Diablo Reactor Shut Down After Radioactive Water Leak

About 100 gallons of radioactive water leaked from a pipe during a three-hour period at the Diablo Canyon nuclear power plant, but no radiation was released outside the plant, officials said.

An “unusual event” was declared early Wednesday morning, the lowest-level emergency at a nuclear plant, said Brad Thomas, spokesman for Pacific Gas & Electric Co. The cause of the leak at the facility’s Unit 2 containment building is under investigation, he said.

No one was exposed to unsafe radiation levels, Thomas said, and power generation was not curtailed during the incident.

Plant operators decided to close the Unit 2 reactor and then pinpoint the location of the leak. That reactor was scheduled to be shut down next month for routine refueling and maintenance.

Workers had noticed late Tuesday night that radioactive water was leaking and flowing through a floor drain to a cooling tank at a rate of about 1.5 gallons per minute. Radioactive water routinely drains into the cooling tank, where it is processed to remove impurities and some radioactivity and then recirculated.

But if the rate exceeds one gallon a minute, the plant must declare a low-level emergency, Thomas said. Workers must then find the leak or shut the unit down, he said. In this case, they shut it down, knowing it was to be shut down soon for regular maintenance.

“We have backup systems, so shutting it down now was no problem,” Thomas said. “It’s a lot easier to work in an environment where the temperature and pressure levels aren’t so high and radiation levels have been reduced.”

The low-level emergency is “not really that unusual and not really an emergency,” said Greg Cook, a spokesman for the Nuclear Regulatory Commission.

“This just means an event has occurred that you’ve got to pay some extra attention to,” Cook said. “You have to notify all the local governmental agencies and the NRC . . . but it doesn’t mean there’s any real crisis going on.”