Cosmos 954, a satellite maritime surveillance Soviet nuclear-powered space launch September 18, 1977, crashed in the region of Great Slave Lake near Yellowknife.

Both Canada and the United States launched an immediate cleanup and recovery, called "Operation Morning Light, which was discovered in the Canadian Armed Forces document broadcast on CBC few months after the accident.

Disintegrated, the Russian satellite because a rain of radioactive debris which covers some 124,000 square kilometers. Two hundred and twenty Canadian Armed Forces and the Nuclear Emergency Search Team, Department of Energy U.S. comb the area until October 1978, trying to recover as much as possible fragments of the satellite. But according to the Control Commission of Atomic Energy (now the Canadian Nuclear Safety), only 0.1% of the energy source atomic Cosmos 954 is recovered.

See the French Canadian documentary film: http://archives.cbc.ca/IDC-0-9-1232-6784/guerres_conflits/norad/clip3