About the Project
This PhD, part of the EPSRC Centre for Doctoral Training in "Materials for Demanding Environments" [M4DE CDT], is sponsored by the National Nuclear Laboratory and will commence October 2018.
Background
Corrosion has been a leading cause of failure in structural materials in most industrial applications for hundreds of years. In the harsh environment of the coolant circuits of Pressurised Water Reactors (PWRs), corrosion of structural materials is inevitable, despite using some of the most corrosion-resistant alloys which are economically feasible. However, it is not in general the structural components‘weight loss’ to corrosion which is of concern, the thickness of alloy lost to corrosion over the course of a plant’s life is typically of the order of a few microns, the concern lies in the behaviour and fate of soluble and particulate corrosion products. These particulates accumulate in parts of the primary circuit, creating deposits which can cause problems, including reduced heat transfer efficiency, and high ex-core radiation fields. Crud, the technical term for these deposits, can occur on fuel assemblies, and their porous structure enables corrosive species and neutron poisons from the coolant (Li and B) to accumulate, potentially causing localized corrosion and uneven core wide power distribution in the reactor. The former effect, known as Crud Induced Localised Corrosion (CILC) can cause fuel failure and release of fission products to the coolant in the most extreme cases. Safety is of great importance to the nuclear industry and specific to this programme is the desire to reduce the radioactive contamination field within plant. While corrosion control is key to the structural integrity of plant, incorporation of radioactive species in corrosion deposits result in an increased collective radiation exposure for workers and limit plant efficiency.
Much research has been conducted over the years in order to better understand the mechanisms by which crud is transported through the reactor primary coolant circuit. Complex whole plant computer models have been developed, such as BOA, to try to take into account all the relevant processes. These processes include release and deposition of particulate material, dissolution of particulate, release and precipitation of soluble species. These can occur in the bulk coolant, on surfaces, in regions of boiling and non-boiling and where significant temperature variations exist. Models of ever-increasing sophistication are now used as a tool for predicting the conditions under which the most serious problems will occur, so that these can be avoided or mitigated, through control of coolant chemistry and other means. Models use data and qualitative findings from experimental and theoretical research regarding processes such as corrosion, particle release and deposition, and metal oxide solubility. The solubility of the oxides which make up crud is a key factor in describing its behaviour in the PWR primary circuit.
Project Outline
There is significant discrepancy between literature solubility data regarding magnetite and nickel ferrite in hydrothermal solutions of pH25C 9 or 10 and above. This study aims to investigate the benefits and limitations of traditional solubility measuring techniques and compare them to emerging techniques such as those using x-ray sources for imaging.
In conducting this investigation the student will be able to use the world-class characterisation facilities within the Henry Royce Institute at the University of Manchester. Specific to this project will be the use of the x-ray imaging/tomography instruments within the Henry Moseley X-ray Imaging Facility (HMXIF). Specific to the HMXIF Facility the student will develop bespoke in situ rigs to better quantify solubility and dissolution rate of several oxides particles over a range of temperatures and pH. The data from these experiments will be compared with data obtained by the student using a more traditional sampling protocol utilising a once-through autoclave system.
The student will also be able to utilise the University of Manchester’s impressive facilities which include suites of the latest electron microscopes and analytical equipment, including in situ FTIR, nano-SIMS, and NAP-XPS, to develop mechanistic understanding of the solubility process.
Funding Notes
Funding covers tuition fees and an annual maintenance payment of £17,000, tax free.
Students with a first class/2.1 degree (or equivalent) in Engineering, Materials Science, Metallurgy, Physics, Chemistry or another aligned science or engineering subject are encouraged to apply. Applications will be reviewed as they are received until a candidate is selected; therefore candidates are encouraged to apply early.
Funding is only available for UK / EU candidates.
References
About the NNL
The UK’s National Nuclear Laboratory provides the experts and technologies to ensure the UK nuclear industry operates safely and cost-effectively today and for the future. NNL seeks to deliver the right amount of innovation to meet our customers’ needs. This can range from simply drilling a hole to analyse underground wastes with our integrated microdrilling technology to the development of state-of-the-art power systems for spacecraft, based on radioactive materials.
NNL offers products and technical services across the whole range of nuclear industry sectors including expertise in Measurement and Analysis, Waste Management Technology, Safety Management, Asset Care, Waste Residues and Processes, Spent Fuel Technology, Security, Environmental Services, and Fuel and Radioisotope Technology.
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