Proliferation risk assessment for large reprocessing facilities with simulation and modeling

Proliferation risk assessment has been investigated to develop a performance-based approach in which the likelihood of diversion incidence, as well as the uncertainty of nuclear material accounting, is simultaneously considered to install intrinsic and extrinsic countermeasures in a conceptual design of a future reprocessing facility. A simulation and modeling approach has been applied to evaluate safeguards performance in a facility-level and diversion pathway analysis, which is demonstrated to detect more efficiently a small and protracted diversion that is usually investigated by trend analysis. Although an incidence probability of diversion is difficult to estimate because of its intentional act, the Markov model methodology originally developed by the proliferation resistance and physical protection working group in the generation IV international forum is incorporated into two-dimensional probability distribution. In a comparative study, a hypothetical reprocessing process for light water reactors and fast breeder reactors are modeled and investigated using the distribution that is derived from an inherent nature in the deterministic International Atomic Energy Agency safeguards criteria. By comparison with conventional diversion scenarios, which are abrupt and protracted loss, and verification measures to conform to the criteria, the diversion path analysis with a simulation and modeling tool is valuable to pursue a risk-oriented performance in safeguards. This simulation and modeling approach has already been carried out in the United States to investigate safeguards performance in future reprocessing processes, and we have been collaborating on the development of safeguards simulation tool to enhance the safeguards by design approach. (author)