Wed - P Mummery
Transcript of Wed - P Mummery
Graphite Research
• Why? – Core of AGRs; irradiation damage during operation leads to weight
loss, change in dimensions & properties, stress and cracking – Life-limiting component of reactors
• See recent (BBC, Times) and upcoming news items
• Current research activity – Funded by industry (EDF), regulator (ONR), EPSRC, TSB, EU – Plant life extension (PLEX) and future systems
• Fundamentals of irradiation damage • Irradiation creep (mitigating stress development) • Strength and fracture • Waste treatment
Irradiation damage • FunGraph (EPSRC)
– Fundamentals of Current and Future Uses of Nuclear Graphite – Consortium of Huddersfield, Leeds, Manchester, Nottingham,
Salford, Surrey universities
• Mechanistic understanding of irradiation effects – Ab initio; kinetic Monte Carlo; dislocation models of defects – Electron microscopy
• Model (thick graphene) and irradiated material • Evolution of damage in situ
– Neutron and synchrotron x-ray studies • Structural changes; crack and void closure; effects of loading
Range of model and irradiated materials
FunGraph mee,ng 29th – 31st October 2012 Huddersfield
Neutron irradiated samples • Manchester’s samples
• Oldbury (PGA 5dpa) • BEPO channel 16 (PGA)
• 80 kV
5 nm5 nm5 nm5 nm
5 nm
5 nm5 nm
5 nm
FFT filtered
Oldbury
Oldbury
Oldbury
Microstructure: Irradiated graphite Irradiated AGR Near surface
120E20 EDND Irradiated AGR Near surface
120E20 EDND
Imaged at Central Labs, NNL
Irradiation Creep
• TSB-funded, EDF-lead – Influence of Irradiation Creep on Plant Life Optimisation – Manchester and Surrey universities – NRG, Fraser-Nash, AMEC
• Mechanistic understanding of irradiation creep – Defect structures and mobility under load
• Configuration; energies of formation – Microstructural changes
• Role of interfaces/boundaries – Stress relaxation
Unbound and bound configurations of the V2,2bb interlayer di-vacancy.
Microstructure-based FE models for irradiation creep
Strength and Fracture
• QUBE (EPSRC) – Oxford, Bristol and Manchester universities
Microstructure-Sensitive Component-Scale Fracture Modelling
Department of Materials University of Oxford Parks Road Oxford OX1 3PH UK tel +44 1865 273700 fax +44 1865 273789 [email protected] www.materials.ox.ac.uk
21 February 2013 Prof. Chris R. M. Grovenor Head of Department [email protected] +44 1865 273737
Re: Dr Saucedo-Mora; Applicant for a Junior Research Fellowship
To whom it may concern
Dr Saucedo-Mora joined the department in November 2012, as a postdoctoral researcher on a 3-year EPSRC funded research project "QUasi-Brittle fracture: a 3D Experimentally-validated approach". He is a self-motiviated scientist, who has fitted well into the Oxford research group, and is clearly on the track to a long-term academic career. His supervisor, Prof. James Marrow, fully supports his application for a Junior Research Fellowship. As head of department, I am happy to confirm that Materials will continue to provide Dr Saucedo-Mora with necessary laboratory infrastructure to support his work if is awarded a Junior Research Fellowship. Yours sincerely,
Prof. Chris Grovenor
6 Author name / Procedia Materials Science 00 (2014) 000–000
Fig. 5. From top to bottom the fracture pattern of the different models in the non linearity initiation, the peak load and the collapse. From left to right the FEM with 145 elements, FEM with 27950 elements and CAFE model with 5 elements, 4702 IPD and 212992 cells.
Acknowledgements
This work was carried out with the support of the UK EPSRC project “QUBE: Quasi-Brittle fracture: a 3D Experimentally-validated approach” (EP/J019992/1).
References
Arroyo, M., Ortiz, M., 2006. Local maximum-entropy approximation schemes: a seamless bridge between finite elements and meshfree methods. International Journal for Numerical Methods 65, 2167-2202.
Saucedo Mora, L., 2012. Meshfree methods applied to tensile fracture and compressive damage in quasi-brittle materials. Ph. D. Thesis, University of Castilla-La Mancha, Spain.
Saucedo Mora, L., Marrow, T. J., 2013a. 3D cellular automata finite element method to model quasi-brittle fracture. Twelfth Intentional Conference on Engineering Structural Integrity Assessment Conference proceedings, (ESIA12), Manchester, UK
Saucedo Mora, L., Mostafavi, M., Khoshkhou, D., Reinhard, C., Atwood, R., Zhao, S., Connolly, B., Marrow, T.J. 2013b. 3D cellular automata finite element (CAFE) modelling and experimental observation of damage in quasi-brittle nuclear materials: Indentation of a SiC-SiCfibre
ceramic matrix composite. Third International Workshop on Structural Materials for Innovative Nuclear Systems (SMINS-3), October 2013, Idaho Falls, USA
Shterenlikht, A., Howards, I. C., 2006. The CAFE model of fracture: application to a TMCR steel. Journal of Fatigue and Fracture of Engineering Materials and Structures 29, 770-787
Example: Fracture energy
Luis Saucedo Mora
Cellular FE model: Meshfree linking of microstructure-dependent heterogeneous model and coarse FE component model
FE (145 elements)
FE (27950 elements)
Cellular FE (5 elements, 212992 cells) EQUIVALENT COMPUTATIONAL TIME Luis Saucedo Mora
CA Model
Cellular FE Model
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The CA model may be used as microstructure dependent input, providing properties of coarser “cells” in the Cellular FE model
Q U B E
AGR BCN
• HSE(NII) established the AGR Brick Cracking Network (AGR BCN) in 2008 to: – develop an improved understanding of cracking observed in
AGR graphite bricks and develop a predic,ve capability – secure, maintain and develop sources of independent advice – ensure NII is well informed on key technical issues and
therefore able to make sound regulatory decisions • AGR BCN is a tripar,te programme
– The University of Birmingham, The University of Manchester, Health & Safety Laboratory
• Two aspects under inves,ga,on – crack driving force parameters (HSL & UoM) – materials resistance parameters (UoB & HSL)
Introduction • Emulator approach
– applied successfully for dimensional change behaviour • inspection data • constitutive equations
– calibrated dimensional changes
• inert similar to baseline
• reduced effect of oxidation
Modelling approach
Calibrated curves
Metric
Design matrix
Emulator Calibrated parameters
Simulator
Calibration data
Strength and Fracture
• Two TSB projects; both EDF-lead – Fracture of Graphite Fuel Bricks
• University of Manchester, EDF NG, EDF R&D
• Modelling crack propagation in fuel bricks – XFEM, energy release rates – Comparison with experiment
• Statistical models of core normal and seismic behaviour • Mimic irradiation damage by bromination
– No external driving forces for crack growth (cf in service) – Criteria for crack initiation as function of local microstructure
Strength and Fracture
Tomographic image of brominated grapite
Comparison of crack paths with prediction
Strength and Fracture
– Influence of Creep and Geometry on Strength of Irradiated Graphite Components
• University of Manchester, EDF NG
• Valid fracture data on irradiated material – Large trepanned specimens at reactor end–of-life
• Ex-Oldbury – effects of notch geometries on properties
• Crack initiation and propagation • Comparison with AGR installed sets • Thermal creep as basis for irradiation creep • Effects of creep on mechanical/fracture behaviour