ORNL-1771 - Oak Ridge National Laboratory

ANP QUARTERLY PROGRESS REPORT
material causing the trouble, it gives a well-exposed
surface for chemically removing the lost traces of
fuel, it permits a cut to he made through the bottom
plug of the capsule so that an examination can be
made for crevice corrosion, and it leaves nearly
one half of the capsule for further and more com-
plete study, if desired. After the fuel is removed
chemically without attacking the metal wall, the
specimen can be electroplated so that the fuel-
metal interface will not be rounded during the
meta I lograph ic pol is hing opsrat ion.
The stability of the fluoride fuel under irradiation
and the extent of the corrosion of the container by
the fuel are determined, in part, by analyzing
samples of the irradiated fuel for the concentration
of the original components and for the maior con-
stituents of the container materio!. The fuel
samples are put into solution within the rnaster-
slave hot cells and ore then transferred to the
Analytical Chemistry Division for analysis. Work
on the necessary transfer shields has been coordi-
nated with the design and construction of the lead
harrier being provided in the analytical chemistry
hot cells to improve transfer conditions and to
reduce personnel exposure.
Two transfer carriers weighing 1150 Ih each and
giving 2 in. of lead shielding have been constructed
and are now in use. Each carrier holds four 30-mI
bottles that are held in place by spring clamps.
A motor-driven decapper for removing the bottle
cap and a remotely controlled pipet that can be
lowered into the bottle are provided. The bottles
may be inserted into the carrier within the cells
and can be left in the carrier during all sample
removal operations. The whole unit may then be
returned to the hot cells for reuse.
Two lead storage units weighing 450 Ib each and
giving 3 in. of lead shielding were also built and
are available for use when all the transfer carriers
are in use, The lead storage units have a capacity
of four 50-ml volumetric flasks and can be loaded
within the master-slave calls.
ANALYSIS OF IRRADIATED FLUORlDE
FUELS FOR URANIUM
M. 7. Robinson G. VI. Keilholtr
Solid State Division
One of the regular steps in in-pile static cor-
rosion testing of fluoride fuels has been the anal-
ysis of the irradiated fuel for uranium. However,
there are several maior problems connacted with
136
sampling operations, described previously,lt2
which have never been fully resolved. In the
cutting and drilling operations it is possible for
small chips of metal, either froin the capsule or
the drill, to get into the fuel sample. To minimize
this possibility, drills used recently have been
carefwlly honed to remove burrs. A search is also
being conducted for new drill materials. In the
early use of the present sampling technique,’ it
was possible for dirt from the hot cells to inad-
vertently enter the fuel samples during cutting
and drilling. Phis possibility has been minimized
in thc newer equipment.2 The transfer operations,
in several of which the salt is exposed to con-
taminotion from hot cell dirt, pieces of rubber
from manipulator grips, and the like, are all possible
sources of contamination. The observation of
opaque material, in some cases in large amounts,
during petrographic examination of irradiated fuel
samples3 indicates that at one or the other of the
stages discussed above foreign material may have
been introduced into some of the samples. Such
contaminants moke the resulting uranium analyses
I‘
IOVb.”
The samples obtained for chemical analysis
have, at times, been very small, often being as
small as 10 mg. They are weighed in tared weighing
bottles on a conventional chain-type analytical
balance, and, since they are so small, the precision
of weighing is about t4% instead of the usual
negligible amount. This lack of precision results
in an abnormally high uncertainty in the uranium
analyses. After being weighed, the samples are
dissolved and the solutions are made up to volume
in the hot cells. The resulting solutions often
contain as little as 500 ppm of uranium. Such
high dilution is undesirable, since the titer may
change appreciably on long standing. It seems
reasonable to conclude that the uncertainty in
uranium analyses may be as high as +5% or more,
even for the usually precise (52%) potentiometric
titration. An increase of ten times in sample size
(easily attainable) would restore this technique
to its normal precision.
’J. G. Morgan et ai., Solzd State Diu. Semzann. Prog.
Rep. Aug. 3, 1953, ORNL-1606, p 40.
2C. C. Webster and J. G. Morgan, Solzd State Diu.
Semzann. Prog. Rep. Feb. 28, 1954, ORNL-1677, p 27.
3G. D. White and M. T. Robinson, Solzd State Dzv.
Srmrat711. Prog. Rep. Feb. 28, 1954, ORNL-1677, p 28.