Corrosion test of Zircaloy-2 specimen in high temperature seawater

Seawater is the last coolant material for a spent fuel pool on emergency safety measures of the station blackout. Therefore, it is necessary to understand corrosion behaviors of fuel claddings in seawater at high temperatures. In this work, we postulated that seawater was injected in to the spent fuel pool and was heated by decay heat form spent fuel for long term, then the corrosion behaviors of fuel claddings were investigated. Stress corrosion cracking (SCC) was not observed on Zircaloy-2 specimen in 3, 10 wt% salinity (concentration of salt in seawater) water at high temperatures. On the other hand, SCC was observed along scribe line in a saturated solution of magnesium chloride at 80degC. High stress concentration and high salinity such as the saturation state are necessary to SCC growth in Zircaloy-2. Calcareous deposit layer was formed on the specimens in 3, 10 wt% salinity water at high temperatures. It was a protective layer and pitting corrosion on the specimen surface was reduced. (author)