Development of a Monte Carlo Modeling Approach to Determine the Enrichment of UF₆ Typical Cylinders

Precise assay of uranium enrichment without time-consuming analysis is a crucial factor in nuclear safeguards process. This paper aims at a computational development using innovative Monte Carlo (MC) method for ²³⁵U mass enrichment (%E) verification for the UF₆ cylinder. This new approach focuses mainly on using different UF₆ physical properties (effective volume and density) and extra ²³⁵U gamma- and X-ray transitions as input parameters for efficient calculations of %E assay. In this work, we used the measured values of the dose rate (μSv/h) due to the emitted gamma- and X-rays of ²³⁵U content at the cylinder external surface for enrichment calculations. The attenuation of the main ²³⁵U gamma- and X-energies due to the cylinder wall (5B-Type Ni Inconel alloy) was also estimated to wide range of energies using XCOM: Photon Cross Sections Database software. Using this suggested model for ²³⁵U enrichment calculation, the calculated value of 19.46 ± 1.28% is within one standard deviation of the certified value of 19.75 ± 0.40%. The mass of ²³⁵U was also estimated and found to be 2.6814 kg. Based on this improved approach, the total uranium activity of the investigated UF₆ cylinder was calculated and found to be (5.52 GBq), which is 98.6% from the declared activity value (5.6 GBq). These accurate and confident calculated values are direct functions in the improved parameters and the developed MC code.