U.S. nuclear power plant operators haven't figured out how to quickly detect leaks of radioactive water from aging pipes that snake underneath the sites - and the leaks, often undetected for years, are not going to stop, according to a new report by congressional investigators.

The report by the Government Accountability Office was released by two congressmen Tuesday in response to an Associated Press investigation that shows three-quarters of America's 65 nuclear plant sites have leaked radioactive tritium, sometimes into groundwater.