ARMS CONTROL. A change of pace: beating nuclear weapons into scrap

Nuclear weapons cannot be thrown away in dumpsters out back of the Pentagon. But United States officials say they are confident they could handle destruction of hundreds of nuclear missiles and warheads, as would be required by a superpower pact on medium-range arms. After all, the US disposes of elderly nukes almost every working day. Among systems thought to be on the disassembly line now are Titan 2 long-range missiles, the Genie air-to-air rocket, and older Minuteman 3 missile warheads.

``It's a very technical thing to destroy these weapons, but we do have experience at it,'' says an arms control official.

Though an INF (intermediate-range nuclear force) pact has yet to be signed, progress made during Soviet Foreign Minister Eduard Shevardnadze's recent US visit eliminated all major obstacles to a treaty. (US official discusses arms control and ``star wars,'' Page 9.)

An INF agreement would mean the first wholesale weapon destruction of the nuclear age, with the US getting rid of its Pershing 2 and cruise missiles, and the Soviets their SS-20s and other medium-range systems.

The general outline of what ``destruction'' means in this case has been agreed on. Besides elimination of the missile launchers, ``what we're talking about is taking the [INF] reentry vehicles, removing the fissile material and guidance systems, and getting rid of the rest,'' says the arms control official.

But details of dismantling have yet to be worked out. The schedule is still a point of contention: The US wants to get rid of the major INF missiles over three years, while the Soviets favor a five-year destruction period. How to verify that the process has taken place has also not been settled.

What the INF destruction process might look like can be seen by examining how the Air Force Strategic Air Command (SAC) handled its most recently decommissioned nuclear weapon, the Titan 2 missile. The last of the 20-year-old Titans, once the most powerful US nuclear weapons, was taken off alert near Little Rock, Ark., in June.

The first step in getting rid of the Titans was removal of their nuclear warheads, says Capt. David Thurston, a SAC spokesman. Then liquid fuel was drained from their two rocket stages, and their carcasses were hauled out of silos by heavy-duty cranes and shipped to Nortan Air Force Base in California, where they remain in storage.

The empty silos were left unattended for some time, so that Soviet spy satellites could see they were empty. Then contractors blew them up.

Dismantling Pershing 2 and cruise missiles would likely be a less involved job. Both use solid fuel, instead of the more volatile liquid variety, and neither are based in dug-in silos. It could still be a touchy process. In 1985, a charge of static electricity ignited the fuel in a Pershing 2 being installed in West Germany, killing three soldiers.

The hardest dismantling job of all, of course, involves getting rid of warheads. This job is handled not by the Defense Department but by the Department of Energy (DOE), which has charge over all US nuclear warhead design and production.

The Pantex plant near Amarillo, Texas, is where this destruction takes place. Almost all Pantex workers work on a particular type of nuclear weapon - Minuteman warheads, perhaps, or W-79 howitzer shells - and are able to both assemble and disassemble their specialty.

Dismantlement goes on just about every day at Pantex (as does production - it is the only final assembly plant for US warheads). Since 1945, the US has retired 42 types of nuclear weapons, from Titans to tiny Davy Crockett troop-carried missiles. According to a nuclear weapons data book compiled by the Natural Resources Defense Council, of the 29 types of warheads in the current nuclear stockpile, six are probably in the retirement process: Titan, Genie anti-bomber rocket, Pershing 1A, MADM atomic mine, Poseidon submarine missile, and Minuteman 3 ICBM.

Actually, the soul of a warhead is never really retired. The fissile materials - uranium 235 and 238, and plutonium - are shipped off for reprocessing at other DOE plants, then used in new warhead production. This recycling would be permissible under the INF pact.

Other parts of the warhead which have become radioactive over time are ``disposed of in an appropriate manner,'' says Anna Bachicha, a spokesman for DOE's Albuquerque, N.M., operations office. In other words, they are held at US government nuclear facilities.

Ms. Bachicha says it's too early to tell whether an INF pact would cause a major disruption in operations at Pantex. ``We're not expecting an immediate impact,'' she says, ``but in the long term there may be some effect.''