Human Error Stopped Reactor 3 Cooling System

Cooling water briefly stopped at Fukushima plant

Injections of water to cool melted fuel in a reactor at the Fukushima Daiichi nuclear power plant stopped briefly due to human error on Monday.
The plant’s operator, Tokyo Electric Power Company, says an alarm system was activated at around 10 AM when a water pump at the No. 3 reactor shut down.
An internal investigation by the utility found that a worker had mistakenly hit the pump’s switch with his elbow while checking instruments. TEPCO resumed the water injections using a different pump about 1 hour later.
The utility notified local prefectural authorities and nearby areas of the problem just one minute before it resumed the water injections.
TEPCO officials say they detected no changes in the temperature at the bottom of the reactor or in radiation levels at monitoring posts around the plant.
Also on Sunday night, cooling operations temporarily stopped in the spent nuclear fuel pool at the plant’s numbers 1, 2 and 3 reactors when some valves inexplicably opened.
TEPCO says it takes these human errors seriously and will do it best to prevent recurrences.

http://www3.nhk.or.jp/nhkworld/en/news/20161205_27/

Fukushima reactor briefly loses cooling during inspection

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

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

TEPCO said the reactor had enough water left inside and there was no temperature increase or radiation leak from the incident.

TEPCO acknowledged some other key switches are in similarly tight locations.

http://www.asahi.com/ajw/articles/AJ201612050069.html

December 6, 2016 Posted by dunrenard | Fukushima 2016 | Cooling System, Fukushima Daiichi, Reactor 3 | Leave a comment

Fukushima reactor N° 3 briefly loses cooling during inspection

TOKYO — 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.

https://www.japantoday.com/category/national/view/fukushima-reactor-briefly-loses-cooling-during-inspection

December 5, 2016 Posted by dunrenard | Fukushima 2016 | Cooling System, Fukushima Daiichi, Reactor 3 | Leave a comment