Tokyo Electric Power Co., the operator of the Fukushima Dai-Ichi plant, said a cooling system for one of its spent fuel pools at the crippled nuclear station stopped today.
Tepco, as the company is known, expects the cooling system to resume operating by the end of today, it said in an e-mailed statement. It would take about two weeks for the pool to reach 65 degrees Celsius (149 degrees Fahrenheit), the regulatory safety limit, from the 15.1 degrees Celsius recorded at 2 p.m., it said.
The earthquake and tsunami of March 2011 caused three meltdowns and a massive release of radiation at the Fukushima plant, forcing about 160,000 people to evacuate and leaving neighboring areas uninhabitable for decades. Last month, a rat caused a blackout at the plant, highlighting the vulnerability of its power and cooling systems more than a year after the government said its damaged reactors had been brought into a stable state, known as cold shutdown.
The cooling system for the spent fuel pool at the No. 3 reactor was found to have stopped after a power supply alarm went off at 2:27 p.m. today, Tepco said. The utility is investigating the cause, it said.
The utility concluded last week that the rat had short-circuited a switchboard at the plant, causing a power outage at four pools used to cool spent nuclear fuel rods. Power was mostly restored the next day before the spent fuel rods started overheating and releasing radiation, according to Tepco.