Safety doors that had closed to prevent nuclear particles from escaping during a heavy water spill at the Point Lepreau Nuclear Generating Station on Tuesday initially would not open for two hours when a cleaning crew was finished.

A radiation alert caused the reactor building to be evacuated on Tuesday after between four and six litres of heavy water was spilled.

A two-member crew was dispatched to clean up the spill. Those two individuals ended up stuck for two hours when the safety doors, which were closed to prevent nuclear particles from leaving, did not open when the crew had completed its work.

The clean-up crew members, who were in special suits with breathing apparatuses, were not in danger, according to NB Power.

Kathleen Duguay, a spokesperson for NB Power, said in an email that the crew was not trapped.

"When the employees were ready to exit the area, the door did not open on first try and the outside support team established that there was not radiation or safety risk to the employees before taking action to open the doors without damaging the airlock," Duguay said in an email.

"We could have manually opened the airlock doors at any time but chose not to do so in this situation."

Energy Minister Craig Leonard told the legislative assembly on Wednesday that four to six litres of heavy water were spilled in the nuclear reactor.

Leonard told the legislature that staff cleaned up the spill but that "it was an issue that occurred with no impact whatsoever."

But the energy minister did not mention that a two-member crew was still inside the reactor building during the evacuation.

The utility was refilling equipment with heavy water as part of preparations for restarting the nuclear reactor, which has been undergoing refurbishments for nearly four years.

NB Power has blamed equipment failure for the spill.

Point Lepreau, Atlantic Canada's only nuclear reactor, is undergoing a $1.4-billion refurbishment.

It was originally expected to be back generating power by September 2009, but has run into problems, particularly with the calandria tubes.

The tubes, which are about six metres long and 13 centimetres in diameter, contain the reactor's fuel channels and fuel bundles.

Several of the 380 tubes that were installed were leaking and had to be replaced.

The Canadian Nuclear Safety Commission is currently considering NB Power's application for a new five-year operating licence for Point Lepreau.