Evaluation of fuel integrity for seawater intrusion event at Hamaoka 5

At Unit 5 of Hamaoka NPS (Hamaoka 5), approximately five metric tons of seawater flowed into the reactor core due to failure of the main condenser tubes as a result the nuclear fuels were exposed to the high-temperature water containing high concentrate of chloride ion for a short period. In order to evaluate the integrity of these fuels, visual inspection, oxide film thickness measurement and crud analysis on the fuel cladding tubes were performed at the spent fuel pool. The pool-side inspection results revealed that there was no unusual appearance on the fuel components. The laboratory material tests using irradiated and unirradiated specimens implied that no crevice corrosion happened in the fuel assembly components under the water chemistry conditions simulating seawater intrusion. (author)