| Neutrinos are uncharged leptons in particle physics.From the starting point of generation to the end point of detection,neutrinos have a very low interaction cross-section with matter and a strong penetration ability,so they can carry information about early nuclear reactions and nuclear processes;It is precisely based on the characteristics of neutrinos that people extend the application of neutrinos to the monitoring of the operating conditions of nuclear reactors.In recent years,many experimental groups abroad have carried out related research work and have made important research progress.Detecting neutrinos can realize all-weather monitoring of nuclear reactors without any interference to the normal maintenance and operation of the reactors,detecting enriched uranium and plutonium content,etc.,and provide core data information for nuclear proliferation prevention.Therefore,neutrino detection is of great practical significance for both basic research and application needs.This topic focuses on small-scale array neutrino detectors,and carries out research work on detector arrays,background shielding,and energy calibration of detector array units.（1）Through the Monte Carlo particle transport program Geant4,the background source interference of 4.0 Ge V muons in the neutrino detection system was simulated and studied.For a plastic scintillator with a thickness of 5.0 cm,the detection threshold can be set down to 8 Me V,effectively eliminating more than 98.0%of cosmic muon ray interference.Complete the design of the anti-cosmic ray detector.For the overall shielding shell of the neutrino detector array,the calculation using the neutron transport program MCNP shows that the thickness of boron-containing polyethylene(11B content is 5.0 wt%)is 15.0 cm,the density is 1.1 g/cm3,the thickness of lead is 10 cm,and the thickness of Cd is 0.1cm.The shielding material system can effectively shield more than 99.6%of the neutron/gamma background with energy in the range of 1.0～2.0 Me V,meeting the requirements of n/gamma background shielding for neutrino detection.（2）The neutron capture reaction process and the positron flooding process were simulated and studied by the Geant4 program.The neutrons generated by the neutrino event are slowed down in the detector and the positron annihilation track length is 13.0cm and 7.0 cm,and the moderation time is 7.5μs and 0.01 ns.The size of the neutrino detector was determined.The outer cladding materials of the neutrino detector array unit are oxygen-free copper（5.0 cm）,lead（10.0 cm）and boron-containing polyethylene（10.0 cm）,which can be further effectively used to shield the reactor and experimental environment.The neutron and gamma ray background,which moderates and absorbs neutron rays.The neutrino detection efficiency is affected by the response threshold of the event energy.Studies have shown that under the condition that the neutron energy threshold is 2.0 Me V and the gamma energy threshold generated by positron annihilation is 300.0 ke V,the（anti-）neutrino event detection efficiency is 5.39%.（3）Using two standardγsources 60Co,137Cs（point source）and Monte Carlo MCNP5program,the energy deposition spectra of 60Co and 137Cs twoγsources in the liquid scintillation detector were experimentally measured and simulated,the energy calibration of the 3×3 array neutrino liquid scintillator detector units has been finished;we carried out the debugging of the electronics plug-in and the construction of the acquisition system.In the future,it is devoted for further developing a experimental technology of high energy resolution,high detection efficiency and lower background rate.This work lays an important preliminary experimental foundation for the use of neutrinos to monitor the operation/shutdown of future new reactors or fast reactors at the China Institute of Atomic Energy.It is an important part of further promoting the application of neutrino beams towards nuclear reactor monitoring. |
