Correlative assay of uranium with calorimetry, neutron counting, and mass spectrometry data

A methodology has been developed for assaying unirradiated enriched uranium that uses calorimetry, passive neutron counting, and historical mass spectrometry data. Calorimetry can be used to measure the thermal power of bulk uranium enriched in the isotope 235U, and neutron counting can be used to determine its spontaneous-fission neutron emission rate. The thermal power and neutron-emission properties of uranium change in a regular way with increasing 235U enrichment that can be quantified using mass spectrometry data. The measured ratio of the thermal power and spontaneous neutron fission rate can be used to determine the 235U enrichment and the total mass of the 234U, 235U, and 238U isotopes.