Diffusion Based Pin-Resolved Neutronics Simulation of a Hexagonal Lead-Cooled Fast Reactor with L-BFGS Optimization of Superhomogenization Factors

In this work, a feasibility study is performed to demonstrate a pin-resolved diffusion simulation for hexagonal lead-cooled reactors. A high resolution mesh is utilized which can explicit model intra-assembly structures and also handle complex control rod assembly designs typical for proposed LFRs found in the literature. The L-BFGS optimization method is employed to obtain superhomogenization factors. Code verification is performed by applying this method on a 2D slice of a LFR with 24 energy groups in the multi-group cross-section library. The accuracy of the method is assessed by comparing the \(k_{{{\text{eff}}}}\) value and assembly-wise power distributions to a reference solution for both cases of control rod inserted and withdrawn.