* updated below *
The Vermont Yankee nuclear power station began an unscheduled shutdown Sunday night after engineers found a new leak in a key system pipe at the Vernon reactor.
The plant shutdown began at roughly 7 p.m., said Entergy Vermont Yankee spokesman Larry Smith, after plant operators has earlier identified leakage of approximately 60 drops per minute from a feedwater pipe located in the plant's turbine building.
Technicians and engineers later located the leak in the feedwater system piping.
VY previously repaired a leak in a feedwater pipe in August 2009. That one leaked about two cups per minute.
"The leak is in a 24-inch pipe located by the feed water pumps in the plant’s turbine building," Smith told Seven Days. The feed water system is not a safety system, Smith notes. It returns water to the reactor from the plant's turbines — but at high pressure and high temperatures.
The leaking pipe is 24 inches in diameter and cannot be repaired with the plant in operation, Smith said. Therefore, a conservative decision was made to take the plant out of service to perform a repair.
The Nuclear Regulatory Commission's (NRC) Resident Inspector has been informed of the issue and of the plan to remove the station from service. The plant had been operating at reduced power for a scheduled rod pattern adjustment and to support line work by Public Service Company of New Hampshire. The plant had been on line for 163 days of continuous operation, Smith added.
Regional NRC spokesman Neil Sheehan told Seven Days that the senior resident inspector was on his way to VY to observe the plant shutdown.
"The leakage is on a feedwater line downstream of the reactor. It is considered non-safety related," Sheehan said.
The new leak comes at an inopportune time for Vermont Yankee's owner Entergy. The company announced last week it was trying to put the reactor up for sale. The reactor's license expires in 2012 and some VY critics see the sale as a last-ditch attempt to keep the plant operating beyond its scheduled operating date.
Entergy has lost the trust of many in Vermont, as well as some key political leaders — including Governor-elect Peter Shumlin, the Democrat who led the charge earlier this year to force a vote in the state Senate on VY's future. By a 26-4 vote, Senators decided that it was not in the best interest of the state to allow Vermont Yankee to continue operating beyond 2012.
The news also comes just two weeks after another leak was discovered. That leak, in a safety-related pipe, was not serious enough to warrant a shutdown. It had been found in late September, but was only made public in late October after members of the media made inquiries.
Earlier in October, the Vermont Department of Health revealed that tritium had been found in an on-site drinking water well. Previously, tritium had only been found in groundwater.
* update - Monday 8 p.m. *
Vermont Yankee officials have found, and isolated, the source of the leak in the 24-inch water pipe that caused the plant to shut down.
"Repair work to a leak on a 24 inch feed water pipe is scheduled to begin this evening. The leak, which was identified late Saturday by plant operators, was found to be coming from a two-inch access plug in the pipe located in the feed pump room of the plant," said VY spokesman Larry Smith in an email to media.
The access plug was used for radiography of pipe welds during original construction of the plant. Technicians will replace the seal weld with a more substantial fillet weld to the plug. Repairs will take approximately 24 hours to complete at which time the plant will be restarted, noted Smith.
A similar plug was the source of a leak in the feedwater system in early 2009. The feedwater system carries slighty radioactive water in a closed-loop system between the turbines and the plant's reactor. Water travels through at very high temperature and pressure.
The faulty plug is approximately a half-inch in size inside a two-inch port, added Neil Sheehan, a regional NRC spokesman. Both the port and the plug are welded into the piping.
"Workers had to remove insulation wrapped around the line to get at this. What initially appeared to be a roughly three-inch flaw was actually this port, or opening," said Sheehan.