson, and L. E. McNeese, MSR Program Semiann. Progr. Rept. Aug. 31, 1971, ORNL-4728, p. 179. 4. C. F. Baes, Jr., "The Chemistry and Thermodynamics of Molten Salt Reactor Fuels," in Nuclear Metallurgy, Vol. 15, ed. by P. Chiotti,
c0~~-690801 (1969), p. 617.
5. D. L o Manning, ORNL, personal communication, Nov. 19, 1971. 8(2), 137 (1970). 6. We R. Grimes, Nucl. Appl. Technol. 7. H. E. McCoy, ORNL, personal communication, Feb. 22, 1972. 8. J. H. DeVan and R. B. Evans 111, "Corrosion Behavior of Reactor Materials in Fluoride Salt Mixtures," in Corrosion of Reactor Materials, Vol. 11, p. 557, IAEA, Vienna, 1962.
9- C. D. Hodgman (ed.), Handbook of Chemistry and Physics, 36th ed., p. 614, Chemical Rubber Publishing Co., Cleveland, 1954. 10. D. L. Manning, F. R. Clayton, and G. Mamantov, in Anal. Chem. Div.
Research and Development Summary (Jan.
-
Dee. 1971, ORNL-CF-72-l-ll
6, 1972), p. 14.
11. L. M. Ferris, Some Aspects of the Thermodynamics of the Extraction of Uranium, Thorium, and Rare Earths from Molten LiF-BeF2 into
Liquid Li-Bi Solutions, ORNL-TM-2486 (March 1969). 12.
L. M. Ferris, J. C, Mailen, and F. J, Smith, "Estimated Free Energies of Formation of Some Lanthanide and Actinide Halides at 600"-800"c Using Molten Salt-Liquid Metal Distribution Coefficient Data," J. Inorg, Nucl. Chem. 34,
491 (1972).
13. R. H. Wiswall, Jr., and J. J. Egan, Thermodynamics of Solutions of Actinides and Fission Products in Bismuth, BNL-6033 (1962).
14
e
L. M. Ferris, J. C. Ma,ilen, J, J. Lawrance, F. J. Smith, and E. D. Nogueira, J. Inorg. Nucl. Chem. 32, 2019 (1970).
15
0
D. M. Moulton, J. H. Shaffer, and W. R. Grimes, MSR Program Semiann. Progr. Rept. Feb. 28,
1970, ORNL-4548,
p.
176.
16. M. J, Bell and L. E. McNeese, MSR Program Semiann. Progr. Rept. Feb. 28, 1971, ORT\TL-4676, p. 237. 17. R. G. Ross, C. E. Bamberger, and C. F. Baes, Jr., MSR Program Semiann. Progr. Rept. Aug. 31, 1970, ORNL-4622, p. 92. 18.
0. K, Tallent and F. J. Smith, MSR Program Semiann. Progr. Rept.
Aug. 31, 1971, ORNL-4728, p.
19. J. C. Mailen, 20.
ORNL,
196,
unpublished results.
C. E. Bamberger and C. F. Baes, Jr., MSR Program Semiann. Progr. Rept. Feb. 28, 1970, ORNL-4548, p. 140.
a
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