Experimental and Computational Verification of a New Remote Monitoring System Design
for Spent Fuel Dry Cask Safeguards

Spent nuclear fuel (SNF) is stored in dry casks following irradiation and initial cooling in spent fuel pools. Dry casks typically hold 2-6 dozen irradiated fuel assemblies. For a cask holding 32 assemblies, the mass of plutonium equates to around 20 significant quantities. Safeguard methods for dry cask storage currently rely on secure containment and constant surveillance. There is a need for increased security for dry casks to deter and detect the diversion of special nuclear material. A remote monitoring system (RMS) was designed to advance the current level of security and reliability of dry cask safeguards. The objectives of this study were to assess the performance of the external RMS as a diversion detection system and to develop a simulation approach for predicting neutron measurements for stable cask conditions as well as diversion scenarios. Smallscale neutron source experiments that mimicked SNF diversion from a dry storage cask were conducted and the non-detection probability was calculated for a variety of measurement times. MCNP simulations were carried out to assess the degree to which the measurement results could be predicted. The study concluded that the external RMS performs well as a neutron detection system and that MCNP simulation can be reliably used to predict measurements made by the RMS and non-detection probabilities in hypothetical diversion scenarios.