A code for simulating a high-resolution gamma-ray spectrum of a fission sample

Abstract A numerical model was developed that fully reconstructs a high-resolution gamma-ray spectrum of a fission sample. The code combines GEANT4 Monte Carlo simulations (used to calculate the response of a germanium detector) with the in-house Koala package (used to calculate the fission product inventory). In order to validate the model against experimental data, a highly enriched uranium sample was irradiated in a reactor and measured for up to 31 days later. A comparison between the simulated spectra and the experimental spectra exhibited a good quantitative agreement, demonstrating the high reliability of the model, especially for early times. While a simple source geometry was used for benchmarking the developed code, it can be easily extended to include complex geometries. The synthetic fission spectra can be used in several applications, e.g. assessing the capability of detector systems in identifying certain radionuclides, verification of gamma spectrometry analysis software and proficiency tests for analytical laboratories.