Nuclear Regulation Authority Chairman Shunichi Tanaka says the plant, which relies on makeshift cooling systems for its broken reactors, remains highly vulnerable.
Police officials say bombs in three Iraqi cities have killed two soldiers, a policeman and a pro-government Sunni fighter.
U.N. chief Ban Ki-moon says inspectors are ready to deploy to Syria within 24 hours to investigate reported chemical weapon attacks in the country's two-year civil war but have no permission yet from President Bashar Assad's government.