Strengths and limitations of cosmic-ray muon tomography for nuclear disarmament verification application

Nuclear disarmament verification (NDV), which is the use of technologies and procedures to verify nuclear weapons reductions without the transfer of sensitive information, is currently a major worldwide field of work. The work presented here demonstrates experimentally the usefulness of muon tomography for the verification of a mock-up of a nuclear warhead. Experimental results are extended further with Monte Carlo simulations to predict results and draw conclusions in the case of enclosures containing a nuclear weapon core. Muon tomography has proven to be effective in the detection of high-density and high-atomic-number materials, even when they are surrounded by heavy shielding such as lead. Although the technique can determine the presence of a high-density and high-Z core, our muon tomography system and analysis algorithm have limited angular resolution and therefore do not provide information on the nature of the material. To overcome this limitation and to mitigate risks associated with swapping a nuclear weapon core with tungsten, gamma rays and neutron techniques are proposed. These are shown to be complementary techniques for NDV applications.