FLASH Portals: Radiation Portal Monitor SNM Detection using Time Correlation Techniques

Abstract

The "FLASH Portals Project" is a collaboration between Arktis Radiation Detectors Ltd (CH), the Atomic Weapons Establishment (UK), and the Joint Research Centre (European Commission), supported by the Technical Support Working Group (TSWG). The program's goal was to develop and demonstrate a technology to detect shielded Special Nuclear Materials (SNM) more efficiently and less ambiguously by exploiting time correlation. This study presents experimental results of a two-sided portal monitor equipped with 16 He-4 fast neutron detectors as well as 4 polyvinyltuolene (PVT) plastic scintillators. All detectors have been synchronized to ns precision, thereby allowing to resolve time correlations from timescales of tens of microseconds (such as (n,γ) reactions) down to prompt fission correlations directly. Our results demonstrate that such correlations can be detected in a typical RPM geometry and within operationally acceptable time scales, and that exploiting these signatures significantly improves the performance of the RPM compared to neutron counting. Furthermore, the results show that some time structure remains even in the presence of heavy shielding, thus significantly improving the sensitivity of the detection system to shielded SNM.JRC.E.8-Nuclear securit