RRFM 2009 Transactions - European Nuclear Society

AN INVESTIGATION ON A HOMOGENEOUS BLENDING FOR LARGE
PARTICLE U-MO AND AL POWDERS BY A SIEVING-THROUGH
METHOD
C.K. KIM, J.M. OH, C. G. JI, J.M. PARK
Innovative Nuclear Fuel Development, KAERI
Daedeokdaero 1045, Yuseong, Daejeon, 305-353, Korea
G.H. CHOI
Chungnam National University
220 Gungdong, Daejeon 305-764, Korea
ABSTRACT
In KAERI a large U-Mo particle dispersion fuel has been under development due to a
smaller specific interface area and more inter-particle space in connection with solving an
interaction problem in a high low enrichment U-density research reactor fuel. A difficulty in
obtaining a homogeneous dispersion of large particle U-Mo particles in the Al matrix of a
fuel meat occurred as an obstacle. Efforts for solving it have been made by applying
various methods, which are manually regular arrangement of large U-Mo particles in the
holes of one plate by suction air, large U-Mo particles by passing them through a multistack
of sieves, and a regular arrangement of large U-Mo particles by placing the
particles into the openings of a sieve. Among them a regular arrangement of large U-Mo
particles by placing the particles into the openings of a sieve was investigated to meet an
acceptable dispersion homogeneity with a simple work. The variations of the 9 measured
values are less than 6 %. The limit of the U-235 homogeneity for the fuel meat rod of
HANARO fuel is +/- 8.5 %. When the mixed powder is extruded, it is expected that the
homogeneity of the extruded fuel meat rod would be improved. If the method and
experimental result is applied to the use of a large U-Mo particle powder for a rod type of
fuel, extrusion work would be reduced from 5 times to only one time.
1. Introduction
In KAERI a large U-Mo particle dispersion fuel has been under development due to a smaller specific
interface area and more inter-particle space, which enables a good thermal conductivity in spite of a
thick interaction formation, in connection with solving an interaction problem in high low enrichment
U-density research reactor fuel [1]. Some of the above fuel specimens were irradiated in the KOMO-3
and the PIE results were revealed to be very promising [2]. However, it is very difficult to obtain a
homogeneous dispersion of large particle U-Mo particles in the Al matrix of a fuel meat by some of the
common blending methods. Two kinds of powders of U-Mo and Al have extremely different densities
as well as particle sizes, which act as adverse effects for a homogeneous blending. Some common
blending methods of on off axis rotating drum mixer, a spex mixer, and a V-shape tumbler mixer are
considered not to be available for the above large U-Mo particles powder and Al powder [3].
Previously a repetitive extrusion was used in order to obtain a homogeneous dispersion in fabricating
fuel meats of large U-Mo particles dispersions in the Al matrix for some irradiation tests. In this work an
acceptable uniform dispersion of larger U-Mo particles of about 300 μm in diameter required more
than 5 extrusions. In order to overcome this difficulty unusual blending methods have been taken into
considerations as follow. Firstly a consideration was taken on a manual regular arrangement of large
U-Mo particles in the holes of one plate with a suction of air through fine nozzle for picking particles
and turning over the plate with picked U-Mo particles. The picked particles were discharged into the
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