Neutron irradiation effects in boron carbides: Evolution of microstructure and thermal properties

Abstract Different boron carbides, potentially used as control rods materials in fast neutron reactors, have been irradiated up to ≈ 25 × 10 20 captures/cm 3 in the French Phenix LMFB reactor. Microstructural and thermal characterizations show very different behaviors, depending on the density (from 70 to 98%), the composition (B 4 C or B 8 C) and the fabrication process (magnesothermal or carbothermal) of the materials. In spite of the low absorbed doses, all the materials show extended intergranular fracture, strong lattice distorsions and drastic thermal conductivity decrease.