Vermont Yankee Nuclear Power Plant is operating at reduced capacity due to a problem with a key component of the reactor system.
A Yankee official says engineers at the plant are investigating an issue with the condenser.
The condenser is original to the 40-year-old plant and functions something like a radiator — it operates under vacuum pressure and condenses steam from the plant into water and then returns it to the reactor. The condenser is made up of two sections, each the size of a three-story house. Each section has thousands of metal tubes inside it that carry river water, over time the tubing has worn thin.
Last November, during a planned refueling outage, plant workers applied a protective coating — an epoxy or plastic — to the tubing in the condenser in an effort to reduce wear and tear on the metal and extend the life of the condenser.
At the beginning of February, nuclear engineers at the plant discovered that the the thermal heat exchange efficiency of the condenser was greatly reduced. Last week, the plant had to lower its power production by 50 percent because back pressure was building up in the condenser.
Larry Smith, communications director for Vermont Yankee, said the cause of the “reduced performance” of the condenser isn’t clear at this point.
For the time being, the plant cannot operate at full power until the problem is resolved, he said.
“We are evaluating all the associated systems to determine the cause,” Smith said. “It could be any number of things that’s causing the issue.”
Smith said the condenser has been upgraded over time and the tubes were “resleeved” several years ago.
Neil Sheehan, regional spokesman for the Nuclear Regulatory Commission, said the plastic coating Entergy used on the condenser tubes has caused the system to run less efficiently. Until the plant can fix the problem, it will have to run at reduced power, he said.
Last week the back pressure level went up to 4.5 pounds per square inch. The maximum level for the plant is 5 psi, according to Sarah Hofmann, deputy commissioner of the Department of Public Service. At that point, the plant has to power down, Hofmann said. At 7 psi, the plant trips on its own and goes into SCRAM mode.
Vermont Yankee officials have told the state that the epoxy could be the cause of the thermal efficiency problem. Hofmann said she hopes the plant is investigating this theory next week. If the epoxy is the source of the issue, the plant will have to run at 50 percent power levels while workers strip epoxy off of the tubing in each of the sections of the condenser.
“It’s one of the lead theories,” Hofmann said. “We’re waiting while they’re investigating going further.”
Arnie Gundersen, a Burlington-based nuclear engineer and frequent national media commentator on the nuclear industry, said the heat transfer problem will worsen in summer when the water temperature of the Connecticut River rises from springtime temperatures of 50 degrees to 70 degrees.
The warmer water could lead to reduced output at the plant. Every time the plant drops 10 megawatts, it costs Entergy Corp., the plant’s owner, $10 million. The plant’s output could be cut in half and lead to a loss of 40 megawatts to 50 megawatts of power per day in the summer, Gundersen said.
Hofmann said the Department of Public Service is concerned about the broader issues with regard to Entergy’s management of the plant. “It brings up how well the plant is running and also the human error factors,” she said.
Bob Stannard, a lobbyist for Vermont Citizens Action Network, an anti-nuclear group, said the condenser problems call into question the reliability of the plant.
“We’ve known for years the condenser needed to be replaced,” Stannard said. “We’ve known Entergy has a history of deferring maintenance. After 40 years they’re still doing trial and error on the repairs to this plant. You’d think we’d be beyond trial and error phase for maintaining a nuclear power plant.”
Since Louisiana-based Entergy Corporation purchased Vermont Yankee from state utility companies CVPS and Green Mountain Power in 2002, the plant has had a string of physical plant problems including a water tower collapse and a transformer fire. In January 2010, the company revealed that underground pipes at the plant were leaking tritium into soil on the compound, which is located on the banks of the Connecticut River.
The plant’s license to operate in Vermont expires on March 21. Pro- and anti-nuclear activists plan protests in the run up to the plant’s 40-year anniversary.
In 2009, the Vermont Senate voted to deny permission for Entergy to obtain a certificate of public good from the Public Service Board for relicensure of the plant, which employs 650 people in the Vernon area where the plant is located. The plant has since become the center of litigation. Entergy sued the state over several statutes, including one that gives Vermont jurisdiction over the continued operation of the plant past the 40-year deadline and a say in the long-term storage of nuclear waste on site.
Entergy won the first round of the suit in U.S. District Court; the Vermont Attorney General has appealed. Scholars and observers say the case could go the U.S. Supreme Court.