The nuclear power plant near Richland began supplying the regional power grid Saturday afternoon after being shut down for nearly 13 days.
Energy Northwest’s Columbia Generating Station was shut down by operators Aug. 20 when an air removal valve in the plant’s turbine building closed, causing a loss of vacuum pressure in the system that turns steam back into water for reuse at the plant.
As part of the shutdown, a supporting cooling system was turned on. Because of recent maintenance work on the supporting system, small amounts of iron entered the reactor water circulation system.
The amounts were at parts per billion, said Energy Northwest spokesman Mike Paoli.
“Reactor cooling water, however, requires the purest water chemistry possible for nuclear fuel efficiency and plant performance,” he said.
Even trace amounts can cause the fuel in the reactor’s core to heat up when the iron adheres to the fuel rods. It can lead to decreased performance or damage the fuel rods.
The valve was quickly fixed, and most of the 13-day shutdown was used to filter the iron out of the reactor water system.
The Columbia Generating Station, which can provide enough energy to power a city the size of Seattle, had set a generation record in July.
Workers were increasing power generation gradually on Sunday.
The plant was at 65 percent power at about 5 a.m. and had reached 85 percent by noon.
Workers were continuing to filter the reactor water circulation system as power increased.
At part of reactor’s generation process, 80,000 gallons of water flow through nuclear fuel rods, which boil the water into steam. The steam turns a series of turbines to generate up to 1,207 gross megawatts of power.
The steam is then condensed back into water and returned to the reactor to repeat the boiling process.
Before the shutdown the plant set a record for power generation in July, after improvements were made during a planned spring refueling and maintenance outage.
Early in August, the Bonneville Power Administration asked Energy Northwest to avoid maintenance and surveillance activities as it braced for a region-wide heat wave and higher-than-usual demand for electricity to power air conditioners in the first week of the month.
Scott Simms, a BPA spokesman, said after the plant shut down Aug. 20 that the federal power agency remained in a strong position because of its diverse power portfolio and because 2017 has been a strong year for snowpack needed for hydro operations.
BPA purchases Columbia Generating Station electricity and distributes it to 92 public power agencies in the Northwest.
The reactor, the third largest generator of electricity in Washington state, can produce enough electricity to power a city the size of Seattle.