Gamma-Free Neutron Detector Based upon Lithium Phosphate Nanoparticles

A gamma-free neutron-sensitive scintillator is needed to enhance radiation sensing and detection for nonproliferation applications.  Such a scintillator would allow very large detectors to be placed at the perimeter of spent-fuel storage facilities at commercial power plants, so that any movement of spontaneously emitted neutrons from spent nuclear fuel or weapons grade plutonium will be noted in real-time. The material must have an efficiency greater than that presently available using scintillating glass fibers and helium-3 tubes, but the most important need is for a detector material that is totally free of gamma interference. This project will develop technology for manufacturing large panels of fluor-doped plastic containing lithium-6 phosphate nanoparticles. In order to detect neutrons, the nanoparticles must be sufficiently small so that the plastic remains transparent. In this way, the triton and alpha particles generated by the capture of the neutron will result in a photon burst that can be coupled to a wavelength shifting (WLS) fiber, producing an optical signal of about ten nanoseconds at the face of a multianode photomultiplier. In Phase I, a patent-pending process for manufacturing the lithium-6 phosphate nanoparticles will be characterized, and the feasibility of embedding the nanoparticles in a plastic scintillator material will be determined. Commercial Applications and other Benefits as described by the awardee: The lithiated plastic should find application to the Linac-based x-ray systems being used at ports of entry for the imaging of cargo located in sea-land containers. The plastic detectors would enable a real-time determination as to whether a container has any fissile material hidden within high density material.