Multiplication Eigenvalue and Thermal Response of Conventional and Idealized Multicomponent Claddings in a Generic PWR-like Fuel-Rod Model

This study presents a sequential neutronic–thermal screening of Zircaloy-4, SS316, and two idealized multicomponent cladding compositions in a generic PWR-like fuel-rod model under beginning-of-life conditions. Neutron-transport calculations were performed using KENO-VI within the SCALE Code System for three parametric fuel compositions containing 4, 5, and 16 wt.% 235U, followed by an independent steady-state analytical thermal analysis at prescribed average linear heat rates of 10, 15, and 20 kW m−1. The calculated neutronic quantity is denoted by keig and represents the multiplication eigenvalue of the complete mirror-bounded model; it is not identified as either the conventional infinite-lattice factor or the effective multiplication factor of a reactor core. Zircaloy-4 produced the highest keig among the executed material definitions. The idealized AlMgZnCuMn model, represented using natural copper, produced the closest calculated response to Zircaloy-4. The independent thermal model showed that the assigned high thermal conductivity of the AlMgZnCuMn composition reduced the local temperature difference and thermal gradient across the cladding, with d(∆Tclad)/dq′=0.192 K/(kW/m), 87.5% below the Zircaloy-4 value. The results demonstrate a model-specific trade-off between multiplication response and local cladding heat transfer. The analysis is a first-order screening of the adopted computational definitions rather than a prediction of complete SMR fuel performance.