No.3 cooling out for a while

December 5, 2016

Fukushima reactor briefly loses cooling during inspection

http://mainichi.jp/english/articles/20161205/p2g/00m/0dm/079000c

TOKYO (AP) -- One of the melted reactors at the tsunami-hit Fukushima nuclear power plant had a temporary loss of cooling Monday when a worker accidentally bumped a switch while passing through a narrow isle of switch panels during an inspection and turned off the pumping system.

The plant's operator, Tokyo Electric Power Co., said cooling for the No. 3 reactor, one of the three that melted following the 2011 earthquake and tsunami, was out for nearly an hour before a backup pump kicked in.

The reactor had enough water left inside and there was no temperature increase or radiation leak from the incident, TEPCO spokesman Yuichi Okamura said at a news conference.

Even though there was no radiation leak or overheating of the core, or any injuries, the incident was a reminder that Fukushima's decommissioning work is running on a very fragile system.

The plant was largely running on makeshift pipes, wiring and other equipment in the first two to three years following the 2011 disasters, suffering a series of minor blackouts -- including those caused by rats chewing cables -- cooling stoppages and other problems.

The plant has since largely stabilized, but it remains vulnerable to unanticipated incidents as it continues to struggle with decommissioning work, which is expected to last decades.

Monday's incident occurred when the worker was passing by a dimly lit isle that was only 85 centimeters (2.8 feet) wide, flanked by tall switch panels on both sides, Okamura said. With radiation levels still high, the worker was wearing a full-face mask and hazmat suit when he lost his balance while carrying equipment. His elbow jammed into the switch, breaking off its safety cover and inadvertently turning the lever to turn off the water injection pump to the No. 3 reactor.

Okamura acknowledged the lack of space at the site and said that the plant will seek ways to eliminate human errors like one on Monday.