ORNL-1771 - Oak Ridge National Laboratory

Two UF3-bearing capsules and two UF4-bearing
capsules in this series will be irradiated for six
weeks each to amplify the apparent differences in
the effects of UF, and UF, on Inconel. It is inter-
esting to note that the UF, capsule in this series is
the first one run in the MTR and the first one run at
800 w/cm3 or greater that has not shown a tendency
toward intergranular corrosion. Whether the differ-
ence between earlier UFq-bearing capsules and
the one in this series is due to improved temper-
ature control or to uranium concentration effects
will be determined by additional irradiations.
FlSSlON PRODUCT CORROSION STUDY
C. C. Webster G. W. Keilholtz
Solid State Division
Steps are being taken to perform corrosion tests
out-of-pile with irradiated fuel in order to separately
study the effects on lnconel of fission-product
concentration and of lnconel irradiation.
A water-cooled facility for irradiation of solid
fuel was constructed and has been installed in
position C-46 of the LITR. The unperturbed
thermal flux is on the order of 4 x loT3. An lnconel
tube has been constructed for casting solid bars
of fuel 1 in. long and 0.1 in. in diameter. The
solid bars of fuel will be transferred to lnconel
capsules for irradiation. The capsule has been
constructed so that it can be welded shut without
the bars being melted and can be reopened in the
hot cell for transfer of the fuel to the corrosion
test capsule.
Upon completion of an out-of-pile heating cycle,
the test capsule will be opened in the hot cell.
The fuel will be drilled out and divided into three
samples: a portion for petrographic study to detect
any oxidation or reduction, a portion for mass
spectrographic study to determine burnup, and
a portion for chemical analysis of the fuel. The
capsule will be slit on the remote slitting machine
described below for a metallographic study. At
least two concentric samples can be taken from a
capsule of this size by remote means.
FACILITIES FOR HANDLING IRRADIATED
CAPSULES
C. C. Webster G. W. Keilholtz
Solid State Division
PERIOD ENDING SEPTEMBER IO, 7954
capsule the corrosion pattern was not consistent
over the length of the capsule but appeared to be a
function of the longitudinal temperature gradient.
One method of obtaining a longitudinal section
would be to grind away half of the capsule on the
milling machine. However, by such a method it
would be difficult to ascertain that a section
through the diameter of the capsule had been made.
Also, the milling operation would create a serious
contamination problem.
The method being used consists in passing the
capsule longitudinally by a 10-mil-thick silicon
carbide fine-grit wheel and thus slitting the cap-
sule down the center. The capsule is clamped
into a vise and then fed into the wheel by means of
a mechanical linkage which is to be replaced by a
variable-speed motor and a contact cutoff switch.
When the capsule is put into the gripping adapter
in the vise, it is automatically aligned so that the
wheel will cut in the plane of a diameter through
the capsule. By making different gripping adapters,
various sizes of tube can be slit lengthwise. Thus
far the apparatus has been used on only MTR-type
fluoride fuel capsules (O.lOO-in.-ID and 0.200-in.-
OD); it has worked very satisfactorily.
Since the abrasive wheel has a rubber base, it
must be kept cool. The area around the cut must
also be kept cool to prevent any high thermal
sfresses from affecting the corrosion results. The
wheel and specimen are over a tray and are covered
with a splash shield so that a liquid coolant can
be used. The coolant level is always kept above
the bottom edge of the abrasive wheel so that by
cutting upward into the specimen the coolant is
carried into the cut; therefore the specimen need
not be in the coolant. Carbon tetrachloride is
used as the coolant because it does not react with
the fluoride fuel at high temperatures. It is forced
into the tray from outside the hot cell through
Tygon tubing by air pressure, The tray and splash
shield are attached to the mount far the vise and
they move with the specimen.
Once installed within the hot cell, the remotely
operated tube-slitting machine can be used with
ease in cutting longitudinal sections from various
sizes of tubing. Thicker abrasive wheels can be
used for heavier walled twbing. The advantages of
this method of cutting are that it permits visual
It was observed metaIIograpliicaIly, in some observation of the amount of fuel left on the tube
cases, that when several transverse sections walls, it permits observation of constrictions
were taken from a single fluoride fuel corrosion without the necessity of removing or disturbing the
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