Lead supervisor: Dr Tomas Martin

This PhD project funded by EDF Energy and the UKRI iCase scheme, will use advanced microscopy to understand the changes in microstructure of the steel reactor pressure vessel (RPV) at Sizewell B (SZB) under long-term thermal ageing in-service. SZB is a Light Water Reactor with aspirations to generate low carbon electricity beyond 2050. SZB uses surveillance programmes to track material properties of the RPV. This consists two schemes, one monitoring the effect of high temperature and neutron irradiation whilst the other monitors high temperature effects in isolation. Each scheme consists of capsules containing test specimens which are periodically extracted, tested and analysed to determine whether properties remain within acceptable limits. Detrimental changes in material properties have been observed in both schemes. Whilst property changes are within current safe operation limits, they may challenge aspirations beyond the current planned end of generation (2035).

The project will use a combination of advanced microscopy techniques to investigate the microstructure of SZB RPV steel at different thermal ageing and stress conditions. The project will aim to identify the following objectives:

•          What mechanism(s) give rise to the observed embrittlement in thermally aged low alloy steel used for the SZB RPV?

•          What kinetics do identified mechanisms display? What are the associated implications for other low alloy primary circuit materials that operate at higher temperatures than the RPV?

•          How does pre-stress affect the ageing process and microstructure, and its associated impact on mechanical properties?

•          If time allows, how does the thermally aged material differ from specimens which have also incurred irradiation effects?

The student will undertake advanced microstructural characterisation at the University of Bristol, in particular scanning and transmission electron microscopy, focused ion beam microscopy and atom probe tomography. The student will be trained in the use of these techniques, and learn the skills required to analyse the resulting data. In addition, the student will be trained in the theoretical background and modelling of thermal ageing in low-alloy steels, and the underlying engineering and scientific principals behind water-cooled nuclear reactors.

As part of the project, the student will be expected to undertake a three month placement with EDF at its central facilities, with potential to visit the SZB site and learn more about the operation of a nuclear reactor.

This project is fully funded under the UKRI iCase scheme, with UK fees covered. The student will receive a £18,622 stipend + £1500 top-up. Note that international fees are not covered. 

Please make an online application for this project at http://www.bris.ac.uk/pg-howtoapply. Please select Physics PhD on the Programme Choice page.

This PhD project funded by Sellafield and the UKRI iCase scheme will use advanced microscopy to characterise the corrosion behaviour of 20-25Nb steels used in advanced gas cooled reactor (AGR) fuel cladding during long-term storage. The student would be based in the Interface Analysis Centre (IAC) at the University of Bristol, within the Materials Degradation research group of Dr Tomas Martin (tomas.martin@bristol.ac.uk)

Following its lifetime in-reactor, AGR fuel is discharged and stored pending a decision on the disposition route. Presently, Sellafield store AGR fuel within a caustic dosed pond until future routes, such as geological disposal, may be carried out. During storage, the 20-25Nb steel AGR cladding provides the primary containment for the radioactivity within the fuel. Intergranular attack (IGA) of the fuel cladding does not occur whilst in-reactor as it is too hot and dry, however, during storage within aqueous environments IGA may occur if chromium depletion due to irradiation and/or thermal annealing becomes severe enough. This can lead to intergranular stress corrosion cracking (IGSCC) and eventual cracking of the clad material.

The aim of the proposed work is to both characterise AGR fuel cladding to support long term storage of AGR fuel, as well as to evaluate the suitability of a thermally sensitised proxy material (such as 304 steel) for the study of corrosion mechanisms and behaviours. The project would build on recent work that has utilised the power of the high-speed atomic force microscope (HS-AFM) developed at Bristol IAC to observe the evolution of stress corrosion cracking of steel alloys in real time. SCC observations will be performed by HS-AFM at the University of Bristol on proxy material and irradiated clad. This will allow us to compare the two materials corrosion behaviour in real-time in-situ observations, to better predict SCC behaviour,

We will also compare irradiated ex-service AGR 20-25Nb steel cladding samples to thermally sensitised proxy samples using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques including electron backscatter diffraction (EBSD) and energy-dispersive X-ray spectroscopy (EDS). The project will also take advantage of the newly funded plasma focused ion beam (PFIB) at Bristol to characterise crystallography and chemistry in 3D.

The candidate should have an undergraduate degree in materials science, physics, chemistry, engineering or an equivalent discipline. The candidate should have an enthusiasm for nuclear materials and materials science, and be comfortable with both computational modelling and experimental work. It would be beneficial for the student to have an understanding of nuclear energy, the microstructure of metals and/or electron microscopy, but all training in these techniques will be provided.

This project is fully funded under the UKRI iCase scheme, with UK fees covered. The student will receive a £18,622 stipend + £1500 top-up. Note that international fees are not covered.

Please make an online application for this project at http://www.bris.ac.uk/pg-howtoapply. 

Characterization of Ceramic-matrix Composites under Extreme Conditions

Applications are invited for a PhD project in the Experimental Mechanics of Advanced Materials Group (EMAM) at the School of Physics, University of Bristol to contribute to ceramics research. This studentship is fully funded for 3.5 years for home students according to the UKRI 2021/22 standard (support for tuition fees and a stipend of £15,609 per year).

Ceramic-Matrix Composites (CMCs) is considered to be one of the prime structural materials to replace metals for high temperature applications such as accident tolerant fuel cladding in nuclear reactor core (post Japanese Fukushima accident) or in an aerospace jet engine. However, there is still a lack of understanding in the failure modes of this class of ceramic-like materials under extreme conditions, for example, at high temperature and post neutron radiation. In this project, you will study the damage tolerance of a range of CMCs with novel designs provided by industrial collaborators in both nuclear and aerospace areas (e.g., Rolls Royce and US Westinghouse).

You will use synchrotron X-ray computed tomography, X-ray/neutron diffraction, Raman spectroscopy and micro-mechanical testing to acquire novel insight in the microstructure, stress-strain behaviour, residual stress evolution and defect development in these materials change with processing parameters and/or neutron irradiation. Ultimately you will develop a microstructure-based, multiple length-scale characterisation for these materials during your PhD.

Excellent team working skills are essential in this project as you will be working with other PhDs and Postdocs in the group on data analysis, collaboration on large-scale experiments (e.g., synchrotron facilities) in the UK, EU and USA, and you will be interacting directly with external industrial partners and deliver milestones in a timely manner. You should have a first or upper second-class (or equivalent) undergraduate degree in Materials, Physics, Chemistry or Engineering and the enthusiasm in ceramics.

This project will be supervised by Dr. Dong (Lilly) Liu and a second supervisor in Bristol, plus an industrial supervisor.

Please submit your online application through Bristol formal online admission system and email the reference number to Dr Dong (Lilly) Liu: Dong.Liu@bristol.ac.uk for a speedy response. 

If you have informal enquiries during the process please also contact: Dr Dong (Lilly) Liu: Dong.Liu@bristol.ac.uk. Please visit the group website for more information. 

Deadline for the applications is 21 March 2021.

Anticipated start date for this PhD project is late September 2021.

If you are interested in finding out more about this project or wish to discuss applying, please contact Dr Neil Fox neil.fox@bristol.ac.uk

Isotopic, Doped Diamond Materials as a Plasma-facing Material for Fusion Power 

Nuclear fusion will make a significant contribution to the world’s high energy, low emission demands from the middle of the next decade. Recent announcements of over £300M from UK government to fund the Tritium handling facility H3AT and the Spherical Tokamak for Energy Production programme, both based at the UKAEA’s Culham site underline the heightened level of activity being directed towards delivering fusion power to the national grid. In terms of energy production, even experimental fusion facilities are nearing break even, and concept designs for energy producing reactors are maturing worldwide. To improve upon this key parameter of energy gain, many factors need to be addressed, one of these being the fusion reactor layout and the structural materials used for the main components. To achieve successful commercialisation the cost of energy production must be minimised, here again materials are the biggest risk factor. Reactor materials also carry out the important job of ensuring that the fusion plasma is safely confined. The inner most wall in the reactor is known as the Plasma-facing Material (PfM) and must be designed to withstand plasma strikes and act as a heat sink for the intense radiation produced during fusion. Factors such as contamination. durability, thermal and electrical conductivity must be taken into consideration when selecting a PfM. Materials such as tungsten, beryllium and carbon-graphite materials have been used up until this point. Other areas where advanced material are required are the divertor and the breeder blankets. These are both harsh environments requiring materials with excellent thermal properties. 

This research project aims to evaluate the use of isotopically pure, single crystal and polycrystalline diamond Schottky structures as a PFM. High quality diamond structures will be synthesised by chemical vapour deposition in the Bristol Diamond Laboratory, and their physical and electrical properties will be characterised using material analysis facilities at Bristol and the Materials Research Facility at Culham. The diamond structures will be infused with hydrogenic atoms by high temperature, high pressure processes conducted at Bristol and at Culham. The diamond PFM structures will be evaluated experimentally by neutron and H,D,T irradiations to simulate PFM operation using facilities at Culham and elsewhere. To support experimental work, model calculations using LAMPS and MCNP will be conducted in collaboration with UKAEA personnel. 

This studentship is co-funded by EUROFusion and EPSRC’s Doctoral Training Partnership, Industrial and International Leverage Fund 2020/21 

If you are interested in finding out more about this project or wish to discuss applying, please contact Dr Dong (Lilly) Liu dong.liu@bristol.ac.uk

Irradiation Creep Induced Nano-/Microstructure and Property Changes in Nuclear Graphite

Nuclear graphite has been employed as a moderator and structural components in more than 100 nuclear reactors worldwide and they are also projected to use in new Generation IV high-temperature reactors (HTRs). Irradiation-induced creep, among one of the three most important properties of graphite under irradiation, has the least amount of experimental data due to its extremely complex and time-consuming requirements for irradiation tests. So far there are only irradiation creep data on three types of graphite grades: German ATR-2E (up to 200x10²⁰ n·cm²), UK PGA and UK Gilsocarbon (up to 60x10²⁰ n·cm²). In this project, the PhD student will have access to the precious neutron irradiated crept Gislocarbon graphite samples (irradiated in the 5-year ACCENT project and have extensive bulk PIE examination data available) to understand the irradiation creep-induced micro-/nano-structural changes before turnaround, to support the use of new graphites in HTRs internationally.

The PhD student will work closely with a Postdoc and another PhD student funded by NNL for a quick start of the project. This project is primarily experimental-based but the PhD student will have access to the NNL polycrystalline model to validate the measured results. Large-scale experiments using synchrotron diffraction and tomography at national labs (e.g., the UK Rutherford Appleton Laboratory and the US Lawrence Berkeley National Laboratory) are essential for this PhD. Candidates with dedication and passion for nuclear materials are of interest.

This project provides full funding for home students (UK NNL and Nuclear Energy Futures CDT).