Sen. Edward M. Kennedy (D-Mass.) yesterday called for an indefinite moratorium on the construction of new nuclear power plants. Operating reactors, he said, should be "looked at on a case-by-case basis."

At the same time, President Carter said it would be "out of the question" to shut down all operating plants, but he added he would like to "minimize" the need for their use.

Both men made their remarks in meetings with delegates to last Sunday's antinuclear rally here.Carter met organizers of the march in the White House and Kennedy received some of the Massachusetts delegation in his office in a meeting planned, his staff said, last week.

"I am in favor of a moratorium on the construction of new power plants," Kennedy said in response to questions. "Operating reactors should be looked at on a case-by-case basis." Aides said the moratorium would extend only to applications for new construction permits and would last long enough for Congress and regulatory bodies to come up with better safety rules.

The 92 nuclear plants currently under construction could continue being built but would be expected to comply with any new regulations, Kennedy's aides explained. They insisted that the senator's position had nothing to do with Sunday's turnout of 65,000 antinuclear demonstrators but had been evolving since hearings Kennedy held two weeks ago into the Three Mile Island nuclear accident in Pennsylvania March 28.

The Massachusetts delegation was among hundreds of nuclear critics who lobbied Congress all day.

Consumer advocate Ralph Nader told a House subcommittee that there are nothing but "paper plans" for evacuation in case of nuclear accident and that the plans provide only "an illusion of credibility." He again called for a shutdown of the industry.

Meanwhile, a report from the General Accounting Office said the public is inadequately protected from radiation in shipments of nuclear materials around the country.

Meeting with organizers of the rally, Carter praised them for bringing it off "peacefully and effectively." He said nuclear safety is one of his main goals but that achieving it "requires a careful addressing of a difficult problem." Chicago, for example, "derives half of its total electricity from nuclear power plants, and it's out of the question to peremptorily shut down all the nuclear power plants in the country," he said.

Carter reiterated a campaign theme that his critics at Sunday's demonstration had accused him of forgetting. "We do . . . want to shift toward alternate energy supplies and also strict conservation programs to minimize the requirement for the use of nuclear power," he said.

Donald Ross, coordinator of the May 6 coalition that organized the protest, said after the meeting with Carter that his group had not asked for an immediate shutdown of the industry but primarily, ad Kennedy did, for a halt to new construction.

"We told him [Carter] he needed to take a much more decisive antinuclear position that he had," Ross said. The group asked Carter to oust Energy Secretary James R. Schlesinger who is pronuclear, and to have the Justice Department intervene against new license applications before the Nuclear Regulatory Commission.

Nader, appearing before the House subcommittee on energy and the environment, also called for the ouster of Schlesinger as well as the resignation as well as the resignation of the five NRC members.

"Military officers are court-martialed for far less levels of neglect" than the commission showed in its handling of the near-disaster March 28 at the Three Mile Island nuclear plant in Pennsylvania, Nader said. "What test do they have to flunk in order to warrant their resignation?"

The neglect, he said, included failure to require or test a full state and local emergency response and evacuation plan for every plant in the nation. "Either we stop nuclear (power) now or it will be stopped after a major nuclear meltdown sometime in the future," Nader said.

The General Accounting Office coincidentally provided evidence that the industry is continuing to grow. A study realeased yesterday said 2 million packages of radioactive materials are shipped around the country every year by plane, truck and train, and that the amount will more than double, to 5.5 million packages, by 1985.

Although no one has died or been seriously injured from exposure to the radioactivity of these wastes, reactor fuels and drugs, the permitted levels of radioactivity are "unnecessarily high," the report said. Faulty packaging had led to some radioactivity release, but none of the overlapping federal agencies has any program to verify the manufacturers' assurances of quality, it said.

Many plutonium and weapons-grade uranium shipments travel unguarded because they are just below the cutoff size at which guards are required, the study continued. The GAO recommended a sliding scale of security for shipments of varying degrees of danger.

In another report released yesterday, the GAO noted that 35 percent of the college students in nuclear engineering courses are foreigners, and that there is no way of knowing how many have or will become involved in their countries' weapons programs. The agency suggested that the government consider refusing such training to students from nations that have not signed the 1970 nuclear nonproliferation treaty.

"It is very difficult to draw a firm line with respect to what is and what is not sensitive; it is a matter of degree," the GAO said, adding that criteria should be established.

Previous GAO reports warning of problems in the nuclear industry have often gone unnoticed in Congress, Nader complained to the energy subcommittee. One that did get some attention came out March 30, two days after the accident, at Three Mile Island, and warned that evacuation plans nationwide were inadequate.

The plan for Pickens County, S.C., next door to the three reactors of the Oconee nuclear power station, includes a corps of volunteers knocking on every door to spread the word to evacuate, county civil defense director William D. Evett testified.

The mountainous region includes 30,000 persons, many without telephones, within 10 miles of the reactors. It would take five to seven hours to notify everyone, Evett said. He estimated that half his 200-member volunteer force would turn out to help.

Subcommittee Chairman Toby Moffelt (D-Conn.) called that a "Paul Reere system" and expressed amazement that South Carolina officials regarded themselves as prepared for a nuclear emergency. CAPTION: Picture 1, Reps. James Weaver (D-Ore), Morris Udall (D-Ariz.) and Austin Murphy (D-Pa.) visit Three Mile Island control room where they were briefed by plant operators. AP; Picture 2, Antinuclear rally organizers Pam Lippe, far left, and Donald Ross, right, meet at White House with President Carter and an adviser, Anne Wexler. They asked Carter to oust pronuclear officials working in his administration. AP