Closing the nuclear fuel cycle: Strategic approaches for NuScale-like reactor

Abstract

The present study proposes the potential implementation of eight different closed fuel cycle strategies for a NuScale-like reactor core using its own spent fuel as a reusable source of fissile material for energy production. For that, the spent fuel composition after three burnup cycles of approximately 12 MWd/kgU of NuScale-like initial core and five years of cooling in a spent fuel pool was theoretically reprocessed by GANEX or UREX+ methods. After reprocessing, these two new fuel compositions were spiked in a mixture of thorium (Th) or depleted uranium (DpU), and afterwards inserted into specific batch positions of the core. Therefore, the proposed NuScale-like core configurations contain fuel assemblies loaded with conventional uranium-based fuel and others loaded with reprocessed fuel, resulting in the following combinations: UO₂ and GANEX spiked with Th, UO₂ and GANEX spiked with DpU, UO₂ and UREX+ spiked with Th, UO₂ and UREX+ spiked with DpU. The main idea is to comprehend the advantages of adopting the closed nuclear fuel cycle for a NuScale-like reactor by comparing the reference case and the cases containing reprocessed fuel. The results exhibited that all instances in which the core was simulated with reprocessed fuel improved the feedback coefficient, maximum excess of reactivity varying the boron concentration in the coolant, and power peak factor (PPF). Furthermore, the closed nuclear fuel strategies also demonstrated savings of about 17.50% in terms of separating work units (SWU) due to plutonium and uranium recycling, and a potential burnup extension of approximately 43%. The Serpent code version 2.1.32 developed by VTT and ENDF/B-VII.0 nuclear data library has been used to perform the simulations.