Power at Exelon Generation's 1,362-MW Nine Mile Point-2 nuclear reactor in Scriba, New York, was reduced late Thursday from 100% of capacity "due to an air leak in an instrumentation line," plant spokeswoman Jill Lyon said in an email Friday.
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The unit was operating at 52% early Friday, according to the US Nuclear Regulatory Commission's daily reactor status report.
Citing "competitive reasons," Lyon declined to estimate the duration of the repair work being done on the line, or when the unit would return to 100% power.
Neil Sheehan, an NRC Region I spokesman, said in an email Friday that one of two of the unit's main feedwater pumps shut automatically at about 4:40 pm EDT (2040 GMT) Thursday. This pump's shutdown, he said, "resulted in a recirculation flow runback, which in turn caused a power reduction to about 51-percent power."
"Troubleshooting has preliminarily identified the cause as an instrument air leak stemming from a 2-inch line failure that caused condensate booster pump valves to unexpectedly open," Sheehan said.
He added: "There is no current timeline for the reactor to return to full power. It will be dependent on the conclusion of troubleshooting activities and any repairs."
NRC's resident inspectors at Nine Mile Point-2, he said, "are following up on the [issue], including the response of plant operators and equipment. They have no immediate safety concerns."
--Jim Ostroff, firstname.lastname@example.org
--Edited by Lisa Miller, email@example.com