Fabrication and characterization of silicon carbide inert matrix fuels through a polymer precursor route.

摘要

Plutonium management is a crucial issue for the nuclear industry since it is an unavoidable by-product of the well established uranium fuel cycle. Inert matrix materials are proposed as a matrix material to carry the plutonium fuel so that plutonium can be transmuted in nuclear reactors. Silicon carbide is a promising inert matrix candidate material because of its low neutron absorption cross section, high thermal conductivity and high temperature stability. The drawback of using silicon carbide as a fuel matrix is the high temperature and pressure required for fabrication. Chemical reactions between SiC and plutonium at higher temperatures may also be an issue.;In this study, a low temperature process of using crystalline beta silicon carbide (beta-SiC) particles and a polymer precursor was developed to synthesize SiC inert matrix fuel pellets.The low temperature process is required to prevent the reactions between SiC and the PuO2 fuel material. The effect of the polymer content and the cold pressing pressure on the packing of SiC particles was investigated. The effect of mixing the coarse and fine SiC particles on the density, the microstructure and the pore size distribution was also investigated. It was found that the density and pore size distribution can be controlled by manipulating the SiC size compositions, polymer content and cold pressing pressure. The polymer infiltration and pyrolysis process was also studied. This process can effectively increase the density and close the open pores.;The mechanical properties of the fabricated pellets as a function of the processing parameters were measured and compared with the reference mixed oxide fuel. A SiC pellet with a theoretical density of 86 %, a hardness of 5.55 GPa, a fracture strength of 201.0 MPa and a fracture toughness of 1.88 MPa•m1/2 was achieved. The fabricated silicon carbide pellets had better mechanical properties than the reference mixed oxide fuels and other inert matrix candidate materials.