Nuclear Future Volume 9 issue 1
Providing skilled graduates to the nuclear industry
M.J.D. Rushton, M.R. Wenman, R. Mella and P.A. Burr explain how materials modelling courses at Imperial College’s Centre for Nuclear Engineering are creating a pool of talented personnel for academia and industry
hub, and now comprises over 30 academic staff members and more than100 PhD students. Centre members work on topics as diverse as the effects of Chernobyl on thyroid cancer and thermal hydraulic modelling of fuel assemblies. In 2012 the Centre’s management took up permanent residence in the Department of Materials, and an official opening is on the agenda for this year. It is directed by Professors Robin Grimes and Bill Lee and focuses on providing industry with the very latest abilities in nuclear engineering research and producing graduates with industrially relevant skills. The Centre runs three undergraduate courses with a nuclear
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emphasis: MEng Materials, MEng Mechanical Engineering and MEng Chemical Engineering, all with Nuclear Engineering. Since 2010 a graduate programme providing an MSc in Nuclear Engineering has also been run. Each of these programmes provides about 35–40 MEng graduates and 10–20 MSc per year, with aspirations to grow based on demand. A strong emphasis is placed on materials modelling, with three
postdoctoral researchers and ten PhD students currently working on projects with industrial emphasis and sponsorship. The Centre also provides a course on Modelling for Nuclear Engineers taken by the MSc students. PhD projects range from the atomic scale – using electronic structure calculations by density functional theory (DFT) – to simulating full-size components such as fuel pins, using techniques such as the standard finite element method (FEM) complemented by more state-of-the art methods such as peridynamics. This research, as well as providing great value to the UK nuclear industry on specific projects, is also providing a pool of talented PhD and postdoctoral personnel for both academia and industry. These people are equipped, not only with prior nuclear knowledge, but also with skills in the most modern techniques of computer programming and materials modelling. They can then take these cutting-edge ideas and embed them into the companies they join. The benefit to industry is someone that can potentially bring a new way of tackling an old problem that can enhance either cost- effectiveness or nuclear safety. Some examples of the materials modelling work we do are described here.
AGR fuel performance modelling Since the year 2000 there have been several fuel failures potentially attributable to pellet-cladding interaction (PCI) in various advanced gas-cooled reactors (AGRs)1
. When radioactivity in the coolant gas indicates that fuel in the reactor may have failed, the operators have 44 Materials modelling at Imperial
he Centre for Nuclear Engineering at Imperial College London was created in 2006 to link the various nuclear research and teaching activities across the university into a coherent
to follow a procedure mandated by reactor safety cases that may involve reducing reactor power or shutting it down. The potential costs include: replacement for generation loss, non-optimum use of fuel and increased fuel disposal costs, as failed fuel cannot be disposed of by the normal route. Within the Centre efforts are being made to understand these kinds of failure; in particular we have developed a fuel performance code, with a strong focus on mechanistic basis, which uses the FEM2
. Solving for physical fields in FEM allows the dependence on
empirically determined material properties, inherent in traditional fuel performance codes, to slowly be replaced. Furthermore, by leveraging modern modelling techniques, predictions can be made for conditions where no experimental data exist. To this end, the fuel model has been built within the framework of a commercial FE package (ABAQUS)3
. This allows the creation of a new generation of fuel performance code based on an industrially trusted platform.
This research is providing a pool of talented personnel equipped, not only with prior nuclear knowledge, but also with skills in the most modern techniques of computer programming and materials modelling
With every new major development in the field of FE modelling being incorporated within ABAQUS, in a stable and verified manner, it is straightforward to incorporate these improvements into the fuel performance code. This attempt at standardisation removes duplicated development effort and its corresponding verification. An example of where this has been of benefit is shown in Figure 1, where the stresses caused by the sharp corners of two fuel fragments impinge on the cladding. By using the error-driven adaptive remeshing, introduced into ABAQUS, this detail was captured, whereas at a lower resolution it would have been lost and in fact an erroneous result would have been obtained. The fuel performance code includes advanced features such
as coupled temperature-displacement-diffusion and highly non- linear fuel cladding properties. Furthermore, fission gas release (parameterised from atomic-scale, first principles simulations), isotope inventory calculation, fission product diffusion and grain growth dynamics are all included in the model. Development of codes of this kind is time consuming, meaning that it is often prohibitive for industry to pursue such endeavours.
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