Drywell Leakage Prompts Shutdown at Nine Mile Point Nuclear Plant

Unit 2 at upstate New York’s Nine Mile Point nuclear plant remains shut down after excess drywell leakage last weekend prompted operators to declare an unusual event at the reactor.

According to a Nuclear Regulatory Commission event notification report, unit 2 was shut down at 3:45 a.m., EDT, Saturday about two hours after a rise in drywell floor drain leakage and drywell pressure triggered an alarm. The control room reduced power to try to mitigate the conditions, but operators eventually declared an unusual event – the lowest of the NRC’s emergency classifications – as leakage reached 11.3 gallons per minute. Operators have shut the reactor down completely to inspect the drywell and terminated the unusual event notice after confirming that leakage rates, radiation levels, drywell pressure and other measurements were normal.

The cause of the leakage was unknown, according to the NRC report. An NRC spokesman told the Lake Oswego Palladium-Times the excessive leakage appeared to come from a valve on a recirculation pump inside the drywell.

The reactor, one of two at the plant 40 miles northwest of Syracuse near Lake Ontario, uses a 1,140-megawatt General Electric Type 5 boiling water reactor with Mark II containment. It is owned by Constellation Nuclear Energy Group – a partnership between Constellation and EDF – with Long Island Power Authority holding an 18 percent stake.

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