A Note from Larry Smith at Vermont Yankee

February 27, 2010

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

As previously reported, yesterday the team 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. Today, an initial integrity test was performed by introducing de-mineralized water into the AOG pipe tunnel. Water was observed flowing from the area at the joint between the concrete encasement of the Off Gas OG-100 drain line and the AOG pipe tunnel wall. The de-mineralized water used during the test was collected and will be processed through plant systems.

It is important to note that the OG-100 drain line itself has not been identified as leaking and no active process leakage has been observed. An engineered catch basin has been installed to capture potential leakage encountered at the unearthed AOG tunnel.

Boroscope inspection of the inside of the AOG pipe tunnel is scheduled to be performed tomorrow. Engineers and technicians will then review the information, but have not ruled out any possibilities and are considering all potential leakage pathways until results are conclusive.

Soil samples continue to be gathered for analysis and will be shared with the Vermont Department of Health. The Vermont Department of Health and Nuclear Regulatory Commission personnel are at Vermont Yankee and are monitoring the investigation. Tritium concentration monitoring is ongoing. The installation of the two new deep monitoring wells is complete and they are in the process of being developed (GZ-13D and GZ-14D). Wells GZ-19 and 19D are complete and in development. Due to interferences, the drilling of GZ-16 has been delayed until a better location can be determined. A new shallow monitoring well GZ-17, to be located just west of the excavation site in the maintenance shop, is being drilled. 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