The outage triggered a sharp drop in the level of cooling water for the radioactive fuel rods, according to the plant operator.
The little-noticed incident did not result in any reactor damage or release of radiation. However, it highlighted some of the vulnerabilities of the aging facility and raises questions about the precautionary procedures and outmoded equipment that operator Tokyo Electric Power, had in place.
According to the company investigation, on June 17, 2010 an automatic shutdown set off an alarm in the control room of the No. 2 reactor, one of six at Fukushima Daiichi. Within minutes, control rods were inserted to stop the nuclear fission. However, without electricity, the water pumps stopped supplying the reactor core with fresh water. Temperatures and pressure levels rose inside the reactor.
Company officials said no meltdown was imminent, and that normal water levels were restored soon after the power outage.
However, some critics say the consequences could have been more serious if not for quick-thinking control-room operators who manually activated the diesel generators and ECCS. They say the accident revealed weaknesses in blackout situations.
Analysts say the 2010 incident had shown holes in the Tokyo Electric safety system. The vulnerabilities in an aging nuclear plant and weak system of implementation, may have been preventable, however, company officials say many of the mistakes made came from human error.
(아주경제 앤드류 이 기자)
reporter
Park Sae-jin
swatchsjp@ajunews.com