Tennessee Valley Authority's 1,210-MW Watts Bar-2 nuclear generating unit in Spring City, Tennessee, remained shut Tuesday as workers investigated the cause of the unexpected drop of control rods into the core Monday, a TVA spokesman said.
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The unit was manually shut by operators after the incident Monday morning, in which several control rods, which are used to shut and start the reactor, dropped into the core, according to an event report filed to the Nuclear Regulatory Commission by the TVA. The shutdown process went normally and there were no safety issues during the incident, the TVA spokesman, Jim Hopson, said in an interview.
The unit had been operating at 97% of capacity early Monday following its return to service from a refueling and maintenance outage last week. It was the first refueling outage for the unit, which started commercial operation in October 2016.
The unit is in hot standby, meaning it is not producing power but reactor coolant is being maintained at operating temperatures, while workers study the cause of the problem and make needed repairs, Hopson said. He did not say when the unit would return to service.
Watts Bar-2 shut October 27 for the refueling outage. It had been operating at 60% of capacity Saturday and 91% Sunday, the NRC said in daily morning reactor reports.
The adjacent and same-capacity Watts Bar-1 nuclear unit was operating at 100% of capacity Tuesday, the NRC said.
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