The nuclear power industry yesterday began a campaign to weaken in the Senate a House-passed nonproliferation bill that U.S. companies fear would reduce their sales and profits abroad.

Those sales now amount to more than $1 billion a year, most of which goes to a few gaints in the nuclear field such as Westinghouse Corp. and Babcock & Wilcox.

Those companies are the behind-the-scenes leaders of the fight that began on the Senate floor yesterday.

Leading the fight for the industry position is Sen. James McClure (R-Idaho) who will offer more than 25 amendments next week to water down the legislation whose leading sponsors in the Senate are John Glenn (D-Ohio) and Charles H. Percy (R-Ill).

McClure, a staunch nuclear industry supporter, is from a sparsely populated state where more than 8,000 people are employed by the government and industry in nuclear related jobs.

The Senate yesterday adopted non-controversial amendemtns to the nuclear bill, which the administration is backing as a part of President Carter's plan to reduce the proliferation of atomic weapons and the danger of nuclear war.

"The nuclear nonproliferators must have dominance over the nuclear salesman . . . just to gain a couple of million dollars in extra sales is not enough," Percy said in his opening speech advocating enactment.

The House-passed bill and the similar legislation Glen and Percy have shepherded to the Senate floor - would stiffen existing restrictions on nuclear exports, and give other countries incentives to adopt U.S. nonproliferation goals.

McClure said he* endorses the nonproliferation objectiives of the bill, but said that his "potentially controversial amendments" will address the "marked decline in the credibility of the U.S. as a reliable supplier."

Citing the drop-off in the U.S. share in nuclear exports from 92 percent in 1972, to about 52 percent now McClure argued that the best way to deal with nonproliferation is to ensure that America's nuclear industry remains competitive.

Industry efforts to shape the bill have been lead by former ambassador to the Internationall Atomic Energy Agency Dwight Porter now a lobbyist for Westinghouse and other Washington-based nuclear executives.

The main issue in the floor fight over the next few days will be McClure amendments to limit the power of the Nuclear Regulatory Commision, which now licenses all exports. One question is what standards should be used in licensing decisions. Some NRC officials have said that IAEA safeguards to prevent military use of nuclear materials may not be adequate; the industry wants these standards accepted as they are.

McClure would like to transfer from the commission to the State Department the power to pass the judgment on these IAEA standards. The industry thinks the State Department might be more accommodating.

This safeguards issue has already surfaced within the NRC where the commissioners are split 2 to 2 on the question, in what one senior congressional aide calls "the oddest turf fight in recent Washington history." That is because some NRC members want to give up power.

Commissioner Richard T. Kennedy, in a January letter to Frank Church (D-Idaho) which McClure used in his opening statement on the Senate floor yesterday, said "Serious problems will remain if the NRC continues to be called upon to make "independent" decisions on safeguards abroad and foreign affairs matters that it is not equipped to do either."

Kennedy has been joined by NRC Chairman Joseph Hendrie who told a reporter he has reservations about the NRC's having a major role in the safeguards question.

Percy and Glenn, on the other hand, cited a letter from another commissioner, Victor Gilinsky, saying, "Blind acceptance of international safeguards of unknown effectiveness discounts safeguards altogether, leaving the United States exports protected by little more than a simple reliance on the promises of recipients that American exports will not be used for nuclear explosives."

Former Rep. Orval Hansen (R-Idaho), who served on the old Joint Atomic Energy Committee when he was in Congress said, "It ought to be an executive branch decision." Hansen, now a Washington attorney specializing in nuclear matters also argues that the 1974 law creating the NRC does not unequivocally spell out the NRC's role in ruling on the critical safeguards questions.

Like many nuclear industry executives, Hansen says passing a stiff nonproliferation bill that unilaterally mandates tougher safeguards standards will lead to a confrontation with European and Japanese trading partners.

"The confrontation will come quickly after the bill passes," he said.

Senate Miniority Leader Howard H. Baker Jr. (R-Tenn.) said yesterday real risk we run if we overlegislated in this area is closing off nuclear exports." Baker also opposed the addministration's effort to close down the Clinch River breeder reactor in his state.

Gilinsky, who has voiced concern over the proliferation issue during NRC proceedings, says, "The nuclear export lobby does not seem to under stand that tough antiproliferation legislation is essential to the continuation of its clients' trade - nothing is going to shut this trade off faster than for the public to decide it is really a trade in bombs."