Development of a liquid scintillator–based active interrogation system for LEU fuel assemblies

Lavietes, Anthony and Plentada, R. and Mascarenhas, N. and Cronholm, L. M. and Aspinall, Michael and Joyce, Malcolm and Tomanin, A. and Peerani, P. (2013) Development of a liquid scintillator–based active interrogation system for LEU fuel assemblies. In: Advancements in Nuclear Instrumentation Measurement Methods and their Applications (ANIMMA), 2013 3rd International Conference on :. IEEE, FRA, pp. 1-4. ISBN 9781479910465

Abstract

The IAEA, in collaboration with the Joint Research Center (Ispra, IT) and Hybrid Instruments (Lancaster, UK), has developed a full scale, liquid scintillator-based active interrogation system to determine uranium (U) mass in fresh fuel assemblies. The system implements an array of moderate volume (~1000ml) liquid scintillator detectors, a multichannel pulse shape discrimination (PSD) system, and a high-speed data acquisition and signal processing system to assess the U content of fresh fuel assemblies. Extensive MCNPX-PoliMi modelling has been carried out to refine the system design and optimize the detector performance. These measurements, traditionally performed with 3He-based assay systems (e.g., Uranium Neutron Coincidence Collar [UNCL], Active Well Coincidence Collar [AWCC]), can now be performed with higher precision in a fraction of the acquisition time. The system uses a high-flashpoint, non-hazardous scintillating fluid (EJ309) enabling their use in commercial nuclear facilities and achieves significantly enhanced performance and capabilities through the combination of extremely short gate times, adjustable energy detection threshold, real-time PSD electronics, and high-speed, FPGA-based data acquisition. Given the possible applications, this technology is also an excellent candidate for the replacement of select 3He-based systems. Comparisons to existing 3He-based active interrogation systems are presented where possible to provide a baseline performance reference. This paper will describe the laboratory experiments and associated modelling activities undertaken to develop and initially test the prototype detection system.