Study On The Characteristics Of The Accelerator Neutron Source Based On ~9Be(d,n) And ~9Be(p,n) Reaction

Controlled nuclear fusion is widely recognized as one of the best choices for solving the future energy crisis.The critical factor in the establishment of fusion reactor is the research on the defects effect in the structural materials under strong radiation field.However,due to the lack of high-flux fast neutrons in laboratories,researches about the defects in fusion reactor materials brought by neutron irradiation has rarely been conducted.The Institute of Modern Physics is propose the compact material irradiation facility（CMIF）in the cooperation with other research groups.In this facility,a high-energy deuteron beam from a superconducting linear accelerator would bombard a flowing beryllium metal granular target,and then fast neutrons with high flux would be generated in the ⁹Be（d,n）reaction.This could simulate the neutron irradiation environment in fusion reactors and thus make it available to carry out the experiments about the structural materials.Based on the requirements of the CMIF project,the simulation as well as theoretical calculations on the neutronics features in the ⁹Be（d,n）were performed in this thesis.Besides the neutron radiation filed,the Monte Carlo simulation about the radiation damage and radioactivity in the samples,as well as the structural materials,were also shown.It could provide foundational data for the design of CMIF.Furthermore,as another potential fast neutron source,neutron produced by ⁹Be（p,n）had been measured by activation methods in this work.It’s not only could study the neutronics performance of the ⁹Be（p,n）,but also could make preparations for the experiments on ⁹Be（d,n）.The main contents are listed as following:1)Aimed at the neutron source produced in the thick beryllium target,the Multi-Layer Method was developed to approximately calculate the neutron spectrums,angular distribution and the neutron yield in the ⁹Be（d,n）reaction with a beam energy range from 0.5 Me V to 102 MeV.In the calculations,the double differential cross section of neutron emissions was obtained the combination of TALYS program.The calculation was compared with the existed experimental data.It was found that the calculation was in good agreement with experiment in the low incident energy area（<=25 MeV）,while there are big differences in the rest energy area（>25 MeV）.A well pronounced bell-like shape was appeared nearly one half of the incident deuteron energy in the neutron energy spectrum and it became more obvious in the higher energy area.These differences mainly came from the elastic break-up and proton stripping reaction of the deuteron,which meant the physical models in the TALYS didn’t completely describe these reaction channels mentioned above and should be modified further.2)There are a lot of reaction channels,such as elastic break-up,stripping,pre-equilibrium and compound as well as multiple pre-equilibrium,in the statistical model.Therefore,the statistical model could describe the elastic break-up and stripping channel in the high energy area.It was applied to recalculate the differential cross section in the energy range of（25MeV¹02MeV）.Additionally,the new results of neutron spectrums,angular distribution and the neutron yield were compared with the experiment again.The comparison showed that the results combined with the TALYS（0.5MeV²5 MeV）and the statistical model（26MeV¹02 MeV）could fit well with the experimental data.3)The neutronics characteristics in the reaction of a 50MeV deuteron beam with a ⁹Be granular target system（⁹Be（d,n））was simulated by a Monte Carlo program MCNPX.The multiplication factor of neutrons produced in the beryllium target was calculated to be 1.046.Moreover,the radiation damage in the back-plate of the skewed slot which belongs to the target system was also obtained.If the beam spot size is 0.5cm×1.0cm,the maximum DPA could be up to 100 dpa/fpy after a 5000-hour run at full-power.Assume that the maximum acceptable DPA value of a 316L back-plate is about 10dpa,then it must be replaced after a continuous irradiation of 500 hours.After one continuous irradiation,with the simulation of a Monte Carlo code PHITS,the maximum radioactivity and the dose around the back-plate could peak at the value of 2.5×10¹²Bq and 3.8×10⁵μSv/h respectively.After a cooling of about 10 years,the activity only reduced to10¹00 Bq while the dose could drop to 1.0μSv/h.Therefore,it was necessary to replace the back-plate and make other subsequent operations in a hot cell.The damage of the irradiated iron-based sample which placed after the back-plate was also analyzed at a full-power run.4)The neutron activation experiment of ⁹Be（p,n）was carried out and analyzed.The proton beam has an energy of 20.34 MeV and an intensity of 0.91uA.The target materials are still beryllium grains.The gamma spectrum of each activated samples placed in four different direction angles were recorded by HPGe Gamma detectors.Then the reaction rates of the activated products,as well as the radioactivities,at the end time of irradiation were deduced.They agreed well with the simulation calculations from MCNPX combined with a burn-up program ORIGEN.Hereafter,fine energy spectrums of produced neutrons in four different direction angles were calculated by a spectrum analysis code SAND-II.They were verified by a comparison with wider energy spectrums with 7-group,which came from the calculation of MCNPX with both single group cross-section and the reaction rates measured in this experiment.At last,we got the integrated total neutron flux was 1.64×10¹⁴n/（s mA）and the neutron yield was 0.026 n/p.