The NUIT code for nuclide inventory calculations

Abstract

This work introduces the NUIT (Nuclide Inventory Tool) code for nuclide inventory calculations, which has been developed by Institute of Nuclear and New Energy Technology (INET), Tsinghua University. NUIT is able to compute isotope density, decay heat, particle spectrum and radioactivity in fuel burnup, material activation and decay calculations. The burnup equations are solved by transmutation trajectory analysis method (TTA) and matrix exponential methods in the NUIT code. The code libraries account for very detailed burnup chains with thousands of isotopes and all major neutron-induced reactions and decays, which adapt to general purpose applications in fission reactors. Besides, NUIT code provides friendly interface to utilize problem-specific neutron spectrum and tabular effective one-group cross sections produced by neutron transport codes. The NUIT code is validated by analytical solutions, experimental data and code-to-code comparisons. The validation results demonstrate the NUIT code's capabilities in wide-range nuclide inventory calculations.