There will be no need to shut down any nuclear power plants or change any safety rules because of faults in the controversial Rasmussen Report on nuclear safety, the staff of the Nuclear Regulatory Commission said yesterday.

In a report to the full commission, staff director Harold R. Denton said the 1975 report was never a major factor in setting regulations or in decisions to license operating nuclear plants. "Its principal application has been to supplement or confirm the main stream of analyses and judgements reached by the staff," he said.

The Rasmussen Report, also known as WASH-1400, assigned major nuclear power plant accidents a very low probability, but was repudiated in part by the NRC last month, after a blue-ribbon panel criticized its calculations.

The NRC, which oversees nuclear licensing and safety, then asked its staff to review ways the report had been used in order to see if any backtracking was necessary.

In checking more than 200 documents, Denton said, patting two foothigh stacks before him, the staff found 119 cases in which WASH-1400 was cited to back or justify a decision. In 40 cases, the staff thought the decision was "less conservative" or "status quo" on safety issues because of WASH-1400, so looked at those more closely. The rest of the uses led to decisions that were more conservative or irrelevant to safety issues.

Three of the 40 cases involved WASH-1400 use in ways that new guidelines would prohibit, but only one of those cases requires active reconsideration, Denton said.

That one case involves an NRC rule requiring two redundant battery systems to supply direct current for instrument sensors and other uses if the power plant's generators should fail. WASH-1400 figures were used to show that the probability all three electricity supply sources would fail at once was "so unlikely as to be incredible," the staff report said.

In light of the downgrading of WASH-1400, the issue should be reconsidered, the report added. In an interview, Denton said he was "pretty sure" independent calculations would lead to the same conclusion.

"Engineers with 20 years' experience with bolts and gears never really relied on (the Rasmussen Report anyway," he said. "They used it as sort of a sop afterward to tack onto conclusions they would have come to anyway... we never really got into a WASH-1400 mode of decision making."

This premise was challenged by the Union of Concerned Scientists, a Massachusetts-based group of scientists critical of nuclear power. The group asked the NRC to shut down 16 power plants it said posed risks as a result of WASH-1400 use, but Denton said yesterday that the staff would recommend against any shutdowns.

"The record has been mischaracterized by the UCS," Denton said.

Robert Pollard of the scientists' group responded that recent NRC responses to other questions he had raised meant he would now like to see 55 plants shut down. "I totally reject this staff response," he said. "It's another case of taking facts that show a thing is white and saying they show it is black." He said the scientists may take the NRC to court to force powerplant shutdowns.

One NRC staff member, Demetrios L. Basdekas of the safety research branch, told the commission he disagreed with the Denton report because it was incomplete. He called for an outside evaluation of WASH-1400 uses, and said in an interview later, "People here (at the NRC) have a tendency to say what management wants to hear."

He noted that WASH-1400 was frequently cited in NRC responses to congressional inquiries about nuclearsafety issues, and may have been misleading. "Improper use of WASH-1400 was more extensive than its users might be forthcoming enough to readily admit now," he told the NRC.

The full commission meeting recessed before completing the report from the staff, but is expected to resume prior to congressional hearings on uses of the Rasmussen Report beginning Feb. 26.