Study on the corrosion assessment of overpack welds (Joint research)

Asano, Hidekazu*; Taniguchi, Naoki; Kawakami, Susumu; Yui, Mikazu

JNC TY8400 2004-008, 30 Pages, 2004/04

JNC-TY8400-2004-008.pdf:2.6MB

It is necessary to understand the corrosion behavior of welds in overpack for ensuring the quality of welding, and improving the long term reliability of overpack. In this study, the method for evaluation of corrosion of welded joint was planned by Radioactive Waste Management Funding and Research Center (RWMC) and Japan Nuclear Cycle Development Institute (JNC). RWMC has been developed the overpack welding techniques and the inspection techniques of welded joint. In this study, RWMC provided the information on current status of welding techniques for applying the overpacks. Electron Beam Welding (EBW) and Tungsten Inert Gas Welding (TIG) were prospected to be available for overpack and the results of the examinations to find adequate conditions for overpack welding were presented. JNC has been studying the corrosion behavior and lifetime of overpack, and provided the information on corrosion of welded carbon steel under repository conditions. According to immersion tests by JNC, it was shown that corrosion rates of carbon steel welded by EBW were almost equal to those of base metal under anaerobic condition, which is representative condition in repository environment. Based on the information provided by RWMC and JNC, the research subjects on the corrosion of welds were extracted and the concept of corrosion tests for overpack welds was given.