The Nuclear Regulatory Commission has eased control of the nuclear industry during the Reagan years, reflecting what a maverick member of the panel calls a "complacency about safety" despite continuing safety lapses at U.S. atomic reactor plants.

Last year, even as the industry compiled its worst safety record since the Three Mile Island accident of 1979 -- with 10 percent of U.S. plants experiencing "significant" mishaps or management lapses -- commission rulings set up procedural hurdles for imposing safety modifications on plants, and gave utilities the right to regulate themselves in important areas of employe training and "fitness-for-work" standards.

Some major decisions have run counter to the recommendations of the professional staff, including the panel's rejection of proposed safety improvements for a New York plant that were predicted to cut in half the chance of an accident.

Two declarations by the five-member panel last year sum up what critics consider to be a laissez-faire regulatory philosophy: Four months after the commission projected a 45 percent probability of a severe reactor core meltdown within the next 20 years, it concluded that today's plants pose no "undue level of risk" to the public.

"This commission believes its job is to protect the industry and not the public," said Commissioner James K. Asselstine, a frequent dissenter from NRC decisions, in an interview. "There's a willingness to accommodate industry wishes and a reluctance to take a strong and aggressive role to regulation. There's a misplaced sense of optimism even to the point of ignoring the messages we're getting from the operating experiences of the plants."

NRC Chairman Nunzio J. Palladino, who has steered the panel since 1981, called the criticism "blatantly untrue." Rather than relaxing its control of the industry, he said, the commission is "clarifying and making sense out of our regulations."

"We are here to protect the public and that's what we do," he said.

Last week's nuclear accident in the Soviet Union serves as a reference point for this debate, with NRC critics saying the meltdown demonstrates the need for dynamic regulation of atomic plants and NRC supporters arguing that it proves the commission's success in fostering a safer system.

After the partial reactor meltdown at Three Mile Island became the worst U.S. nuclear accident, the NRC under President Jimmy Carter ordered thousands of safety improvements to reduce the chance of another accident.

But utility companies protested that the incremental modifications ordered by the commission caused "regulatory instability," and that many of the changes ran up heavy costs -- about $50 million per reactor -- without significantly improving safety.

As membership of the commission changed with administrations, so did the approach to safety improvements. Critics say the most important concession to industry came last September in the form of a new "backfit" rule, which established formal guidelines for the imposition of safety modifications at existing plants.

Instead of the previously informal process of staff recommendation and commission approval, the new rule requires the staff to prove a "substantial increase in the overall protection of the public health and safety or the common defense and security."

A cost-benefit analysis is also required for each proposed modification, using a nine-step model that critics contend is weighted in favor of costs and all but precludes new safety improvements.

Asselstine, in a dissenting opinion, said the rule typifies the commission's "inexorable march down the path toward nonregulation of the nuclear industry. I can think of no other instance in which a regulatory agency has been so eager to stymie its own ability to carry out its responsibilities. Indeed, the adoption of this rule is the most compelling evidence to date of the commission majority's open hostility to the regulatory mission of this agency."

Palladino said in an interview that the backfit rule was intended to put "sense and discipline" into a regulatory process that had previously led to costly plant modifications that added little to safety.

The rule, he said, requires the staff to determine whether an equipment change "brings about safety improvement that is worth the expenditure. Every one we put on means somebody has to spend money." No analysis is required if the top staff regulator believes the modification is vital to public health and safety.

One of those rulings came in the case of the Indian Point nuclear plant, which is located 25 miles north of New York City. An NRC licensing board recommended certain safety procedures, including measures to monitor high winds and prevent ruptures in steam generation tubes, that were estimated at the time to reduce by half the likelihood of an accident.

Last May, the commission overruled the board, concluding that the level of safety at Indian Point was adequate.

The Indian Point case set the stage for another controversial ruling known as the "severe accident policy." The NRC, shaken by the Three Mile Island accident, had decided to evaluate the risk of meltdown at other plants, especially in populous areas, to determine the need for new safety measures.

By last August, the majority concluded that "existing plants do not pose undue level of risk to the public" and found "no need for immediate action" to fortify U.S. plants against the risk of severe accidents.

Four months earlier, in answer to a request from a House subcommittee, the NRC staff had reported that over the next 20 years the statistical probability of a severe core meltdown among the 100 U.S. plants was 45 percent. The projection, however, did not state the likelihood of a release of radiation beyond the containment vessel.

Asselstine said in an interview that whether or not there is a radiation release, an accident that goes beyond the safety systems of a nuclear plant creates a "totally unacceptable" risk to the public.

"The commission finds that level of risk acceptable," he said. "Every member of the public would acknowledge that a Three Mile Island accident is unacceptable, whether it resulted in public health problems or not . . . . The memory of Three Mile Island has faded, and complacency about safety has set in."

He said that last year's record in the nuclear industry of two near-miss accidents that tested the plant's safety systems indicates "you have the potential for a more serious accident. That means to me you have an undue risk."

Palladino denied any contradiction between the severe accident policy and the meltdown projection, saying "one is based on assumption, one is based on reality."

"If we can't proceed on the premise that our plants are safe," he said, "we shouldn't license them . . . We'd be duty-bound to shut them down."

The commission's deferral to industry of responsibility for training and fitness-for-duty standards designed to purge employes of alcohol and drugs may lead to stronger controls, Palladino said, because utilities will have an incentive to go beyond "minimum" government requirements.