Liquid Scintillator-Based Neutron Detector Development

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-flashpoint, 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 He-3-based systems in many applications. As such, a comparison to an existing He-3-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.