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I
id
PERIOD ENDING JUNE 10, 1956
and iodide chromium. The iodide chromium was given in Table 2.2.3 that the particular alkali
obtained from Battelle Memorial Institute and con- fluoride used in combination with ZrF, influences
tained 10 ppm or less of oxygen. This pure chro- the reaction markedly. The different alkali fluorides
mium was not hydrogen-fired, and therefore a corn- affect the activity of the UF, to varying degrees.
parison of the blanks obtained for this metal with The activity of the CrF, is also influenced through
those found for the electrolytic chromium (used in complexing of the GF, by both the alkali fluoride
all previous studies), which was hydrogen-fired and the ZrF,. Studies will be made shortly with
under the usual conditions, should demonstrate the an RbF-ZrF, mixture as reaction medium to comeffectiveness
of the hydrogen treatment. The plete the alkali fluoride series.
chromium values of 190 and 250 pfim obtained for Studies of the reduction of UF, by iron at 600
the unfired iodide chromium and the hydrogen-fired and 800OC with LiF-ZrF, and KF-ZrF, (both 52-48
electrolytic chromium, respectively, suggest that mole %) as reaction mediums were made at UF,
the hydrogen-firing is successful (unfired electro- concentrations of 12.0 wt % (3.9 mole 96) for the
P
lytic chromium gave a blank of 900 ppn). Evidently LiF-ZrF mixture and 10.6 wt % (4.0 mole %) for
the major portion of the blank arises from oxidizing the KF-trF, mixture. The data are presented in
materials (H,O and HF) present in the LiF-ZrF, Table 2.2.4. As may be seen from the data the
.,
mixture.
The equilibrium chromium concentrations and the
equilibrium iron concentrations are not significantly
changed by replacing LiF with KF. It may be
equilibrium constants calculated from mole frac- noted that somewhat smaller values result at 800OC
tions for the reaction of UF, with chromium in the than at 600OC for both solvents. These values
various solvents are presented in Table 2.2.3 for also are in good agreement with those found when
comparison. The effect of varying the NaF-to-ZrF, NaF-ZrF, (SO-SO mole %), NaF-ZrF, (53-47 mole
ratio in the various NaF-ZrF, mixtures on the %), and NaF-ZrF, (59-41 mole %) were used as
chromium concentration has been shown and dis- the reaction mediums. The iron values obtained
.) cussed previ~usly.~ The values are included in by using NaF-LiF-ZrF, (22-55-23 mole %) as the
Table 2.2.3 for comparison with the KF-ZrF, and
LiF-ZrF, data. It is evident from he values
solvent fell in the same range, but in this case the
values were slightly larger at 800OC than at 60'C
W
TABLE 2.2.3. EQUILIBRIUM CONCENTRATIONS AND CONSTANTS FOR THE REACTION
Cro + 2UF4$2UF3 + CrF, IN VARIOUS SOLVENTS
Temperature "F4 G
Solvent (OC) (mole %) (PPd Kx*
LiF-&F4
(52-48 mole %I
No F-Zr F,
(SO-SO mole %)
'*
NaF-ZrF,
(53-47 mole %)
NaF-ZrF,
(59-41 mole %)
KF-tF,
(52-48 mole %I
Na F-Li F-Zr F,
(2255-23 mole W)
NaF-Li F-KF
(1 1.5-46.5-42 mole %)
600 4.0
800 40
600
800
dl
41
600 4.0
800 40
600 3.7
800 3.7
600
800
600
800
3.9
3.9
2.5
25
600 2.5
800 2.5
*K, = XiF3 XcrF2/Xcr X:F,, where X is concentration in mole fractions.
2900 7x loA
3900 7 x 10-3
2250 4 x IO:,
2550 sx io-,
1700 1 x IO-,
2100 3 x 10-4
975 1.4 x 10'~
1050 1.6 x 10-5
1080 2 4 ~
1160 3.2~ 10-5
550 1 x 10-6
750 4x 104
1100
2700
95