In assessing the contribution of the Comprehensive Test Ban (CTB) Treaty to U.S. security, there are three fundamental technical questions involving nuclear weapons themselves that must be addressed. First, will the United States be able to retain confidence in the safety and reliability of its existing arsenal of nuclear weapons under the treaty? Second, to what extent will the treaty constrain the development of new types of nuclear weapons by the United States and other nuclearweapon states? And third, how much will the treaty contribute to preventing the further proliferation of nuclear weapons? Article I of the CTB Treaty obligates the parties "not to carry out any nuclear weapon test explosion or any other nuclear explosion" and "to prohibit and prevent any such nuclear explosions at any place under its jurisdiction or control." The negotiating history makes clear that in banning nuclear explosions the treaty permits no yield from nuclear explosions-not 1 kiloton, not 1 kilogram, not 1 milligram of yield, but zero yield. This provision applies to both fission and fusion explosions. The treaty, however, is less clear about what constitutes a "nuclear explosion." The Clinton administration's article-by-article analysis, which accompanied the formal submission of the treaty to the Senate for its advice and consent to ratification, said the United States decided that a formal definition of "nuclear explosion" was "unnecessary and would be problematic." The document then lists "illustrative" examples of activities that are not prohibited by the treaty, including hydrodynamic experiments that might involve sub-critical amounts of fissile materials, inertial confinement fusion (ICF) experiments, experiments using pulsed-power facilities and the operation of nuclear power or research reactors. Despite these qualifications, the intent of the treaty is clearly to preclude any prompt (explosive) release of fission or fusion energy that could be used as or lead to a nuclear weapon.
Given the U.S. interpretation of the basic obligation of the CTB Treaty, the treaty will have the following impact on the future of nuclear weapons: Available experience demonstrates that, under the CTB Treaty, nuclear-weapon states will be able to maintain their nuclear weapon stockpiles safely and reliably for at least several decades, by means of appropriate programs of inspection, analysis and remanufacture.
Each nuclear-weapon state may accomplish this by putting different emphasis on full funding of the mechanisms that it has used in the past, on a U.S.-style science-based Stockpile Stewardship and Management Program (SSMP) or on periodic automatic remanufacture. The nuclear-weapon states will be unable to develop radically new designs of nuclear weapons, such as the nuclear explosion-pumped X-ray laser.
Any state will be prevented from acquiring new-design, two-stage thermonuclear weapons in which it could have much confidence. Although a state might design and even build new weapons within its existing range of experience, it would not have full confidence in their performance or reliability.
A non-nuclear-weapon state could with reasonable confidence clandestinely build, under a CTB Treaty but in violation of its nuclear Non-Proliferation Treaty (NPT) obligations, a "gun barrel"-design weapon using uranium-235 (U-235), and with greater difficulty and somewhat less confidence could reproduce a first-generation implosion-type weapon using weapon-grade fissile materials. (In some cases, a competent nonstate group might also be capable of such a design if it had access to fissile material.) Somewhat greater uncertainty and difficulty would be associated with the use of plutonium from the reprocessing of commercial, reactorgrade spent fuel. Increasing uncertainty would be associated with more advanced implosion systems that use less fissile material than the original solidsphere design.
Still greater uncertainty would be incurred if a non-nuclear-weapon state designed and produced "boosted" fission weapons without testing, and very little confidence would be associated with two-stage thermonuclear weapons that had never been tested. …