Currently, the challenge of nuclear safety, security, and safeguards (3S) exists with both the Molten Salt Reactor (MSR) and the Pebble Bed Reactor (PBR), owing to the nature of the constantly flowing fuel. The current technology for gamma spectroscopy is the High-Purity Germanium (HPGe) semiconductor detector. Microcalorimetry offers next-generation capability regarding energy resolution, with a 10x greater energy resolution than HPGe [1]. This increase in resolution reveals peaks indistinguishable by HPGe to better identify fissionable nuclides, short-lived fission products, and long-lived radionuclides in the used fuel [2]. Simulation of microcalorimetry offers a direct avenue of progressing this novel technology, eliminating the need for the resources required for the physical microcalorimeter. The existing model of the Spectrometer Optimized for Facility Integrated Applications (SOFIA) from Los Alamos National Laboratory (LANL) [3] is currently being updated in both GEANT4 [5] and MCNP6.3 to a higher energy resolution model. Two models are in development for direct comparison to ensure similarities exist across different simulation programs. GEANT4 was used to implement detector efficiency and resolution, using average values and a Gaussian distribution as the first step. This has already produced favorable spectra when compared to energy deposition in a setup comparable to that of a primitive detector that absorbs the gamma energy at an efficiency and resolution at unity and null, respectively. The gamma spectra are generated by Monte Carlo simulation. Current future implementations prior to INMM 2025 are true efficiency and resolution from actual experimental and calculated data, the addition of complex geometries for photon scattering, implementing a python script for accurate spectrum broadening, and machine learning algorithms for spectra analyzation. This work directly advances the timeframe in which microcalorimetry would be implemented into advanced reactor facilities for non-destructive reactor monitoring thereby enhancing nuclear 3S standards and fuel accountability in near-real time.
