Testing Soil for Radiation

Soil samples were taken from various locations and depths below the excavation area outside the Advanced Off-Gas (AOG) pipe tunnel that was found to have caused the leak reported on January 7, 2010. Strontium-90, cesium-137, zinc-65, manganese-54 and cobalt-60 were detected at greater concentrations and deeper in the ground than would be expected from nuclear fallout or weapons testing from long ago. This is evidence that radioisotopes, in addition to tritium, washed out of the AOG pipe tunnel into the environment with the leaking nuclear reactor water.

In the February 26, 2010 set of soil samples, strontium-90 and cesium-137 were measured at much greater concentrations than are found in surface soils in Vermont and around the world. See soil sample results for February 26, 2010

In the March 17 and 18, 2010 set of soil samples, cesium-137 was found at as much as 75 times what would be expected in surface soils. Analysis by Vermont Yankee of concrete mud and construction debris in the AOG pipe tunnel also confirmed the presence of cesium-137. See soil sample results for March 17, 2010

At the request of the Health Department, samples of mud and construction debris from within the tunnel were also taken for analysis. Split samples were analyzed by the Health Department Laboratory. Samples were also analyzed by an independent laboratory under contract with the Health Department for “hard to detect” radionuclides such as strontium-90, iron-55 and nickel-63.

Soil testing done immediately after another leak was discovered by Vermont Yankee on May 28, 2010 also detected these as well as several other radioisotopes that decay quickly and are no longer detectable within days or months: chromium-51, cobalt-58, barium-140 and lanthanum-140.

As part of its ongoing environmental surveillance, the Health Department has tested soil samples from two sites in the state not associated with Vermont Yankee and confirmed cesium-137 at concentrations consistent with past nuclear fallout. In 2008, cesium-137 was measured at 86 and at 168 picocuries per kilogram (pCi/kg).

Radioactive Elements Found in the Soil at Vermont Yankee