Vermont Yankee confirms 'A' line leak stopped

The work to isolate the remaining internal leak from the A AOG recombiner steam trap drainline into the AOG tunnel is complete, according to a statement released Tuesday afternoon from Vermont Yankee. Monday night, the A drainline was successfully isolated. On Tuesday, inspection of the AOG tunnel using a remotely operated camera indicates that the internal leak from the A drainline to the tunnel has stopped. When the inspections are complete, the A drainline will be rerouted and be put into standby status.
Vermont Yankee engineers and technicians are continuing to plan for soil and groundwater remediation. The installation of the well and equipment to support the pumping operation for extracting groundwater continues. To date, there has been no detectable tritium levels found in any samples taken from drinking water wells or the river. The Vermont Department of Health and Nuclear Regulatory Commission personnel are monitoring the investigation.
Steam Trap Drain Lines Re-routed The 'B' train of the Advanced Off-Gas (AOG) hydrogen recombiner steam trap drain line has been temporarily re-routed to take it out of the AOG pipe tunnel. The B train is now back in service, allowing shut down of the A train last night. Workers will now modify and re-route the A train in the same manner.
Once both the A and B trains are re-routed, this leak pathway to the AOG pipe tunnel and out into the environment will be eliminated. A camera will be installed in the AOG pipe tunnel to monitor conditions there, and another remotely operated vehicle (ROV) inspection of the pipe tunnel will be completed to make sure all leaks have been elimated by these temporary modifications. Both A and B trains will be permanently re-routed during the April/May 2010 refueling outage.
Extraction Well Drilled Drilling of the groundwater remediation extraction well was completed today, March 23. This well, GZ-EW1 and water filtration equipment should be ready sometime this week to begin pumping out significant quantities of tritium-contaminated water from the ground. This extracted water will be treated and stored on-site to be re-used by Vermont Yankee.
Monitoring Well Test Results Monitoring Well Test Results Testing by the Vermont Department of Health and Vermont Yankee of on-site and off-site drinking water well samples, as well as water taken from the Connecticut River, continue to show no tritium in excess of the lower limit of detection (
The most recent well results reported by Vermont Yankee are listed below. All results are expressed in terms of picocuries per liter (pCi/l), or below the lower level of detection (
GZ-1:

Background
On January 7, 2010 the Vermont Department of Health was notified by Vermont Yankee Nuclear Power Station that samples taken from a groundwater monitoring well on site (identified as GZ-3) contained tritium.
Tritium is a radioactive form of hydrogen. It is a by-product of the nuclear fission process in a nuclear reactor, and also occurs naturally in the environment in very low concentrations. Most tritium in the environment is in the form of tritiated water, which easily moves about in the atmosphere, bodies of water, groundwater and through soil and around rock. The finding of tritium in groundwater signals that there has been an unintended underground release of radioactive material, and that other radioisotopes may have contaminated the environment.
Vermont Yankee officials are conducting an investigation to identify the source(s) of the tritium, and the magnitude of contamination, with the Nuclear Regulatory Commission (NRC) in an oversight role. The groundwater monitoring well initiative is a voluntary program sponsored by the NRC to detect unintended releases such as this.
On February 14, one major source was identified and stopped. A pair of steam pipes inside the Advanced Off-Gas (AOG) pipe tunnel were found to be badly corroded and leaking nuclear steam.The floor drain of this concrete tunnel was clogged with debris and mud. As a result, the condensate from the steam pipes pooled inside the tunnel and leaked out at a failed joint in the tunnel. (This is depicted as blue water drops on the AOG Building Schematic.)
Soil testing in the area around the leak has measured concentrations of the radioactive metals cobalt-60, manganese-54, zinc-65 and cesium-137 consistent with a leak of nuclear reactor water. This confirms the pathway of tritium into the environment. Steadily decreasing tritium concentrations in samples taken from the groundwater monitoring well next to the pipe tunnel confirm that this leak has been stopped. Well test results from other groundwater monitoring wells drilled since January show the movement of tritium contamination in the groundwater generally west to east into the Connecticut River. (see Monitoring Well Location Map)
Since the leak was first reported, the Vermont Department of Health has been closely monitoring and reporting on the investigation, has stepped up the frequency and number of water and environmental samples tested at the public health laboratory, and has been independently analyzing health risk. With assistance from Vermont's Agency of Natural Resources, Vermont Emergency Management, and other state agencies, a team of health and environmental experts have been regularly on site as independent analysts. This work is ongoing as Vermont Yankee continues its investigation and study of other plant systems and components to identify, repair, or remediate similar extent of conditions that could result in a leak.
Regular updates are presented here. See the Investigation Archive for the history of this investigation.
Sources: Vermont Yankee, 3.23.2010. Vermont Department of Health, 3.23.2010.