The Department of Defense yesterday said it would not remove short-range, nuclear-tipped missiles from strategic aircraft on war "alert" before the Air Force completes a special study on the possibility that they might explode in an aircraft fire.

The decision to maintain Short-Range Attack Missile-A, or SRAM-As, on B-1, B-52 and FB-111 strategic bombers ready for takeoff on short notice at Air Force bases came after directors of the three U.S. nuclear weapons laboratories urged that the weapons be withdrawn from service and placed in storage.

The scientists have expressed strong concerns that an accidental aircraft fire will cause a SRAM-A to explode, likely dispersing a fine dust of cancer-causing, radioactive plutonium or uranium from the core of the W-69 nuclear warhead at the weapon's tip.

Two such accidents in the 1960s involving a different nuclear warhead carried by U.S. strategic bombers cost millions of dollars to clean up.

DOD spokesman Pete Williams told reporters at the Pentagon that the SRAM-A "meets all our current safety standards" and "it would be unwise and premature to predict the outcome of that {safety} study and to make any decisions now before it's done" later this summer. Undersecretary of Energy John Tuck expressed a similar view Wednesday, although he added that his agency was "going" in the direction of the scientists' recommendation.

The Energy Department and the Defense Department share formal responsibility for nuclear weapons safety, a topic on which the directors of nuclear weapons laboratories in Los Alamos, N.M.; Albuquerque, N.M., and Livermore, Calif., serve as advisers.

Williams disparaged the scientists' unanimous recommendation as an expression of "personal opinion" that reflected more than "the scientific questions" involving the SRAM-A.

One of the three scientists had said that the policy of stationing the missiles aboard "alert" aircraft, which poses special safety risks, should be reconsidered in light of easing U.S.-Soviet military tensions.

Another senior defense official, who insisted on anonymity, similarly accused the laboratory directors of making "seat-of-the-pants risk-benefit calculations" that were inappropriate before the SRAM-A safety study was completed. "Everyone is entitled to their view of having those weapons on alert aircraft, but the lab directors' views are certainly not authoritative," said the official, who deals regularly with the topic.

"There is one very real area of concern" involving nuclear weapons safety, the official said, "and that is the slowdown in {weapons} production in the DOE complex {which has delayed} the introduction of bombs with modern safety features." He was referring to environmental and safety hazards that have forced closure of a key plant for weapons parts near Denver.

Williams disclosed for the first time some of the procedures that have been established by the Air Force in recent years to improve the weapon's safety. He said certain officers and the base fire departments must now be notified during any "alert" bomber exercises, and that the Air Force had adopted a safer method of operating B-52 and FB-111 bomber engines during maintenance checks.

But other officials have said that the Pentagon vigorously opposed mentioning the SRAM-A concerns in a joint DOE-DOD report to the White House on nuclear weapons safety, and also opposed establishment of a special safety committee proposed by Secretary of Energy James D. Watkins because of the SRAM-A dispute.

"There were a lot of pressures about that" from the Pentagon, Watkins said in an interview earlier this week. "But mostly it came from low level {officials} faceless bureaucrats. You get down about the sixth level {at the Pentagon} and they hate DOE, even the third level does."

He said, however, that Secretary of Defense Richard B. Cheney eventually concurred in the safety report and deserved "a lot of credit" for approving the safety committee.