The US Nuclear Regulatory Agency is investigating "safety system and equipment problems" during the unplanned shutdown of Entergy's 688MW Pilgrim nuclear power plant in Plymouth, Massachusetts when a major winter storm hit New England on 27 January.
The single-reactor plant shut safely and the outage has not affected New England's wholesale power markets. But the US nuclear agency is concerned about the loss of two off-site 345kV transmission lines connecting Pilgrim to the regional grid during the storm.
The first of the lines tripped in the early hours of 27 January as a result of the storm. The power plant started to power down according to a protocol but the loss of the second 345kV line forced the reactor to shut fully at 4am ET.
Access to external sources of power is a crucial safeguard for nuclear plants, which in their non-generation mode still consume significant amount of energy for safe reactor operations.
The loss of external power after the Fukushima-Daiichi nuclear plant powered down following a devastating tsunami in Japan in March 2011 sparked the sequence of events that incapacitated the plant's operations and eventually resulted in a meltdown. The US agency has pledged to "continue lessons-learned activities related to the Fukushima nuclear accident," so it has paid special attention to external supply violations at the US plants.
The plant operator relied on two emergency diesel generators and would have been able to rely on the third, 23kV external power line. But the US nuclear agency also said one of the condensate pump motors in the plant's coolant injection system failed during the shutdown and one of four safety relief valves malfunctioned.
Entergy said it is investigating the cause of the events and is sharing information with nuclear regulators about "procedures and actions taken that helped assure safety at the plant before, during and after the storm."
Nuclear plants in New England and elsewhere in the US have had to cope with significant public opposition, which increased in the wake of the Fukushima disaster. Commercial prospects for nuclear plants also have soured in the deregulated US power markets. Entergy permanently shut the 605MW Vermont Yankee plant late in 2014 for economic reasons.
The US nuclear agency's fiscal year 2016 budget proposal was unveiled yesterday. It provides for a 2.5pc decrease in planned spending to $1.03bn. The agency is cutting staff and funding for the New Reactors and Fuel Facilities office, citing decreased workload. Investors' interest in new US nuclear facilities has fizzled as four out of five US reactors under construction face significant delays.
Net proposed appropriations for the agency will be $122mn in the fiscal year starting 1 October, as it funds about 90pc of its budget from nuclear license fees.
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