Canadian officials have sought aid from Soviet satellite experts to help them determine whether the nuclear reactor of the Cosmos 954 spy satellite could have returned to earth intact, officials said here yesterday.

The Soviets were contacted three days ago by senator Canadian officials and asked to provide "objective non-political experts" who could answer critical questions about the satellite's nuclear reactor, said Col David Garland, head of the Canadian satellite search team.

"We have heard it is under consideration" Garland said.

U.S. scientists said today that despite official claims of cooperation from the Soviets about the satellite, they still know almost nothing about the dimensions or type of nuclear fuel the Cosmos satellite was carrying when it dropped out of orbit last Tuesday and broke up over northern Canada.

William E. Nelson, a nuclear engineer and a chief U.S. scientific adviser to the search headquarters here, said that if they knew the type of enriched uranium the Soviet satellite was carrying, scientists could tell whether the reactor fuel would have disintegrated or made it through the upper atmosphere intact.

If the estimated 100 pounds of nuclear fuel was uranium oxide, for example, Nelson said, it is more likely to have penetrated to the earth's surface. A reactor core of uranium carbide would probably have burned and disintegrated when the satellite reached a point about 300,000 feet above the earth and began heating up.

nelson said the several hundred scientists and nuclear experts working on the satellite puzzle have made only slight progress in the absence of such specific data. "We know perhaps 10 per cent of the hardware puzzle and probably will never know more than 50 per cent," Nelson said.

Richard Wagner, associate director for nuclear testing at the Lawrence Livermore Laboratory in Berkeley, Calif., told a news conference here yesterday that two definite and two other possible pieces of satellite debris have been located at the far northeastern end of Great Slav Lake in the Northwest Territories.

On Sunday search parties identified a fifth satellite fragment at a site known as Warden's Grove, 200 miles from Great Slave Lake. Officials said the fragments at Warden's Grove were only slightly radioactive indicating they were not part of the reactor core.

The Warden's Grove fragments were giving off about a hundred milliroentgens of radioactivity and Nelson estimated their total radioactivity as only tens of curies. A curie is the unit used in measuring radioactivity. By contrast, he said, the reactor's nuclear core may contain hundreds of thousands of curies of radioactivity if it made it to earth.

The fragments on Great Slave Lake also showed higher levels of radioactivity than those at Warden's Grove but Nelson said it was not likely they were actually pieces of the reactor core.

Scientists said today they had narrowed their search area to a 250-mile long rectangle stretching east from the Great Slave Lake. They said the reactor would probably have carried further east than the rest of the satellite because of its weight, an estimtaed 1,000 pounds out of the satellite's total 10,000-pound estimated weight.

Officals here said efforts to reach the identified radioactive satellite fragements have been hampered by fogs of ice crystals suspended in the -30 degree air. Ice in that area of the Canadian Arctic remains frozen until June, officials said.

Residents of several tiny fur-trapping and trading communities around the edges of the search area have been told by Canadian officials that no danger of radiation contamination exists from the satellite fragments. Brig. Gen. Ken Thorneycoft visited the town of Snowdrift, 45 miles southwest of Greta Slave Lake, to convey similar reassurances to the 90 chippewa Indians there today.