辐照作用下铍在动态EDM-1流体中的冲刷腐蚀性能及机械性能研究

Beryllium is one of the most important material in particle physics and nuclear physics experiments, which is used as the material of particle collision tube—beam pipe in the operational Beijing Electron and Positron Collider (BEPC Ⅱ)/ Beijing Spectrometer Ⅲ (BES Ⅲ) and Circular Electron Positron Collider (CEPC) being planned to build up. High-speed particles produce large amounts of γ and neutron irradiation and heat load on the beam pipe. The beam pipe must be cooled by the scouring fluid to keep the temperature stable for BES Ⅲ detecting particles, which will induce fluid erosion on the beam pipe. The erosion-corrosion properties and mechanical properties of beryllium in scouring fluid under the effect of irradiation are not known yet. The project aims to study the change of erosion-corrosion properties and mechanical strength and the microcosmic mechanism of beryllium in No.1 electrical discharge machining oil (EDM-1) under the effect of γ and neutron irradiation. The change rules of erosion-corrosion properties and mechanical strength of beryllium in EDM-1 under irradiation will be presented, and a theoretical system for erosion-corrosion and a theoretical model of mechanical strength for beryllium in EDM-1 under irradiation will be established. The microcosmic mechanism causing erosion-corrosion properties and mechanical strength of beryllium will be revealed, and the reaction mechanism theory of internal structure of beryllium under irradiation will be built. The research results of the project will provide an important security for the normal particle detection of BES Ⅲ, construction of CEPC and operation of beryllium component in particle physics and nuclear physics experiments, and offer a theoretical and technological support for developing and manufacturing beryllium with corrosion protection and high mechanical strength in radiation environment.

铍是粒子物理和核物理实验中的重要材料，我国现运行北京正负电子对撞机（BEPCⅡ）/北京谱仪（BESⅢ）和正谋划建设的环形正负电子对撞机（CEPC）都将铍作为粒子对撞管——束流管的制作材料。高速运行粒子对束流管产生大量γ和中子辐照及热负荷，须有流体介质对其冲刷冷却，目前辐照作用下铍在动态流体中的冲刷腐蚀性能及机械性能国内外鲜有研究，还不得而知。本项目拟在γ和中子辐照作用下对铍在动态一号电火花加工油（EDM-1）中的冲刷腐蚀性能及机械性能进行研究，给出辐照作用下铍在动态EDM-1中的冲刷腐蚀性能及机械性能变化规律，建立辐照作用下铍在EDM-1中的冲刷腐蚀理论和机械强度理论模型；揭示引起铍性能变迁的微观机理，构建辐照作用下铍内部结构反应机理理论构架。本项目为BESⅢ粒子探测、CEPC建设以及铍构件在核物理实验中的应用提供安全支撑，为适用于辐照环境的抗腐蚀和高强度铍的设计和制备奠定理论和技术基础。

铍因其密度低、强度高、热性能好、中子吸收截面小等优点成为我国北京正负电子对撞机（BEPCII）中的束流管的主要材料。BEPCⅡ运行过程中，束流管在受到大量的γ和中子辐照的同时，还会受到冷却介质一号电火花加工油（EDM-1）的冲刷腐蚀。在此条件下，铍的冲刷腐蚀性能和机械性能会发生变迁，从而影响设备的正常运行。本项目针对辐照作用下铍在EDM-1流体中的冲刷腐蚀性能和机械性能开展研究，主要内容包括：.（1）辐照作用下铍在EDM-1中冲刷腐蚀性能研究。设计研制管流式冲刷腐蚀实验台，开展辐照后冲刷腐蚀试验，通过失重法和表面微观形貌表征，发现铍腐蚀过程中机械冲刷和化学腐蚀交替起主导作用，造成试样质量和表面微观结构发生相应变化；辐照对铍的腐蚀具有促进作用，且γ辐照单独作用强于中子和γ辐照共同作用、辐照剂量越大促进作用越明显。.（2）辐照与腐蚀作用下铍机械性能研究。通过拉伸性能试验和压缩性能试验，发现辐照和冲刷腐蚀都会降低铍的抗拉强度、杨氏模量、延展率等机械性能，且随着辐照剂量的增大和冲刷时间的延长，降低作用愈加明显，而铍的的抗压强度受试样表面粗糙度、腐蚀产物、辐照剂量等多种因素的影响呈复杂变化；引入辐照剂量参量，建立了铍Z-A改进本构模型，定量表达γ辐照剂量对铍应力应变间关系的影响。.（3）辐照作用下铍腐蚀性能与机械性能变迁的微观机理研究。通过微观表征和数值模拟，揭示了腐蚀过程中铍表面蚀孔的孕育过程，发现铍的结构缺陷是点蚀核形成的关键因素，而EDM-1中的S及其氧化物对铍的腐蚀起到了促进作用；辐照会在铍内产生大量缺陷，降低铍机械性能的同时促进铍的腐蚀，且辐照能量越大产生缺陷越多，同剂量下γ辐照产生的缺陷最多，中子-γ综合辐照次之，中子辐照最少。.本项目为现有BEPCII的正常运行和未来环形正负电子对撞机（CEPC）的安全建设提供保障，并为具有抗辐照性能铍的研发和铍构件在高能物理、核物理等辐照环境中的应用提供理论和技术支撑。