A Method for Nondestructive Assay of Nuclear Materials in Facilities with a Pulse Neutron Generator and a Digital Technology for Discrimination between Neutrons and Photons

摘要

A method for determining the ~(235)U concentration in fuel assemblies of a high-power channel-type PBMK reactor is described. The measure of ~(235)U content of an analyzed sample is the number of neutrons from thermal-neutron fission of ~(235)U, normalized to the number of γ quanta produced in thermal neutron capture by hydrogen nuclei in the scintillator or by ~(10)B in the glass of a photomultiplier tube. A pulse neutron generator based on DT reaction is the neutron source, and an organic scintillator with the pulse shape discrimination between neutrons and γ rays with the aid of the digital technology is a detector. The scintillator is also used as a neutron moderator. Simulation of the method shows that the ~(235)U content of the analyzed sample can be determined for 1 min with an accuracy of 1% or better. The efficiency of the method has been confirmed by experimental investigations on a model of the setup.