Nuke Plant Leak Isolated; Reactor Cooling

Technicians were still cooling down the San Onofre Nuclear Generating Station Unit 3 Wednesday morning after what a plant official called an "extremely small leak" was detected in the steam generator system Tuesday.

Plant spokesman Gil Alexander said it was impossible to say how long the assessment and repairs would take to bring Unit 3 back up to par because the damage has not yet been able to be assessed, but said there continues to be no threat to workers or the public.

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Alexander and a Nuclear Regulatory Commission official confirmed that the leak is isolated and the cool-down of the unit is proceeding without a hitch.

"I was in the control room the whole time," said Greg Warnick, the senior resident inspector for San Onofre. "They followed their procedures as required. They isolated the suspected leak... They closed all the valves that go into [the compromised water system] and out of it to bottle it up."

The leak, detected at about 3 p.m. Tuesday, comes from the primary system containing water that actually touches the nuclear fuel, making the water itself radioactive. When the plant is functioning properly, the water in this system remains sealed; it boils clean water through a series of tubes to make steam to turn a massive turbine to make electricity.

Now, Warnick said, some of the mildly radioactive water from the primary system has leaked into the secondary.

The steam generator system in this unit is only a little more than a year old—it was replaced 

Warnick said this kind of leak is not common in nuclear power plants.

"It's not common," he said. "In fact, that's one of the reasons they replaced the system; the new one is made of more durable materials."

Warnick said the diagnosis of the precise problem was still several days away, however, so there is as yet no way to say exactly what went wrong.

"It's hard to comment on that because there is still discovery to take place," Warnick said. "However, it is a thing the plant is designed for. Most of the operators [in the control room Tuesday] coincidentally had gone through training in the simulator the night before on this exact same scenario."

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Meanwhile, Warnick said Wednesday morning that the leaking system had been cooled to about 320 degrees and the pressure was down to about 450 pounds-per-square-inch from its operating pressure of about 2,500 psi.

Once the plant is cool enough, inspectors will start their work.

"Based on that, there won't be any developments for several days," Warnick said.