VERNON — Technicians at Vermont Yankee are removing a motor generator in the nuclear plant's reactor building to determine the cause of an electrical failure that produced smoke Monday afternoon.
Rob Williams, a spokesman for Vermont Yankee, said the plant was operating at 38 percent power Tuesday morning. It reduced its power to 36 percent Monday.
“This morning, we are making preparations to remove the motor and continuing our investigation as to what happened,” Williams said.
There are two motor generator sets at the plant. The generators vary the flow of reactor coolant water which, in turn, changes the reactor power level.
The motor generator sets are not safety related, Williams said.
He said the plant will remain at reduced power while the investigation is being conducted and repairs are completed.
Williams said there appears to be damage to the electrical parts of the motor. The other motor is functioning normally.
Critics of the nuclear plant say the electrical failure is another indication of the 40-year-old plant showing its age.
Arnie Gundersen, chief engineer for the consulting company Fairewinds Associates, said the issue will probably keep the plant at reduced power for a significant period of time.
“This is not something you start back up in 12 hours,” he said.
Gundersen said the fact that there was smoke in the reactor building is a bad sign.
“Where there's smoke, there's fire,” he said.
Gundersen said the nuclear reactor is about 100 feet from the motors, but it is contained.
The plant, which is the subject of federal litigation and proceedings before the Vermont Public Service Board, is seeking a new license.
The plant has experienced problems with its condenser - a mechanism that acts like a giant radiator - also this year.
David Lochbaum, director of the nuclear safety program at the nonprofit Union of Concerned Scientists, had also looked into the motor generator's failure.
“[VY] did exactly what they were suppose to do,” he said about the company's response to the equipment issue.
Still, he did not give the plant a gold star.
In his press release on the event, Williams wrote that the motor generators were “not safety related."
According to Lochbaum, Williams' characterization in regards to nuclear regulation followed “more the letter of the law than the spirit of the law."
The motor generators, classified as “non-safety,” are a “complex set of moving parts” that use large quantities of oil. As a precaution these generators contain their own fire suppression systems.
“You never want smoke,” said Lochbaum, adding that fires in these generators can be quickly contained.
Still, the motor generators sit a portion of the building that also contains critical equipment. A problem in one piece of equipment could “domino."
Turning off the pumps can also lead to the plant becoming unstable in terms of delivering power to the grid and a plant's functioning, he added.
According to Lochbaum, energy output in Boiling Water Reactors like VY's depends on a combination of water flow and the removal or insertion of power rods. Turning off the pumps can cause power fluxes.
The LaSalle nuclear plant in Illinois, owned by Exelon Nuclear, experenced a similar issue in 1988 when the recirculation pumps were shut down. The plant's output fluctuated every 2 seconds to as low as 35 percent power until it finally shut down at 120 percent.
“This one [VY] didn't,” said Lochbaum. “But you don't want to take too many steps in that direction."
Without knowing what caused the generator motor to fail, he said. It's hard to know if the issues stem from the plant's age or other conditions.
According to Power Reports from the Nuclear Regulatory Commission, since January, VY has operated below 50 percent power 14 times. The lowest output was 20 percent on Jan. 31. The power output was 41 percent on June 12.