Impacts of Recycling Time on Fuel Cycle Transition

The purpose of this work is to show the importance of assumptions regarding the recycling time for time-dependent fuel cycle scenarios that involve transition from the current state of the U.S. fuel cycle to cycles based on continuous recycling via fast reactors. The recycling time is defined here as the total time between when the fuel is discharged from the reactor core and when its recovered heavy metals (HM) are recycled back into the core as part of the fresh/new fuel. The main processes occurring within the recycling time include cooling, separations, and fuel fabrication. The minimum recycling time required for fast reactor fuel largely depends on the minimum cooling time, which will be longer if discharged fuel needs to be moved to a centrally-located separations facility. A longer cooling time is needed for the heat load and fuel characteristics to reach safer levels for handling and transportation. Therefore, if the separation and fabrication facilities were co-located with reactors on-site, then the total recycling time could be reduced by several years. For fuel cycle transition scenarios in which external fissile materials (Pu or TRU) are limiting, these longer recycling times may prolong the transition to the continuous recycling system of fast reactors as well as impact the fuel cycle system performance during the transition. Therefore, in order to demonstrate the quantitative impacts of these recycling time assumptions, an example scenario of transition to the fast reactor fleet with continuous recycle was modeled in the fuel cycle systems code DYMOND. It must be emphasized that this is a point study that demonstrates how a longer recycling time can impact the rate of transition under specific conditions and assumptions. For alternative scenarios, such as those in which there are no fissile material constraints, there are likely no significant impacts due to recycling time. (authors)