NB Power said in a statement that the water spilled Monday at the Point Lepreau nuclear power plant, Atlantic Canada's only nuclear facility.
The spill happened when a test equipment relief valve opened prematurely as officials were working on the plant's refurbishment, said Rod Eagles, the refurbishment project director for the provincial Crown utility company. Heavy water then overflowed from a collection system inside the reactor building.
"Unfortunately, the amount of water was greater than what we expected and overflowed to the floor and the test was ceased immediately," he said in an interview Thursday.
He said the water has been recovered for reuse and there is no risk to workers, the public or the environment. About four workers conducting the test left the area and were tested with two cleanup workers for any exposure to radioactive material.
He said none showed any signs of abnormal doses of radioactivity.
Eagles said NB Power has launched an investigation into the spill, adding that it was too early to say what caused the incident. He expects to have more information over the next week and then continue the so-called hydrostatic test.
In December, four to six lit res of radioactive heavy water spilled because of a leak at the plant, which prompted an evacuation. No one was hurt.
"This event is fundamentally different than the event that occurred in December 2011," NB Power said in its statement. "There were no requirements to evacuate the reactor building as the spill occurred in a room that was designed to contain and collect heavy water."
Point Lepreau has been out of service since March 2008 for a major refurbishment that's meant to extend the life of the reactor by 25 years.
The project is about three years behind schedule and $1 billion over the original $1.4-billion budget.
It is scheduled to return to service this fall and Eagles said this latest incident shouldn't delay that.
Also on HuffPost