A California physicist, the latest anti-nuclear cult hero for his role in discrediting a rosy report on nuclear power safety, says his new admirers have the issue all wrong.

Nuclear power, says Harold W. Lewis, is actually safer than the discredited Rasmussen report said it was. And he should have said so before, Lewis added, but nobody asked him.

The 1975 report by MIT Prof. Norman Rasmussen said after $4 million worth of paperwork that the chances of dying in a nuclear power plant accident were about those of being hit on the head by a falling meteorite. The study became the statistical bedrock for industry defenders.

Lewis, a physicist at the University of California at Santa Barbara, and six other nuclear specialists dissected the report last year and found that its calculations of accident probability were badly done. The margins for error that Rasmussen left were too narrow, Lewis said.

He told the Nuclear Regulatory Commission when they asked that he couldn't tell whether the accident probability figure was too high or too low without redoing the four-year study, but he could say for sure that the figures were unreliable. As a result, the NRC repudiated the Rasmussen report in part last month, leaving industry defenders to weather the fallout of anti-nuclear forces' cries of triumph.

Those cries are premature, Lewis said in a recent interview.

"Personally, I think Rasmussen's numbers were too high," he said. Major nuclear catastrophe, in other words, is less likely than Rasmussen thought.

He didn't tell the NRC that because "I haven't got the numbers to back it up. Nobody has the numbers. It may be there is no way to get the numbers. But it's just obvious from the overall conservatism of every single thing Rasmussen did."

In figuring the likelihood of disaster, for example, Rasmussen continually assumed people would act stupidly, and that most human intervention would make a situation worse rather than better. In loading his numbers, Rasmussen would add "a percentage here and there, always on the negative side," Lewis said.

"After a lifetime of engineering in which one always prepares for the worst, he [Rasmussen] seemed unable to go down the middle for once," Lewis said.

He added he sees little value in trying to redo the Rasmussen study. "We should spend less time evaluating how safe reactors are and more time making them as safe as possible," he said "The [scientific] community wastes a lot of time trying to come up with probability estimates."

Lewis is philosophical about having been misinterpreted. The Rasmussen report "had given people the idea that the debate was over, the things are safe. Well, there are risks... If there is an accident it will come from complacency and the feeling that things are safe without anyone paying attention to them."

Now, he said, the debate on nuclear power can proceed on a more rational level. "The question, 'Are nuclear reactors safe?' is really, "Are they safe enough so we can worry instead about Iran or detente?'... You're really trying to determine the acceptable level of risk. It's a political decision, not a technical one."

The NRC this week said very few decisions or rules had beenbased on the Rasmussen report and so no plant shutdowns or policy changeswould be necessary. Nuclear power's critics challenge that assertion and say now that Lewis' critique is still useful in their efforts to shut the industry down.

It will have a ripple effect," said Richard Pollock, head of Ralph Nader's Critical Mass organization. "Lewis is entitled to his opinion, but the full report still suggests that the consequences of a major accident are underestimated. We're back at square one."