Pilgrim nuclear plant is back on-line

The Pilgrim Nuclear Power Station in Plymouth went back in service late Friday night after being off-line since last weekend’s powerful winter storm, according to the Nuclear Regulatory Commission.

The plant, owned by Entergy Corp. of Louisiana, originally went out of service Feb. 8 when the storm knocked out the plant’s off-site power lines. Power was restored on Sunday morning but lost again that afternoon when ice fell on a switchyard line and caused a transformer electrical fault.

Power was restored Tuesday, but the plant remained out of commission to repair a leaky safety relief valve, the NRC said.

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“Our resident inspectors assigned to Pilgrim kept close tabs on the loss of off-site power throughout the storm and afterwards,’’ Neil Sheehan, an NRC spokesman said in an email Saturday morning. “They also tracked the company’s work to fix the safety relief valve. They did not identify any immediate safety concerns.”

Pilgrim’s shutdown was its third this year. The first two — both in January — were caused by equipment issues at the plant.

The leaky safety valve now being repaired caused one of the January shutdowns. The other one happened when the plant’s recirculation pumps, used to adjust power levels, stopped working.

Pilgrim, which began operating in 1972, was relicensed by the NRC last year. The license extends until 2032.

An Entergy spokesman confirmed that operators returned the plant to service at 10:49 p.m. Friday when it was reconnected to the New England electric transmission grid.