Tokyo Electric Power Co. admitted Wednesday that one of the critical cooling pipes at its Fukushima No. 1 nuclear power plant's reactor unit 3 may have been damaged in the March 11 megaquake.
Tepco suggested earlier that no major damage, including ruptures in the facility's main steam pipes, had occurred at the reactor until the massive tsunami hit after the magnitude 9.0 quake.
But if the temblor had actually damaged the High-Pressure Core Flooder system — which is used to supply coolant water to a reactor core in emergencies to keep nuclear fuel from overheating — power suppliers across the country might be forced to reconsider the quake resistance designs for their reactors.