N.C. State University officials say they have patched up a leak that shut down the campus nuclear reactor nearly three weeks ago.

The small research reactor had been leaking about 10 gallons of water an hour from a 15,600-gallon pool used to cool the superheated reactor core and radioactive fuel rods. Total leakage came to about 3,500 gallons.

The leaking water was tainted with radioactivity but posed no public health risk, university officials said. The water was presumed to flow through the Burlington Nuclear Engineering Laboratory on campus and into the ground below.

N.C. State University said this afternoon it shut down its research reactor after a leak was discovered at the nuclear facility.

The small nuclear reactor is leaking about 10 gallons an hour and poses no public health risk, the university said.

N.C. State said it is not required to report leaks under 350 gallons per hour, but it chose to do so. The public notice comes five days after the leak was discovered on Saturday.

"The leak is the size of a pinhead," said N.C. State spokeswoman Caroline Barnhill.

Federal nuclear safety regulators have begun a special investigation at N.C. State University's research reactor in Raleigh after a technician was inadvertently exposed to radiation during routine work.

The NRC did not identify the technician, who works for a private company that uses the university's reactor. The technician was testing airplane components for fissures and defects using a radiography procedure similar to X-rays.

He entered the chamber and noticed the shutter of the equipment that emits neutrons was open. The technician left the chamber after 18 seconds.