Assessing differential scanning calorimetry as a retrospective dosimetry method for the verification of uranium enrichment activities

Abstract

Fissile material produced for non-peaceful purposes may require some level of verification that it has all been accounted for in a nuclear disarmament scenario. Physical signatures from the uranium enrichment process can support and validate declared production. This thesis proposes a method to measure the signature from radiation effects in uranium enrichment equipment, using a retrospective dosimetry approach. Proof-of-concept experiments are performed to demonstrate sufficient sensitivity for the application, based on polytetrafluoroethylene (PTFE) and the thermal analysis techniques differential scanning calorimetry (DSC) and fast scanning calorimetry (FSC). The DSC-PTFE system shows statistically significant sensitivity in the dose ranges expected. The FSC-PTFE system demonstrates reduced precision compared to the DSC-PTFE system, but it also shows potential for extracting additional information about the radiation, like the particle type and energy. To improve precision in the FSC-PTFE system, additional data reduction and error propagation methods are developed, with a specific focus on the FSC "hook." These are demonstrated using an energy-conservation model to calculate the mass of the sample through the magnitude of the hook. The DSC-PTFE and FSC-PTFE systems demonstrate enough potential to justify further investigation into radiation effects as physical signatures. Through these methods, histories of unsafeguarded enrichment facilities can be reconstructed, and fissile material produced therein can be confidently transitioned to peaceful uses.