Yuanzineng kexue jishu (Sep 2022)
Development and Application of Neutron Generator at Lanzhou University
Abstract
In 1988, a 3×1012 s-1 neutron generator named ZF-300 was built at Lanzhou University. The neutron source was used in the programs involving basic nuclear data measurements, irradiation effect researches of materials. Recently, a new intense neutron generator named ZF-400, is being developed for the purposes of fast neutron physics research, such as fast neutron nuclear data measurement by activation method and fission physics. The Cockcroft-Walton accelerator was designed to accelerate the D+ beam of 30 mA to the energy of 400 keV. The designed neutron yields of ZF-400 neutron generator were greater than 5×1010 s-1 for D-D and 5×1012 s-1 for D-T, respectively. In the field of fission physics, a potential-driving model by uniting the empirical asymmetric fission potential and the empirical symmetric fission potential was successfully developed to precisely calculate the pre-neutron-emission mass distributions for neutron-induced actinide nuclei fission. A Monte-Carlo method based on the potential-driving model and Geant4 code was also developed to simulate the fission-fragment yield distribution, kinetic energy distribution and fission neutron spectrum. A twin frisch-grid ionization chamber (TFGIC) detector for the measurement of fission products was also designed and tested. In the field of neutron application technology, in order to meet the development requirements of neutron application technology system, a compact neutron generator with a length of 984 mm and a diameter of 234 mm was successfully developed at Lanzhou University. A bias voltage between the target and the extraction accelerating electrode was produced by a resistance to suppress the secondary electron from the target. D-D neutron yield of the compact neutron generator could be greater than 5×108 s-1 under a pure molybdenum as the drive-in target and the beam energy of 150 keV. The compact neutron generator has the potential to produce D-T neutrons with a yield of more than 1010 s-1. A beam-shaping-assembly (BSA) based on a compact D-T neutron generator was designed for fast neutron radiography, and a fast neutron imaging detector based on micro-channel plates was also developed. Preliminary fast neutron imaging test using D-T neutron generator shows that the spatial resolution of the image is about 500 μm. A detection system to measure 235U enrichment uniformity in nuclear fuel rods based on a compact D-D neutron generator was also designed. Simulation results show that the confidence probability can reach 99% for a relative 235U enrichment deviation of 10% under a D-D neutron yield of 5×108 s-1.
