The National Academy of Sciences reported yesterday that it could discover no evidence that U.S. security has been damaged by open scientific discussion.

But the panel said the nation does have a "substantial and serious" problem of technology leakage from ordinary, legal sales of equipment to the Soviet Union as well as illegal sales and espionage.

The report, produced by a panel of 19 scientists and academics, also said attempts by the government to censor research papers and meetings could damage American military, economic and technical progress.

Government officials for several years have expressed increasing concern that the Soviets are able to gain militarily from their access to open scientific literature and meetings in America, as well as by the more usual methods of espionage and illegal purchase of U.S. equipment.

Government officials have confiscated unclassified papers from scientific meetings in an attempt to keep the Soviets from gaining access to them. In the most recent case in August, more than 170 unclassified papers were censored at a meeting of the Society of Photo-Optical Instrumentation Engineers.

The National Academy's panel, which had briefings at secret and top secret levels, said virtually the whole problem of leakage comes from direct and indirect Soviet purchase of U.S. equipment as well as espionage.

The panel said that according to estimates by the intelligence community "70 percent of the militarily significant technology acquired by the Soviet Union has been acquired through . . . intelligence organizations, using both overt and covert methods. Most of the rest is acquired through legal purchases of equipment or data."

The panel's assertion that it found no direct evidence of technology leakage from the universities contradicts what some advisers have been telling Defense Secretary Caspar W. Weinberger, said Dale Corson, chairman of the National Academy's panel.

Corson met with Weinberger this week to discuss the panel's report, and said the secretary is "torn between his impulses" toward openness in research "and the reports by some of his staff there is a lot of outflow from the universities to the Soviet Union."

"In our report," Corson said, "we say there is simply no evidence for that."

The report said that it would be better to try to protect the nation's technological lead by continued rapid scientific advance, not by security measures that may choke off communication even among U.S. scientists.

The panel said apart from some small amount of government-supported research in universities that is classified, there is also a small area of work "for which limited restrictions short of classification are appropriate." An example of this is research in which "on-campus research merges directly into process technology with possible military application."

For this kind of situation to warrant controls, the panel said it must meet all four of these tests: it must be rapidly developing technology; it must have direct, identifiable military application; it must be seen to provide the Soviets a near-term within five years military benefit, and the only possible source for the information must be the United States.