STP Nuclear Operating Co.'s 1,312-MW South Texas Project-1, which automatically shut Feb. 15 amid bitter cold, connected to the grid at 9:07 pm CT Feb. 17 "and is currently ascending to 100% power," company spokeswoman Vicki Rowland said Feb. 18.
The unit, located in Bay City, Texas, was operating at 36% of capacity early the morning of Feb. 18, the US Nuclear Regulatory Commission said in a daily reactor status report.
Rowland said Feb. 16 the unit shut "due to cold weather-related issues in the plant's feedwater system." Weather conditions did not impact the 1,312-MW South Texas Project-2, which operated at 100% early Feb. 15-18, according to NRC.
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Rowland said the unit shut at 5:37 am CT Feb. 15. STPNOC said in an event report filed with NRC that the unit tripped at 5:26 am due to low steam generator levels. "The low steam generator levels were due to loss of Feedwater pumps 11 and 13," according to the report.
The unit had operated at 100% early Feb. 14, according to NRC.
The Electric Reliability Council Of Texas Inc., or ERCOT, which operates the electric grid for most of the state, was hit particularly hard by Arctic cold, with state officials, grid operators and regulators asking residents to reduce electric consumption after more than 30 GW of capacity was forced offline, the worst blackouts in the state in decades.
ERCOT issued an emergency alert Feb. 15 as reserve margins, the difference between total power supply and demand, dropped below 1,000 MW. At its highest point, the grid shed about 10.5 GW of customer load, enough to power two million homes.
In the early hours of Feb. 15, generators began tripping offline in ERCOT, grid officials said in a Feb. 15 call. Natural gas generators faced low gas supplies, while ice froze wind turbines, the officials said.
In turn, transmission providers faced difficulties balancing supply and demand. The majority of plants that went offline overnight were thermal generators, they said.
