The Brattleboro Reformer reported today:
As of Monday evening, Vermont Yankee technicians were troubleshooting a recirculation pump system in an attempt to return the nuclear power plant to maximum output.
On Sunday at 11 p.m., an electrical problem in a motor-generator in one of the plant’s two reactor recirculation pumps forced the plant to power down to 36 percent.
A leading expert on nuclear issues blamed the problem on Vermont Yankee’s age:
Arnie Gundersen, a nuclear safety advocate and a critic of Entergy’s operation of the plant, said the electrical problem is indicative of the plant’s age.
“Power is being controlled by varying the speed of the recirculation pumps,” he said. “Normally the rods absorb neutrons, but at end of life (of the core fuel), steam bubbles are what controls the power output. The faster the pumps go, the fewer steam bubbles and the more power can be produced.”
During the “coast down,” the reactor is being controlled by the recirculation pumps, said Gundersen, and the speed of the pumps is changed by the motor generator.
“The motor controllers are under high-use conditions at end of life,” he said. “It looks like one of the motor controllers is showing its age and has failed.”
The problem occurred amid ongoing legal attempts to close Vermont Yankee:
During the upcoming refueling outage, 120 new fuel bundles will be installed, which is normal procedure, despite the fact that Entergy, which owns and operates the plant, has not received permission from the state to continue operation past 2012.
Another disturbing aspect of this incident is that it has not shown up on the NRC’s Event Reports page. Apparently, a defective pump and resulting decrease in power is not reportable unless the problem lasts more than eight hours:
According to Larry Smith, communications manager for Yankee, plant operators had eight hours to reconfigure the plant to run with only one pump.
“We accomplished that much earlier (on Monday),” he said, and the plant was up to 44 percent at 6 p.m. on Monday night.
And yes, the plant containment does look a lot like some of the Fukushima reactors. Vermont Yankee is a General Electric boiling water reactor like those at Fukushima.