Second Radioactive Substance at Vermont Yankee

Second Radioactive Substance at Vermont Yankee

Test results have confirmed the presence of another, more dangerous, radioactive substance in the soil at Vermont's only nuclear power plant, officials said Tuesday, five days after announcing they had found and stopped tritium leaks at Vermont Yankee.

The state Health Department said Tuesday that cesium-137 was found at the site. The substance has a half-life of 30 years, about 2 1/2 times that of tritium, which was found in early January. A half-life is the time it can be expected to take for a substance to lose half its radioactivity. Unlike tritium, cesium-137 does not occur naturally in the environment; it is a product of nuclear fission.

Both radioactive substances can increase the chances of developing cancer depending on the intensity of exposure.

The presence of trace amounts of cesium-137 was first reported Feb. 24, but Vermont Yankee officials said it was ''consistent with what would be found in soil'' due to atmospheric testing of nuclear weapons in the 1950s and '60s and the accident at the Chernobyl reactor in the Soviet Union in 1986.

The Health Department statement on Tuesday said the cesium-137 found in the Vermont Yankee soil samples was three to 12 times as high as the background levels attributed to the other causes, meaning it ''appears likely the Cs-137 comes from Vermont Yankee reactor related sources.''