[3H07-09] Severe Acident

[3H07] Effect of heating during the severe accident on the microstructure and the strength of LWR structural steels

(1)Experimental estimation on the change of microstructure and strength of the containment vessel steel during the severe accident

*Kento Takahashi¹, Takumi Hashimoto¹, Taro Fumimoto², Kouki Matukata¹, Shiro Jitukawa¹ (1. National Institute of Technology, Fukushima College, 2. Tokyo Institute of Technology)

Keywords:Fukushina-Daiichi nuclear plan, Reactor decommissioning, Strength of the containment vessel steel , Effect of temperature history, Fracture toughness, Micro structure

Effect of heating on the microstructure and the strength of the containment vessel steels has been examined. Aging at temperatures about 700℃, decreased yield stress by 30-40%, while increased fracture toughness. Rapid cooling reduced the fracture toughness depending on the cooling rate. Heating to the temperatures in delta-ferrite region increased hardness. Examination on the microstructures has been also conducted.