A Note from Larry Smith at Vermont Yankee

February 26, 2010

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

Overnight, 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. It is important to note that no active process leakage was observed this morning when the condition was identified. Soil samples are being 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. As previously reported, an earlier visual inspection identified a separate defect in the concrete surrounding the pipe, where the line makes a 90 degree turn into the AOG building.

Work continues in our effort to excavate and expose the AOG concrete pipe tunnel area for inspection. Excavation overnight exposed a majority of the concrete encased Off Gas OG-100 drain line, which comes off the AOG pipe tunnel. Excavation is scheduled to be completed today. An engineered catch basin will then be installed to capture potential leakage encountered at the unearthed AOG tunnel. Engineers will then perform an integrity test and observe leakage paths to the ground from the AOG concrete pipe tunnel and the concrete encased OG-100 drain line using de-mineralized water. The de-mineralized water used during the test will be collected and processed through plant systems.

A temporary shelter placed over the excavation area is in place to ward off snow/rain and allow work to continue. The final enclosure above the excavation area will be completed after the final excavation is completed.

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, will commence tomorrow. Today, down hole geo-physics testing of six monitoring wells will begin. 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.

As reported earlier this week, as a prudent precaution, the Construction Office Building (COB) drinking water well has been taken out of service. The COB well pump has been removed and an alternate water supply from the main well to the COB water tank is complete. The COB well will be included as one of the deep wells that will be part of geo-physics testing. After the geo-physics testing, a determination will be made if the well can be maintained as a monitoring well or if it will be closed and filled.

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