The nuclear power industry, with its traditional optimism, decided yesterday that the president's Commission on Three Mile Island gave the industry "a simple message: proceed, but proceed with caution."

That summation from Floyd W. Lewis, chairman of the Edison Electric Institute's ad hoc committee on the March accident in Pennsylvania, was typical of the reaction from nuclear supporters and critics alike.

The critics wished the commission had gone further in its recommendations, discussing -- and, they hoped, attacking -- the overall value of nuclear power. Supporters quarreled with individual points in the commission's thick stack of documents but looked on the sunny side: there was no recommendation for a moratorium on reactor plant construction.

But at least one key legislator, chairman Morris K. Udall (D-Ariz.) of the House Interior Committee, said the report had helped move him from opposition to "tentative support" for a moratorium. And at the NRC, two members mustered strong arguments against the key recommendation for restructuring their agency.

"We conclude that what the Kemeny Commission says is that we can have safe nuclear power if we manage it well, and our response is that the industry is committed to doing just that," said Carl Goldstein of the Atomic Industrial Forum, a trade association.

"The commission found that the plants as now designed and built are safe. They did not uncover any basic design defect. That's important to us . . . there are many managerial and operational things that need fixing and we agree, but nothing in there supports a freeze or a delay in the licensing of new power plants," Goldstein said.

Chiefs of Metropolitan Edison Co., the utility that owns Three Mile Island, and its parent company, General Public Utilities Inc., said they "disagree strongly" with Kemeny Commission criticisms of their staffs and expertise.

"We regret that conclusion . . . it is incorrect and taken out of context," said William G. Kuhns, GPU board chairman. Instead, he said, studies had found TMI personnel "near the top of the list in any industry comparison."

He stressed that problems the commission identified were not unique to Three Mile Island but were common to the whole industry. "Vast changes have already been made and more will be done," he told a press conference.

Herman Dieckamp, vice president of Metropolitan Edison, indicated that the utility plans to fight a $155,000 fine for TMI procedural violations announced last week by the NRC. He said his firm was "very concerned" that information about a similar valve malfunction at the Davis Besse nuclear power plant in Ohio "fell through the cracks" and was not disseminated by Babcock & Wilcox Co., which built both Davis Besse and Three Mile Island.

At Critical Mass, a Ralph Nader organization opposed to nuclear power, director Richard Pollock called the NRC reorganization proposal "long overdue." He said, however, that the Kemeny Commission performed "a grave disservice by avoiding a final political decision on the overall value of nuclear power."

Daniel Ford, head of the Union of Concerned Scientists, a Massachusetts-based group critical of the industry, said the commission ought to have discussed the future of the 70 nuclear plants now operating. "It is what we've been trying to tell people for several years: that this country does not have a competent nuclear regulatory program," he said. "But the fact is that the assurance of safety is all based on NRC approval . . . they left the major question dangling."

Rep. Edward Markey (D-Mass), another outspoken nuclear power critic, called the commission report "tragically flawed" for not recommending a moratorium on new plants. "It's like saying the car is defective but we can repair it while it's running down the road," he said.

Rep. Udall said the Kemeny report has had "a major impact on my thinking."

He said he is considering a proposed suspension of the NRC's authority to issue construction permits until it incorporates the Kemeny recommendations into its regulations and procedures. "The report might stimulate overall support (in Congress) for a moratorium," he said.

On the Senate side, Gary Hart (D-Colo.), whose nuclear regulatory subcommittee held hearings on Three Mile Island, said he opposed the idea of reorganizing the NRC.

"This would be a serious mistake and one bound to increase the problems of nuclear regulation rather than correct them," he said. He added later, however, that the idea "deserves discussion, but the burden will be on those that want the change."

Hart agreed with the industry assessment that the Kemeny report does not endanger the future of nuclear power. "The jury is still out on that. The future of the industry is going to be determined as much on Wall Street as in Washington," he said. He referred to problems in financing nuclear plants, and to plummeting stock prices of companies involved in Three Mile Island.

Sen. Richard Schweiker (R-Pa.) praised the Kemeny report as "objective and evenhanded." The response to the accident in his state, he said, was "alarming picture of an industry becoming dangerously complacement about safety." He supported the idea of NRC reorganization.

At the NRC, however, two commissioners attacked that recommendation. Commissioners Peter A. Bradford offered the view that reorganization was "something of a distraction" from what he called " a fundamental change in the attitude toward safety" that has occured at both the NRC and within the industry.

If the argument for a single-administrator NRC is one for efficiency, Bradford said, "God knows the Atomic Energy Commission was efficient . . . and that in large measure was what led us to Three Mile Island. It isn't going to get us out."

To say a single-chief NRC would be more accountable to the public, Bradford continued, ignores the fact that NRC errors do not show up immediately but five to 10 years later. "This is not a meat inspection program," he said.

Commissioner Victor Gilinsky said he largely agreed with Bradford.