BRATTLEBORO -- Two recent incidents at Vermont Yankee have nuclear safety advocates concerned about personnel issues at the nuclear power plant in Vernon.
On Oct. 12, a technician accidentally flipped the circuit breakers on the shut down cooling system, which is used to keep the reactor vessel cool during refueling and maintenance outages.
And on Dec. 2, a technician disconnected a fuel line on one of the plant's emergency diesel generators, disabling it at the same time the other generator was down for maintenance. The generator was out of commission for two minutes, according to the Nuclear Regulatory Commission, which stated both incidents were of low-safety significance.
In an e-mail to the state's nuclear engineer, nuclear safety advocate Arnie Gundersen stated the mistakes were indicative of concerns raised by the Public Oversight Panel, which reviewed a reliability audit of the plant.
Gundersen was a member of the panel.
"The Oversight Panel felt pretty strongly about the need to improve VY's procedures to include human factors issues as the plant staff ages and retires," stated Gundersen in the e-mail. "These latest problems at VY cause me to remain concerned about issues that were identified by the Oversight Panel three years ago."
Ray Shadis, technical consultant for the New England Coalition, which opposes the operation of Yankee, said the events prove the plant's quality assurance and corrective action programs are inadequate.
"Employees are repeatedly having similar, if not identical, Homer Simpson moments," noted Shadis, in an e-mail to the media.
He added the events are indicative of a "sub-standard nuclear safety consciousness" at the plant.
Despite the fact that the incidents did not affect safety at the plant, said Neil Sheehan, spokesman for the Nuclear Regulatory Commission, "It doesn't excuse the fact that there needs to be a greater awareness in these situations. They need to be sure they're doing work on the right piece of equipment."
There also needs to be better coordination between the team leading the maintenance and the actual technicians performing the work, he said.
In the Oct. 12 incident, the flipping of the circuit breakers resulted in a 2-degree increase in the temperature of the reactor's coolant water.
"The error was not on the part of the operator who closed the breaker to remove it from service but rather the team that was guiding the operator based on a plant data base and associated drawings," stated Sheehan in an e-mail to the media.
The mistake caused the shutdown cooling system to stop functioning, which actuated an alarm.
"We would note that because the reactor vessel head was out at the time, and the cavity around the head location flooded up, the water circulating through that area was in connection with the spent fuel pool water," stated Sheehan. "The systems used to keep the spent fuel pool water cooled remained in operation throughout."
In his response to Gundersen's e-mail, state nuclear engineer Uldis Vanags responded that the flipping of the circuit breakers was due to "a lack of clarity in the Control Wiring Diagram."
"That drawing is 40 years old, and now they discover it lacks clarity?" asked Gundersen in an e-mail to the Reformer. "If this problem existed for 40 years, that is not an adequate root cause analysis. The POP was very concerned about this knowledge transfer issue. This proves our point."
Vanags also wrote that Entergy, which owns and operates the plant, and the NRC are reviewing whether there is a "common cause" between the circuit breaker and fuel line incidents.
"If there is a common cause among these two events we will not know until the root cause is completed for the tripping of the A Emergency Diesel," wrote Vanags. "NRC is aware of both events but I cannot discuss any actions they may or may not be taking."
According to Sheehan, the resident inspectors determined the plant remained safe during the circuit breaker incident.
"They subsequently did interviews with personnel involved and evaluated the company's corrective actions, which include updating the data base used for this ‘tag-out' activities," stated Sheehan.
Entergy has until Feb. 12 to file its official review of the events.
Sheehan said even though both emergency generators were inoperable during the Dec. 2 incident, the plant had access to emergency power if needed -- back-up batteries, a tie-in to the Vernon Hydroelectric Dam and a connection to the New England power grid.
Bob Audette can be reached at firstname.lastname@example.org, or at 802-254-2311, ext. 160.