A hydrogen explosion at Hamaoka nuclear power plant last November was caused by structural defects in a ruptured pipe, and a radioactive water leakage was due to an accumulation of platinum in a separate tube.
Chubu Electric Power said that the flawed structure of the pipe in unit 1 allowed hydrogen and oxygen to accumulate, which weakened the pipe, leading it to rupture and causing the explosion.
The latest report said hydrogen and oxygen had accumulated at an area about 7m from the ruptured area.
Meanwhile, the report also found that a radioactive water leak detected after the explosion at the reactor came from a tube due to stress corrosion caused by welding processes at the reactor. Platinum, a known hydrogenation catalyst, was placed inside the cooling system to improve water quality management. The report said a high concentration of platinum was later found to have accumulated in the tube.
The company suspended operations in its No 2 reactor since the accident as a precaution, but has not found any defects in the second reactor, and is set to resume it operations soon.