Monitoring Nuclear Weapons and Nuclear-Explosive Materials An Assessment of Methods and Capabilities (2005) / Chapter Skim
Currently Skimming:
2 Nuclear Weapons
2 Nuclear Weapons
Pages 45-108
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 45... ...
Nuclear weapons are operationally deployed and ready for use when they are mated to ballistic missiles and placed in launchers, loaded onto aircraft, or stored at air bases for nuclearcapable aircraft.2 Nuclear weapons may be removed from operational deployment from time to time for inspection and routine maintenance of the weapon or its delivery vehicle and launcher. Weapons also may be kept in long-term storage as spares, as a source of parts for remanufacture or the manufacture of other weapons, or held in reserve as a responsive force that may augment deployed forces.
|
From page 46... ...
Component transport Nuclear Weapons Development, Non-NEM Components Assembly, Surveillance, Main- (high explosives/detonators, trit tenance, Remanufacture, Dis- ium, safing/arming/fuzing/firing mantling systems, neutron generators, case/reentry vehicle) Weapon transport Nuclear Weapons Storage Weapon transport Delivery Vehicle and Launcher Operationally Deployed (ballistic or cruise missile; silo, Nuclear Weapon land-mobile, submarine, aircraft launcher)
|
From page 47... ...
The measures related to nuclear weapons stockpiles include declarations of weapon inventories at various levels of detail; onsite inspections and other methods to confirm the accuracy of declarations disaggregated by facility; continuous monitoring of certain weapon stocks, such as excess or retired weapons in storage; transparency measures at weapon assembly facilities to confirm the dismantling and permitted remanufacture of weapons; and declarations and transparency measures covering the storage and fabrication of NEM components (pits and secondary assemblies; see Box 2-1 for an explanation of these terms)
|
From page 48... ...
This proved to be a problem with the informal Presidential Nuclear Initiatives on nonstrategic nuclear weapons announced by the United States and Russia in 1991-92, where lack of a formal agreement, detailed exchanges of information, or transparency measures at one point led some to charge that Russia was redeploying weapons in violation of its previous pledge, despite Russian denials.3 Proposals for U.S.-Russian Declarations Proposals for weapon declarations and related transparency measures emerged in the wake of the breakup of the Soviet Union. 3 See Rose Gottemoeller, "Offense, Defense, and Unilateralism in Strategic Arms Control," Arms Control Today 31 (September 2001)
|
From page 49... ...
, part of this effort included a significant amount of joint work between the U.S. and Russian nuclear weapons laboratories to explore transparency and monitoring measures that could make this increased openness possible while still protecting sensitive information about weapon designs.
|
From page 50... ...
chair of the joint working group that had been exploring the arrangements, some Russian members of the group "gave the impression that the scope of the data exchange went well beyond what they were prepared to consider."7 The United States nonetheless continued to seek agreement on stockpile declarations. At their March 1997 summit in Helsinki, Presidents Clinton and Yeltsin agreed that a START III agreement, to be negotiated following ratification of START II, should include "measures relating to the transparency of strategic warhead inventories and destruction of strategic nuclear warheads" and that transparency measures related to nonstrategic nuclear weapons and to nuclear materials would also be explored.8 When the United States presented a draft protocol dealing with transparency and monitoring for weapons in early 2000 for consideration in connec 5Joint Statement on Strategic Stability and Nuclear Security by the Presidents of the United States of America and the Russian Federation (Washington, DC: The White House, Office of the Press Secretary, September 28, 1994)
|
From page 51... ...
No nuclear weapon state has revealed the precise number of nuclear weapons in its current stockpile; however, the United States, the United Kingdom, and France have released some information. The United States released an official accounting of the total number of nuclear weapons in its stockpile each year from 1945 to 1961; the total yield of the stockpile and the number of weapons retired or dismantled each year from 1945 to 1994; and, for fully retired weapon types, the total number assembled each year.11 Although it did not provide such historical details, the United Kingdom has stated that in the future it would maintain fewer than 200 operationally available weapons of a single type.12 In the mid1990s France announced that it would eliminate its land-based nuclear forces, reduce the number of strategic submarines it would deploy, and dismantle the facilities used to produce NEM for nuclear weapons.13 9 Rose Gottemoeller, "Parsing the Nuclear Posture Review," A ACA Panel Discussion With Daryl G
|
From page 52... ...
4 For each weapon: serial number, weapon type, status, and current loca tion. Total Inventories The simplest declaration would give the total number of nuclear weapons currently possessed by each state.
|
From page 53... ...
States also could share information on their future plans for the weapon stockpile, giving, for example, the projected number of weapons to be assembled and dismantled each year for the next five years. Inventories by Type and Status The next level of detail would disaggregate total inventories by weapon type and/or associated delivery vehicle.
|
From page 54... ...
As with total inventories, it could also be useful to release comparable historical data and share future plans. For each weapon type (including types not in the current stockpile)
|
From page 55... ...
Much of this information has already been exchanged by the United States and Russia, as part of the START Treaty. Going beyond START, they could share information on facilities where nonstrategic weapons are deployed, and the location and inventory of weapon storage, maintenance, and assembly-disassembly facilities.
|
From page 56... ...
That said, sharing and confirming weapon inventories at this level of detail ultimately would be necessary -- though not sufficient -- to achieve very deep cuts in U.S.-Russian nuclear arsenals. One of the most difficult technical issues associated with very deep cuts would be gaining high confidence in a state's baseline inventory of nuclear weapons.
|
From page 57... ...
Each record would 15National Institute of Standards and Technology, "Specification for the Advanced Encryption Standard," Federal Information Processing Standards Publication 197 (November 26, 2001)
|
From page 58... ...
To see how message digests might be used, assume that a detailed declaration is prepared in an agreed format as described above, with a record for each weapon, and that parties have agreed on an algorithm for producing message digests. The declaring party could produce and provide the inspecting party with a separate digest for each record in the declaration.
|
From page 59... ...
Regular data exchanges should not impose a significant additional burden on states, as they presumably maintain a complete, detailed, and up-to-date database of weapon inventories for their own use. In the event of very deep reductions in the number of nuclear weapons, there could be a desire for more frequent exchanges of information.
|
From page 60... ...
CONFIRMING WEAPON DECLARATIONS Declarations of weapon stocks could have value as a confidence-building measure even without measures to confirm their accuracy. If, however, declarations were intended to serve as the basis for agreed reductions in nuclear weapon stockpiles, we assume the parties to such an agreement would want verification measures, such as site visits and mutual inspections, to confirm their accuracy.
|
From page 61... ...
Operationally Deployed Weapons on Missiles Russia and the United States have already devised procedures to confirm the number of operationally deployed weapons on missiles. START I provides for on-site inspections at ICBM and submarine-launched ballistic missile (SLBM)
|
From page 62... ...
If parties deploy fewer than the permitted number of weapons on some missiles, additional procedures may be necessary to confirm a declaration of the actual number of deployed weapons; for example, the inspecting party could determine the number of weapons by moving a radiation detector around the perimeter of the missile. Procedures for using a neutron detector to distinguish between the single-weapon SS-25 missile and the three-weapon SS-20 missile were worked out for the INF Treaty.
|
From page 63... ...
If, for example, the inspecting party believed, before the inspections began, that there was a 10 percent chance of cheating as described above (i.e., a prior probability of compliance of 0.9) , then ten inspections that uncovered no evidence of cheating would result in a posterior probability of compliance of 99 percent.
|
From page 64... ...
64 MONITORING NUCLEAR WEAPONS AND NUCLEAR-EXPLOSIVE MATERIALS (A) 100% SS-19 Trident-II 80% SS-N-18 Violation 60% Minuteman-III Detecting of 40% Number Warheads per Missile Probability Missile Deployed Declared Maximum 20% MM-III 500 1 3 Trident-II 288 5 8 SS-19 130 1 6 SS-N-18 224 3 7 0% 0 5 10 Number of Missiles Inspected (B)
|
From page 65... ...
20Exceptions might include strategic defensive weapons on antiballistic missile interceptors; weapons in transit between facilities; weapons undergoing maintenance, remanufacture, or dismantling; and, perhaps in the case of China, certain nonstrategic weapons. Transparency measures could be developed to cover these exceptions, if desired; for example, confirming nuclear weapons on antimissile interceptors could be accomplished in much the same way as described above for ballistic missiles.
|
From page 66... ...
and Russian nuclear forces over the last decade means that many facilities at which nuclear weapons were stored in the past are now empty or have been converted to other uses. In order to confirm declarations of stored weapons, the declaration could include the location of each facility, site maps indicating the weapon storage area and the location of each bunker, and the number of nuclear weapons in each bunker or vault.
|
From page 67... ...
Inspection of the chosen bunker could be accomplished in much the same manner as a regular inventory check: a visual inspection that matched each weapon in the bunker with a weapon in the declaration. It is likely that most weapons are in containers and that a visual inspection would not reveal any sensitive information, but if this were a concern the inspected party could be permitted to cover or drape weapons prior to inspectors entering the bunker.
|
From page 68... ...
(The use of a detector in conjunction with a low-intensity neutron source would indicate that the object is suspicious, however.) Moreover, some nonweapon objects that may be stored in bunkers (e.g., weapon components, radioisotope thermal generators, or nuclear-explosive-like objects)
|
From page 69... ...
The portal is typically the facility's main gate. The inspecting party monitors the portal for the possible entry and exit of controlled items -- in this case, nuclear weapons and weapon components.
|
From page 70... ...
The portal could be equipped with radiography equipment to scan selected vehicles, but this would add substantially to the cost of the system unless it significantly reduced the need for human inspectors. If ambiguities arose, the burden of proof would be on the inspected party to demonstrate that objects and vehicles passing through the portal do not contain undeclared nuclear weapons or weapon components.
|
From page 71... ...
for remote monitoring of the status of nuclear facilities and stocks of nuclear material. Except in an emergency, the inspected party could be required to give several days notice prior to opening the bunker doors, to allow inspectors to arrive and confirm any movement of weapons in or out of the facility.
|
From page 72... ...
In addition to monitoring facility inventories, one might also wish to monitor or track the movement of weapons between facilities; for example, parties might desire assurance that particular weapons removed from deployment sites were delivered to monitored storage, or that weapons removed from storage were delivered to dismantling facilities. Establishing the authenticity or provenance of items, tracking their movements between facilities, and confirming that they have not been tampered with is sometimes referred to as a "chain of custody." The least intrusive way to maintain a chain of custody involves the use of tags and seals.
|
From page 73... ...
The inspected party would declare that a particular weapon was slated for dismantling. The inspecting party could confirm that this weapon was removed from a monitored storage facility; tags and seals on the weapon container could be used to confirm that the same weapon was delivered to the dismantling facility.
|
From page 74... ...
Fission Product Tagging It has been suggested that the inspecting party might "tag" weapon components while they are still inside the weapon by irradiating the weapon with neutrons before it is delivered to the dismantling facility.26 This would induce fissions in the plutonium and uranium components, giving them a characteristic gamma-ray signature that could be analyzed after the weapon is dismantled to determine whether it is consistent with the irradiation. A relatively large neutron flux is required to produce a measurable signature over the period required to dismantle a weapon.
|
From page 75... ...
Template or Attribute Matching Weapon components also might be associated with weapons using templates or attributes (see Boxes 2-4, 2-4A, and 2-4B) ; for example, the inspected party could present the separated components for templating along with the fully assembled weapon, and the templates could then be used to confirm, on a sampling basis, that the components placed in storage correspond to the type of weapon delivered to the dismantling facility.
|
From page 76... ...
Radiation detectors and other equipment and procedures could assure that no undeclared weapons or weapon components could pass through the portal without detection. Inspections of the facility might be permitted before and after dismantling campaigns to provide assurance that large stocks of weapons or components were not accumulating inside.
|
From page 77... ...
Inspectors could then monitor the entrance, or sensors could be installed at the bay or cell doors similar to those described above for continuous remote monitoring of weapon storage bunkers. When a weapon container arrived at the entrance, the inspectors or sensors could confirm its identity and authenticity by checking the tags and seals applied earlier (at a storage facility or the entrance to the dismantling facility)
|
From page 78... ...
Weapons may also be assembled to replace those dismantled or destroyed in routine (non-nuclear) reliability testing or to fix safety and reliability problems that may be uncovered in a particular weapon type.
|
From page 79... ...
If, for example, Russia observed that the United States was rebuilding a particular class of weapons, it might conclude that this weapon type suffered from a major reliability problem. Russia would be likely to discover the existence of such a problem without the benefit of transparency measures, however.
|
From page 80... ...
If transparency measures were applied to weapon assembly, they would need to be tightly integrated with the measures adopted for weapon dismantling. If dismantling was confirmed with inspections or automatic tracking of weapons and weapon components between bays and cells within the assembly facility, weapons to be remanufactured or replaced could be tracked in exactly the same manner.
|
From page 81... ...
TRANSPARENCY MEASURES FOR NEM COMPONENTS Because the pits and secondary assemblies that remain after weapons are dismantled could be used to build new weapons, the storage and ultimate elimination of these components could be subject to transparency and monitoring measures similar in nature to those applied to nuclear weapons. Fabricated NEM components are discussed here because many of the transparency measures and technologies discussed above for nuclear weapons could be applied with little modification to these components.
|
From page 82... ...
The prototype attribute identification system described in Box 2-4B was developed to confirm that plutonium pits placed in the Mayak facility are authentic; similar systems could be developed for secondary assemblies and other NEM components. Russia has announced that the materials placed in the Mayak facility will be reshaped to remove sensitive weapon design information, ostensibly to facilitate IAEA inspection of the material (see Chapter 3)
|
From page 83... ...
Transparency measures to confirm the conversion of HEU weapon components into bulk materials were developed in connection with the HEU purchase agreement, under which the United States agreed to purchase over a 20-year period 500 tons of Russian HEU from dismantled nuclear weapons in the form of low enriched uranium (LEU) .34 The main steps in this process are as follows: · the HEU weapon component is machined into metal shavings; · the metal shavings are oxidized and the resulting oxide chemically purified; 33U.S.
|
From page 84... ...
These transparency measures provide high confidence that the LEU delivered to the United States was derived from HEU. By coupling this process with an attribute or template identification system to confirm that the HEU delivered to the facility was in the form of genuine weapon components, one could have similarly high confidence that these components had been eliminated.
|
From page 85... ...
Component Fabrication A complete accounting system would also include additions as well as subtractions to the inventory of key weapon components. Future requirements for component manufacture are largely unknown.
|
From page 86... ...
Similar measures could be applied to nuclear weapon components.
|
From page 87... ...
3. Depending on the design of the system, cooperative appli cation of these transparency and monitoring measures would make it possible to confirm the accuracy of declara tions of weapon stocks and to monitor weapon storage, as sembly, and disassembly at declared facilities while pro tecting sensitive weapon design information.
|
From page 88... ...
For the more demanding purpose of monitor ing agreements to control or reduce the stocks of nuclear weapons held by nuclear weapon states, the more intrusive measures would also be required.
|
From page 89... ...
The term includes such a weapon or device in unassembled and partly assembled forms, but does not include the means of transport or delivery of such a weapon or device if separable from and not an indivisible part of it." This definition is not entirely satisfactory, inasmuch as "capable of releasing nuclear energy" remains undefined, but it underscores the importance of understanding at what point a weapon is considered dismantled and no longer counted as a "nuclear weapon." Like past treaties, agreements dealing with weapon transparency measures could simply refer to "nuclear weapons or other nuclear-explosive devices" without adopting a more detailed definition. As discussed in this chapter, there are several approaches for confirming, with varying degrees of confidence, whether or not an object is a weapon.
|
From page 90... ...
In a thermonuclear or two-stage weapon, the implosion device is called the "primary." Thermal radiation from the detonation of the primary is used to compress a physically separate "secondary." The secondary assembly contains both fusion fuel and in most cases uranium (some or all of which may be HEU) ; this package, as it is delivered to the weapon assembly facility, is called a "canned subassembly" (CSA)
|
From page 91... ...
Even though they may contain NEM, they cannot produce a nuclear explosion and thus do not satisfy our definition of a nuclear weapon.
|
From page 92... ...
Alternatively, the declaring party could supply the PL along with the corresponding key and the receiving party could apply the encryption algorithm to confirm that the previously transmitted CL resulted. Encryption involves protecting new secrets -- the encryption keys -- in addition to the original information in the declaration, but the keys can be protected at least as well as the original information.
|
From page 93... ...
This is important, because otherwise the declaring party could find a nonce field which, when combined with any given set of nuclear weapon data (e.g., chosen to match the results of an inspection) , would produce the previously exchanged MD, rendering the commitment meaningless.
|
From page 94... ...
94 MONITORING NUCLEAR WEAPONS AND NUCLEAR-EXPLOSIVE MATERIALS hashes to find a preimage and 280 trials to find a collision. The recently approved SHA-256, which produces 256 bit digests, would provide preimaging resistance equivalent to symmetric encryption with 256 bit keys, and collision resistance equivalent to a key size of 128 bits.
|
From page 95... ...
Tags and seals are used routinely by the International Atomic Energy Agency to safeguard civilian nuclear materials and by the U.N. Monitoring, Verification and Inspection Commission (previously the UN Special Commission on Iraq)
|
From page 96... ...
The challenge is to select technologies and procedures that make counterfeiting and spoofing by the inspected party much more difficult, time consuming, and costly than detection by the inspecting party of such counterfeiting or spoofing. The best choice may be an inexpensive tag or seal that is readily validated in the field, with a small sample collected by the inspecting party for detailed laboratory analysis.
|
From page 97... ...
U.S. and Russian nuclear weapon laboratories have done considerable collaborative work to develop both approaches for arms control purposes and have produced several prototype systems to identify both nuclear weapons and weapon components.*
|
From page 98... ...
The attribute approach is particularly vulnerable to scenarios in which the inspected party creates a number of low-cost dummy weapons that display the selected set of attributes, which could be substituted for genuine weapons. The inspecting party might believe that the genuine weapons had been retired or dismantled, when only the dummy weapons had been dismantled and the genuine weapons were stored in a secret facility.
|
From page 99... ...
Template systems based on gamma-ray spectra have been used for decades by the United States and Russia to identify their own weapons and weapon components; in Russia these gamma-ray templates are called "radiation passports." The key components of nuclear weapons contain NEM, which are radioactive. Most of these isotopes emit gamma rays at a particular set of energies, and the isotope can be positively identified by its gamma-ray spectrum.
|
From page 100... ...
The most fundamental challenge is establishing the authenticity of the template -- that the template was produced using an authentic weapon or weapon component. If the inspecting party is allowed to select, from the complete list of declared weapons or components, one or a few of a particular type for the template, one could be fairly confident that the selected weapon or component is authentic.
|
From page 101... ...
This could be done by placing the disk in a safe that requires two combinations to open, one held by each side; additional protection could be provided by encrypting the data with a two-part cryptographic key, with one part held by each side. Alternatively, the inspected party could have sole possession of the template and the information barrier could provide the inspecting party with a digest or "secure hash" of the template when it is made and each time it is subsequently used (see Box 2-2)
|
From page 102... ...
Because the low-energy gamma rays emitted by uranium-235 are readily absorbed by other weapon materials or easily shielded, the gammaray emissions from such weapons may be too weak to provide a useful template, if they do not include plutonium as well. Template for Weapon Type Object A B C D E Weapon Type A, #1 0.8 92 32 7.7 42 Weapon Type A, #2 0.9 90 31 8.2 45 Weapon Type A, #3 0.8 91 32 8.5 45 Weapon Type B 496 0.8 140 336 491 Weapon Type C 63 43 0.9 34 128 Weapon Type D 11 102 26 0.6 46 Weapon Type E 55 174 86 31 1.0 Pit, Type A 558 91 319 547 794 Pit, Type E 858 203 566 821 1071 CSA, Type A 52 118 88 64 66 CSA, Type E 27 156 77 22 6.4 The "reduced chi-square" is a measure of the goodness-of-fit between the object's spectrum and the template.
|
From page 103... ...
Templates that do not contain sensitive weapon design information would be useful, because they would eliminate the need for information barriers and would greatly simplify template storage and the certification and authentication of the measurement system. It may be possible, for example, to distinguish weapon types based on a combination of their acoustic, electromagnetic, and/or thermal signatures.
|
From page 104... ...
Similarly, the relative intensities of gamma rays emitted by the Am-241 decay products of 14-year half-life Pu-241 can be used to determine its age (the time elapsed since the plutonium was last chemically purified)
|
From page 105... ...
Because HEU emits few high-energy gamma rays and almost no neutrons, passive radiation measurements are able to do little more than indicate the mere presence of HEU. As with templates, an "active" system would be necessary to provide a reasonable set of attributes for components that contain only HEU; for example, the Nuclear Material Identification System (NMIS)
|
From page 106... ...
a greater concern for the attribute approach.
|
From page 107... ...
Detector System Computer Hardware Data Barrier Unclassified and Display Software Template Classified Information Information Barrier Because an information barrier prevents access to the data and the analysis upon which the results of an inspection are based, the inspecting party must authenticate the system. The inspecting party
|
From page 108... ...
If these guidelines are followed, the system can be authenticated by thoroughly examining the hardware and software and confirming that they correspond to the documented design. The inspected party could build multiple identical units and allow the inspecting party to choose one for weapon inspections and another for detailed examination, including the removal of selected components for laboratory testing.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.