In April 2025, Tomas Cisneros developed a FastFlux energy group structure for the terrapower/armi repository, enabling advanced fast neutron flux calculations. He defined the new energy grouping using the HIGH_ENERGY_EV and FAST_FLUX_THRESHOLD_EV constants, expanding the platform’s neutronics and physics calculation capabilities. Working in Python, Tomas focused on enhancing model fidelity for fast flux scenarios, addressing the need for more accurate and flexible fast-flux modeling. His contribution laid the groundwork for future improvements in fast neutron analysis, with clear traceability and maintainability in the codebase. The work demonstrated depth in neutronics and a methodical approach to physics calculations.