Radioactive Contamination of Carbon Steel in a Boiling Water Reactor

Deposition of ⁶⁰Co contained in reactor water results in contamination of boiling water reactor out-of-core components. To elucidate the deposition mechanism, the deposition kinetics of radionuclides on carbon steel were evaluated through exposure tests in actual reactor water. On the basis of the data, a radiation buildup model was developed. Cationic ⁶⁰Co and ⁵⁸Co were difficult to transmit through the oxide film, which was probably charged positively, and incorporate into the inner oxide layer; consequently these amounts on the steel did not increase even after 1000 h. However, anionic ⁵¹Cr was easily captured by the growing oxide film, and the amount showed an increasing trend up to 500 h.