(Reuters) - Entergy Corp said on Wednesday it found elevated levels of tritium, a weak radioactive isotope of hydrogen, in groundwater samples at the Indian Point nuclear power plant in New York state.
The company said the tritium has not migrated off site and poses "no threat to public health or safety." The company first announced it found tritium in groundwater samples on Feb. 6.
New York Governor Andrew Cuomo, who wants Indian Point shut because he does not believe the population around the plant - including New York City - could be evacuated if there was an emergency, said over the weekend that the state would investigate the incident.
Entergy said it continues to look for the source of the tritium leak with the likely cause related to the processing of water in preparation for a regularly scheduled refueling at the plant's Unit 2 reactor.
The U.S. Nuclear Regulatory Commission said in a report in December that there are 65 locations in the United States where commercial nuclear power plants are or have been recently operating and records indicate 46 of these sites have had leaks or spills that involved tritium levels above the legal limit for safe drinking water at some time during their history.
In December 2015, the NRC said 13 sites were reporting high tritium levels from a leak or spill but no site was detecting reportable tritium in the offsite environment or drinking water.
(Reporting by Scott DiSavino; Editing by Diane Craft)