Passive Detection and Active Interrogation for Nuclear Disarmament Verification -
Outcomes and Challenges from Canadian Technology Demonstration Exercises

Nuclear Disarmament Verification (NDV) requires reliable technologies and procedures to verify nuclear weapons reduction without the transfer of sensitive information. Key challenges include (1) authenticating the presence or absence of well-shielded nuclear weapon material, and (2) preventing “cheating” by the disarming state. As non-nuclear and nuclear weapons states are conscious and supportive of the need to address NDV challenges, several international forums have been initiated to discuss and demonstrate the feasibility of proposed NDV methodologies. Exercises have been conducted worldwide to demonstrate technologies, and to test NDV concepts and procedures. Canadian Nuclear Laboratories (CNL) recently held a technology demonstration exercise for three passive detection technologies – Muon Scattering Tomography, Neutron counting, and Gamma-Ray spectroscopy – to verify nuclear material inside mock-ups of nuclear weapons without determining any sensitive design information. This exercise demonstrated that the complementary information provided by the simultaneous application of the three passive techniques could be used to verify the presence of nuclear material in scenarios where any one of the techniques used in isolation could be defeated. However, there still remain challenges in verifying the presence and absence of nuclear material in plausible shielding and concealment configurations. As a result, CNL is undertaking an active interrogation technology demonstration exercise, to explore the efficacy of neutron and gamma interrogation techniques for verifying the presence and absence of nuclear material in NDV scenarios. In this paper, the results and challenges of the passive technology demonstration exercises will be presented as well as prospective measurement scenarios and simulation results for the active interrogation exercise.