RRFM 2009 Transactions - European Nuclear Society

particles. A flat leveling work is then done with a blade. The U-Mo power and Al powder with a uniform
layer are dropped in to the container fitted with a plug at the bottom of the container. This kind of
charge is repeated until the purposed height is achieved. The container is closed with a plug and
charged in the pressure-sintering chamber of the MTS. A pressure-sintering was done for 4 hours at
480 °C with a 2 ton pressing force. The pressure acting on the sample is estimated to be about 440
kg/cm 2 . After a sintering, the sample is cut into several pieces and then observed using an optical
microscope. Some density measurements by immersion methods were done for examining the
homogeneity.
Fig. 2. A jig for dispersing U-Mo large particles with placing the particles into the openings of a sieve
Al powder
Ring
U-7Mo powder
Fig. 3. A pressure-sintering system available for MTS
3. Results and Discussion
Fig. 4 shows a compacted and sintered lump for the mixed powder by passing them through a multistack
of sieves for a proper quantity of U-Mo powder and an equivalent Al powder, alternately. U-Mo
particles are observed to be more densely dispersed at some local regions. This segregated
phenomenon is presumed to be induced by an asymmetry during the vibration of the sieves. Also 12
sievings for a homogeneous distribution seem not to be enough. The sintered lump was easily broken
through a more densely U-Mo particle dispersion region due to a weak sintering bond. Especially the
bottom part of the mixed lump showed that the U-Mo particles were severely and densely dispersed
by the strong kinetic energy from the accelerated downward flowing velocity.
Fig. 5 shows a pressure-sintered lump for the mixed powder by arranging U-Mo the large particles by
placing them into the openings of a sieve. The lump seems to be sintered soundly. No pores can be
seen. The shell of the pressure-sintering jig was observed to be atom-bonded with the sintered fuel
meat. It was impossible to separate the fuel meat from the jig. Therefore the sample with the jig was
cut into 9 pieces for 9 sample parts. An observation for particles dispersion was done as shown in
Fig.5.
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