Comparison of thermal and structural performance of conventional concrete and UHPC for spent nuclear fuel storage structures

Spent nuclear fuel (SNF) is currently stored in a growing number of dry cask storage structures across the US. With concrete aging risks, licensing renewals challenges, and the absence of a permanent SNF repository, there is a pressing need for extending the service life of the existing storage systems and rethinking the design of new systems for longevity using durable materials. Ultra-high performance concrete (UHPC) possesses superior mechanical and durability properties and presents a promising solution for retrofitting existing or building new SNF storage facilities. Only very limited research is available on the possible utilization of UHPC in dry storage systems. As such, this study takes a first look at rethinking the design of current SNF reinforced concrete horizontal modules storage facilities using UHPC, and focuses on the comparative thermal and structural performance of conventional concrete and UHPC in a typical horizontal storage module. The study considers computational fluid dynamics (CFD) analysis to establish temperature distributions that are used subsequently in structural finite element analysis. Demands from various load combinations are compared to respective concrete and UHPC section capacities for assessment. The results show that UHPC components have a bigger reserved structural capacity and better thermal performance than conventional concrete, and could provide a significantly enhanced structural performance besides the outstanding durability and extended service life.