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point marked with a cross is the value of 2 ’
O(1-i)
found earlier by equilibrating metallic beryllium
with Si-Bi amalgams. Its distance from the line in
this experiment may be the result of slightly in-
creased lithium activity at higher coiicentration
‘XLi(Bi) - 0.161. The line marked “Argonne” is
for lithium calculated from the data of Foster
and Eppley ’ on the excess chemical potential of
Li in Bi. The rather small uncertainty here probably
does not matter much in the separation
process, but it is important, in preparing the electromotive
series, to refer all potentials to the same
lithium or beryllium potential. The potentials at
600°C measured in this experiment are .. 1.89,
-1.81, and -1.46 for Li, Be, and Ce respectively.
The extraction coefficients for the reaction are
given in Table 12.3. This method of presentation
shows more clearly than the potentials the substantial
decrease in extraction with rising temperature.
The difference between this value of Q at 600°C
and that reported earlier by Shaffer13 is mainly due
to his use of 2.3 rather than 3 as the exponent.
The extraction equilibria look very favorable for
using this process in MSX-1II fuel reprocessing. Recovery
of 7Li froni the bismuth will be helpful and
should not be difficult. A peiplexing problem
which has occurred frequently is the apparent loss
of total reductant species during the course of the
extraction. The extent of this loss is not easy to
measure because of uncertainties in the lithium
analyses, but averages 25 to 50% of the lithium
added. We think we have eliminated the possibility
that the loss is due to extraneous reactions
such as lithium volatilization, dissolution of Li,
Re, or Ei3- in the salt, or formation of solid beryllium
or beryllides. In the Zr-U separation, the
usual experiniental technique was changed to minimize
the possibility of air coming in the access
ports (normally filled with hot helium) during additions
or sampling. The reductant loss was cut
sharply to -,10%, which is within the accuracy of
the measurements. In another expeiiment we observed
a substantial increase in oxide content over
the initial value; because of probable BeQ precipitation,
the amount of oxygen added could not be
.......... ~..
.~
12
M. S , Foster and R. Eppley. Chnm Engr Serniann
Progr. Repi July-Dec 1963, ANL6800, p. 405..
13 J. H. Shaffer, MSIi Program Semrann Progr. liept
Feb 28, 1966, OKNL-3936, p. 144.
156
Table 12.3. Extraction Coefficient for Cerium
Extraction into Bismuth
XCe(rn)
~-
xce(s)
-
Q X;.i(rn)
0 T (-c)
9 1 x 108 496
4 0 Y 108 545
8 7 x lo7 600
2.1 x 107 697
2.1 x 105 817
determined. A few back oxidations with a meas-
ured aiiiount of BiFJ have given more or less 100%
efficiency, indicating that no unknown reduced
species takes part in the reoxidation step. It
seems, therefore, that at least a substantial part of
the reductant loss is due to air entry and can be
eliminated by improved experimental techniques.
Since there is no evidence that any other reduction
process is going on, we do not feel that this reduc-
tant balance anomaly in the laboratory experiments
will have any important bearing on the process
when it is put on a practical scale.
UCTlVE EXTRACTION OF CEWaUM
FROM LiF-BeF, (66-34 MOLE %) INTO
Pb-Si EUTECTIC MlXTblRE
W. J. ~ ~ u n t ’ ~ w. E Hull’
J. H. Shaffer
Current investigations on liquid-liquid extraction
as a method for reprocessing the MSBR fluel are directed
toward the use of bismuth-lithium iiiixtures
for renioving fission products froni the reactor fuel
solvent. A complementary program will survey
other metal phase extractants for possible adaptation
in the reprocessing iilethod. This proposed
experimental program will treat the distribution of
cerium, for reference purposes, between I,iF-BeF2
(66-34 mole %) and various molten metal mixtures
14
ORAU summer student from University of Mississippi.
15
Consultant, University of Tennessee.