Investigation Of Proton Beam Window And Collimator Of High Energy Proton Beam Transport Line Of C-ADS

The global climate and environment deteriorated sharply in recent years, at the same time, the energy crisis in the world increases seriously. Meanwhile, the traditional nuclear power development is affected by many constraints, in this condition, the development of new clean energy has attracted attention in worldwide. As a kind of new generation clean nuclear power system, more and more attention has been given to the ADS (Accelerator Driven Sub-Critical System) at home and abroad. Relevant study and physical concept design of ADS has been carried out in many international research facilities. ADS project in China (C-ADS) had been included in the "973Plan" since1999and developed rapidly and has made key breakthrough in last decade. The high intensity and power accelerator of C-ADS is in physics design phase presently. The accelerator with proton beam energy of1.5GeV and power of15MW and the demonstration transmutation reactor with power>1GWt are plans to be built by2023.Compared with the domestic and foreign existing accelerator, the characteristics of the accelerator in C-ADS includes:higher power, higher reliability and the running time more than99%. More stringent requirements are imposed on physics design of the accelerator. C-ADS high energy proton beam transport line (HEBT) connected the linear accelerator and the transmutation reactor/waste beam box. The main function of the HEBT includes:transportation of the beam spot (on request of the target system and the transmutation reactor), monitor of the proton beam and beam collimation. Vacuum proton beam window (PBW) is the important component located at the HEBT terminus and used to isolate the accelerator vacuum and non-vacuum circumstance of the target system. The PBW is important in ensuring the vacuum environment of accelerator and the stable operation of the whole C-ADS system. When the high energy proton beam passing through the beam window, the interaction between the proton and the beam window materials will cause beam scattering and energy deposition. The proton beam will also induce radiation damage to the beam window. Beam scattering effect will bring a larger beam halo on the target surface and more power loss out of the target. The proton beam loss out the target will induce damage to the target vessel and increase the difficulty of shielding design of the target system. The beam energy deposition in the window can cause the temperature rising of the beam window and affect the mechanical properties of the beam window. The radiation damage will produce influence on the service life of the beam window. So the beam scattering effect, energy deposition and radiation damage are the most important factor in vacuum beam window design. Primary parameters of vacuum proton beam window of C-ADS are given through calculation. Collimator is another component of HEBT used to protect the magnet and other compnents of accelerator from radiation damage of backscattering neutrons emitted by the target. Primary simulation of collimator of HEBT of C-ADS-III is made.When the proton beam pass through the proton beam window, interaction between protons and proton beam window material will cause beam scattering, energy deposition and radiation damage of the window. A larger beam halo and power loss at the target will be induced by beam scattering. This will increase the performance reqirements of the target structure material and shielding design of the target system. Energy deposition of the beam will induce the temperature rise of the beam window and influent the mechanical properties of the window, so effective cooling system is needed in the beam window design. Property and lifetime of the beam window material will be effected by radiation damage. Therefore, beam scattering effect, energy deposition and cooling, radiation damage and mechanical property of the beam window are main factors. In present thesis, these factors are included in the calculations.Firstly, we summary the beam window design of existing accelerator system (mainly the spallation neutron source). According to the characterstics of the preliminary beam parameters of the C-ADS-Ⅰ, C-ADS-Ⅱ and C-ADS-Ⅲ, the improved multiple pipes vacuum proton beam window is studied thoroughly.We use Monte Carlo particle transport code FLUKA to calculate and analyze the beam scattering effect of the beam window with different parameters and materials. Material adoption and primary structures parameters of the proton beam window are given for different requirements of power loss control. DPA, production rate of gas and other residual nuclides, estimation of the lifetime of the proton beam window are given.Accordion to the energy deposition calculated by FLUKA, we use computational fluid dynamics software FLUENT to carry out the one-way fluid-solid coupling calculation of the beam window. Cooling condition and the temperature distribution of the beam window are obtained for C-ADS-Ⅰ, C-ADS-Ⅱ and C-ADS-Ⅲ.The large engineering technology simulation platform ANSYS Workbench is used to analysis the stress distribution of the beam window. The primary beam window design expected using in the C-ADS is given on basis of the comprehensive analysis of the simulation results.In C-ADS, the neutrons generated by high current proton beam incident to the target (liquid Pb-Bi) are neutron source driving the transmutation reactor, but back-scattering neutrons along adverse direction of the incident proton contributed by isotropic evaporation neutrons in the target will cause radiation damage of magnets and beam monitoring equipment and other components of HEBT. Beam collimator is equipped at the beam waist to protect the components of HEBT from the radiation damage induce by the back-scattering neutrons. The simplified model of the C-ADS-III HEBT and the target is constructed and the prompt and residual radiation fields are computed using FLUKA. The position and primary size of the collimator and its influence on radiation field in the vacuum beam pipe induce by back emission neutrons and magnet service lifetime is given.Summary of the limit of the present simulation and proposal of next design and implication of the proton beam window and collimator are made.