Effect of neutron irradiation on thermal diffusivity of tungsten–rhenium alloys

Thermal diffusivities of W–Re alloys were examined before and after neutron irradiation by a laser-flash method. W and W–Re alloys (up to 25 mass% Re) were irradiated in the Japan materials test reactor (JMTR) reactor at 330 K to thermal and fast neutron fluences of 1.03×1020 and 3.37×1019 (E > 1 MeV), respectively. After irradiation thermal diffusivities of W and W–5% Re decreased, while those of W–10% Re and 25% Re increased. In the unirradiated condition, though the diffusivities of W and W–5% Re decreased with an increase of temperature, those of W–10% Re and W–25% Re increased. These temperature dependencies were the same after the irradiation. After annealing at 973 K for 10 min, the thermal diffusivity was restored for W–5% Re at room temperature, while a difference still existed between those of the irradiated and unirradiated W and W–25% Re. The observed changes are discussed in terms of lattice constant measurements and precipitation behavior.