Feb. 1 San Onofre Emergency Triggers Probe

An electrical problem at the San Onofre Nuclear Operating Station Unit 2 halted a key cooling system for 26 minutes and prompted the first emergency declaration since 1992 at Southern California’s only nuclear plant complex, government and plant officials said Friday.

The Feb. 1 incident was labeled an “unusual event,” the least serious of four emergency categories. The electrical problem was caused by human error and was swiftly resolved, plant spokesman Ray Golden said. No radiation or coolant water escaped from the plant, he said.

The U.S. Nuclear Regulatory Commission has sent a special inspection team to the plant to determine why the problem occurred, but no decision has been made whether to fine plant operators.

“Our enforcement staff will look at what occurred and determine if there were any potential violations,” NRC spokesman Roger Hannah said.

The Southern California Edison nuclear plant, which is just south of San Clemente, has been shut down since Jan. 2 for two months of refueling and maintenance work. But even when the massive plant is not generating electricity, its fuel remains hot.

“A cooling system is needed even during a shutdown for removing the heat,” Hannah said.

In fact, the plant is equipped with two separate systems to cool the fuel. One of those, however, was out of service for maintenance the morning of Feb. 1.

That left the second system for cooling. But it needed work, and workers accidentally interrupted the flow of electricity, which in turn froze the system’s pumps.

The workers quickly recognized the problem, and electricity was restored, officials said. But in the interim, neither cooling system was operating for 26 minutes, prompting the emergency declaration.

The reactor vessel was in no danger of overheating, for it was flooded with 23 feet of water at the time, Golden and Hannah said.