Liquid scintillator-based neutron detector development

Abstract

The IAEA, in collaboration with the Joint Research Center (Ispra, IT) and Hybrid Instruments (UK), is developing a liquid scintillator-based neutron coincidence counting system to address a number of safeguards applications. Interest in this technology is increasing with the advent of high-flash point, non hazardous scintillating fluids coupled with significant advances in signal processing electronics. Together, these developments have provided the enabling technologies to allow liquid scintillators to be implemented outside of a laboratory environment. Another important aspect of this detector technology is that it can be used with the current installed infrastructure of safeguards assay instruments and data acquisition electronics. It is also an excellent candidate for the replacement of 3 He-based systems in many applications. As such, a comparison to an existing 3 He_ based system will be presented to contrast the differences and benefits for several applications. This paper will describe the experiments and associated modeling activities engaged to carefully characterize the detection system and refine the models.The latest version of MCNPX-PoliMi Monte Carlo modeling code was used to address the specific requirements of liquid scintillators. Additionally, this development activity has driven the collaborative development with Hybrid Instruments of a high-performance pulse shape discriminator (PSD) unit. Specific applications will be described with particular emphasis on those in which liquid scintillators provide immediate benefit over traditional detection methods.

Real-Time Capabilities of a Digital Analyzer for Mixed-Field Assay Using Scintillation Detectors

“…The MFA technology has supported many real-time measurement campaigns, has been used with four different EJ309 detector geometries [14] and is compatible with several multiplicity analyzers. Some of the most novel measurements, made possible using this technology, are reviewed.…”

“…The controller includes an FPGA-based data acquisition card and custom-built analysis software developed in LabVIEW [7], [14]. 2) custommade de-randomizing electronics (Los Alamos National Laboratory, NM) connected to a JSR-15 multiplicity shift register (Canberra Industries Inc., CT) for the measurement of Uranium-235 enrichment in small samples of low-enriched triuranium octoxide [15], and 3) a bespoke 32-bit, 64-channel, binary counter with a serial PC interface (Lancaster University, UK) for reactor imaging [13] and neutron tomography using an isotropic source [16].…”

“…Other studies utilizing fast-neutron multiplicity and coincidence counting with a diverse range of potential applications including nuclear material accountancy in storage, criticality assurance, non-proliferation, nuclear safeguards and security have also benefited from the capabilities of this technology [7], [9], [14], [22], [23], [24], [25], [26], [27].…”

Progress in alternative neutron detection to address the helium-3 shortage

“…Liquid scintillators have long been used for fast neutron detection, relying on pulse shape discrimination to differentiate between gamma ray interactions and recoil protons from neutron interactions. New non-flammable liquid scintillators are being explored for coincidence counters for safeguards where their very fast response is an advantage for coincidence analysis [33]. Liquid scintillators are sensitive to neutrons with energies above a few hundred keV and pulse shape analysis is used to separate gamma ray and neutron signals.…”

A 16-Channel Real-Time Digital Processor for Pulse-Shape Discrimination in Multiplicity Assay

“…I N RECENT years, the advent of real-time, embedded pulse shape discrimination (PSD) [1] has enabled high-flashpoint liquid scintillation detectors [2] to be considered for the replace- in safeguards assay applications [3]- [5] because 1) intervention by experts during assay to adjust PSD settings is no longer required and 2) PSD is done on-the-fly without the need for post processing. Alternative detector technologies are needed to replace existing non-destructive assay systems because is supply-constrained.…”