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Kaji, Yoshiyuki; Kondo, Keietsu
no journal, ,
In order to investigate the influence of neutron dose rate on crack propagation behavior of type 304 stainless steel, crystallographic analyses around the cracks were conducted by Electron Backscattered Diffraction (EBSD) on crack growth rate (CGR) tested specimens irradiated at the Japan Materials Testing Reactor (JMTR) up to about 1dpa under the dose rate conditions from 1E-8 to 1E-7 dpa/s. Although CGRs of specimens with different dose rates suggested that specimens with the higher dose rate irradiation showed the slightly larger CGR than that with lower dose rate irradiation, estimation of the plastic strain by means of the EBSD measurement revealed that plastic strain around the crack in both low and high dose rate specimens was estimated to approximately 1%, and the significant difference was not observed. Furthermore, the distribution of plastic deformation around the crack is estimated on the specimens irradiated up to about 2 dpa and the influence of neutron dose rate on crack propagation behavior is discussed in this study.
Chimi, Yasuhiro; Kasahara, Shigeki; Hata, Kuniki; Nishiyama, Yutaka; Seto, Hitoshi*; Chatani, Kazuhiro*; Kitsunai, Yuji*; Koshiishi, Masato*
no journal, ,
In order to investigate effects of environmental mitigation and water radiolysis caused by 
-rays from radioactive material on irradiation-assisted stress corrosion cracking (IASCC) growth behavior for highly irradiated material, crack growth tests in simulated BWR water conditions (at 563 K) are performed. The specimens made of 316L stainless steels are irradiated with neutrons up to 
12 dpa in the Japan Materials Testing Reactor (JMTR). One of the specimens is annealed at 973 K for 1 hour to show almost recovered mechanical and micro-chemical properties corresponding to the unirradiated material. For low electrochemical corrosion potential (ECP) condition, the crack growth rate (CGR) is suppressed by about one order of magnitude in high stress intensity factor (K) condition. This result indicates that environmental mitigation for crack growth can be found even under severe conditions on material and stress factors. The effects of water radiolysis on the CGRs are discussed.