Monitoring of 235U content of fuel assemblies for nuclear reactors based on neutron and γ-ray scintillation detector systems

Abstract

A model of the setup for determining the ²³⁵U content of a fuel assembly for WWER-440 reactors is described. The setup operates based on the digital technology for discriminating neutron and photon scintillation responses. An AmLi source is used as an external neutron source. A three-channel system for detecting fission particle coincidences is based on EJ-309 scintillators. A set of digital codes for obtaining and analyzing neutron-neutron (nn), neutron-γ (nγ), and γ-γ (γγ) coincidences has been developed. Dependences of double coincidences have been experimentally obtained and analyzed with the aim of determining the ²³⁵U content of the fuel assembly. It is shown that fission neutrons and coincidences of the nn and nn + γn + nγ types are the best informative parameters for the ²³⁵U content of the fuel assembly.