Expanded analysis of transition to an alternative fuel cycle

Quantitative benefits for an alternative nuclear fuel cycle system are often calculated under idealized steadystate conditions, while time-dependent analyses of transition to these systems typically focus on only the reactor/facility start-up rates and mass flows over time. This study establishes and applies a detailed quantitative analysis approach to time-dependent systems that can be considered as an "expanded analysis", which is needed to evaluate the time-dependent performance in areas of interest beyond simply start-up rates and material flows. In this study, a wide range of system performance and challenge metrics have been considered for inclusion in fuel cycle transition analysis and expanded to include time-dependent behavior. This work represents a major step in the process of informing on the impacts of time, system size, choice of transition technologies, etc. on the benefits, costs, and challenges of different transition pathways to a new nuclear fuel cycle option. This expanded analysis provides not just the benefits of the future fuel cycle, but the performance of the mixed system over the duration of the transition. It identifies when those benefits will begin, how quickly the system transitions to the expected equilibrium performance, and differences between transition approaches to the same end-state fuel cycle. For this study, evaluating the time-dependent behavior during transition required significant effort to develop the methodologies in some areas. For example, it was necessary to understand the time-dependent behavior of all of the different contributions to low-level waste such as operational and D&D waste from a given type of facility, the temporary status of land used for operational facilities needed to be considered since it is often re-used or returned to Greenfield status, and many of the timedependent metrics were inter-related and depended on assumptions about the retirement profiles of the existing fleet, technical details of each reactor design, etc. Therefore, methods to properly model the behavior were developed in many areas and were applied to an example transition scenario (to a continuous recycling fleet of fast reactors) to demonstrate the time-dependent metric calculation approach. In addition, the equivalent scenario in which the alternative fuel cycle was not deployed was also modeled and analyzed in terms of lowlevel waste, high-level waste and spent fuel disposed, environmental metrics, natural resource utilization, expenditures, technology development, and other areas of interest. This example scenario provided significant insight into the complexity, issues, and challenges of fuel cycle transitions, and the findings can be applied to a range of alternative transitions or to design different pathways that may exhibit improved transition performance.