The Nuclear Regulatory Commission has begun a Special Inspection at the Millstone Unit 2 nuclear power plant to review issues associated with an “Unusual Event” declared at the facility on Oct. 4. The two-member team arrived at the Waterford, Conn., plant Oct. 13 to begin the review.
Operators at the plant declared an “Unusual Event” – the lowest of four levels of emergency classification used by the NRC – at about 9:30 a.m. on Oct. 4. The declaration was based on reactor coolant system leakage of greater than 25 gallons per minute. The leakage came from a relief valve on the plant’s shutdown cooling system, which is used to provide cooling to the reactor when it is out of service. The Dominion-owned and operated plant was preparing to enter a refueling and maintenance outage at the time of the event.
In response to the leakage, the shutdown cooling system was isolated from the reactor coolant system, allowing repairs to be made and the return of the system to operational status. The emergency declaration was terminated at 11 a.m. All of the leakage was contained within other plant systems, as designed.
After conducting a preliminary assessment of the event, the NRC has determined that it meets the criteria for a Special Inspection. Among other things, the team will review operator response to the event, equipment performance and immediate corrective actions.
““Our initial review of the event has raised questions regarding operator performance,” NRC Region I Administrator Dan Dorman said. “We have determined that the use of a Special Inspection is appropriate in this case to help the NRC better understand Dominion’s response to the event.” A report documenting the team’s findings will be issued within 45 days after the conclusion of the inspection.