The South Texas Project reported yesterday to the Nuclear Regulatory Commission that its Unit 2 reactor shut down Tuesday morning. Problems with the reactor actually went back more than a week, as an NRC Event Report from today spells out.
On Sunday, November 20, maintenance workers placed a jumper on both channels of the turbine trip circuit. This action disabled the reactor’s ability to generate a turbine trip in three different incident scenarios. The jumper remained on the circuit for about four hours. It was removed about 9:30 Sunday morning.
According to the Event Report, this maintenance error constituted “a safety system functional failure. If not corrected, this condition could have prevented the fulfillment of the accident mitigating and control of the release of radiation safety functions.”
A review of the 2010 Unit 2 reactor refueling outage is underway to see if the same problem was in effect during that outage.