The Energy Department, trying to make sure no terrorist ever lays hands on the nation's store of nuclear data, has proposed controlling it with a set of rules that critics say could subject librarians and environmental activists to stiff penalties, put a severe crimp in academic research and frustrate states' efforts to protect their citizens from nuclear hazards.

DOE officials say those fears are groundless, based on a "misapprehension of the scope of the rule." But the concerns have forced the department to delay its proposal until public hearings are held next month.

The rules were proposed in April, under a recent amendment to the Atomic Energy Act designed to give DOE additional power to shield information that was sensitive but not secret.

The department already has the authority to protect some unclassified data under an executive order, the Atomic Energy Act nd Freedom of Information Act exemptions. But last year, it asked Congress for more, arguing that some nuclear data, while not a national security concern, still should be protected from terrorists, extortionists and the like.

It wasn't long before some labor unions, scientists, environmentalists and state officials took a look at the rules and decided that "the like" included them. And a group of congressional Democrats recently complained to Energy Secretary Donald P. Hodel that, where Congress agreed to give a few inchees, DOE has taken a few miles.

The letter, signed by 18 Democratic senators and representatives, warned Hodel that, instead of the "minimum restrictions" Congress authorized, DOE "has in fact proposed an extremely broad rule to give itself sweeping powers to withhold a whole new category of information."

The DOE says it wants to protect any information that "could reasonably be expected" to increase the likelihood of illegal production of nuclear weapons, theft of materials or sabotage of facilities. The proposal specifcally includes information on design and security measures.

But the DOE's proposal also gives the energy secretary broad discretion to decide what else needs protecting. It defines nuclear material, for example, as "any material that the secretary determines to be nuclear material," and adds that "nothing in these regulations precludes the secretary or his delegate" from withholding information "not specifically described in these regulations."

The proposed penalties for violating the rule are severe: a civil fine of upp to $100,000, at the discretion of the secretary, and a possible criminal penalty of up to 20 years' imprisonment for willful violation.

Representatives of academia immediately lambasted the rules as "obscure, confusing and inappropriate for university campuses."

Harvard University complained that, even under a narrow reading, the rules "would likely chill or thwart academic and public discussion in the nuclear field." Stanford University said the proposal was "fatally flawed" and ought to be withdrawn.

The NationalArchives, which has thousands of nuclear-related documents in its files, told DOE "it is very bad policy to propose to protect a category of information which is yet to be defined."

Environmental groups were no less direct. The Environmental Policy Institute called the proposal "a new secrecy grab" that "threatens to reduce still further the slow trickle of information that DOE reluctantly provides to citizens' groups and state officials."

South Carolina's health department worried that such a rule would shut off its access to information about DOE's Savannah River Plant--data it recently used to document "several very serious cases of environmental degradation."

The head of the Nevada energy department, James I. Barnes, said that his state, "with its long history of involvement with defense-related nuclear activities," found the rule "unnecessary, extremely vague" and an attempt "to infringe upon the right of the public to gain access to information that belongs in the public view."

"The state will maintain a watchful eye on this propposed rule and will not hesitate to pursue a legal remedy should the final rule remain as vague and as obtrusive as the proposed rule," Barnes said.

The American Civil Liberties Union complained that individuals, such as librarians, might be liable for stiff fines "for even wholly unwitting violations." Environmentalists and state officials warned that citizens and health authorities, in pursuit of information about nuclear hazards, could be forced to defend themselves against criminal prosecution.

DOE officials sharplydisagree with what one termed a "spectre of arbitrary punishment."

Herman E. Roser, assistant secretary for defense programs, said in a recent letter that the rule "would not result in wholesale censorship of texts or denial of library and archival materials."

Roser also said that no one would be liable for "innocently disseminating material," at least until the material had been clearly marked as protected.

But he conceded that "it is quite possible the proposed regulations will be modified to reflect legitimate conncerns of the scientific and academic communities, as well as those of the public at large . . . ."