Investigating the effect of Zn addition to corrosion of Alloy 600 in water-cooled reactors

本博士项目的主要目的是了解喷锌在600合金焊接材料(一次水应力腐蚀裂纹)裂纹萌生和扩展中的作用。学生将使用布里斯托尔大学的高压灭菌器在压水堆温度和压力下进行短期水暴露，改变测试期间添加的锌的量。学生将测试一系列不同的热功能测试；使用和不使用H2以及使用或不使用锌。这项工作将研究热功能测试中注射锌的效果，然后是连续注射和间断注射。开始喷锌后，氧化物发生了怎样的变化？这将如何影响裂纹的萌生和扩展？学生将使用包括透射电子显微镜、聚焦离子束和X射线断层扫描在内的先进显微镜来了解氧化物结构如何随着锌添加量的增加而变化，并使用原子探针断层摄影术和二次离子质谱仪等技术来了解氧化物中的化学分离。一旦更好地理解了短期测试制度和机制，该项目将进行一项或多项长期测试，以了解锌添加如何影响SCC行为。以后的工作将研究600合金喷锌焊接材料的长期PWSCC阻力，尽可能接近压水堆一次回路的条件。

The main aim of this PhD project is to understand the role of Zn injection in crack initiation and propagation in alloy 600 weld material (Primary Water Stress Corrosion Cracking, PWSCC). The student will use autoclave facilities at the University of Bristol to do short-term exposures to water at PWR temperatures and pressures, varying the amount of Zn added during the test. The student will test a matrix of different hot functional tests; with and without H2 and with or without Zinc. This work will investigate the effect of zinc injection during the hot functional testing, followed by continuous injection and discontinued injection. How does the oxide change after Zn injection is initiated? How does this affect crack initiation and growth?The student will use advanced microscopy including transmission electron microscopy, focused ion beam and X-ray tomography to understand how the oxide structure varies with increasing Zn addition, and techniques such as atom probe tomography and secondary ion mass spectrometry to understand the chemical segregation within the oxide.Once the short-term testing regime and mechanisms are better understood, the project will perform one or more longer-term tests to understand how Zn addition affects SCC behaviour. Later work will to study the long-term PWSCC resistance of alloy 600 weld material with Zn injection, replicating the conditions of primary loop in a PWR as closely as possible.