Only one consistent source of uneasiness was apparent yesterday among members of the Senate Foreign Relations Committee as they questioned Secretary of State-designate George P. Shultz: would Shultz' former job as president of the huge Bechtel construction company affect his future decisions on American foreign policy?

The senators made it clear that they all supported Shultz and had great respect for his abilities and integrity.

But the specter of the powerful and somewhat mysterious Bechtel Group--with vast business interests in the Middle East, especially Saudi Arabia, and in nuclear power plant construction around the world--seemed to haunt the first day of Senate confirmation hearings.

Repeatedly, senators came back to Bechtel, whose business volume reportedly totaled $11.4 billion last year and whose construction projects range from the Metro subway system in Washington to the industrial city of Jubail in Saudi Arabia.

Sen. Larry Pressler (R-S.D.) wanted to know about Bechtel's lobbying last year in support of the decision to sell airborne warning and control system (AWACS) equipment to Saudi Arabia and what Shultz would do about questions of nuclear proliferation in view of Bechtel's involvement in the construction of numerous nuclear power and waste-disposal projects.

Sen. Alan Cranston (D-Calif.) asked whether Bechtel had sought to undermine previous U.S. policy on restricting exports of nuclear technology.

Sen. Paul S. Sarbanes (D-Md.) wanted to review Bechtel's role in previous Arab attempts to enforce boycotts of firms doing business with Israel.

Sen. Joseph R. Biden Jr. (D-Del.) asked how Shultz would feel if a crunch came between Israeli and Saudi Arabian interests.

While it is not unusual for senators to probe the business backgrounds of future Cabinet officers, the Bechtel question has taken on greatly added interest because Shultz would become the third former Bechtel executive at the center of American government power.

Secretary of Defense Caspar W. Weinberger is a former Bechtel vice president, and a key official at the Department of Energy, Deputy Secretary W. Kenneth Davis, also came from a top position at Bechtel.

Weinberger and Shultz also have advocated a more balanced American policy toward the Middle East and have been critical at times of the Israeli government of Prime Minister Menachem Begin.

Shultz emphasized throughout today's questioning that he would not be influenced by past associations and has no apologies to make for his association with the San Francisco-based, family-owned Bechtel, which he described as "a truly remarkable organization, astonishing in the range of its capabilities and impressive in the quality of its people."

He answered all questions calmly and in detail, except when Cranston produced letters from Bechtel's business development manager, Joseph A. Damm, to Brazilian officials in 1975, a time when Shultz was Bechtel president.

Cranston said that these showed an attempt to undermine the effort by President Ford to stop West Germany from selling to Brazil advanced nuclear technology with potential weapons applications.

The letters, Cranston said, showed Bechtel's willingness, through a consortium called Uranium Enrichment Associates, to offer Brazil "the entire gamut" of nuclear technology at a time when Brazil was in the market for about $8 billion worth of equipment.

Asked whether he was aware of this, Shultz shot back, "I resent what I regard as kind of a smear on Bechtel. I think it is a marvelous, honorable, law-abiding company that does credit to our country here and all over the world."

Shultz said he had heard about the "incident" involving Brazil "long after the fact," and attributed it to "an over-enthusiastic business development person."

"Salesmen are always enthusiastic," Shultz said, adding that he considered the action "inappropriate" and that it was stopped.

Shultz also attacked what he called Cranston's inference that Bechtel had violated U.S. law dealing with the attempted Arab boycott of Israel in the mid-1970s. Shultz said that was incorrect, although Cranston pointed out that he hadn't made such a charge.

Pressler referred to "allegations that your company lobbied for AWACS" and added that, of course, there was nothing wrong with that. Shultz replied that "not only was there nothing wrong with it, there is everything right about it." Shultz said Bechtel had been entirely open about its efforts and had publicized them intentionally.

When Pressler asked if Shultz' background as head of one of the world's largest builders of nuclear power plants could influence his decision-making on questions of nuclear non-proliferation, Shultz said, "If I'm not qualified to take part in discussions of non-proliferation, then I'm not qualified to be secretary of state and you want somebody else in this job."

Shultz said he was as concerned as anyone about the spread of atomic technology and that the subject was too important for him to deal himself out of it.

He pointed out in his prepared statement and under questioning that he had taken all legal steps to remove himself from decisions on any "particular matter--as defined in the federal conflict-of-interest laws and applicable regulations--involving any Bechtel company or related company."

Obviously anticipating questions about his past association, Shultz said in his opening statement that there was no question at all about whether that would influence him as secretary.

If confirmed, he said, documents already executed by him and in the hands of the committee "will result in my resignation from my officerships in all Bechtel entities. I will retire as an employe, retaining only vested rights to medical and insurance benefits and to assets already accumulated under Bechtel trust and thrift plans. I will sell, at a price determined by an established process, all my Bechtel-related investments."

"Are you going back to Bechtel?" Biden asked.

"I have no plans or invitation to go anywhere," Shultz answered.

"If you were required as secretary of state to take a position in the interests of the United States that was viewed as very supportive of Israel and against Saudi Arabia," Biden asked, "might you be reluctant to do so because it could mean you couldn't re-assume a position with Bechtel?"

"Oh, no," Shultz replied. "I don't have any such concern in my mind at all."

Shultz said he had some assets and a tenured job at Stanford University if he needed one.

"People on tenure are tough," he joked, "so I have a free hand."