Deposition of Radioactive Ions on Boiling Water Reactor Component Materials

The deposition mechanism of radioactive ions (such as ⁶⁰Co) on stainless and carbon steels under boiling water reactor (BWR) operating conditions was determined through exposure tests in actual reactor water. Deposited amounts of radionuclides and oxide films were measured. A secondary ion mass spectrometry (SIMS) study and electrophoretic mobility (EM) measurements of oxidized metal powders were also performed. The oxide films primarily grew Inward on both steels at the oxide/metal interface, and radioactive ions were assumed to be incorporated at the same position. The oxide films tended to assume a positive fixed charge and be anion selective. Hence, the deposition of cationic cobalt was suppressed compared to anionic chromium. This trend was observed clearly for carbon steel and initial exposure period stainless steel (SS).