Improved Method For Determining Uranium Enrichment From Active Delayed Neutron Measurements In The Context Of Nuclear Disarmament Verification

In the context of nuclear disarmament verification, unambiguous detection of highly enriched uranium poses a particular challenge due to its low passive neutron and gamma emission. For the identification of an object to be dismantled as a true nuclear warhead, measurements of various attributes such as mass or enrichment are required during an inspection. Measurement of delayed neutrons after irradiation with an external neutron source provides a non-intrusive means of enrichment determination. Since the method is based only on the time course with known decay constants and probabilities, it does not require calibration standards nor detailed assumptions about the warhead’s geometry. An improvement of the most recently proposed evaluation method based on delayed neutron six-group calculations is presented. Results of the current and improved technique are compared via Geant4 Monte Carlo simulations. The potential pitfalls of this measurement technique are discussed as well as its optimal integration in the disarmament process.