TEPCO via EPA
Attempts stop rats getting inside a reactor at the Fukushima Daiichi nuclear power plant led to a cooling system shutdown. Debris on the fuel rack in a spent-fuel pool is seen in this handout photograph taken in mid-February.
TOKYO -- A cooling system at a tsunami-damaged nuclear plant in Japan failed Friday for the second time in a month after an outage caused by construction work to keep out rats suspected of setting off the earlier blackout.
Power for the cooling system for a storage pool for fuel was restored after a two-hour break at reactor No. 3, and there was no immediate danger from the breakdown, according to Tokyo Electric Power Co., the utility that operates Fukushima Daiichi in northeastern Japan.
TEPCO via Reuters
A dead rat is seen near a temporary switchboard used to supply power to cooling systems at three fuel pools in the Fukushima facility in this handout photograph taken on March 20.
Work to put up nets to keep out rats and other animals at Fukushima Daiichi plant in northeastern Japan inadvertently caused the power outage, TEPCO spokesman Akitsuka Kobayashi said. Details were not clear, and the outage was still under investigation.
A dead rat found near a switchboard was suspected of the power outage last month that led to a cooling system not working for two days at the plant.
Nuclear Regulation Authority spokesman Takahiro Sakuma said an alarm went off in the afternoon about the latest problem at reactor No. 3.
The cooling system can be turned off for two weeks before temperatures approach dangerous levels at the spent fuel storage pools.
But if the water runs dry, the fuel rods, even spent ones, will spew enormous levels of radiation.
The plant went into multiple meltdowns after the March 2011 tsunami damaged backup generators and all cooling systems failed, including those for the reactors.
Journalists have been given a rare glimpse inside Japan's Fukushima Daiichi nuclear power plant, which was crippled in the 9-magnitude earthquake and tsunami that hit the country two years ago. NBC News' Arata Yamamoto reports.
The plant is being decommissioned, but continues to have glitches.
Fears are growing about the safety of nuclear plants, and people have periodically staged streets protests that are rare in Japan.
Only two of the nation's 50 working power plants are up, and the government is running beefed up safety checks on the plants, including scrutinizing quake faults right below or near the plants.
Shinzo Abe, who became prime minister about three months ago, has expressed a desire to restart nuclear plants.
Japan lacks natural resources and relied on nuclear energy for about a third of its electricity needs prior to March 2011. Energy imports have soared over the last two years, putting a strain on the economy.
Richard Engel goes to Japan a year after the devastating earthquake and subsequent tsunami to see how people live just miles away from the Fukushima nuclear plant.
This story was originally published on Fri Apr 5, 2013 8:13 AM EDT