IT'S tough to be a United States nuclear weapons designer.
For the first time since the dawn of the atomic age, no new warheads are rolling off production lines, while underground nuclear tests will be strictly limited or even banned in coming years.
But that doesn't mean the warhead-development business has dried up. Department of Energy (DOE) scientists are continuing to plan new nuclear weapons they feel the US might need in the future.
Among concepts being considered, according to newly-released budget documents, is a very low- yield nuclear warhead capable of destroying the chemical or nuclear warhead of an attacking missile with assurance.
"There will be requirements for new nuclear weapons in the future. We cannot with confidence say what they will be," says John H. Birely, deputy assistant to the secretary of defense for atomic energy, in a written response to a congressional inquiry.
Improved warhead safety is one reason to forge ahead with weapons work, according to Department of Defense and DOE officials. For instance, in recent years scientists have been developing warheads capable of withstanding the heat of a fire without dispersing plutonium.
The requirements of new delivery systems, or new "deployment environments," might also require new warheads, according to the DOE documents. Besides the antimissile nuclear weapon, this might mean an earth-penetrating warhead to threaten deeply-buried targets.
In fiscal year 1992, DOE scientists are in the first phase of design work on two new kinds of aircraft-carried nuclear weapons: * A "precision low-yield" warhead that would "reduce collateral damage to acceptable levels," according to the Pentagon. * A hypervelocity warhead that would fly to targets so fast it would defeat possible defenses.
The US also is continuing study work on both tactical and strategic radio-frequency weapons. These are nuclear warheads tailored to produce as much electromagnetic pulse as possible, destroying electronics and communications over a wide area.
To some critics, these continuing studies are evidence that part of the US security structure just does not get the fact that the cold war is over.
William Arkin, Greenpeace's military research director, says in a recent article in the Bulletin of the Atomic Scientists that such nuclear work is due partly to "inertia," but is also "a product of an unreformed belief in the permanence of the nuclear-war-fighting system."
OTHER experts point out that much of this work consists, in essence, of scientists sitting around and discussing new ideas.
"The military itself is not interested" in many of these applications for nuclear weapons, says Robert S. Norris, a senior analyst at the Natural Resources Defense Council.
Indeed, the growth area in weapons-lab research and development (R&D) is not in weapons work per se, but in environmental improvements, dismantlement techniques, and safety and security projects.
"We have already shifted substantial resources - about $120 million for FY 1993 - from weapons development to other activities," says a DOE budget document.
The Energy Department says that one of its prime objectives is stabilizing the lab work force devoted to weapons R&D. This work force will have shrunk by 25 percent between 1987 and 1993, while many of its most senior members will reach retirement age shortly thereafter.