Metal fatigue is the suspected culprit of last month's nuclear plant accident in Tsuruga, Fukui Prefecture, where a massive amount of radioactive coolant water leaked from a cracked reactor pipe, the plant operator announced Monday.
The Ministry of International Trade and Industry reported the finding to the government's Nuclear Safety Commission.
The plant operator says further investigations are needed to specify the cause of the metal fatigue, but some experts say it may have been the result of the repeated temperature changes of the primary coolant that runs through the pipe.