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would be expected to have an equilibrium quotient (0) of
55
where the brackets indicate mole fractions of the aissoivea species, H
only 2% of the uranium Were prese1I8: as UF39 the Patio of PuF3bPuP4 Would
be near 2-5 X IO4, and, to sustain a PuF3/PuFk ratio of 1, only about b
part TJF2 per million parts UF4 could be tolerated. Clearly, unless very
oxidizing conditions are maintained in the melt, the plutonium is essen-
tially all PU3+.
The solubility of PuF3 in LiP-BeFz-ThFq (92-16-12 mole x> has been
measured in two laboratories. 29330 Bamberges et a129 show the solubility
of Pup3 in m~le X (%puF3) to be given by
log SpuQ = (3.01 0.06) - (2.41 -%- 0.05) x (IOOO/T) *
with a heat of sol~ti~n (AH,) of 46.8 f 1,O kJ/mole (k1.008
mole). If so, the solubility of PuF3 at 565"C, the likely minimum tem-
perature within the BMSW circuit, should be near 1.36 mole %. This value
is nearly identical (as is the heat of solution) to that obtained by
Barton et for ~ e in ~ the 3 same solvent.
gave significantly lower values; for example, at: 565°C that study would
suggest that SpU~3 should be near 1.1 ~l~le 2.
done is undoubtedly much higher than is required for its rase in a DMSW,
However, as described in a later section, difficulties possibly could
ultimately result from the combined solubflities of a number of trifluo-
rides that f ~ m solid solutions.
0.237 ked/
ow ever, the Indian study30
The solubility of PuF3
Given reasonable W,/~P, ratios, americium, curium, ealifomfm, and
probably neptunium also exist as trifluorides in the welt.
No definitive
studies of their solubilities in EiF-BeF2-ThF4 melts have been made. Such
studies are needed, but their individual solubilities certainly will pr~ve
to be far higher than their concentrations in DMSB fuel.
Our knowledge of the thermodynamics of molten LiF-BeF2-ThF4 soiu-
tions appears adequate to guide the necessary development studies, but
considerable research ana development (as well 8s data analysis) renain