The hydrogen explosion that spewed radioactive materials from the Fukushima No. 1 nuclear power plant’s No. 4 reactor building on March 15 was likely caused by gas leaking from the neighboring No. 3 reactor.
The hydrogen explosion that spewed radioactive materials from the Fukushima No. 1 nuclear power plant’s No. 4 reactor building on March 15 was likely caused by gas leaking from the neighboring No. 3 reactor.
Investigators found extensive damage on the fourth floor of the No. 4 reactor building near an air duct connected by pipe to the No. 3 reactor, the plant’s operator, Tokyo Electric Power Co., said on Nov. 10.
During a Nov. 8 inspection, TEPCO also found subsidence of the floor of the fourth level and evidence that the floor above had been pushed upward. A net covering an air intake on the fifth floor appeared to have been blown outward.
TEPCO’s theory is that hydrogen released by a core meltdown at the No. 3 reactor passed backward through the pipes of an emergency gas processing system into the No. 4 reactor building, causing an explosion near the fourth floor duct. Evidence consistent with such a backflow has also been found.
The theory runs counter to TEPCO’s initial suspicion that the explosion at the No. 4 reactor involved hydrogen released because of damage to fuel rods in the reactor’s own spent fuel storage pool.
Camera footage of the pool has shown no damage to the fuel rods, and TEPCO officials say hydrogen would have accumulated on the fifth floor or the top level if it had been generated by fuel rods in the storage pool.