Opposition MPs rapped the government in question period Tuesday about an early-December leak at the Chalk River nuclear plant, about 185 kilometres northwest of Ottawa.

Liberal MP Geoff Regan wanted to know why the government hadn't informed Canadians about this "grave security problem."

Natural Resources Minister Lisa Raitt said the leaks were brought under control and didn't pose a hazard to anyone.

A spokesman for Atomic Energy of Canada Ltd., Dale Coffin, said that on Dec. 5 a seal failed in the reactor and about 50 litres of heavy water spilled and was contained in stainless steel barrels of water.

Coffin said four litres evaporated up the stack, carrying what he called a minute amount of radioactive tritium. He said the amount was less than what AECL is required to report.

He admitted that a cracked pipe is also leaking water into the Ottawa River. But the water is not radioactive, he said.