The Vermont Department of Health has a well organized page detailing the results of the search for the source(s) of tritiated water leaks at Vermont Yankee. It includes regular updates, site maps and detailed sample results.
Based on an update dated March 5, 2010, a remotely operated pipe inspecting vehicle has helped workers discover a hole in the wall of a pipe that is located in the Advanced Off-Gas piping tunnel. The pipe is leaking enough water and steam to be responsible for the 100 gallons per day that has been previously computed as the suspected leak rate. Inspections will continue even after this leak is repaired to ensure that there are not any more sources.
Though the pipe is enclosed inside a tunnel, there is also a crack in the tunnel that is allowing the water to leak into the ground around the tunnel. All of the wells that have tested above the lower limit of detection for tritium are within 50 feet of the plant buildings. here is what the site says about the extent of testing for other radionuclides:
Since Jan. 7, the Vermont Department of Health has stepped up its environmental surveillance of Vermont Yankee by testing water samples taken from drinking water wells and ground water monitoring wells on site at the plant, and in the surrounding area. Water is now being sampled at least weekly for independent testing by our public health laboratory. Other samples, such as soil, milk, river sediment, and vegetation (when available), are being taken for testing as needed.
No isotopes other than tritium have been found at levels greater than normal background. Entergy has contracted with a testing service for “hard to detect” isotopes. Here is the summary of that testing so far:
The first results of analyses performed for radioactive materials that are hard to detect were reported by Vermont Yankee today (March 5, 2010). These include strontium-90, iron-55 and nickel-63. Water samples from wells GZ-3, GZ-4 and GZ-14 were analyzed by the plant’s contract laboratory, Teledyne Brown of Tennessee.
No evidence of any of these hard to detects was found. Other well samples, including from GZ-10 near the leakage path are being tested now for hard to detects. The Vermont Department of Health will have these analyses conducted independently by a private commercial laboratory.
The Vermont Department of health is also testing private drinking water wells. Here are the results so far:
Once every week, the Vermont Department of Health Laboratory is testing private drinking water supplies of selected residences near the Vermont Yankee site boundary.
To date, none of these wells have shown evidence of contamination with tritium or other radionuclides that would be associated with a nuclear reactor.
That should be reassuring to people – one of the characteristics of radioactive material is that it can be reliably detected at levels that give doses that are far below the normal background radiation dose expected for living on earth. If the isotopes cannot be detected, they are not present in concentrations that can increase the risk of any illness.
Aside:After reading the above fact sheet, I learned that I have been incorrectly computing the potential doses from tritium based on obsolete information. The drinking water limit in the US is 20,000 picocuries per liter. When that was determined in 1976, it was based on a computational assumption that a person drinking water for an entire year at that concentration would receive an additional dose of 4 millrem. A 1991 revision, based on careful science, revealed that estimate as being off by a factor of 3. A dose of 4 mrem/year from drinking water actually requires a concentration of 60,900 picocuries per liter.
Not surprisingly for those of us who understand the politics around nuclear energy – especially in the 1990s – the scientific result did not result in a relaxation of the standard. In fact, it is hard to find that information on an EPA web site, but I have no reason to distrust the NRC’s report of the computational refinement. End Aside.