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

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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.