A Note from Larry Smith at Vermont Yankee
February 18, 2010
Vermont Yankee engineers and technicians continue their investigation into the source of tritium in the plant’s groundwater.
Inspection has identified water in the Advanced Off Gas concrete pipe tunnel. The water has been removed and additional boroscopic inspections of the tunnel will be conducted tomorrow. Monitoring tritium concentrations in the well installed in this area (GZ-10) continues. Workers are finalizing plans to excavate from 12 to 15 feet below grade to check the tunnel for leakage. Thus far, the well monitoring data is not conclusive as to whether the AOG tunnel is the source of tritium in groundwater at the site and the investigation of this and other potential sources is ongoing.
Engineers and vendor experts continue to finalize the plans for the adjustments to the design for shoring and bracing work at the AOG building excavation site. Materials required for the work have arrived onsite and personnel resources needed are being gathered and work schedules developed. The new design accounts for all the necessary worker and nuclear safety requirements, and allows more flexibility in how the shoring supports are installed. The actual size of the excavation area has been modified from the original size using this new design and now includes the area around GZ-10, the monitoring well that continues to give the highest reading of tritium. GZ-10 has stayed at 1.99M pCi/L for the past two days. A new beam to support an electrical duct bank has been installed and additional test bore holes will be dug today. Erection of the enclosure building over the excavation site continues.
The installation of new monitoring wells continues. The first deep well, GZ-13D which is coupled with existing well GZ-13, is complete and in the process of being developed. Work on well GZ-14D commenced today. The installation of two additional shallow groundwater monitoring wells will also commence during the week. The information from these new wells will help engineers and experts better understand 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: https://email.entergy.com/exchweb/bin/redir.asp?URL=http://healthvermont.gov/enviro/rad/yankee/tritium.aspxhttp://healthvermont.gov/enviro/rad/yankee/tritium.aspx
Also helpful is the Nuclear Regulatory Commission web page on tritium monitoring: https://email.entergy.com/exchweb/bin/redir.asp?URL=https://email.entergy.com/exchweb/bin/redir.asp?URL=http://www.nrc.gov/reactors/operating/ops-experience/grndwtr-contam-tritium.htmlhttp://www.nrc.gov/reactors/operating/ops-experience/grndwtr-contam-tritium.html
In an unrelated matter, Operators at Vermont Yankee this morning reduced plant power to approx. 80% to perform a scheduled control rod pattern adjustment. The evolution is complete and the plant is returning to full power.
Laurence M. Smith
Manager of Communications
Entergy Nuclear Vermont Yankee 802-258-4118
lsmit14@entergy.com
Vermont Department of Health Investigation into Tritium Contamination at Vermont Yankee Nuclear Power Station
Update for February 18, 2010
Excavation Work
The new approach for excavating the area around the Advanced Off-Gas (AOG) Building is in its initial stages. Successful excavation of this area is important because it may positively identify the source or sources of leaks responsible for contaminating groundwater with tritium.
AOG Sump Pit
AOG pit sump appears to have pumped 100 gallons of water to the rad waste building over the last 24 hours. This is a possible indicator of leakage within the pipe tunnel which drains to this sump. This is the drain that was recently unclogged, and may have collected water from nuclear steam leaking into the tunnel.
On-Site Water Testing
Vermont Yankee’s test results for today of on-site groundwater monitoring wells are provided below for seven wells that have shown contamination with tritium so far. There are seven other wells on site that have shown no contamination. None of the wells have shown any other radioisotopes associated with a nuclear power plant.
The location of the wells can be seen on the Investigation Site Map. Wells GZ-3, GZ-4 and GZ-14 are about 100 feet from the river. GZ-10 is near the excavation area, about 400 feet from the river. GZ-7 is closer to the excavation site, about 350 feet from the river. GZ-15 is about 250 feet from the river. GZ-12 is about 200 feet from the river. None of the river water samples tested so far have shown contamination with tritium or any other reactor-related materials.
Feb. 18 ground water monitoring well test results (all in picocuries per liter):
GZ-3: 31,000
GZ-4: 2,700
GZ-7: 990,000
GZ-10: 1.99 million
GZ-12: 18,000
GZ-14: 113,000
GZ-15: 305,000
New Wells and Related Testing
Additional wells are also being drilled or in development. Well GZ-13D is nearing completion, and drilling of GZ-14D is underway. These will be used to better characterize the hydrogeological conditions underground at the site. Wells GZ-16, GZ-17 and GZ-19 will be prepared next week.
Planning is underway for geophysical testing of numerous drinking water wells on the site, looking for fractures in the bedrock. The locations of these fractures in the drinking water wells allows for characterization of the bedrock and the separation of drinking water and ground water.
Independent Water Testing
Independent testing by the Vermont Department of Health Laboratory has generally verified test results by Vermont Yankee’s contractor. The Health Department continues testing a number of off-site drinking water wells. To date, no drinking water wells have shown contamination with tritium or any other radioisotopes associated with a nuclear reactor. (See Health Department Laboratory Testing)
http://healthvermont.gov/enviro/rad/yankee/tritium.aspx
