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UP3/UF4 ratio would be possible.
DMSR operation possibly may result.
69
knm.rer, a more subtle constraint on
The lanthanide trifluorides are only moderately soluble in w~lten
LiF-BeP2-ThP4-UF4 mixtures; if more than one such trifluoride is present,
they crystallize as a solid solution of all the trifluorides on cooling
of a saturated melt. Though not definitive, there is evidence that the
actinide triflusrides (including W3> might also join in such solid solu-
tions. If so, the total (lanthanide plus actinide) trifluorides in the
end-of-life reactor might possibly exceed their combined solubility.
The solubilities of PuFq (Ref. 29) and CeF3 (Ref. 31) have been cape-
fully determined im %~F-B~F~-T~F~ (72-16-12 mole %> and em be eo~~ihfered
to be moderately well known in DMSR fuel. According to Baes et al 929
the solubility of PuF3 in the LiF-BeF2-ThFq melt at 565°C (the minimum
temperature anticipated within the BMSR fuel circuit) is 1.35 mole %. The
solubility of CeP3 umder the same conditions appears to be very slightly
smaller ( 1.3 mole %) .29 9 3 1
are not well known.
trifluorides ( including CeF3 ) have been shown83 to be considerably smaller
and to vary with some more and some less soluble than CeF3. As a reason-
able approximation (~bviously, many additional data are needed), the
solubility of the lanthanide-actinide trifluoride solid soluti~n may be
assumed to be near 1.3 mole 2.
Solubilities of the other pertinent fluorides
In L12BeF4, the solubilities of several lanthanide
From Table 9, the BMSR fuel at end-of-life will contain some 11.404 x
185 moles of uranium isotopes and 3.64 x PO3 moles of transuranium iso-
topes. The end-of-life inventory of lanthanide plus yttrium isotopes will
be near 4.7 x 104 moles. If 5X of the uranium is present as U F and ~ if
all transuranic and lanthanide species are assumed to be trivalent, the
end-of-life reactor fuel will contain about 5.77 x 104 moles of trifluo-
rides.
fore, would contain about 1.1 mole % of trifluorides. The solubility of
the combined trifluorides likely would not be exceeded within the reactor
circuit, but additional solubility data are needed to make this point
certain.
'Fke DMSR system (with about 5.3 x IO6 moles of fluorides), there-