President Carter yesterday nominated Albert Carnesale of Harvard University's John F. Kennedy School of Government to be the new chairman of the troubled Nuclear Regulatory Commission.

Carnesale, 44, is a nuclear engineer who also has a background in environmental studies as well as nuclear arms control. Subject to Senate confirmation, he will replace Richard T. Kennedy on the five-member commission and displace acting chairman John Aherne, who will remain on the panel.

In a statement issued by the White House, Carter said he expected Carnesale to provide the "strong, concerned leadership" that several studies have said the NRC needs.

Carter said, "I also know that we will be especially sensitive to the overriding importance of safety and environmental protection in the development of our nuclear power resources."

At his office in Cambridge, Mass., Carnesale said his first priority as chairman would be ensuring the safety of the 70 reactors now in commercial operation.

"People think of the future and of the potential for growth, but in point of fact you must not neglect the present," he said. Operating reactor safety, he continued, would include dealing with generic safety issuses as well as implementation of safety changes ordered after the Three Mile Island accident last year in Pennsylvania.

Asked about his feelings on joining a commission often described as a can of worms, he said he would rather focus on the potential for future action. "A can of worms can be used for catching fish. There's a positive side to everything," he said.

The Three Mile Island accident that rocked the industry also shook up the commission. Probes, studies and hearings led to a series of bitterly divisive commission votes. The recurring lines of argument have been drawn over the degree to which all safety concerns should be heard and addressed in relation to the vast expense of delay in the licensing of new power plants.

Carnesale's position is likely to be pivotal in these debates in the future.

In addition, a newly approved NRC reorganization will give him much more day-to-day power and authority in hiring and firing than any predecessors. mHe would also take over NRC operations in the event of any future nuclear emergency like Three Mile Island.

Ahearne, who was named acting chairman last December and will step aside for Carnesale, said he was delighted at the nomination and called it "a very wise choice." Carnesale, he said, is "very knowledgeable and has demonstrated great objectivity in approaching many significant issues."

Other nuclear community observers were more cautious. "He has a good technical background, which is a plus, but not much management background, which is a minus," said George Gleason of the American Nuclear Energy Council, an industry lobby. "We wish him luck and intend to work with him to get the NRC moving again."

Richard Pollock, head of Ralph Nader's antinuclear Critical Mass Energy Project, called Carnesale "an unknown quantity." The agency, he said, "needs a strong chairman to get it back into shape, and we hope he has the fortitude to do what needs to be done."

Carnesale holds a doctoral degree in nuclear engineering and headed the nuclear division of Martin Marietta Corp. in Baltimore from 1957 to 1962. He took part in SALT I negotiations as head of defensive weapons systems for the U.S. Arms Control and Disarmanent Agency, and later headed environmental studies at North Carolina State University, where he had received his Ph.D.

Since 1974 he has been professor of public policy at the Harvard school as well as associate director of the Center for Science and International Affairs. He was chief of the U.S. delegation to the International Fuel Cycle Evaluation Conference last year and co-authored the 1977-Ford-Mitre study, "Nuclear Power Issues and Choices."