The defect structures after varying-temperature and constant-temperature neutron irradiation were studied by means of transmission electron microscopy. In the case of irradiation at 473K, micro-voids were detected by means of positron annihilation lifetime measurement. In the case of irradiation at 673K, a few interstitial-type dislocation loops grew and the total number-density of loops decreased with increasing irradiation dose. In the case of varying-temperature irradiation at 473 to 673K, the absorption of interstitials to interstitial-type dislocation loops, after a shift to high temperature, was suppressed by micro-voids which were introduced at low temperatures. The loops then shrank, or disappeared, due to vacancies which were released from micro-voids. As the cycle of varying-temperature irradiation became shorter, the effect of the suppression of defect development became smaller.

Defect Structures Introduced in Iron under Varying Temperature Neutron Irradiation. M.Horiki, T.Yoshiie, Q.Xu, M.Iseki, M.Kiritani: Journal of Nuclear Materials, 2000, 283-287, 282-5