The Nuclear Regulatory Commission has decided that current international safeguards against the spread of nuclear material will not work in some situations and is so concerned that it has begun to review its export licensing policy, it was learned yesterday.

In a letter Friday from Chairman Nunzio J. Palladino to members of Congress with jurisdiction over the NRC, the agency joined several recent critics of the International Atomic Energy Agency and its efforts to prevent the spread of nuclear weapons.

But the NRC position is crucial, because any slowdown in licensing the nation's hundreds of annual nuclear exports would rock the industry and cast a shadow over the entire administration policy of promoting nuclear power.

Palladino's letter, endorsed by the other four commission members, reiterated a longstanding NRC complaint that "little or no safeguards information" is generally available from the IAEA when the NRC must decide whether to license commercial shipments of reactors, components, fuel and other radioactive materials. About 200 shipments subject to safeguards go out each year.

Recent developments have prompted the NRC "to update our assessment of IAEA safeguards," Palladino wrote.

"The NRC is concerned that the IAEA safeguards system would not detect a diversion of nuclear materials in at least some types of facilities. In addition, we are not confident that the member states would be notified of a diversion in a timely fashion," the letter said.

Palladino did not specify the "recent developments," but NRC sources said they included Israel's bombing of Iraq's Osirak reactor last June and subsequent congressional testimony from former IAEA inspectors that IAEA safeguards might not have detected the bomb factory Israel said was at Osirak.

Internal IAEA politics and pressure mean a violation might be sidetracked within the the bureacracy and not come to public attention, the inspectors said.

IAEA Director Sigvard Eklund told the IAEA general conference in September that the agency, an arm of the United Nations, could not guarantee that nuclear materials might not be diverted during "on-line refueling of heavy water reactors" of the type used in India and Pakistan.

The safeguards, agreed to by the 112 signatories to the Nuclear Non-Proliferation Treaty, include on-site inspections, but host countries can choose the IAEA inspectors, always know in advance when inspectors are coming and can refuse to provide documents or access to areas they have not previously said may be inspected. The inspectors have no authority to look for undeclared material.

In addition, NRC jurisdiction over safeguards has never been clearly defined. The Nuclear Non-Proliferation Act of 1978 provides that the NRC must certify that IAEA safeguards "will be applied" to U.S. nuclear exports before it approves them, but the act says nothing about evaluating adequacy of the safeguards.

A spokesman for the State Department, which also must approve nuclear exports, said the IAEA performs an essential function. "We don't see any alternative to it, and we're working on improving the safeguards," he said.

Sen. Gary Hart (D-Colo.), ranking minority member of the Senate nuclear regulatory subcommittee, called for an NRC moratorium on licensing nuclear materials and technology exports. "If we cannot tell whether they are being diverted to make nuclear weapons, we should not be licensing them," he said.

Hart joined Reps. Richard L. Ottinger (D-N.Y.), chairman of the House energy conservation subcommittee, and John D. Dingell (D-Mich.), chairman of the Energy and Commerce Committee, in worrying that IAEA safeguards may be "nothing but a facade" of protection.

They asked the NRC for evidence of safeguard problems and for information on any material diversions.