Watts Bar Unit 2, the country's newest nuclear reactor, which reached first criticality on May 23, reached 42 percent of full power on Thursday, the highest level to date, as testing continues on power generation and active physics of the new plant.
The Tennessee Valley Authority, which owns the plant, has kept quiet about the ups and downs of the reactor's first month since being synched to the grid, which occurred on a Friday, June 3. On Sunday, June 5, the reactor automatically shut down. The event is listed in the Nuclear Regulatory Commission's (NRC) daily plant status reports as a “forced outage – automatic reactor trip and SI actuation due to failure of TG governor valve.”
The unit was listed at 10 percent of full power when the forced outage occurred. The notation for that Sunday, June 5, says operators were holding the unit steady for turbine testing and “repair of small secondary steam leak.”
Before the shutdown, Unit 2 had reached a peak of 14 percent of full power on June 3. The prior week, it was shut down May 31 for turbine trouble shooting.
There are no added notations to the figures for the rest of June, except for notes that say “increasing power” after it was brought back up to 3 percent of full capacity on June 8 and “rolling the turbine, preparing to synch to the grid” on June 9, when the unit reached 12 percent.
Power ascended slowly through June 20, when it reached 33 percent of full power. The next day, the unit was listed at zero power. On June 24, a Friday, power returned, reaching 13 percent, which was increased to 29 percent on Sunday, only to be returned to zero on Monday June 27.
Power was not revived until July 2, when the unit was listed at 3 percent of full power. It jumped to 29 percent on July 3, to 35 percent on July 5, a Tuesday. On Wednesday: 41 percent. Thursday: 42 percent.
The fits and starts pattern to a reactor startup is predictable and the TVA says that power ascension testing “continues to validate that Unit 2 will operate as designed and that a quality asset will be put into operation in the near future.”
The plan, says the TVA, is to bring the unit up to full power, while plant systems and controls are fully monitored and tested. The plant will then be shut down and brought back up to full power. The TVA then says it will not declare the plant an officially commercial operation until it has operated for 20 days at full power.