LONDON (AP) _ Greenpeace asked the Soviet Union on Monday to seek world help to recover from the bottom of the Norwegian Sea, one mile down, a wrecked submarine and its two nuclear reactors and nuclear weapons.

A technical report commissioned by the environmental organization said the Soviet submarine on April 7 took ''a significant amount of highly active and toxic radioactive materials'' to the bottom, 5,296 feet beneath the surface.

''If the submarine is not recovered intact then it is, in our opinion, inevitable that all of this material will disperse to the marine environment,'' said the report by the independent nuclear engineering consultants John Large and Associates Ltd. of London.

Forty-two seamen were killed and 27 survived when the vessel, armed with two nuclear torpedoes and reportedly fueled by uranium 235, caught fire and sank 120 miles southwest of Norway's Bear Island.

The report said the nuclear reactors may have contained up to 20 million curies of radioactivity and the reactor hull parts 1 million curies. Greenpeace said its figures are conservative because they do not include the radioactivity of the reactors' liquid metal coolant or the toxic plutonium of the torpedoes.

The No. 4 reactor at the Chernobyl nuclear power plant, by comparison, emitted an estimated 50 million curies of radiation after it caught fire in the Soviet Union in April 1986.

The report said much of the radioactive material aboard the Mike Class submarine will continue to emit radiation and be harmful to marine and human life for many tens of thousands of years.

''This vast quantity of radioactivity is mainly from highly active materials which will remain highly toxic to organisms almost indefinitely,'' said Greenpeace spokesman Damian Durrant.

''Inevitably, they will be released and a proportion absorbed into the marine food chains, through fisheries and toward man. The only question is when the reactors breach and this process begins.''

Director Johan Baarli of the Norwegian National Institute of Radiation Protection said in response to the report, ''There is no reason to doubt that the sub's reactor is in its containment. According to all information we have, there is no radiation leakage.''

The institute said last month that tests showed the submarine's reactors and weapons have apparently withstood tremendous water pressure. Water samples collected near the submarine showed no radiation that could be attributed to it, the institute said.

The Soviet news agency Tass quoted Deputy Prime Minister Igor Belovsov last month as saying a decision on whether to raise the submarine is months away.

The report does not discuss the possible impact of leaked radioactivity on the marine environment.

''This requires a further study dependent on the provision of more information from the Soviet Union, as requested by Greenpeace as well as the Norwegian government, but which neither have thus far received,'' Greenpeace said.

The report noted that when the United States tried to raise a Soviet Golf Class nuclear submarine in 1974 the vessel broke in half.

It said recovery should not be regarded as a ''quick technical fix for this or future nuclear submarine accidents'' and called for elimination of all 544 military nuclear reactors from ships and submarines worldwide.