November 15, 1996
<title><h4> 
The Case for the Comprehensive Test Ban Treaty


David Hafemeister
School of Public Affairs, Univ. of Maryland

A slightly shortened version appears in:
FAS Public Interest Report 50, pages 9-12, January 1997
It is ironic that in 1954 Indian Prime Minister Jawaharlal Nehru led the world by proposing the Comprehensive Test Ban Treaty (CTBT) and 40 years later India tried to crush the CTBT. However, on an over-abundant vote of 158 to 3 (India, Bhutan, Libya), the UN accepted the CTBT for signature and already 125 nations have signed the treaty. In the intervening years, Kennedy and Khrushchev almost agreed in 1963 to a CTBT, but Kennedy wanted 7 annual on-site inspections and Khurshchev would only accept 3. Basic logic suggests that had they compromised at 5 per year and if the treaty had been ratified, the world would most likely have been spared the MIRVed world of SS-18s and MXs But such was not to happen and 1500 more explosions took place, only now below the surface of the Earth. With the end of the Cold War and a strong push, first by Gorbachev and second by the U.S. Congress, the CTBT is alive and well and awaits ratification by the U.S. Senate. Yes, entrance-into-force may take several years, but the Geneva Convention on Treaties requires the signatories not to undercut the terms of the treaty. Legally this means that Russia, China, France, UK, US, and a growing list of nations have an international, legal commitment not to test nuclear weapons. This means freezing the nuclear weapons technologies of the Nuclear Weapons States (NWSs), preventing the de-facto nuclear states from escalating to hydrogen bombs, and preventing Nonnuclear Weapon States (NNWSs) from obtaining reliable, sophisticated nuclear weapons. When coupled together with the obligations of the Nuclear Non-Proliferation Treaty (NPT), the world will have a considerably strengthened barrier to nuclear weapons. But, incredibly enough, there will be those in the Senate who will fight this treaty. Nuclear Proliferation For 40 years, the CTBT has long been considered the quid pro quo by the 175 NNWSs to give up their sovereign right to develop nuclear weapons. Without cooperation by the NWSs, the NNWSs will limit their cooperation in the International Atomic Energy Agency and in other proliferation arenas, and some of them might move towards nuclear weapons. Because of these sovereignty concerns, the CTBT and the NPT are forever politically linked together in the global norm to prevent nuclear proliferation. As part of the political bargin, the NNWSs have reminded the NWSs of this NPT language: "Recalling the determination expressed by the Parties to the 1963 [LTBT] Treaty ... to seek to achieve the discontinuance of all test explosions of nuclear weapons for all time and to continue negotiations to this end." The linkage between the CTBT and the NPT was expressed much more clearly by Mexico: "A comprehensive test ban treaty would make the single most important contribution toward strengthening and extending the international barriers against the proliferation of nuclear weapons.... the continued testing of nuclear weapons by the nuclear-weapon States Parties to this Treaty would put the future of the Non-Proliferation Treaty beyond 1995 in grave doubt." (August 24, 1990, LTBT Amendment Conference) During the 1995 renewal of the NPT, the U.S. and the other NWSs stated their intention to "seek a complete ban on nuclear explosions," which considerably helped convince the NNWSs to extend the NPT without dissent and to call for a CTBT "no later than 1996." Yes, it is possible to build first-generation nuclear weapons without nuclear testing, but military leaders would be unsure if the weapons were reliable and effective. A CTBT would constrain the development of miniaturized weapons for missiles and MIRV, boosted primaries and hydrogen bombs. Arms Control The CTBT is both a nonproliferation and an arms control treaty. The CTBT constrains the NWSs from making new types of weapons. For China, this means forgoing a viable MIRVed missile system. The U.S. and Russia have conduced 85% of the nuclear tests (see table below) and thus they have an advantage over the other nations on information obtained from tests. Banning nuclear testing lessens tensions between the NWSs whereas doing nuclear tests raises tensions. Without a CTBT, the other NWSs will at some point begin testing anew. The two main questions that will be raised during Senate Ratification will be: "will the U.S. national security be harmed by not testing nuclear weapons" and "how much verification is enough?" U.S. Russia France U.K. China India Total Tests 1,030 715 210 45 45 1 2,046 U.S. National Security The JASON Committee, an independent group of senior non-government scientists, advises the U.S. Departments of Defense and Energy on technical aspects of national security issues. The unanimous report on nuclear testing by the group of 14 prominent scientists, including four DOE weapon designers, concluded (in brief): (1) The JASON Committee has high confidence in the safety, reliability, and performance margins of the present U.S nuclear stockpile which will continue to be needed for deterrence. (2) The U.S. must maintain the quality of its nuclear weapons with the Science-Based Stockpile Stewardship and Management Program which does not include nuclear testing. (3) The range of performance margins of the weapons are adequate at this time, and changes should be made to a weapon type only under extreme circumstances. (4) Continued testing under 500 tons would only marginally assure the quality of the weapons, much less so than the much more important Stockpile Stewardship Program. (5) Experiments with high explosives and fissionable material that do not reach criticality are useful in improving our understanding of the behavior of weapon materials. (6) In the past, problems that occurred were primarily the result of incomplete or inadequate design activities. The JASON Committee is convinced that these problems have been corrected and that the weapon types in the enduring stockpile are safe and reliable in the context of explicit military requirements. (7) Conclusions 1-6 are consistent with the CTBT, recalling the fact that U.S. has the option to withdraw under conditions of "supreme national interest." The JASON Committee and the nuclear weapon laboratory directors have certified that the U.S. stockpile is reliable with plenty of performance yield. Both agree that the Scientifically-Based Stockpile Stewardship Program should be able to maintain this status without nuclear testing. In the unlikely possibility that this is not true, the "supreme national interest" clause can be used to withdraw from the CTBT and start testing anew. Some will say that we will spend too much to maintain the weapon designers with new research machines, but I would say that for a CTBT this is a small price. Under START II, the U.S. will retain some 10,000 warheads, with 3500 of them deployed in the force structure below. It is unlikely that financially-strapped Russia can maintain these numbers and, therefore, would prefer to a lower number of about 2000 warheads. ICBM SLBM HBomber Non-Strat Total U.S. (START II) 500 1680 1300 950 5,000 Russia (START II) 600 1700 700 ? ? B61/4 (600, tactical, 170 kt, 1980) B61/7 (750, strategic, 300 kt; 1986) B83 (650, strategic, 1.2 Mt, 1983). W62 (610, MM III, 170 kt, 1970) W76 (3000, Trident C4, 100 kt, 1979) W78 (920, MM III, 335 kt, 1980) W80/1 (1400, ALCM, 150 kt, 1981) W80/0 (350, SLCM, 150 kt, 1984) W84 (400, GLCM, 50 kt, 1983) W87 (525, MX, 300 kt, 1986) W88 (400, Trident D5, 475 kt, 1988). These forces are very considerable and flexible. And it is very stable in the unlikely possibility of a worst-case attack by Russia which would still leave us with almost 2,000 nuclear weapons in addition to 6,000 in reserve. During future certifications by the lab directors, it would be illogical to automatically apply the DOE definition of warhead reliability without examining the targeting missions of U.S. warheads. A sensitivity analysis shows that very large (and unlikely) reductions of 50% in the MX and Trident yields (when used against very hard targets of 5000 psi) reduce the two-shot-kill probability by only 4.5%. Reductions of 20% in the reliability, reduces the two-shot-kill probability by only 8%. With declines in the Russian forces, the U.S. forces are clearly supreme. China will not bother to contest the U.S. in counterforce silo-busting ability by giving up MIRV. China will retain the potential option to threaten U.S. cities, but continued U.S. testing will not remove that threat. Further National Security Issues Aging has not affected the safety of the warheads. The aging effects on reliability of current warheads have been in the arming/firing/safeing, the parachute, the gas transfer, and the neutron generator systems. None of these problems needed nuclear testing to resolve them. If one is worried about reliability, the most important act would be to increase missile reliability and not warhead reliability. To save money on remanufacturing, increase the amount of tritium in the primary, the extra boosting further ensures that a very old primary could still trigger the secondary. In the years when the U.S. tested some 20 times per year, only 1 or 2 tests were for reliability. This was clearly not enough testing to determine reliability of the many warhead types with high confidence. In general, non-explosive tests have been the most important way to determine the status of warheads; this is particularly true for warheads that have been in the stockpile for over two years. Major changes were taking place in the U.S. nuclear arsenal when the moratorium of 1958 was established, which is not the case for the present nuclear stockpile which has not changed significantly in design for a number of years. Safety of Weapons U.S. and Soviet nuclear weapons have been very safe since no one has been killed by nuclear yield from accidents over the one million nuclear-weapon-years of experience by the Americans and the Soviets. Since bombers no longer fly with nuclear weapons, the most dangerous cause of accidents has been removed. The cost per life saved of replacing the warheads with new designs is extremely high, much more than a thousand times what we spend for expensive medical practices and for occupational safety. For these reasons, the safety issue is not relevant to the CTBT. Seismic Verification Using all of the seismic capabilities available, nuclear explosions will be detected with high confidence (90% certainty) down to seismic mb levels of about 4. This mb value corresponds to that of a tamped explosion of about 1 kiloton in hard rock. This assessment is too cautious in that it does not take into account the combination of teleseismic stations (more than 2200 km away) with the growing number of regional stations. A dual system using long-distance, teleseismic and regional networks is now available in many places and it can improve the ability to detect by about one 1 mb unit as the process matures. The more-open process of CTBT monitoring by many nations should incorporate the data from regional seismographs to reduce the CTBT measuring threshold and improve the location determinations. If there is a suspicious region, a neighboring state can place a regional seismograph close to the suspected region and the ability to monitor will improve. Finally, chemical explosions are readily detectable since they are generally not spherical explosions, but rather ripple-fired in a linear array in order to greatly reduce costs for breaking rock and to reduce off-site damage. In order to lessen misunderstandings, there will be voluntary notifications of chemical explosions larger than 0.3 kilotons. The Cavity Scenario There is very little data on decoupled tests in cavities, only one was carried out with a yield greater than one kiloton. If a nuclear weapon is placed in a cavity of sufficient size, such that the blast pressure on the cavity wall is below the elastic limit of the surrounding media, the seismic signal strength can be reduced by a factor of about 7 at 20 Hz and 70 at lower frequencies. The cavity size necessary to obtain these decoupling factors has a radius of 20-25 meters per cube-root kiloton. Thus, a 30 kt explosion would need a cavity radius of 60-75 m (the size of a 25 story building) to achieve full decoupling -- an extraordinary engineering challenge when one considers the requirement for secrecy. Many experts have concluded that the higher frequencies of the decoupled signal would still be detectable and identifiable with regional seismographs. The tester's problems would be further complicated by possible venting of radioactivity which could be easily detected; 30% of Soviet tests vented and the U.S. had severe venting problems with its earliest tests. In particular, it appears that smaller tests can be harder to contain than larger ones. The last four U.S. explosions that vented were from explosions with yields less than 20 kilotons. It is hypothesized that smaller explosions would not sufficiently glassify the cavity, and also would not rebound sufficiently to close fractures with a stress cage. Thus, the smaller explosions, which one might think were easier to hide, are more likely to vent and could be detected by the release of radioactivity. For these same reasons, it is further hypothesized that partially decoupled tests would also be difficult to completely contain. Other intelligence means, such as satellites and electronic intelligence gathering, can also gather evidence on clandestine decoupled nuclear tests. It is widely felt that a clandestine test of a kiloton (or larger), that was decoupled to a degree that enabled the test to escape detection by seismic means and which did not have yield excursions and venting, would require the resources of a very technologically sophisticated nation. The International Monitoring System The IMS will also incorporate 60 infrasound stations (global threshold detection of about 1 kiloton in the atmosphere), 11 hydroacoustic stations (global detection of much less than a kiloton in the ocean) and 80 radionuclide stations (global detection of less than 1 kiloton in the atmosphere, and capabilities to determine venting from underground explosions). In addition the U.S. presently monitors with satellites for optical electromagnetic pulse (EMP) signatures from a possible nuclear weapon test in the atmosphere. In addition the National Technical Means (NTM) of satellite reconnaissance, humint and the other "ints" will combine synergistically to make the intelligence whole greater than the sum of its parts to both deter cheating and to enhance detection and identification. States Parties can call for an on-site inspection (OSI) to examine locations of suspicious activity. The definition of "effective verification" as defined by Paul Nitze and James Baker of the Reagan and Bush Administrations contains a reasonable criteria on military significance of violations and timely warning: "we would be able to detect such a violation well before it becomes a threat to national security so that we are able to respond." By this definition, the CTBT is clearly verifiable. The CTBT is much more verifiable than START since it is verifiable down to the level of one kiloton, and below that level in many locations. ______________________________________________________ David Hafemeister was the technical lead for the State Department on nuclear testing matters (1987) and for the Senate Foreign Relations Committee ratification of the TTBT (1990) and the passage of the CTBT precursor, the Hatfield-Exon-Mitchell Act (1992). He is currently at the University of Maryland on sabbatical from the California Polytechnic State University.