Officials with the Nuclear Regulatory Commission now say that some radioactive gas may have escaped the San Onofre Nuclear Generating Station, but it was undetectable by monitors and therefore posed no threat to anyone.
A unit at the station was shut down Tuesday when sensors detected a leak in one of the unit's steam generator tubes.
NRC spokesman Victor Dricks said because the equipment-housing building into which the gas leaked is not airtight, it is possible a "very, very low level'' of radioactivity escaped into the environment. Dricks said those traces would be
"barely measurable against [existing] background levels'' and would pose no
danger to the public.
Technicians were still cooling down the San Onofre Nuclear Generating Station Unit 3 today 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.
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, senior resident NRC 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 heat-exchanging tubes to make steam, which turns 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 problem was still several days away.
"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."
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.
San Clemente Councilwoman Lori Donchak Wednesday urged residents to remain calm. Donchak and the rest of the council spent a lot of time last year researching the plant and responding to resident concerns over safety after the earthquake, tsunami and subsequent nuclear disaster at the Fukushima Daiichi plant in Japan.
"We have a very strong emergency preparedness community program in place and it worked yesterday as planned," Donchak said. "The interruption at SONGS was handled efficiently and constantly."
She also mentioned that a blue ribbon commission about on-site nuclear waste storage at plants had completed its findings last week, a commission President Obama started in 2010.
Donchak said the report is on the agenda as an educational item at the Feb. 7 Council Meeting. The full text of the report is attached to this article in PDF form.