Numerical simulation of irradiation effects in low-powered laser fusion test chamber under continuous operation

Abstract Quantification of irradiation damage is a key challenge for fusion energy deployment. This study presents an irradiation damage modeling campaign using the Monte Carlo-based PHITS (Particle and Heavy Ion Transport code System) code to evaluate candidate plasma-facing materials under deuterium–deuterium (D–D) and deuterium–tritium (D–T) fusion conditions. Within a broader phased-approach to commercial reactor development, the analysis focuses on an assessment of a currently installed laser fusion test chamber driven by a low-power direct-drive central-ignition laser system. The objectives are to (1) compare a conventional dry-wall architecture against a wetted first wall architecture incorporating a 3 mm flowing lead–lithium (PbLi) layer and (2) to quantify activation product generation. Neutron spectra, spatial energy deposition, displacement-per-atom (DPA), and activation profiles were computed for Reduced Activation Ferritic-Martensitic steel (F82H), stainless steel 316 L, tungsten, and ODS FeCrAl using PHITS tallies. Results show that the PbLi layer absorbs over 30× more energy and reduces surface DPA in the underlying solid substrate by up to three orders of magnitude. Activation analysis indicates fewer gamma-emitting isotopes and tritium-dominated activity in the wetted configuration compared to the dry wall. These results confirm the irradiation-mitigation benefits of thin liquid–metal wetted walls and provide guidance for first-wall design in small-scale fusion test reactors.