快中子增殖反应堆燃料元件包壳材料的晶界工程技术应用展望

Feasibility and benefits of applying grain boundary engineering to fuel cladding materials of liquid metal cooled fast breeder reactor

针对钠冷快中子增殖反应堆(简称快堆)燃料元件包壳材料316以及15-15Ti奥氏体不锈钢,讨论了通过晶界工程(grain boundary engineering,GBE)技术进一步提高材料抗辐照肿胀以及抗蠕变性能的可行性.通过GBE技术能够大幅增加材料中与孪晶相关的低Σ重合位置点阵(coincidence site lattice,CSL)晶界比例.快堆燃料元件包壳在固溶退火处理后还要经过20%左右的冷加工变形,目的是在显微组织中引入大量位错,吸收由辐照产生的点缺陷,并增加吸收裂变产物的陷阱.如果在这样的冷加工变形前大幅提高材料的低ΣCSL晶界比例,使冷加工变形时的位错滑移在具有特殊取向关系的晶粒间的传播以及位错在特殊结构晶界处的堆积排列发生变化,那么就有可能使冷加工后位错的分布状态有利于吸收更多的由辐照产生的点缺陷,提高材料抗辐照肿胀的能力.

Feasibility and benefits of applying grain boundary engineering （GBE） to the fuel cladding material 316 or 15-15Ti austenitic stainless steels of sodium-cooled-fast- reactor for reducing void swelling and creep is discussed. GBE can be used to greatly enhance the proportion of low Z coincidence site lattice （CSL） grain boundaries that are mainly of annealing twins and its variants. The cladding tubes are normally subjected to 20% cold working after solution annealing before using, which by virtue of providing a dislocation strewn matrix microstructure, contributes to the annihilations of irradiation- induced point defects. If the proportion of low ECSL grain boundaries are greatly enhanced prior to the cold working, transfer of slip across the special-structured grain boundaries or pile-up against them during deformation may alter the distribution of dislocations of the microstructure, which may accommodate more defects generated during being irradiated.