Energy Northwest expects to have its nuclear power plant near Richland supplying electricity to the grid by Christmas.
The Columbia Generating Station automatically shut down Sunday morning because of a Bonneville Power Administration transmission line problem.
A high voltage transmission line connected to the BPA Ashe Substation, but not the nuclear plant, tripped. A breaker then should have immediately opened to cut off power to the line at the substation. The breaker was slow to open, according to BPA.
Because of the breaker malfunction, a secondary system kicked in and opened other breakers, including for the line that transmits power from the nuclear plant to the nearby Ashe Substation.
BPA continues to investigate the breaker malfunction, including whether it was related to subzero temperatures. The plant will not be restarted until the issue is identified and fixed.
About 12 hours after the nuclear plant shut down, a leak of uncontaminated water was discovered in a line supporting a spray system to keep the reactor core cool in an emergency. It is one of six systems in place to cool the core in an emergency. The water leak was quickly repaired, according to Energy Northwest.
The Columbia Generating Station is a 1,190-megawatt plant, which can supply the electricity requirements of a city the size of Seattle.