A Note from Rob Williams at Vermont Yankee
February 5, 2010
Vermont Yankee engineers working to identify the source of tritium in the plant’s groundwater now have ten monitoring wells in service and four others being prepared for sampling. As I have noted previously, the well data is being used to further characterize the tritium concentration in the groundwater near equipment and buildings. The wells between the plant and the river show concentrations about the same as yesterday. However, the well just to the east of the plant’s condensate water storage tank and underground piping that had the higher concentration of about 775,000 yesterday has varied some and is now at about 834,000. Since those figures are indicative of being much closer to the source than the other wells, the investigators are focusing on underground piping in that area.
One underground structure in that area is the offgas pit sump (a concrete vault) which is designed to collect and hold water from various sources in the plant. A sample of water in the sump was analyzed and found to contain a tritium concentration at 2.7 million picocuries per liter. This is not unexpected because it contains piping that contains water with similar tritium concentrations. The team does not believe the sump itself is a likely source. However, the sump pump discharges into buried piping connected to the radwaste facility. Even though the sump pump operates infrequently for very short periods of time, as a precautionary measure, the pump has been removed from service. Additional investigation of this sump is in progress.
While this investigation continues, it is important to note that there has been no elevated tritium level found in any drinking water well samples or at any location not on plant property.
For more details on the tritium investigation, the Vermont Department of Health has a thorough status report on the investigation at this web link: http://healthvermont.gov/enviro/rad/yankee/tritium.aspx
Also helpful is the Nuclear Regulatory Commission web page on tritium monitoring: http://www.nrc.gov/reactors/operating/ops-experience/grndwtr-contam-tritium.html
- Rob Williams
Entergy Vermont Yankee
Rwill23@entergy.com
