It’s been a rough week at the Diablo Canyon nuclear power plant after a scheduled refueling left one reactor inactive and some unwelcome visitors caused the second to be reduced to only a small fragment of its capacity.
Pacific Gas & Electric, the utility that operates the facility, announced on April 23 that the Unit 1 reactor was shut down for a scheduled refueling. Roughly 1,000 temporary employees were brought in to perform the operation, as well as test components and other systems not accessible during regular plant operation, according to a news release.
The refueling is scheduled to last approximately “several weeks,” according to PG&E Spokesman Tom Cuddy. Each of the plants’ two reactors are refueled approximately once every 18 months.
But the reactor shutdown didn’t go smooth at first. According to a log on the Nuclear Regulatory Commission’s website, which tracks events at the plant, there was a problem when crews attempted to transfer the unit’s power to its offsite source at approximately 4 p.m. on April 21. They were eventually able to successfully manually transfer power without causing any harm to equipment, according to Diablo’s NRC Resident Inspector, Michael Peck.
Then on April 23, as the first unit remained down, the second reactor had to be reduced to only 15 percent of its capacity after a group of salps—barrel-shaped invertebrates similar to very small jelly fish—clogged the reactor’s seawater cooling intake filter, Cuddy confirmed.
NRC Spokesman Victor Dricks said the incident didn’t create a safety hazard, and that power was reduced as a precautionary measure. As of press time, Dricks said the plant’s second reactor was operating at 25 percent as crews worked to fix the intake problem.
Given that the San Onofre nuclear plant has been inactive due to issues with its reactor steam generators since January 2012, the recent combination of events at Diablo led to the first time in recent memory that California has been operating on no more than a quarter of its nuclear power supply, according to officials.