Abstract
Measurements of the geometric configuration of objects and their material composition are needed for nuclear treaty verification purposes. We experimentally demonstrate a simple method based on monoenergetic fast neutron transmission to realize crude imaging of the geometric configuration of special nuclear material, confirm its fissionable content, and obtain information on its approximate fissile mass. In the experiment, we used monoenergetic neutrons from D(d, n)3He and T(d, n)4He reactions and a linear array of liquid scintillation detectors to perform spectroscopic neutron imaging of up to 13.7 kg of highly enriched uranium in a spherical geometry. We also show an example of detection of material diversion and confirm the presence of fissionable material based on the measurement of high-energy prompt fission neutrons, including estimating the quantity of material from the comparison of measured and predicted fission neutron emission rate. The combination of crude imaging and fissionable material detection and quantification in a simple approach may be attractive in certain treaty verification scenarios.
Highlights
The effectiveness of international treaties aimed at preventing nuclear weapons proliferation and promoting disarmament relies on the technological capability to monitor and confirm the compliance of all participants
The goal of this study has been to demonstrate the capabilities of a simple spectroscopic neutron transmission measurement system to realize crude geometric imaging of an special nuclear material (SNM) target, as well as confirm the presence of fissionable material and approximate its quantity
Using monoenergetic neutrons from DD and DT reactions, we successfully constructed low-resolution transmission profiles from which one could readily detect the removal of the central core (3.7 kg) of a 13.7 kg highly enriched uranium (HEU) sphere
Summary
The effectiveness of international treaties aimed at preventing nuclear weapons proliferation and promoting disarmament relies on the technological capability to monitor and confirm the compliance of all participants. The protection of state secrets represents a significant hurdle that must be cleared for a verification technique to be considered viable. While this problem has traditionally been addressed through engineered information barriers, which prevent the inspector from directly observing the classified information being measured, this approach involves a high degree of complexity and susceptibility to tampering through the use of information trapdoors to falsify results or leak sensitive information.[2,4] Current information barrier systems can be expensive to implement and reduce confidence in verification measurement results.[5] The political reality associated with such mechanisms presents a significant barrier to their adoption
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