What is apparently the complete atomic power plant of the Soviet satellite that broke up Tuesday in the atmosphere over Canada's Northwest Territories is on the ground emitting "extremely dangerous" radiation.

Canadian Defense Minister Barney Danson said that debris from the nuclear-powered surveillance satellite has been pinpointed near Baker Lake. a remote outpost of 1,000 people in the frozen tundra of north-central Canada less than 100 miles west of Hudson Bay and less than 100 miles south of the Arctic Circle.

"We're sure there's something on the ground and almost certain that it's man-made." Danson told reporters in Ottawa yesterday. "There is a high degree of radiation in the area that is likely part of the nuclear power package."

Members of Canadian and American "nuclear response" teams were in the vicinity of Baker Lake last night attempting to make positive identification of the source and content of the radiation. They had flown there in a pair of twin-engined Chinook helicopters that apparently located the nuclear package on the ground with airborne Geiger counters.

Danson said the radiation coming from the debris on the ground was "so dangerous" that it might have to be covered with tons of lead shielding before it can be removed. Danson said it was still impossible to estimate the size of the object on the ground and that it might takes days before Canadian and American teams can be ready to move it.

The defense minister said there was a "90 per cent chance" the radiation came from the atomic power plant of the disintegrated Cosmos 954 satellite, which carried 10 pounds of highly enriched uranium.

"It's either a piece of the nuclear debris," Danson said, "or the greatest uranium mine in the world."

U.S. sources said it is "highly likely" the entire uranium core - containing at least 1 million curies of alpha, beta and gamma radiation - lay intact on the ground at Baker Lake, where sources said it is likely that the Soviets design their spaceborne nuclear plants the same way the United States does, in a small box inside a larger box inside the satellite.

"It sounds as if the entire uranium core came down intact," one source said. "It sounds as if it were designed to survive re-entry, which is our approach too."

The source of the radiation is not the 110 pounds of uranium in the power plant, but the radioactive fission products like strontium-90 and cesium-137 that have built up as the uranium fuel burned itself up. There is also a small amount of plutonium in the spent fuel as well.

The Cosmos 954 satellite was launched from Tyuratam in the Soviet Union Sept. 18. Presumably, its nuclear power plant was turned on when it reached an orbital altitude of 150 miles and began the task of tracking with radar the ocean-going warships of the U.S. Navy.

The estimate that the core contained at least 1 million curies of radiation came from U.S. sources familiar with spaceborne nuclear power plants of both the United States and the Soviet Union.

"We ran a small reactor on 10 pounds of uranium in space for 43 days in 1964," said one source at the Department of Energy, "and at the end of the 43 days, we calculated there were 100,000 curies inside the power package. This one has got to be at least 10 times that potent.It's a hot package."

If it's anywhere near as "hot" as suggested, the uranium power source on the ground near Baker Lake will have to be approached by technicians wearing lead-lined suits and helmets visored with lead-tinted glass. The suits look like the space suits the Apollo astronauts wore on the moon, though they are not as heavy. These suits come equipped with oxygen tanks, worn on the backs of the men wearing the suits.

The debris might have to be lifted into armored cars by remote-operated cranes. The debris might have to be dropped in a pool before it can be examined.

Canadian Defense Minister Danson said that Soviet Premier Alexei Kosygin sent a personal message to Canadian Prime Minister Pierre Trudeau offering full Soviet cooperation. At his weekly news conference, Trudeau said the Soviets offered to put Soviet personnel at Canada's disposal in looking for the downed satellite.

Trudeau did not say if he accepted the offer, but said he was satisfied. The Soviets said they thought the satellite would land in the Bering Straits between Alaska and Siberia, not in Canada.

"Whether their predictions could have been more accurate," Trudeau said dryly, "I don't know."