Damage in neutron-irradiated molybdenum

Abstract

Abstract The as-irradiated microstructure of molybdenum, irradiated in the EBR-II reactor at six different temperatures in the range 430–1000°C (0.24–0.44 T m ) to a fast neutron fluence of ≈ 1 × 10 22 n · cm −2 ( E > 1 MeV ), has been characterized as black spot clusters, loops, rafts, voids (random and ordered) and dislocations. Present results show that both the void density, N v and the void size, d v , are independent of irradiation temperature in the range 430–700° C. Above the 700° C irradiation temperature the void density decreases and the void size increases exponentially with increasing irradiation temperature and they have been expressed empirically as N v = 3.6 × 10 20 exp (−26.9 T/T m ) , d v = 1.5 exp (9.44 T/T m ) , where T/T m is the irradiation temperature presented as a fraction of the melting point. The void density of all available published data has been used to show that the void density is (a) a strong function of irradiation temperature for a constant number of displacements per atom (dpa) and (b) a function of reactor power and spectrum when normalized to dpa.