Applications of HPGe-detected high energy gamma rays toward quantifying neutron emission rates and 234U enrichment in UF6 cylinders

This study presents a 234U enrichment meter that uses high energy gamma and neutron count rate as measured by a portable, high-purity germanium gamma ray detector. Twenty-one 30B cylinders containing UF6 of varying origin were analyzed with an HPGe detector for high-energy gamma ray and neutron counts. Excellent correlations (R2 ≥ 0.95) between various regions of ≥3.0 MeV gamma rays, neutron count rate, and uranium enrichment were found. These neutron and high-energy gamma data are used to create calibration-dependent enrichment meters for 234U. The 234U enrichment calculated from the neutron count rate and 4 – 6 MeV gamma count rate is more accurate than methods that rely on the 120.9 keV peak which is strongly attenuated inside commercial sized UF6 cylinders. These neutron and high-energy gamma enrichment calculators can also be used to determine a 235U enrichment, assuming mass-based enrichment from natural uranium, but the results are not as accurate as the traditional 185.7 keV peak enrichment meter.