Executive Summary

THE SCOPE OF THE STUDY

This study has explored the extent to which current and foreseeable approaches to transparency and monitoring can support verification for all categories of nuclear weapons—strategic and nonstrategic, deployed and nondeployed—as well as for the nuclear-explosive components and materials that are their essential ingredients. We believe that increasing the categories of items subject to transparency and monitoring would be valuable—and may ultimately be essential—as the United States and the world attempt to address the urgent and interrelated goals of reducing the dangers from existing nuclear arsenals, minimizing the spread of nuclear weaponry to additional states, and preventing the acquisition of nuclear weapons by terrorists.

In the specific case of reductions in existing nuclear arsenals, we believe that more comprehensive verification would almost certainly be deemed essential if the United States and Russia decided to pursue substantially deeper cuts in nuclear weaponry than those agreed in the Moscow Treaty of 2002. Extending agreed limits to nuclear weapon states with smaller arsenals (for example, China, France, and the United Kingdom among the de jure weapon states and India, Pakistan, and Israel among the de facto ones) would likewise increase the desirability if not the necessity of more comprehensive verification.

The motivation and scope for this study were not confined to understanding the transparency and monitoring possibilities and requirements germane to more ambitious arms control regimes. The study has also focused on potential applications to the continuing challenges of keeping nuclear weapons out of the hands of proliferant states and terrorists; for example, the United States has emphasized the need for verification in the complete elimination of North Korea’s nuclear weapons program. Likewise, as the United States continues to work with Russia to ensure that nuclear materials are adequately protected and accounted for, the partners will continue to require transparency measures to facilitate the process, as has been the case in the implementation of the 1993 Highly Enriched Uranium Purchase Agreement.

This study has addressed the technical and institutional approaches and capabilities in transparency and monitoring that



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Monitoring Nuclear Weapons and Nuclear-Explosive Materials Executive Summary THE SCOPE OF THE STUDY This study has explored the extent to which current and foreseeable approaches to transparency and monitoring can support verification for all categories of nuclear weapons—strategic and nonstrategic, deployed and nondeployed—as well as for the nuclear-explosive components and materials that are their essential ingredients. We believe that increasing the categories of items subject to transparency and monitoring would be valuable—and may ultimately be essential—as the United States and the world attempt to address the urgent and interrelated goals of reducing the dangers from existing nuclear arsenals, minimizing the spread of nuclear weaponry to additional states, and preventing the acquisition of nuclear weapons by terrorists. In the specific case of reductions in existing nuclear arsenals, we believe that more comprehensive verification would almost certainly be deemed essential if the United States and Russia decided to pursue substantially deeper cuts in nuclear weaponry than those agreed in the Moscow Treaty of 2002. Extending agreed limits to nuclear weapon states with smaller arsenals (for example, China, France, and the United Kingdom among the de jure weapon states and India, Pakistan, and Israel among the de facto ones) would likewise increase the desirability if not the necessity of more comprehensive verification. The motivation and scope for this study were not confined to understanding the transparency and monitoring possibilities and requirements germane to more ambitious arms control regimes. The study has also focused on potential applications to the continuing challenges of keeping nuclear weapons out of the hands of proliferant states and terrorists; for example, the United States has emphasized the need for verification in the complete elimination of North Korea’s nuclear weapons program. Likewise, as the United States continues to work with Russia to ensure that nuclear materials are adequately protected and accounted for, the partners will continue to require transparency measures to facilitate the process, as has been the case in the implementation of the 1993 Highly Enriched Uranium Purchase Agreement. This study has addressed the technical and institutional approaches and capabilities in transparency and monitoring that

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Monitoring Nuclear Weapons and Nuclear-Explosive Materials could be applied to any or all of these purposes. It has not tried to analyze or make recommendations about the choices in U.S. nuclear weapon and nonproliferation policies and priorities that will continue to shape the context within which such approaches and capabilities might be applied. THE CURRENT CONTEXT The risks associated with the world’s stockpiles of nuclear weapons, nuclear-explosive components of weapons, and nuclear-explosive materials (NEM)1 include: the dangers in the potential for use of existing arsenals, including the possibilities of deliberate use of nuclear weapons by their authorized possessors and also the possibilities of accidental, inadvertent, or unauthorized use; the risks that the existing arsenals and perceptions about their characteristics and intended uses will provoke further, potentially destabilizing nuclear weapon developments and deployments either by the countries already possessing such weapons or by additional countries; and the danger that the existing stockpiles of weapons, components, and NEM will be the enablers rather than merely one of the motivators of proliferation, through illicit transfer to or theft by (or on behalf of) proliferant states or terrorist groups. The risks posed by nuclear weapons are exacerbated in many respects by the size of the current arsenals and by the magnitude of the worldwide stockpiles of NEM. The United States and Russia possess about 95 percent of the approximately 30,000 existing nuclear weapons, with the remainder held by the United Kingdom, France, China, Israel, India, Pakistan, and possibly North Korea. Enough additional NEM exists in military and civil nuclear facilities worldwide to make something like 100,000 additional nuclear weapons. These stockpiles of NEM, in addition to presenting a 1   A “nuclear-explosive material” is a mixture of fissionable nuclides in which the proportions of these are such as to support an explosively growing fission chain reaction when the material is present in suitable quantity, density, configuration, and chemical form and purity. Uranium containing more than 20 percent U-235 or more than 12 percent U-233 (or an equivalent combination of proportions of these two nuclides) is considered NEM, as are all mixtures of plutonium isotopes containing less than 80 percent Pu-238. See Chapter 3 and Appendix A for more detail.

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Monitoring Nuclear Weapons and Nuclear-Explosive Materials ready resource for further production of weapons by the states holding them, also constitute a potential source of materials that could be used for the fabrication of nuclear weapons by non-nuclear weapon states and even terrorist groups. Any assessment of the potential future availability of NEM, moreover, must include not only military stocks of these materials but also the NEM in research reactors and the growing quantities of it in civilian nuclear power programs. The degree of transparency that countries have permitted concerning their nuclear weapons inventories and NEM has tended to increase over time, albeit with some reversals and persistent regional exceptions, because the countries agreeing to the increased transparency have regarded these changes as bringing bigger benefits than liabilities for their security. The benefits include improved opportunities for monitoring that can increase confidence in the verification of agreements and reduce the uncertainties in assessing potential threats that can feed worst-case scenarios. The liabilities against which such benefits must be balanced include the danger of revealing sensitive information that could aid proliferators or increase a nation’s vulnerability to attack. Both the United States and Russia have moved slowly and cautiously to share information regarding even well-known aspects of their nuclear arsenals and remain reluctant to provide each other with information they regard as closely related to the details of weapon design. Countries with small nuclear arsenals have particularly acute concerns about sharing information regarding the locations of their nuclear weapons. Most of the measures and technologies for transparency and monitoring assessed in this study were developed in the course of continuing efforts to find ways to limit the risks from existing nuclear arsenals and their proliferation to additional countries and groups. Attempts to limit numbers and characteristics of nuclear weapons and their delivery systems have often been controversial; belief in the value and practicality of nonproliferation efforts has also varied over time and across groups. Verification issues frequently have been at the heart of these controversies, with debates focusing on the likelihood of cheating and the capability to assess compliance in fundamentally adversarial circumstances. On a number of occasions, however, the bilateral or multilateral political will needed to increase transparency and the availability of suitable monitoring technologies for these purposes allowed the completion of measures and agreements—including some previously thought unattainable—in both the arms control and nonproliferation domains. Controversies about what is desirable and feasible in these

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Monitoring Nuclear Weapons and Nuclear-Explosive Materials domains will continue, as will caution about revealing too much. But opportunities will also continue to emerge to exploit capabilities related to transparency and monitoring. Nuclear Weapons and Nuclear Weapon Components Traditionally, the nuclear weapon life cycle was closed to outside scrutiny. Nuclear weapons in themselves, once produced, were not considered suitable candidates for direct, verified control because they are small, easily concealed, and cloaked in secrecy. The introduction in the early 1960s of reconnaissance satellites carrying high-resolution cameras and other sensors, as well as other “National Technical Means” (NTM), made it possible to monitor with confidence the numbers and types of strategic delivery systems, however. Counting strategic delivery vehicles (that is, missiles, missile launchers, and aircraft) became available as a surrogate for verifying the nuclear weapons themselves in determining and limiting the size of strategic nuclear forces. The maximum number of weapons that each type of land- or sea-launched ballistic missile was designed to carry could be determined by NTM, including the collection of telemetry from flight tests (which in an early and crucial manifestation of transparency the principal parties agreed not to encrypt). Although nuclear weapons themselves have never been the subject of agreed direct verification, past and current arms control agreements have provided significant practical experience in the design and implementation of monitoring options for nuclear weapon delivery systems, including their production and storage. In addition, since the end of the Cold War, U.S. and Russian nuclear weapon laboratories have carried out substantial cooperative work on extending these arrangements directly to nuclear weapons and their components (as part of broader lab-to-lab programs of joint threat reduction activities). Our assessments in this study support the conclusion that the necessary technical tools are either available today, or could be in hand with some additional development, to support significantly enhanced transparency and monitoring for declared stocks at declared sites throughout the nuclear weapon life cycle; Developments in cryptography now widely used in banking and other commercial transactions offer a way to exchange, in a limited and controlled but still very useful way, sensitive information about nuclear weapons that countries would not be willing to share more

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Monitoring Nuclear Weapons and Nuclear-Explosive Materials openly and comprehensively because of security concerns. Methods are available to examine from a short distance the radiation from a nuclear weapon or to interrogate a declared weapon container with an external radiation source. The radiation signature can be matched against templates of actual nuclear weapon signatures, or some portion of the radiation signatures can be singled out to identify attributes that confirm that the object is indeed a weapon. These techniques permit identification without revealing sensitive weapon design information. A wide array of tags and seals, ranging from bar codes and tamper-indicating tape to electronic chips, can be applied to containers and storage rooms for weapons and be interrogated to check their status. Monitored perimeter-portal systems, which exploit radiation and other distinctive signatures, can be installed and operated to confirm that what enters and leaves any given facility is what it is supposed to be. Facilities and areas within facilities can be equipped with appropriate sensors and accountability systems to monitor declared activity and detect undeclared activity, the recordings from which can either be examined during periodic inspections or uploaded via the Internet or satellites for transmission to a monitoring center. This array of tools makes it possible to contemplate a set of transparency and monitoring measures that would cover declared stocks at declared sites during all stages of the nuclear weapon life cycle, which might include: Declarations of nuclear weapon stocks at progressively increased levels of detail, ranging from total numbers of weapons; to specification of numbers of different types, including their operational status and associated delivery vehicle; to declarations for each weapon by serial number, weapon type, status, and current location. Declarations of the name and location of all facilities at which nuclear weapons are currently deployed, stored, assembled, maintained, remanufactured, dismantled, or otherwise handled, along with detailed information about each site and its operating history. Continuous monitoring of weapon stocks at facilities at all stages throughout the nuclear weapon life cycle, either with personnel on-site or remotely.

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Monitoring Nuclear Weapons and Nuclear-Explosive Materials Confirmation of weapon remanufacture and assembly as well as weapon elimination. Provisions for routine on-site inspections at declared facilities to confirm declarations and any updates, as well as for inspections of both declared and suspect sites in the event of detection of suspicious activity or unexplained discrepancies. Similar measures could be applied to nuclear weapon components. Depending on the design of the system, cooperative application of such measures would make it possible to confirm the accuracy of declarations of weapon stocks and to monitor weapon storage, assembly, and disassembly at declared facilities while protecting sensitive weapon design information. Some of the less intrusive measures, such as declarations of current weapon stocks or of plans for future changes to those stockpiles, can have value in their own right as confidence-building measures. These measures could be undertaken unilaterally or through formal agreements. In general, however, tools and measures that provide a higher degree of confidence come at the cost of greater intrusiveness and potential impact on normal operations. They also require more effort to protect sensitive weapon design information. They are therefore more suited to formal agreements, where the rules for the system’s operation can be agreed upon—including provisions for resolving questions or clarifying ambiguities. Experience suggests, however, that reaching such agreements can be a difficult and protracted process. Even a modest subset of the measures outlined here could provide a degree of openness concerning weapon stockpiles and a framework for access to weapon sites that would greatly ease the difficulties of cooperation to improve security of nuclear weapons everywhere against theft or unauthorized use. For the more demanding purpose of monitoring agreements to control or reduce the stocks of nuclear weapons held by nuclear weapon states, the more intrusive measures would also be required. Nuclear-Explosive Materials Nuclear-explosive materials are readily convertible by nuclear weapon states (or other states or groups that have knowledge of nuclear weapon technology) into the nuclear-explosive components of actual weapons. And the size of the NEM stocks determines, to a reasonable approximation, how many weapons of particular types could be made. The difficulty of producing such

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Monitoring Nuclear Weapons and Nuclear-Explosive Materials materials means, moreover, that their acquisition is and will remain a limiting factor for states or subnational groups aspiring to make such weapons. Applying transparency and monitoring measures to military and civilian stocks of NEM poses challenges that are comparable in overall difficulty with those of applying such measures to nuclear weapons, but different in some important respects. Accounting, management, control, and protection for NEM—the measures collectively referred to as MPC&A—are pursued by nations for both economic and security reasons and by the international community as part of the nuclear nonproliferation regime, and these efforts interact with transparency and monitoring in important and multifaceted ways. Transparency and monitoring are of limited value without competent MPC&A. Thus strengthening MPC&A, in addition to its direct benefits for security, is sometimes the most important step that can be taken toward improved transparency and monitoring. At the same time, improved transparency and monitoring can lead to identification and thus remedy of weaknesses in MPC&A. Increases in transparency and monitoring of NEM, if accepted, could also accelerate efforts to strengthen MPC&A through cooperative measures. Increased transparency, however, can also complicate the task of MPC&A by providing information useful to those who would steal NEM. The work of the International Atomic Energy Agency (IAEA) has provided extensive multilateral experience with monitoring and transparency for civilian NEM and also some limited experience with military NEM. The United States and Russia have also acquired substantial bilateral experience through their cooperation to improve the security of Russian stocks of NEM, including joint work on technologies and methods for enhanced transparency and monitoring. Transparency and monitoring measures for declared stocks of NEM at declared sites, comparable with those for nuclear weapons, could include: Comprehensive declarations describing the quantities and locations of all existing inventories of NEM, together with information on chemical forms and isotopic composition on the material; Declarations of inventories of NEM surplus to military and civilian needs; and Provisions for inspections of all declared facilities as well as of any undeclared suspicious activities.

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Monitoring Nuclear Weapons and Nuclear-Explosive Materials As in the case of nuclear weapons, such “cooperative transparency” for NEM could be supplemented by information gathered unilaterally by individual states. A number of additional measures could help to reduce the stocks and flows of NEM as well as to reduce the number of sites at which NEM are stored; all could be beneficial both in reducing the opportunities for theft and diversion and in easing the task of monitoring. The possibilities include: Accelerated disposition of excess Highly Enriched Uranium (HEU) inventories through down blending and eventual use in reactor fuel; Replacement of HEU fuels in research reactors with high-density low enriched uranium fuels, where feasible, and decommissioning of nuclear reactors using HEU fuels when replacement is not possible; Disposition of excess separated plutonium either by conversion to fuel for use in civil reactors or by immobilizing with fission products in a glass or ceramic matrix; A comprehensive cutoff of production of NEM for weapons; A serious international effort to develop nuclear fuel cycles for civil reactors that minimize or eliminate the exposure of NEM; and Centralization under multinational control of all facilities capable of enriching uranium or reprocessing plutonium. Beyond the measures to reduce NEM stocks and flows and storage sites, two much broader efforts would provide great benefits for international efforts to increase transparency and monitoring for NEM: Continued substantial improvements in national management, protection, control, and accounting of national holdings of NEM so that individual countries are fully aware of the quantity and status of all of their holdings of NEM and have provided effective protection against theft or diversion for all stocks of NEM; and Continued efforts to strengthen the safeguards regime administered both bilaterally and by the IAEA, including universal applicability of the Additional Protocol, with increased manpower and funding to carry out the expanded mandate.

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Monitoring Nuclear Weapons and Nuclear-Explosive Materials Important efforts to support both these goals are under way, but they should be enhanced and accelerated. Greatly improved management and decreased inventories of NEM, which are priorities on their own account, would be critical if limits on total numbers of weapons were contemplated. The lower such limits became, moreover, the greater would be the need for reduction of NEM stockpiles and high confidence in monitoring the stocks that remained. While the technologies exist to achieve monitoring of NEM quantities with considerable accuracy and confidence under a cooperative framework, a strengthened international consensus on the value of doing this would be necessary to solve cooperatively the many difficult problems involved. Clandestine Stocks and Covert Production We have concluded that procedures and technology are available to verify with high confidence the declarations of stockpiles of nuclear weapons and NEM at declared sites. But undeclared nuclear weapons and NEM could exist as a consequence of retention of undeclared existing nuclear weapons and NEM or could come into existence by the clandestine production of nuclear weapons from existing NEM. In addition, undeclared NEM for weapons might be produced clandestinely or diverted covertly from peaceful nuclear power programs. Current non-nuclear weapon states and possibly terrorist groups might also acquire nuclear weapons or NEM. The potential for clandestine activities in these categories poses the largest challenges to efforts to strengthen transparency and monitoring for nuclear weapons, components, and materials on a comprehensive basis. The public record of the ability of U.S. intelligence agencies to identify the emergence and evolution of the nuclear weapon programs of countries of interest in the past is one indication of the likelihood of future success in detecting covert programs. Historically, U.S. intelligence has become aware of the efforts by other countries to develop nuclear weapons relatively early in their programs and well in advance of their actually obtaining a weapon. Estimates of the date of the initial fabrication of an actual nuclear device and future inventories of materials and weapons have often underestimated or overstated actual capabilities, however. On the other hand, methods for detecting and evaluating clandestine efforts have been improving over time and should continue to do so. The methods available for the detection of a clandestine effort to acquire a nuclear weapon capability include:

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Monitoring Nuclear Weapons and Nuclear-Explosive Materials A range of NTM, including real-time, high-resolution satellite photography and other satellite sensors. Satellite, ground-based, and sea-based receivers also collect a broad range of signal intelligence, the extent and quality of which is closely held information. While traditionally such intelligence collection is limited to sensors outside the borders or above the sensible atmosphere of the state being observed, sensors could also be located on or flown above the territory of a state subject to inspection as part of a formal agreement. The United States invests substantial resources in research and development to continue improving its already impressive NTM capabilities. Audits or inspections carried out as part of formal agreements. These measures, which can include the use of forensic techniques to reveal illicit alteration of records, may call attention to discrepancies or suspicious activities that suggest potential clandestine activity. Inspections can gather a variety of kinds of physical evidence, including forms amenable to use of the techniques of “nuclear archaeology” to help determine what a facility has actually produced over time. Human sources, including travelers, emigrants, defectors, “whistle-blowers,” and intelligence agents working within the institutions of a state engaged in illegal activities. Beyond the well-established value of these types of sources, the probability that individual citizens of a country would report to international authorities on activities that contravene treaties may be increased by requiring countries to pass domestic laws making it illegal for individuals to participate in such activities. Individual participation in or concealment of such activities could also be criminalized under international law. The most difficult task is detection of clandestine stocks accumulated from past undeclared production or from materials transferred from other states. Independent knowledge of the actual total size of the Russian stockpiles of nuclear weapons and NEM, for example, is sufficiently uncertain that verified declarations alone cannot preclude the possibility that significant undeclared stockpiles might exist at undeclared locations. A similar situation exists with respect to the nuclear stockpiles of other nuclear weapon states with much smaller programs, where the absolute size of the uncertainty would be proportionately smaller. The declared NEM

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Monitoring Nuclear Weapons and Nuclear-Explosive Materials holdings by non-nuclear weapon states with peaceful nuclear programs also involve uncertainties, which would be smaller in the case of states whose nuclear programs had always been subject to international verification, but the possibility of some undeclared stocks could still not be entirely excluded. Small clandestine weapons fabrication facilities utilizing NEM obtained from an external source would be very difficult to detect. All of this under-scores the importance of global accounting, monitoring, and protection for all NEM from past and future production. The Nuclear Non-Proliferation Treaty (NPT) obligates non-nuclear-weapon-state parties to that treaty to conclude an agreement with the IAEA to safeguard civilian nuclear installations against diversion of NEM. In the past IAEA agreements have focused on declared facilities and have limited the authority of the IAEA in carrying out inspections. IAEA has now created an “Additional Protocol” that explicitly permits unannounced inspections of suspect undeclared facilities and adds many other intrusive constraining measures, but many states have not yet signed that document. If the Additional Protocol were universally enacted and were coupled with use of the best available monitoring technologies, the potential for illegal diversion of NEM from the declared peaceful programs of participating states could be reduced to a minimum level. Similarly, with effective approaches and adequate resources applied to the task, the peaceful nuclear energy programs of nuclear weapon states could be adequately monitored to reduce to a very low level the risk of undetected diversions by those states and by unauthorized personnel for transfer to proliferating states or terrorist groups. Given the extensive knowledge of existing nuclear programs, the significant amounts of additional information that would result from the process of verifying declarations, the new inspection capabilities provided by the Additional Protocol, and above all the demonstrated capabilities of NTM, it is very unlikely that any state, including Russia, participating in a cooperative fashion involving detailed declarations could develop a complete, stand-alone covert nuclear weapon production program that would not be discovered over time. If, however, undeclared stocks of NEM exist or can be diverted without detection from civilian stocks or production facilities, then it is much more likely that the assembly of new weapons could escape detection.

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Monitoring Nuclear Weapons and Nuclear-Explosive Materials GENERAL CONCLUSIONS As a result of the assessments described above, we have come to the following general conclusions: Current and foreseeable technological capabilities exist to support verification at declared sites, based on transparency and monitoring, for declared stocks of all categories of nuclear weapons—strategic and nonstrategic, deployed and nondeployed—as well as for the nuclear-explosive components and materials that are their essential ingredients. Many of these capabilities could be applied under existing bilateral and international arrangements without the need for additional agreements beyond those currently in force. There are some tensions between sharing information about nuclear weapon and NEM stockpiles and maintaining the security of these stockpiles, but cooperative use of available and foreseeable technologies can substantially alleviate these tensions. The nature of NEM production and the characteristics of NEM and nuclear weapons place some fundamental limits on the capabilities of any system of monitoring and transparency to provide assurance of compliance. Accordingly, a degree of uncertainty is inescapable. The biggest challenge to the kinds of cooperation-based verification discussed here would arise if countries tried to give the appearance of cooperation while covertly retaining undeclared stockpiles of nuclear weapons or NEM and/or undertaking clandestine production programs. Where concerns about compliance exist, the synergistic effect of multiple technical and management measures, supported by increased transparency and robust national technical means of intelligence collection, could reduce the risk that significant clandestine activities would go undetected and over time could build confidence that verification was effective. Important transparency measures for both nuclear weapons and NEM need not necessarily be imposed as part of formal treaties but could be undertaken on the basis of informal understandings or unilateral initiatives, for example, as part of broader confidence-building efforts. There are both liabilities and benefits of seeking, in the long run, to incorporate measures governing transparency and monitoring of nuclear weapon and NEM stockpiles into formal agreements. The complexity and intrusiveness of the most ambitious measures mean that negotiation of such agreements may be difficult and protracted. But it is precisely the complexity and intru-

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Monitoring Nuclear Weapons and Nuclear-Explosive Materials siveness of some of the relevant measures that, together with the national security stakes, make formal agreements useful to avoid misunderstandings and to provide mechanisms to clarify ambiguities. In addition, formal agreements provide more durable assurance that measures will be sustained over time and across changes in governmental leadership. In the committee’s judgment, the synergistic effect of the approaches discussed in Chapters 2, 3, and 4 in a cooperative environment, coupled with robust NTM capabilities, would substantially reduce current uncertainties in U.S. assessments of foreign nuclear weapon and NEM stockpiles over time. Nevertheless, in view of the sheer size and age of the Russian stockpile (where current uncertainties amount to the equivalent of several thousand weapons), Russia probably could conceal undeclared stocks equivalent to several hundred weapons. In the case of other countries with much smaller programs, absolute uncertainties would be much less, leading to the possibility that these countries could conceal undeclared stocks equivalent to one or two dozen weapons in the case of China, and at most one or two weapons in the cases of Israel, India, and Pakistan. Confidence that declarations were accurate and complete, and that covert stockpiles or production facilities did not exist, would be increased by the successful operation of a monitoring program over a period of years in an environment of increased transparency and cooperation.

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