硝酸溶液中でのステンレス鋼の耐食性に及ぼす共存核分裂生成物の影響

抄録

Spent nuclear fuel contains not only nuclides such as uranium or plutonium, but many kinds of elements as fission products produced from nuclides in a nuclear reactor. In a reprocessing plant, solutions dissolved spent nuclear fuel with nitric acid would be treated by chemical equipment mainly made of stainless steel. In this paper, corrosion behaviors of two kinds of austenitic stainless steels, which are Types 304 ULC and Types 310Nb, in nitric acid solutions containing simulated fission products were studied. Corrosion behaviors of these metals were evaluated through examining electrochemical characteristics and corrosion rates which were obtained by weight loss measurements. From the results of the corrosion test, it was found that the corrosion rates of stainless steels are enhanced by co-existant ruthenium ion in nitric acid solutions, whereas immune from other elements. Corrosion potential measured only in ruthenium added solution shifts to the noble region where high corrosion rates are exhibited. It is thought that such a potential shift to noble region is caused by enhancement of cathodic reactions on metal surface due to co-existance of ruthenium in nitric acid solutions.