2月1日 アメリカ・バイロン原発停止の続報とカリフォルニア・サンオノフレ原発3号機で『漏えいの可能性を検知』の続報です。

San Onofre: tiny gas release, more damage
Orange County Register Communications February 2nd, 2012, 10:38 am
As workers prepared Thursday to inspect a leaky tube in one of the San Onofre nuclear plant’s reactors, federal regulators said sensors showed a tiny amount of radioactive gas may have leaked out of a building near the reactor, which was shut down late Tuesday.
And a spokesman for the Nuclear Regulatory Commission said there were also signs of damage to hundreds of tubes in a second reactor, which is offline for maintenance.

A spokesman for plant operator Southern California Edison was working to confirm both NRC statements Thursday.
All four of the plant’s steam generators, and their tubes, are less than two years old, installed after being delivered to the West Coast by the Japanese manufacturer of the generators, Mitsubishi Heavy Industries.
More than 9,000 tubes carry water from the reactor and through the generator
“They have inspected 80 percent of the tubes in one of the steam generators at unit 2,” said NRC spokesman Victor Dricks. “Two of the tubes have thinning so extensive that they need to be plugged and taken out of service. Sixty nine other tubes have thinning greater than 20 percent of the wall thickness, and a larger number have thinning greater than 10 percent of wall thickness.”
The tubes with 10 percent thinning number more than 800, he said.

Dricks said that sensitive alarms were tripped in an auxiliary building near San Onofre’s unit 3 reactor after the leak was detected about 5:30 p.m. Tuesday, indicating that at least some radioactive gas was present.
Both Dricks and San Onofre officials said any release would have been extremely small, posing no hazard to workers or the public. Detectors elsehwere on the property picked up no signs of radiation above background levels.
“Had there been any change in radiation levels elsewhere in the plant, Edison would have immediately taken the appropriate steps, such as declaring the first of the four levels of emergency used by the industry,” said Edison spokesman Gil Alexander.
New details also emerged about an unrelated accident on Friday, when a contract worker slipped into a pool above the unit 2 reactor, now offline for maintenance, while trying to retrieve a flashlight.
The man, whose name Edison declined to release, was not injured, and did not suffer harmful radiation exposure, but might have ingested the mildly radioactive water, Alexander said. No internal contamination was found.
Alexander was unable to confirm early Thursday that damage had been found in unit 2′s steam generator tubes. He also was working to confirm that alarms were tripped in the auxiliary building near unit 3, indicating a release of a small amount of radioactive gas.
Meanwhile, the unit 3 reactor, shut down by operators Tuesday as a precaution when the generator-tube leak was detected, will likely be cool enough for workers to enter and begin their inspection Thursday.
Normally, water that is heated by the reactor and flows through the tubes is kept separate from another loop of water, from another source, inside the steam generators.
Instead, the tubes are immersed in the water inside the steam generators, heating the water, which turns to steam that powers the plant’s turbines to produce electricity.
But a small leak in one of the tubes could have allowed radioactive water circulating from the reactor to mix with the water in the steam generator.
If so, it could have resulted in the escape of a small amount of radioactive gas.
Although both of San Onofre’s reactor units are now offline, with no word on how soon unit 3 can be restarted, Alexander said Edison has “ample reserve power” to supply customers.
Activist Gary Headrick, founder of a group called “San Clemente Green” that advocates shutting down the nuclear plant, said the leak will likely raise questions about the plant’s safety — though Edison has made repeated assurances.
(ゲイリーヘッドリク―原子力発電所の閉鎖を提唱する"サンクレメントグリーン"と呼ばれるグループの創設、エジソン繰り返される保証をしたものの、「 この漏えいはおそらく工場安全性に関する問題を提起するだろう」と述べた。)
Of special concern, he said, is the fact that new steam generators were recently installed in both reactors.
“These are brand-new generators, less than a year old,” Headrick said. “It’s not looking like a very good investment.

Environmental groups also criticized San Onofre officials in November for delaying by an hour notification of the public about a non-radioactive ammonia leak in a storage tank that prompted some worker evacuations.
That leak also was described as posing no danger to the public, though it did prompt an alert, the second lowest of four emergency classifications
Tuesday’s unrelated steam-generator tube leak was not classed as an emergency.
U.S. Rep. Ken Calvert said his office was notified within about three hours of Tuesday’s leak, and while he was satisfied with that response, he, too, questioned the failure of new equipment.
“Obviously there’s something wrong here. They need to get to the bottom of it,” he said.
In 2010, San Onofre completed a $674 million steam-generator upgrade, with two of the behemoths replaced in each reactor.
The Associated Press contributed to this report.






にほんブログ村 環境ブログ 原発・放射能へ