Hierarchical Shape Optimization of Nuclear Fuel Assemblies Using Multi-Level Pin to Assembly Analysis in MOOSE

We apply the MOOSE framework’s optimization module to Hierarchical Shape Optimization for
a PWR fuel assembly design, adaptively optimizing the fuel pin’s shape. Accounting for changes
in neutronics behavior is captured with cross section generation in Serpent while changes in heat
transfer is considered by dynamically updating convective heat transfer coefficients during the optimization process. We employ the derivative-free Nelder-Mead algorithm to optimize the fuel
pin geometry, demonstrating notable improvements in performance metrics. The hierarchical approach avoids local minima by gradually increasing geometric complexity, achieving a final kef f
improvement of 1390 pcm over the non-hierarchical baseline.