Radioactive tritium found in leak at South Carolina nuclear plant CHARLESTON, South Carolina (Reuters) - More than 100 gallons of water containing radioactive tritium has leaked from a discharge pipe at the Catawba Nuclear Station near Lake Wylie, South Carolina, and could reach groundwater, the Nuclear Regulatory Commission said on Wednesday. The leak, which was found Tuesday night in a fiberglass discharge pipe from the turbine building sump pump, occurred about a half-mile inside the station's grounds, said officials at Duke Energy Corp, the plant's operator. Although the leak has the potential to reach groundwater, samples indicated a small concentration of tritium, officials said. "If you do the calculations on that amount of tritium, it's less than half of the Environmental Protection Agency's drinking water standard," said Roger Hannah, a spokesman for the Nuclear Regulatory Commission's regional office in Atlanta. Tritium is a radioactive isotope of hydrogen. A byproduct of nuclear reactor operations, tritium also occurs naturally in air and water. "This radiological dose of tritium is equal to about one-fifth of a chest X-ray or a cross-country flight," said Duke spokesman Scott Andresen. It must be drunk in large quantities to pose any health risk. Water has stopped flowing through the pipe and the spilled water contained no radioactive isotopes other than tritium, Andresen said. He said it would be some time before officials know exactly how much water was spilled because they must determine the flow, test pump logs and test soil around the underground pipe. According to the U.S. Environmental Protection Agency, exposure to tritium increases the risk of developing cancer. But because it emits very low energy radiation and leaves the body relatively quickly, it is one of the least dangerous radionuclides. Duke, the largest electric power holding company in the United States with more than $110 billion in total assets, serves about 7.2 million electric customers in six states in the Southeast and Midwest. Reporting by Harriet McLeod.; Editing by Colleen Jenkins, Scott Malone and Andre Grenon