A Note from Larry Smith at Vermont Yankee

March 1, 2010

Vermont Yankee engineers and technicians continue their investigation into the source of tritium in the plant's groundwater.

As previously reported, the team has identified a pathway in the concrete encasement of the Off Gas OG-100 drain line that could allow leakage from the Advanced Off Gas (AOG) pipe tunnel to the soil. An initial integrity test was performed that validated that water can flow from this path. A boroscope inspection of the inside of the AOG pipe tunnel confirmed that the connection of the OG-100 pipe to the drain line was intact and showed no leakage. The inspection did show that leakage could occur through the concrete wall of the AOG pipe tunnel around the outside of the drain line pipe.

Engineers and technicians continue to review the information, but have not ruled out any possibilities and are considering all potential leakage pathways until results are conclusive. Currently, plans are being developed to remove concrete blocks at the junction of the tunnel and the OG-100 connection to allow for remote inspection of the tunnel. That test is expected to occur mid to late week. Engineering is also continuing plans to identify pipe and locations where guided wave technology can be used to inspect piping.

It is important to again note that during the testing, no active process leakage has been observed. An engineered catch basin has been installed to capture potential leakage encountered at the unearthed AOG tunnel.

As expected, soil samples gathered for analysis from underneath the concrete encasement of the Off Gas OG-100 drain line showed low levels of plant related radionuclides. However, the soil acts as a filter for the particles and they are only located within a few feet of the leak source. Mitigation plans for the removal of this soil are being developed.

The Vermont Department of Health and Nuclear Regulatory Commission personnel are at Vermont Yankee and are monitoring the investigation.

Down hole geo-physics testing of six monitoring wells is in progress. The purpose of this testing is to determine the structure of the bedrock. Geo-physics testing takes several days to complete. The information from the new wells and geo-physics testing will help engineers and hydrology experts to better understand how groundwater flows beneath the site.

While this investigation continues, it is important to note that there has been no tritium levels found in any samples taken from drinking water wells or the river.

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