The Tennessee Valley Authority (TVA) Sequoyah 1 nuclear plant remained offline early Sept. 15 after a problem with an instrument board during the pre-dawn hours of Sept. 14, according to Nuclear Regulatory Commission (NRC) data.
“At 0426 EDT on 9/14/2015, Sequoyah Unit 1 was at 100% power when the Vital Instrument Power Board (VIPB) 1-II de-energized,” according to an NRC event report. A manual reactor trip was initiated.
“”Current Temperature and Pressure – Reactor Coolant System (RCS) temperature is 547 degrees F and stable and RCS pressure is 2235 psig and stable. There is no indication of any primary to secondary leakage. All rods fully inserted on the reactor trip and remain inserted. The electrical alignment is normal with shutdown power supplied from off-site power,” according to the NRC report.
A post-incident investigation is in progress “and planned restart timeline has not yet been determined,” according to the NRC report.
There was no operational impact on Sequoyah Unit 2, which continues to operate at 100% power.
Sequoyah Units 1 and 2 are pressurized water reactors (PWRs) and each has a generating capacity in excess of 1,100 MW. The Sequoyah complex is located in Hamilton County, Tenn.