Development of an analysis method for electrochemical corrosion potential in PWR primary coolant under irradiation

照射下PWR一次冷却水環境における腐食電位(ECP)解析手法の開発

端 邦樹 ; 内田 俊介; 塙 悟史 ; 知見 康弘

Hata, Kuniki; Uchida, Shunsuke; Hanawa, Satoshi; Chimi, Yasuhiro

Stress Corrosion Cracking (SCC) is one of the key phenomena to determine material degradation in nuclear power plants, and the electrochemical potential (ECP) is known as an environmental factor of SCC initiation and propagation. In the PWR primary coolant, the low ECP level is maintained due to H injection. On the other hand, material degradation attributed to H attack was also reported. Thus, the optimization of H concentration has been still discussed. In JAEA, an ECP analysis method has been developed. This method was originally prepared for BWR primary coolant, but it is improved to apply to PWR primary coolant. In the recent study, this ECP analysis method was modified by introducing pH adjustment based on boron-lithium combined control, and ECP calculation for stainless steels and Ni-based alloys were carried out. ECP calculation assuming a reactor core region and a steam generator region was also tried and the optimal hydrogen concentration without any serious adverse effect was discussed.