(Host) The Vermont Yankee nuclear plant has been forced to reduce power because a key component is causing problems.
And the state says Yankee technicians made a mistake and left a metal plate inside the component as they were trying to troubleshoot the issue last week.
As VPR’s John Dillon reports, that incident prompted the Shumlin Administration to ask federal regulators about a recent series of human errors at the plant.
(Dillon) The component that’s acting up is called the condenser. It’s like a giant, house-sized radiator that turns steam back into water. The condenser tubes have leaked and the entire part is scheduled to be replaced in four years -at a cost of around $150 million.
Yankee cut its power output in half last week as it tried to find out why the condenser was not working properly. Here’s plant spokesman Larry Smith:
(Smith) We’re seeing a loss of efficiency in our condenser. It’s due to what’s called air in leakage. It’s air that’s getting into the whole condenser system which shouldn’t be there.
(Dillon) The state says that when Yankee reduced power and inspected the condenser last week, technicians discovered that a metal deck plate had been left inside during a recent refueling outage. The plate was a piece of metal large enough for workers to stand on.
Neil Sheehan is a spokesman for the Nuclear Regulatory Commission. He says the agency is aware of the incident.
(Sheehan) It’s an issue that’s affected not only Vermont Yankee but numerous other plants over the years where there’s foreign material that’s left behind when a job is completed. We don’t think that’s acceptable and we certainly had that discussion with them and our inspectors will certainly be addressing that in an upcoming inspection report.
(Dillon) The NRC recently released an annual report on Yankee that cited a number of what it called non-safety issues at the plant. The NRC concluded that the plant does not need additional safety inspections or oversight.
But Public Service Commissioner Elizabeth Miller says the most recent incident of the metal plate left inside the condenser raised questions about whether Yankee was experiencing a pattern of human errors. She’s asked the NRC for an explanation.
(Miller) In looking at the reports I had a concern that there had been a number of incidents and felt it was appropriate to ask the NRC to explain why that pattern of incidents didn’t deserve further attention or further action by the NRC and so that’s why we sent the letter.
(Dillon) Miller’s letter to the NRC cites other mistakes, including a case last fall when Yankee technicians misread a work order and shut down a breaker, resulting in a brief loss of the shutdown cooling system. Another case occurred in December when workers mistakenly tripped the wrong diesel back up generator.
Yankee spokesman Larry Smith said he could not comment on Miller’s letter. The NRC said it would review it.
Meanwhile, Yankee is still trying to figure out what’s wrong with the condenser. The NRC says a leading theory is that epoxy coating used to control leaks may be reducing the ability of condenser tubes to convert steam back to water.
For VPR News, I’m John Dillon in Montpelier.