ORNL-1771 - Oak Ridge National Laboratory

ANP QUARTERLY PROGRESS REPORT
10. ANALYTICAL STUDIES OF REACTOR
The primary analytical problem continues to bs
the separation and determination of trivalent and
tctravalent uranium in both NaZrF,. and NaF-KF-
LiF-base fuels. A successful potentiometric titra-
tion of UF, in molten NaZrF, with metallic zir-
conium was accomplished by means of polarized
platinum electrodes, The observed end point
occurred at a weight of titrant which corresponded
to one-half an squivolent of zirconium metal per
mole of UF,. This stoichiometry indicates reduc-
tion of UF, to a mixed oxidation state. Polaro-
giaphic studies of uranium fluorides in reactor fuels
dissolved in molten ammoniirni formate at 125OC
were initiated. Preliminaiy experiments reve"aled
that tetravalent uranium was not reduced at the
dropping-mercury electrode. Molten ammonium
formate appears to be o useful solvent for fluoride-
base fuels containing various oxidation states of
uranium. The conversion of UF, to UCI, in fluoride
fuels was shown to be quantitative when the fuel
was heated with boron trichloride at 40O0C for
90 min. Trivalent uranium fluoride is converted to
UCI, under these conditions. The solubility of
UF, in NaAICI, was found to be 18 mg/g at 200OC
os contrasted to o solubility of UF, of less than
1 mg/g. Molten NaAICI, is expected to dissolve
telkavalent uranium selectively from the fuels.
Calibration measurements have been completed
on the apparatus for the determination of oxygen as
metallic oxides in reactor fuels. The reaction in-
volver thc hydrofluorination of the oxide and
measurement of the increase in conductivity of
liquid HF as a function of the water formed,
Investigations were also made on the oxidation
of UF, with oxygen at elevated temperatures. At
30OoC, UF, is converted quantitatively to UF,
and UO,. The mechanism of the oxidation of UF,
with oxygen is being studied. An oxide residue of
about 11% of the original material was found when
UF, was heated in oxygen at 3OOOC for 2 hr.
An improved method for the determination of
lithium in NaF-KF-LiF-base fuels WQ5 developed,
The chloride salt is extracted with 2-ethylhexano1,
and the chloride is titrated in the nonaqueous
mediums,
148
c. D, Susan0
Anal yt ical Chemi stry Di vi si on
J. M. Warde
Metallurgy Division
Studies were also made on the solubilities of
potassium, TZI bi d iom, and cesi urn tetrapheny i borate s
in various organic solvents to ascertain differential
solubilities. The feasibility of a spectrophoto-
metric titration of fluoride in NaF-KF(RbF)-Li F-
base materials by decolorization of zirconium or
aluminum complexes was investigated. Determina-
tion of the concentration of oil in helium was mode
by absorbing the hydrocarbons in petroleum ether
and weighing the residue obtained after evaporation.
It was found that prior bleeding of the line effec-
tively eliminated contamination by oil.
ANALYTBCAL CHEMISTRY OF
REACTOR MATERBALS
J. c. White
Analytical Chemistry Division
Research and development were continued on the
problem of determining UF, and UF, in NaZrF,-
and NaF-KF-LIF-base reactor fuels. A number of
new opproachss to this problem were investigated,
including redox titrations of the fluoride mixtures in
the molten state, for which polarized platinum
electrodes were used, and polarographic studies of
fluoride mixtures in molten ammonium formate.
Work was continued on the determinotion of oxygen
in fluoride fuels and on the determination of alkali
metals and fluoride ion in NaF-KF-LiF-base ma-
terial s,
Determination of Oxygen in Fluwide Fuels
A. S, Meyer, Jr. J. M, Peele
Analytical Chemistry Division
The apparatus for the determination of oxygen as
oxides in fluoride fuels, which was described
briefly in a previous report, ' has been constructed.
A schematic drawing of this apparatus is shown in
Fig, 10.1.
The hydrogen fluoride purification still, which
was fabricated from mild steell is equipped with
a 24 x 1 in. packed column with an estimated
efficiency of 25 theoretical plates. Conductivity
'A. S. Meyer, Jr. and J. M. Peele, ANP Quar. hog.
Rep. lune IO, 1954, ORNL-1729, p 110.