A Coupled analyses of water radiolysis and ECP for evaluation of the corrosive conditions in BWRs and PWRs

BWR及びPWRにおける腐食環境評価のための水の放射線分解と腐食電位(ECP)解析

端 邦樹 ; 内田 俊介; 塙 悟史 ; 知見 康弘; 佐藤 智徳  

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

The coupled code of water radiolysis and electrochemical corrosion potential (ECP) calculations (WRAC-JAEA) has been proposed for evaluating ECP both for boiling water reactor (BWR) and pressurized water reactor (PWR) systems. In the present study, some updates, such as pH control based on boron (B) and lithium (Li) concentration, were carried out. The calculated ECP were compared with the measured results in the INCA in-pile loop in the Studsvik R2 reactor for validation of the code. It was confirmed that the calculated ECP agreed with the measured ones in the INCA loop. The suitable rate constant set for water radiolysis calculation is also discussed. In particular, the rate constants for the chemical reaction of hydroxyl radical and molecular hydrogen and its backward reactions were carefully examined to evaluate the effects of pH and hydrogen concentration on hydrogen peroxide concentration. Moreover, the polarization curves were calculated, and the effects of Li and the other species on ECP were estimated. In order to apply the code for both type of reactor systems, verification and validation (V&V) procedures of the code are proposed.