RRFM 2009 Transactions - European Nuclear Society

inside of a compaction die by blowing air through the nozzles in the holes of the plate. Then an
equivalent proper quantity of aluminum powder was loaded over the uniformly dispersed U-Mo
particles and an evening work for a flat level can be done with a straight bar. In an actual experiment in
this way the manufacturing of a plate with very fine holes for seizing U-Mo particles has been
investigated to be almost impossible or very expensive for the estimated cost. Secondly a uniform
dispersion of large U-Mo particles by passing them through a multi-stack of sieves was taken into
account. In an experiment 10 sieves were stacked so that the height of the stacked sieves was
relatively high such as about 25 cm. When some U-Mo powder was input into the top sieve, the large
U-Mo particles with a high density and very spherical shape dropped freely with an accelerated
velocity for passing then through the many sieves due to their spherical shape and smooth surface
and then hit the bottom firmly. The U-Mo particles exhibited a tendency of penetrating into the
accumulated aluminum powder. The 3 rd method for a uniform dispersion of large U-Mo particles is a
regular arrangement of U-Mo large particles by placing the particles into the openings of a sieve. In
this paper, for the 2 nd and 3 rd ideas, some experimentation has been carried out and then some of the
obtained results are described.
2. Experiments
Regarding the idea of a uniform dispersion for large U-Mo particles by passing them through a multistack
of sieves, experimental equipment was designed as shown in figure 1. 12 sieves were taken for
enough dispersion from 12 distributions by hitting each sieve net. The sieve mesh is larger than the U-
Mo particle size. The container placed under the stacked sieves is a kind of die available for a
compaction. The 10 stacked sieves are vibrated for efficiently passing not only U-Mo but also Al
powder through them. But the receiving container is fixed without any influence from the movement of
the sieve vibration for the two steadily accumulating kinds of powders. One layer of a close-packed
dispersion for U-Mo particles is taken for one charge. The quantity of one charge for U-Mo is input into
the top sieve and then the equivalent quantity of Al powder for the target fuel meat composition is input
in turns. The blended powder is compacted with a 15 ton force, which corresponds to a pressure of 1.6
ton/cm 2 on the compact.
Fig. 1 Experimental equipment for uniform dispersion of large U-Mo particles by passing through multistack
For the 3 rd idea of a regular arrangement of U-Mo large particles by placing the particles into the
openings of a sieve screening net, a jig was designed and manufactured as shown in figure 2. This
system is much simpler than the above method of passing the particles through a multi-stack of sieves.
A sieve screening net was taken with a little larger opening size of the sieve than the U-Mo particle
size. The screening net was obtained by cutting it out from a suitable size of sieve. The bottom of the
sieve screening net was assembled with a moving plate for blocking the regularly situated U-Mo
particles. The jig was designed so that the loaded powers can be pressed and sintered under
pressure.
A pressure-sintering system available for MTS was designed, manufactured, and then installed in the
MTS equipment as shown in Fig. 3. A proper quantity of U-Mo powder, for situating the U-Mo particles
in all the sieve screen openings, is loaded and a spreading work is done for situating all of the particles
into the openings of the sieve. After checking for the right situation of all the U-Mo particles in the
openings, an equivalent quantity of Al powder to U-Mo powder is charged over the arranged U-Mo
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