轻水堆关键焊接接头环境致裂机理与残余寿命预测方法

Because it is one of the key engineering problems affecting the long-term safe operation of nuclear power equipment that environmentally assisted cracking (EAC) of welded structure materials in light water reactors, the EAC behavior and mechanism and related factors in welded joints under the interactive effect of inhomogeneous materials, residual stress and water chemistry in the high temperature aqueous environmental of nuclear power plant will be investigated in the proposal, which is for obtaining prediction approach and accurate evaluation of EAC crack growing process and residual life of welded joints in light water reactor. The main study included: 1) The action of the micro mechanical parameters at the growing tip of EAC crack on the repeated cycle process will be investigated, which is from the oxide film rupture, to electrochemical anodic reaction, and to oxide film reform; 2) The prediction model of EAC growth rate and the related parameters of various austenite stainless steel and nickel base alloys in high temperature water environment will be analyzed; 3) Mechanism of release and redistribution of the welded residual stress induced by EAC growing and its effects on micro mechanical field at the tip of EAC will be investigated; 4) The predicting model of EAC growth rate of the critical welded joints in light water reactor under the interactive effect of residual stress and mechanical inhomogeneity will be established. Based on solving the scientific issues in the safe operation and regulatory of nuclear power plants, the cross action of the environment, materials and mechanical factors on the EAC in welded joints is considered and investigated, which provide a scientific basis for life design and the safety evaluation of the critical welded structure in light water reactor.

针对轻水堆焊接接头及材料环境致裂(EAC)影响核电设备长期安全运行这一关键工程问题，本项目拟通过探索核电高温水环境中焊接接头非均质材料、残余应力及水化学交互作用下的EAC行为机制及影响因素，研究建立轻水堆关键焊接接头EAC裂纹扩展历程和残余寿命的评价和预测方法。主要研究包括：1)裂尖微观力学参量在EAC裂尖氧化膜破裂、电化学阳极反应到氧化膜再生成反复循环过程中的作用；2)基于氧化膜破裂理论的高温水环境中不锈钢与镍基合金EAC扩展速率预测模型及主要参量解析；3) EAC裂纹扩展所引起的残余应力释放与再分布的机理及对裂尖微观力学场的影响；4)焊接接头材料力学性能不均匀性和残余应力交互作用下的轻水堆关键焊接接头EAC裂纹扩展历程预测模型。项目立足于解决核电站安全运行与监管中的科学问题，涉及到环境、材料及力学因素对焊接接头EAC的交互作用，为轻水堆关键焊接接头的全寿命设计及安全性评价提供科学依据。

轻水堆焊接接头及材料环境致裂(EAC)是影响核电设备长期安全运行的关键工程问题之一。本项目通过探索核电高温水环境中焊接接头非均质材料、残余应力及水化学交互作用下的EAC行为机制及影响因素，对轻水堆关键焊接接头EAC裂纹扩展历程和预期寿命的评价和预测方法进行了研究。完成的主要研究内容和研究结果如下：一是以氧化膜破裂理论为基础，深入分析了轻水堆压力容器及管道环境下核电焊接接头材料环境致裂(EAC)机理，并通过分析基于标准断裂试样的焊接接头相关材料EAC扩展速率实验数据，初步确定了高温水环境中核电焊接结构材料EAC裂纹扩展速率定量预测模型；二是以压水堆一回路安全端异种金属焊接接头为研究对象，从EAC裂纹扩展所引起的残余应力释放与再分布计算分析方法研究入手，深入研究了焊接残余应力和力学性能不均性交互作用下的EAC裂尖微观力学场的分析与计算方法，建立了具有复杂几何和力学条件的轻水堆实际焊接接头EAC裂纹前沿微观力学场的表征参量和获取方法；三是在充分考虑实际焊接接头EAC裂纹前沿与实验室标准EAC试样裂尖力学状况异同的的情况下，初步建立了轻水堆关键焊接接头EAC寿命预测与评价方法；四是为了填补基于直流电压降法的裂纹扩展实时监测仪的国内研制空白，搭建了基于直流电压降法的裂纹扩展实时监测仪开发平台，为早日开发出具有自主知识产权的基于直流电压降法的裂纹扩展实时监测仪奠定了基础。本项目的研究为搞清轻水堆关键焊接接头环境致裂机理，以及最终建立残余寿命定量预测与评价方法奠定了一定的基础。特别是通过本项目的研究，我们与以英国布鲁奈尔大学王彬教授为代表的国内外同行建立了比较深入的合作关系，申请获得了国家自然科学基金委与英国皇家学会的合作交流项目，并联合培养博士生2名。本项目的部分研究成果已发表在相关国际学术期刊和会议上，并得到国内外同行的关注和多次引用。

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