Neutronic Analyses for the Design of the Chamber of Xcimer’s Athena Fusion Pilot Plant

Inertial fusion energy presents a promising pathway for delivering fusion-generated power to the electrical grid. Xcimer Energy Corporation is advancing the design of a fusion pilot plant named Athena, inspired by the well-established HYLIFE-II fusion power plant concept. The HYLIFE-II approach utilizes a thick-liquid flibe (2LiF-BeF2) wall to accommodate the threats of x-rays and debris ions from the fusion reaction and absorb most of the neutron energy, thereby breeding tritium through Li–n reactions and shielding structural components from neutron-induced damage. Athena will incorporate Xcimer’s novel laser architecture, combining only two high-energy lasers with high-yield targets to achieve 355 MW of fusion power at a low repetition rate of 0.25 Hz. Two-sided laser illumination and low-frequency operation alleviate key challenges faced by earlier designs, such as chamber clearing and neutron leakage through laser beam ports. This study presents a detailed nuclear analysis for the Athena fusion chamber, focusing on energy deposition, tritium breeding performance, structural resilience, and radioactive waste generation. A comprehensive neutronics model, incorporating major design features, is used to evaluate radiation doses during both operational and maintenance phases, including activation of the breeder fluid. These analyses leverage advanced radiation transport and material activation tools. The UNED-TECF3IR group supports the Athena design by providing high-fidelity nuclear assessments. This work also outlines the state-of-the-art computational methods employed and discusses current limitations encountered in specific analysis domains.