A Parametric Study of Neutron Signatures from UF6 Cylinders

As the nuclear industry moves towards advanced reactors utilizing High-Assay Low Enriched Uranium (HALEU), new cylinder designs are being considered for the safe storage and transport of HALEU in the form of uranium hexafluoride (UF6). These new cylinders, such as the 30-BX, contain neutron absorbing materials for criticality safety. These neutron absorbers may have an impact on the ability to perform material accounting through non-destructive assay (NDA). In this work, a parametric study was performed to characterize these impacts on relevant signatures for neutron NDA. High-fidelity Monte Carlo N-Particle (MCNP) simulations of 30B and 48Y cylinders were performed to determine the total and coincident neutron emission signatures over multiple parameters that potentially affect the accuracy of any neutron-based material accounting method. These neutron signatures provide a baseline that can be compared to signatures from modified cylinder designs in future. Given a model of a modified cylinder, the same analysis would quickly indicate whether existing neutron NDA methods and instruments are applicable to the new designs—thus reducing one barrier to HALEU-based technologies—or whether further development is required. LA-UR-25-21070.