Effects of downward temperature change on microstructure in vanadium alloys during irradiation

Abstract

In fusion reactors, structural materials are expected to experience non-steady histories of irradiation temperature, neutron flux and other parameters during reactor start-up/shut-down, plasma disruptions, etc. The objective of the present study is to clarify the effects of the downward temperature change during irradiation. Vanadium that is the one of candidate materials for the first wall of fusion reactors was irradiated with heavy ions during the downward temperature change. TEM observation, nano-indentation and HVEM observation were carried out. It was reported that the growth of defect clusters including cavities and precipitates occurred under neutron irradiation and heavy ion irradiation during the downward temperature change. In the present paper, the detailed mechanism of growth of defect clusters was investigated by changing the lower temperature as a parameter. The growth of defect clusters occurs just after the downward temperature change followed by re-nucleation of defect clusters at lower temperatures. © 2005 The Japan Institute of Metals.