Ill. nuclear reactor loses power, venting steam

AP Associated Press January 30, 2012

イリノイ州BYRON, Ill.—A nuclear reactor at a northern Illinois plant shut down Monday after losing power, and steam was being vented to reduce pressure, according to officials from Exelon Nuclear and federal regulators.

Unit 2 at Byron Generating Station, about 95 miles northwest of Chicago, shut down at 10:18 a.m., after losing power, Exelon officials said. Diesel generators began supplying power to the plant, and operators began releasing steam to cool the reactor, but from the part of the plant where turbines are producing electricity, not from within the nuclear reactor itself, officials said.

The steam contains low levels of tritium, a radioactive form of hydrogen, but federal and plant officials insisted the levels were safe for workers and the public.

The U.S. Nuclear Regulatory Commission declared the incident an "unusual event," the lowest of four levels of emergency. Commission officials also said the release of tritium was expected.

Exelon Nuclear officials believe a failed piece of equipment at a switchyard caused the shutdown.

The switchyard is similar to a large substation that delivers power from the plant to the electrical grid, they said. Officials were still investigating the equipment failure.

Nuclear Regulatory Commission spokeswoman Viktoria Mitlyng said releasing steam helps "take away some of that energy still being produced by nuclear reaction but that doesn't have anywhere to go now." Even though the turbine is not turning to produce electricity, she said, "you still need to cool the equipment."

Candace Humphrey, Ogle County's emergency management coordinator, said county officials were notified of the incident as soon as it happened and that public safety was never in danger.

"It was standard procedure that they would notify county officials," she said. "There is always concern. But, it never crossed my mind that there was any danger to the people of Ogle County."

Unit 1 was operating normally while engineers investigate why Unit 2 lost power, which comes into the plant from the outside power grid, Mitlyng said. Smoke was seen from an onsite station transformer, she said, but no evidence of a fire was found when the plant's fire brigade responded.

Mitlyng said Nuclear Regulatory Commission inspectors were in the control room at Byron and in constant contact with the agency's incident response center in Lisle, Ill.

In March 2008, federal officials said they were investigating a problem with electrical transformers at the plant after outside power to a unit was interrupted.

In an unrelated issue last April, the commission said it was conducting special inspections of backup water pumps at the Byron and Braidwood generating stations after the agency's inspectors raised concerns about whether the pumps would be able to cool the reactors if the normal system wasn't working. The plants' operator, Exelon Corp., initially said the pumps would work but later concluded they wouldn't.

Backup generators kick in after shutdown at Exelon's Byron plant
By Julie Wernau Tribune reporter
Chicago Tribune 3:25 p.m. CST, January 30, 2012
Backup diesel generators are supplying power to one of two units at Byron nuclear power plant after the plant lost power this morning.

Viktoria Mitlyng, spokeswoman for the Nuclear Regulatory Commission's Region III office Lisle, said two diesel generators are keeping the plant cool, with battery backup systems at the ready as well.

"It is not a huge concern," Mitlyng said. "It is the lowest of (the four) power emergency level declarations."

Mitlyng said one of two units at the plant -- a 1,136 megawatt nuclear unit -- was automatically shut down and is stable. Another unit -- at 1,164 MW -- is operating at full power.

Employees at the plant reported seeing smoke coming from a transformer on site after the outage. The plant's fire brigade responded, Mitlyng said, but didn't find a fire.

To aid in cooling, steam is being released, she said, and the NRC staff are monitoring. Byron Fire Protection District Chief Galen Bennett said the steam contained "expected levels of tritium" -- an isotope of hydrogen with a weak level of radioactivity. He said the public and plant workers were "never in any danger" and no one was hurt.
(「冷却を助けるために蒸気が放出されている」と彼女は言った。さらにNRCスタッフが監視している バイロン防火地区チーフは、蒸気に一定のトリチウム―弱いレベルの放射性物質、水素同位体が含まれると述べたは、周辺住民作業員は決して危険にさらされることは無く、けが人はいないと述べた。)
Steam releases may continue throughout the day

Byron nuclear plant is owned by Chicago-based Exelon Corp. and is in Byron, about two hours northwest of Chicago.,0,7041106.story

米イリノイ州の原発、緊急停止 外部電源喪失
2012/01/31 09:23 【共同通信】



にほんブログ村 環境ブログ 原発・放射能へ