San Onofre

The San Onofre nuclear power plant’s Unit 1 reactor was started up Thursday morning, despite damage to bolts that hold an important thermal shield, a Southern California Edison spokesman said.

The plant received the go-ahead from the federal Nuclear Regulatory Commission earlier this month after the commission determined that the damage would not affect safe operation of the reactor.

Three bolts of 30 that hold down the thermal shield were discovered earlier this year to be partly unscrewed, and others appear to be damaged.

The thermal shield, a 2 1/2-inch-thick cylinder that absorbs gamma rays from the nuclear core, rests on six supporting blocks and is linked to the reactor floor by the 30 bolts.

The utility will inspect the thermal shield in June, 1990, to see if repairs are needed, the spokesman said. At the latest, the repairs will be made about January, 1991, when the reactor is again shut down for servicing.

SCE officials have said they want to delay replacing or repairing the bolts because all the fuel from Unit 1’s reactor core would have to be removed at a time when storage space for spent fuel is scarce.