NEUTRON-IRRADIATION EFFECT ON THE THERMAL-CONDUCTIVITY AND DIMENSIONAL CHANGE OF GRAPHITE MATERIALS

Several kinds of graphite materials, such as fine-grained isotropic graphites, a carbon/carbon composite material, glassy carbon and bulk bronized graphites, were neutron irradiated at temperatures from 200 to 400-degrees-C to fluences of 0.01 to 0.82 dpa in JMTR. It was found that the neutron irradiation markedly reduced the thermal conductivity of the graphite materials, and that the materials irradiated under the same irradiation condition had the same value and the same temperature dependence of the, thermal conductivity irrespective of the original values. When the graphite materials were irradiated to over 0.1 dpa, the annealing at temperatures up to 1500-degrees-C was necessary to reach 50% of unirradiated value. The effect of boron in the bulk-boronized graphites on the thermal conductivity and dimensional change are also discussed.