Carbide Fuel Development: Phase 1 Report, Period of May 15 to September 15, 1959 Page: 48
viii, 100 p., some folded : ill. ; 28 cm.View a full description of this report.
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4.4.2 Hot Pressing
One hot pressing was made in a graphite mold at 18000C, resulting in a pellet with a bulk den-
sity of 12.6 g/cc. X-ray analysis indicated that the UC2 content had increased moderately due to
intimate contact with the graphite mold. An aluminum nitride mold has been made for further hot
pressing experiments.
4.5 METALLOGRAPHY
Carbide pellets were sectioned.by a diamond wheel, with the sample and wheel submerged in
cutting oil. Oxidation of the sample during the cutting operation was prevented this way, and the
pyrophoricity hazard was reduced. Specimens were mounted by casting and setting a polyester
resin around them. The procedure was used because it is simple, and does not require an el-
evated temperature.
Specimens were polished with 600 grit SiC paper, diamond paste Grades 15, 6, and 1, and
finally a grade containing diamond particles 1 p.or smaller. Cutting oil was used as a lubricant in
all cases, and the specimens were kept out of contact with air and moisture as much of the time
as possible. Eventually, the PuC-UC specimens will be polished in a helium atmosphere. Photo-
micrographs of stoichiometric UC and UC containing nitrogen are shown in Figs. 4.5 and 4.6.
4.6 COMPATIBILITY
In order to study possible fuel-cladding interactions under conditions similar to those which
would prevail in an actual fuel element, a series of diffusion capsule tests will be made. In these
capsules the carbide fuel material will be held in contact with various cladding materials at
650 to 800*C for periods up to several months. Following this, the capsules will be sectioned
and the carbide-cladding interface examined by metallography, x-ray diffraction, and autoradio-
graphy. The interaction of uranium carbide with type 304 stainless steel, 2/% Cr-1% Mo steel,
Inconel-X, niobium, Zircaloy-2, Hastelloy-B, and beryllium will be studied initially.
The diffusion capsule design is shown in Fig. 4.7. The carbide and cladding materials are
held in contact by means of the stainless steel insert. Continued contact at elevated temperatures
is assured since the stainless steel has an appreciably higher coefficient of thermal expansion
than the Inconel container. The diffusion capsules are ready for assembly.
4.7 THERMAL CYCLING TESTS
The effect of thermal cycling on fuel carbides containing excess amounts of uranium metal
will be studied, to see whether or rot the uranium metal additions have any deleterious effects
on the dimensional stability of the material. The pellets will be sealed under vacuum in small
Inconel capsules and then cycled between 540 and 1100 C. The specimens will be wrapped with
tantalum foil to prevent interaction between the carbide and capsule.
In order to achieve more rapid cycling than possible by simply allowing the specimens to heat
and cool with the furnace, the furnace is kept at a constant temperature and the capsules moved
in and out of the hot zone. This is accomplished automatically by means of an Inconel carriage
attached to a solenoid-actuated air cylinder. The solenoid responds to the signals of a Wheelco
temperature controller which in turn responds to the signals of a control thermocouple located
in a well of the capsule being cycled. The equipment has been constructed and set up.48
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Bolomey, R.; Lazerus, S.; Sapir, J.; Sofer, G.; Steinmetz, H.; Strasser, A. et al. Carbide Fuel Development: Phase 1 Report, Period of May 15 to September 15, 1959, report, October 15, 1959; Washington D.C.. (https://digital.library.unt.edu/ark:/67531/metadc502678/m1/58/: accessed July 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.