U.S. Navy policies probably create "a greater likelihood of accidental or unauthorized launch of sea-based nuclear weapons" than those on land, according to a study this month by Desmond Ball, an expert on nuclear strategy and head of the Strategic and Defence Study Center of the Australian National University.

Ball, in a study published this month by Harvard University's Center for Science and International Affairs, calls the Navy's procedures for authorizing the release of nuclear weapons "more relaxed than those that pertain to land-based systems."

Those procedures, combined with planned and actual recent deployments of new Navy tactical nuclear weapons on submarines and surface ships raise "a high risk of nuclear weapons being used fairly quickly in any major East-West conflict at sea," Ball concludes.

The Army and Air Force have physical locks that prevent their nuclear weapons from being armed, and thus used, without receipt of a special code as well as a presidential authorizing message. The electronic code from the White House or the national command authority at the Pentagon or some other higher command is necessary to close a link needed to permit the weapon involved to be armed.

The Navy also requires a presidential authorization message but not the outside electronic code or other release mechanism to arm its weapons. They "can be fired without any technical or other action [from] anyone outside the individual submarine," Ball says.

Navy officials have acknowledged that because of difficulties in sending long messages to submerged submarines, it would be impossible to send a coded electronic "key" to release the long-range ballistic missiles carried by Poseidon and Trident submarines.

Despite this lack of outside safeguards, such as those found in Air Force nuclear missiles, Navy officials insist that no nuclear weapons launch could take place without an authenticated order from the national command authority. They also assert that there has never been a threat of a launch thanks to the security procedures aboard Navy ships.

Ball says such "arguments advanced by the U.S. Navy to justify its refusal to equip naval nuclear weapons with 'permissive action' devices [as they are called in Army and Air Force weapons] are unpersuasive."

Since the first sea-launched cruise missiles were deployed in mid-1984, the Navy has not officially commented on release practices with them and other nuclear antiair and antisubmarine weapons carried aboard ships and submarines.

But in answer to congressional inquiries last spring, the Navy told the House Armed Services Committee in testimony released last month that the new nuclear weapons would be subject to the same rules that applied to the old ones.

Retired rear admiral Eugene Carroll, deputy director of the Center for Defense Information and a critic of the tactical nuclear weapons policies, said yesterday that the Navy has "insisted that it can't tie its [sea-based] weapons to constraints from shore."

If communications from land fail, Carroll said, the Navy wants its weapons in "a go-mode" ready for use, rather than in what he said was a "fail-safe" mode that would prevent firing.

Ball said Navy policies for use of its tactical nuclear weapons "have never been officially presented in a form that would permit informed critiques" and details of their deployment "are generally closed to public scrutiny."