President Carter yesterday unveiled the first substantive details of his program to stop other nations from turning nuclear reactor fuel into nuclear weapons. In doing so, he prepared for an almost certain fight with Congress, and protests from many other nations.

The 55-page bill Carter sent to Capitol Hill follows the same "carrot-and-stick" approach as key congressional bills introduced earlier offering other nations a guaranteed supply of nuclear fuel for peaceful uses in exchange for their promises not to turn it into bombs. The United States supplies more than 90 per cent of the uranium used by other countries for peaceful purposes.

But in an accompanying message Carter said the congressional proposals, which were introduced earlier and designed to accomplish the same goals, are too strict, and do not allow the President enough flexibility.

They might drive other countries to turn elsewhere for nuclear fuel, White House aides said, and the United States would then lose its ability to influence what those countries do with the fuel.

Carter announced his tougher U.S. stand April 7, when he ended government support for the production of plutonium, which can be used in bombs, and called on other advanced nations to help halt its spread around the world.

Congressional bills, the President said yesterday in hiss message, " . . . could force an immediate moraortium on our nuclear exports, adversely affecting certain allies whose cooperation is needed if we are to achieve our ultimate objective of non-proliferation."

His own bill, Carter said, lays out conditions on the export of nuclear fuel "which we we can reasonably ask other nations to meet while we negotiate stricter arrangements."

There two sets of conditions in his proposal, one for countries with which the United States already has nuclear cooperation agreements, and an additional set for countries negotiating new cooperation agreements.

Those applying to new agreements include:

U.S. supplies of nuclear fuel would be cut off if the country detonates a nuclear device.

In nations without nuclear weapons, all nuclear fuel and equipment, whether supplied by the United States or not, must come under International Atomic Energy association safeguards.

The United States would have to approve the reprocessing and transfer of any nuclear fuel produced with the help of U.S. equipment.

Conditions which Carter's proposals would apply to existing agreements include:

No nuclear fuel or equipment supplied by the United States could be used for research or production of any nuclear explosive device.

No U.S.-supplied nuclear fuel could be reprocessed without prior U.S. approval. Reprocessing produces plutonium, which can be used in bombs.

The United States would have to approve any transfers of nuclear fuel that it originally supplied.

The Carter proposals would allow the President to exempt any nation that violates the conditions from having its supply of U.S. nuclear fuel cut off if he finds that " . . . such a cutoff would hinder the achievement of U.S. non-proliferation objectives, or would jeopardize the common defense and security."

They would also require administration approval before the independent Nuclear Regulatory Commission could grant export licenses for nuclear fuels and equipment.

Rep. Jonathan B. Bingham (D-N.Y.), author of one of the congressional bills, said in a statement that Carter's proposals don't go "nearly far enough in seeking to restrain the spread of reprocessing overseas."

Bingham's bill would cut off U.S. exports of nuclear supplies to any country that began reprosessing the spent fuel. Carter's message said the administration would prefer using incentives to encourage countries not to acquire reprocessing facilities.

The details of Carter's proposals were made public just one day before the formal opening session in London of a meeting of countries that export nuclear fuel. They are trying to work out an agreement to curb the spread of weapons-grade nuclear material.

A number of countries that get some or all of their nuclear fuel from the United States protested Carter's position when the sketchy outlines of it were first presented April 7.

Israel, India and Japan expressed particular concern. The United States is negotiating a new nuclear cooperation agreement with Israel, which wants two new nuclear reactors.