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Human Error Stopped Reactor 3 Cooling System

reactor-3

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 | Fukushima 2016 | , , | Leave a comment

Fukushima reactor N° 3 briefly loses cooling during inspection

reactor 3.jpg

 

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 | Fukushima 2016 | , , | Leave a comment

Probe of Fukushima Daini’s N°3 Reactor Cooling System Knocked Offline After Earthquake

Fukushima Daini.jpg

Fukushima Daini

Japan Probes Nuclear Cooling System Shutdown After Earthquake

Japan is investigating why a cooling system used to store nuclear fuel rods was temporarily knocked offline at Tokyo Electric Power Co. Holdings Inc.’s shuttered Fukushima Dai-Ni atomic plant after a 7.4 magnitude earthquake struck the same region devastated by a tsunami in March 2011.

The temblor early Tuesday caused water in the pool at the plant northeast of Tokyo to move, according to the utility known as Tepco. Sensors registered the motion as a decline in water levels, triggering an automatic shutdown, the utility said.

One of at least two cooling pumps supplying water to the spent fuel pool at Dai-Ni’s No. 3 reactor was shut around 6:10 a.m. Tokyo time, according to Tepco. The utility started another pump to resume cooling the fuel rods around 7:47 a.m., it said in an e-mailed statement.

More than five years after the Fukushima earthquake and tsunami that wrecked the utility’s Dai-Ichi nuclear plant and resulted in the shutdown of Japan’s atomic fleet for safety checks, just two of the country’s 42 reactors are back in operation. Returning the plants to service is a goal of Prime Minister Shinzo Abe’s government and is critical to Japan’s aim for nuclear to account for as much as 22 percent of its energy mix by 2030.

The fact that today’s earthquake caused the pumps at the Fukushima nuclear plant to shut down temporarily will certainly not help the government in its goal to restart the reactors,” Daniel Aldrich, a professor and director of the Security and Resilience Studies Program at Northeastern University in Boston, said by e-mail. “Perhaps one interesting change has been Tepco’s transparency about the ongoing problems at the site, including those that occurred during today’s earthquake.”

Government Response

Fifty-seven percent of the Japanese public oppose resuming operations of the country’s nuclear reactors, while 29 percent approve, according to an Asahi newspaper poll conducted in October.

Japan’s government quickly moved to allay any concerns following Tuesday’s earthquake, which was an aftershock of the magnitude 9 quake five years ago.

Safety is the top priority of Japan’s nuclear industry and the country has the world’s strictest rules for atomic plants, Japanese Chief Cabinet Secretary Yoshihide Suga told reporters in Tokyo Tuesday.

The stoppage of the system wouldn’t immediately have led to a release of radiation, Suga said. Earthquakes and tsunamis are among possibilities envisaged under new safety standards for nuclear plants issued by Japan’s Nuclear Regulation Authority since the 2011 disaster, he said.

Power would need to be cut for about a week before temperatures in the spent-fuel cooling system would reach the upper safety limit, according to Yutaka Ikoma, a spokesman at the regulator. Temperatures would rise about 0.2 degrees Celsius per hour without the cooling system, reaching 65 degrees Celsius in about seven days, according to the spokesman.

https://www.bloomberg.com/news/articles/2016-11-22/japan-probes-nuclear-cooling-system-shutdown-after-earthquake

November 24, 2016 Posted by | Japan | , , | Leave a comment