THE RADIOCHEMISTRY OF PLUTONIUM - Sciencemadness.org

TABLE IV- 27. Slope of the Dependence of the Distribution Coefficient on the
Concentration of the Added Reagent for Mixtures of Phosphorous Esters, Amides,
Alcohols and Ketones with TTA. 41
Ion Valence Synergism region Antis ynergism region
Th Iv +1 -2
Am, Pm DI +2 -4
Uo. VI +1 -2
Fused Salt Systems
Some research has been done on the solvent extraction properties of
actinide and other elements in relatively low-temperature eutectic mixtures of fused
salts because of their potential use in homogeneous power reactors. Gruen et al. 154
give a general discussion of otidation states and spectra of actinides in LiN03-KN03
mixtures, and indicate that TBP extracts a number of elements efficiently from the
eutectic mixture. Isaac @.20’ determined the distribution coefficients between
CO(H), M{III) (where M is a trivalent actinide or lanthanide), Np(V) and NP(VI), and
U(VI) in this eutectic mixture (MP 120”C) and dilute solutions of TBP in a mixture of
polyphenyls at 150”C. In general, the distribution coefficients were a factor of 102 or
103 higher than the corresponding concentrated aqueous nitrate solutions. The dis-
tribution coefficients all showed the same TBP concentration dependency as in acqueous
solutions, indicating that the extraction mechanism is the same, the higher distribution
being due to the increased salting-in effect. The effect of added chloride was to lower
the distribution coefficients. Quadrivalent actinides would be expected to behave
similarly, although none was determined.
Borkowska ~.
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used a KC1- CUC1 eutectic mixture at 180° to study the ex-
traction of Pu, U, and Am by solutions of TBPJ TOA, and HDBP in diphenyl. For TOA
they find the extractability is in the order
DPu(rrr) < ‘Am(III) < ‘U(III) ‘< ‘U(IV)”
In this system a maximum in the D vs concentration of TOA curve occ~s at ’40%
TOA, where Du(ml -3. TBP shows similar behavior. The maximum in this case is
at 67% ‘Bp’ ‘here %(IV) -50” ‘or ‘(IV)’
HDBP is similar to TBP.
Moore28’ measured the distribution of a number of ions between the immiscible
salt pair LiC1-AlC14-K+ at 650°C. It is perhaps not proper to speak of this system as
extraction; however significant distributions (Kd > 1 on a mole fraction basis) in favor
of the LiCl phase were noted for UC14 (for which SnC12 was added as a reluctant),
PUC14, and FeC13. The ratio of the distribution coefficients for tri- and tetravalent
actinides was > 40. Since the SnC12 used to stabilize the U(IY) also reduced Pu to
the trivalent state an easy separation is possible in this system. Similar results were
290
obtained by -Moore and Lyon for the system KC1-A1C13-A1. In this case the
separation factor for U from Pu and Th is approximately 100, while that for Th from
Pa is up to 800.
Cafasso et al. 73 determined the partition coefficient of a number of elements,
including U and Pu. between liquid lead and zinc at 703”C. The results (Zn/Pb) are
Pd:600, U:21.5, Pu:7.3, Ce:3.4, Sr:O.05,
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