Understanding Nuclear Weapon Risks John Borrie, Tim Caughley and Wilfred Wan Editors UNIDIR RESOURCES About UNIDIR The United Nations Institute for Disarmament Research (UNIDIR)—an autonomous institute within the United Nations—conducts research on disarmament and security. UNIDIR is based in Geneva, Switzerland, the centre for bilateral and multilateral disarmament and non-proliferation negotiations, and home of the Conference on Disarmament. The Institute explores current issues pertaining to the variety of existing and future armaments, as well as global diplomacy and local tensions and conflicts. Working with researchers, diplomats, government officials, NGOs and other institutions since 1980, UNIDIR acts as a bridge between the research community and governments. UNIDIR’s activities are funded by contributions from governments and donor foundations. 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They do not necessarily reflect the views or opinions of the United Nations. www.unidir.org © UNIDIR 2017 Table of Contents Acknowledgments ................................................................................................... 4 About the Authors ................................................................................................... 5 Foreword ................................................................................................................. 8 Executive Summary ................................................................................................. 9 Chapter 1. Understanding Nuclear Weapon Risks Tim Caughley and Wilfred Wan ............................................................................... 11 Introduction ............................................................................................................. 11 A study of risk ................................................................................................. 11 The concept of risk .......................................................................................... 12 Existential risk assessment .............................................................................. 13 Risk and nuclear weapons ....................................................................................... 15 The humanitarian initiative ............................................................................. 16 Continuing the conversation ........................................................................... 17 Edging towards the nuclear precipice? ........................................................... 17 Elements of nuclear risk .......................................................................................... 18 Technological aspects ..................................................................................... 19 Human and operational factors ...................................................................... 19 Doctrinal dimensions ...................................................................................... 20 Significance of risk today ......................................................................................... 20 A foundation for risk mitigation ...................................................................... 22 Chapter 2. Risk and Nuclear Deterrence Mark Fitzpatrick and Marc Barnett .......................................................................... 23 Introduction ............................................................................................................. 23 Nuclear deterrence: theory, practice, and pitfalls .................................................. 23 Lessons from the Cold War ............................................................................. 24 Numerous pitfalls ............................................................................................ 25 Nuclear deterrence in South Asia ............................................................................ 26 The stability/instability paradox ..................................................................... 26 The question of credibility .............................................................................. 28 Nuclear deterrence in Northeast Asia ..................................................................... 28 DPRK provocations .......................................................................................... 29 Escalatory scenarios ........................................................................................ 30 Conclusion ............................................................................................................... 31 Chapter 3. The Quest for More Useable Nuclear Weapons Hans M. Kristensen .................................................................................................. 33 Introduction ............................................................................................................. 33 Modernization and evolution ......................................................................... 33 1 United States of America ......................................................................................... 34 The W76-1/Mk4A life-extended sea-launched ballistic missile warhead ....... 34 The B61-12 guided gravity bomb .................................................................... 36 Additional capabilities ..................................................................................... 39 Russian Federation .................................................................................................. 40 Multiple independently targetable re-entry vehicles ..................................... 40 Tactical nuclear weapons ................................................................................ 41 Conclusion ............................................................................................................... 42 Chapter 4. The Unique Risks of Nuclear-Armed Cruise Missiles Christine Parthemore .............................................................................................. 45 Introduction ............................................................................................................. 45 The state of affairs .......................................................................................... 45 An expanded awareness ................................................................................. 45 Risks of nuclear-armed cruise missiles .................................................................... 46 Risks to nuclear state credibility ..................................................................... 50 A risk-reduction path ............................................................................................... 51 Conclusion ............................................................................................................... 52 Chapter 5. Risks of Nuclear Command and Control Accidents Pavel Podvig ............................................................................................................ 53 Introduction ............................................................................................................. 53 The risks of launch-on-warning ............................................................................... 53 A history of false alarms .................................................................................. 54 Limits of prevention ........................................................................................ 55 Contemporary challenges ........................................................................................ 55 Complex interactions ...................................................................................... 56 New technologies ........................................................................................... 57 Increased capability ........................................................................................ 57 Risk mitigation options and their limits ................................................................... 58 Conclusion ............................................................................................................... 59 Chapter 6. Cyber Threats and Nuclear Weapons Systems Beyza Unal and Patricia Lewis ................................................................................. 61 Introduction ............................................................................................................. 61 Cyber technology vulnerabilities ............................................................................. 62 Differential impacts ........................................................................................ 62 The ubiquity of interconnectivity .................................................................... 63 The future of command, control, and communication ................................... 64 Space-based systems and cyber vulnerabilities ....................................................... 66 Insider threats ......................................................................................................... 69 Conclusion ..............................................................................................................