DJ: Rodent May Have Caused Major Outage at Fukushima Nuclear Plant

TOKYO--A recent blackout at the crippled Fukushima Daiichi nuclear power plant may have been caused by a rat and the facility's operator is investigating the possibility.

The power outage halted the cooling system at the stricken reactors for nearly a full day this week, temporarily disrupting clean-up efforts before full power was restored early Wednesday.

The prospect that a small animal could trigger the blackout underscores the facility's vulnerability, two years after a massive earthquake and tsunami knocked out power to the reactors, triggering a nuclear disaster.

Operator Tokyo Electric Power Co. (9501.TO) said Wednesday that affected fuel rods remain at safe temperatures, despite the recent outage, adding that it would have been several days before the rods were in danger of overheating.

After some investigation, Tepco found a burned spot on an electricity supply system inside the still-crippled plant with a singed, dead rat lying nearby.

"It is true that there was a dead small animal lying around the switchboard, but we don't know yet whether it was the cause" of the power problem, Tepco spokesman Akio Kobayashi told Dow Jones Newswires. He said the company is examining whether the animal was the main reason behind the outage.

The Fukushima plant lost power Monday evening to systems pumping water to cool several pools where it stores used nuclear-fuel rods.