The two-unit San Onofre nuclear power plant in the northwest corner of San Diego County, Calif., remained shut down today, more than a week after a leak from a tube in one unit released a small amount of radiation. On Thursday, regulatory officials found extensive wear on tubes in the second unit, which is offline for maintenance. Also this week, reports confirmed that a worker had fallen into and climbed out of a reactor pool at the facility.

Southern California Edison (SCE), operator of the plant, said it shut down Unit 3 as a precautionary measure after sensitive monitoring instruments detected a steam generator tube leak. Operators safely shut the plant down and isolated the component that contained the leaking tube within four hours of detecting the indications. Operators also cooled down Unit 3 to reduce pressure in the plant, which is the procedural method to stop the tube from leaking.

"There was no threat then, nor is there now any danger to the public or to plant workers," Pete Dietrich, SCE’s senior vice president and chief nuclear officer, said last week. "Our operators performed exactly as they are trained to perform and took prompt action to ensure we did not create a situation involving any challenge to the health and safety of the public."

The plant saw added troubles when officials from the Nuclear Regulatory Commission (NRC) found extensive wear on tubes that carry radioactive water in a steam generator at Unit 2, which was offline for a planned maintenance, refueling, and technology upgrade outage. The tubes were reportedly installed less than two years ago. Two tubes showed more than 30% wall thinning, 69 had 20% thinning, and more than 800 had 10% thinning, the NRC said.

On Jan. 27, a private contractor employee “momentarily lost his balance" and fell into the pool while leaning over to retrieve a flashlight, SCE spokesman Gil Alexander told the Los Angeles Times.

The worker was wearing all required safety equipment, and a medical screening was performed to ensure no injuries had been sustained. Workers had previously removed the highly radioactive uranium fuel that normally sits at the bottom of the pool, officials said.

Sources: POWERnews,  Los Angeles Times