Postgraduate Research Conference 2009
The Prize Winners
PRESENTATION: Simulation and Modelling of Damage Mechanisms in Nuclear Graphite
student: Lewis Luyken
supervisor: Dr Abbie N Jones, Prof Barry J Marsden and Dr James Marrow
Abstract
The VHTR is a leading contender of the Generation IV nuclear reactors. This design requires
graphite components that will operate efficiently at higher temperatures and over a longer core
life than designs from previous generations. This will require an improved fundamental
understanding of the graphite aging processes.
By way of an introduction to the subject area this presentation opens giving an overview of the methods used to characterise of nuclear graphites. Common structural features of polycrystalline graphites will be described and displayed at increasing magnifications from the micro scale to the nano scale. The mechanism of damage by fast neutron irradiation shall be introduced and the effect it has on structural and mechanical properties.
The main thrust of this presentation is to present methods for simulating and modelling the damage produced by fast neutron irradiation. The first method simulates irradiation damage through the intercalation of bromine into graphite crystal structrure. [1-4]. Resulting strain curves will be presented. This section shall finish describing future experiments using this method.
The second method develops work into finite element modelling of irradiation damage on the microstructure of graphite[5, 6]. A model has been made of crystals at the nanoscale and used to show the effect of load within graphite on the co-efficient of thermal expansion.[7]
 Figure 1. Anisotropic Polycrystaline Graphite |
 Figure 2. Isotropic Nuclear Graphite
|
 Figure 3. Bromination Rig |
 Figure 4. Strain Curves Due to Bromination
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 Figure 5. FE Model of Graphite Crystallites |
 Figure 6. Effect of Load on CTE |
References
- Brocklehurst, J.E. and R.A. Bishop, The dimensional changes produced in graphite by absorption of bromine. Carbon, 1964. 1(3): p. 370-370.
- Brocklehurst, J.E. and J.C. Weeks, Dimensional changes in graphite: The relationship between those produced by absorption of bromine and those produced by irradiation. Journal of Nuclear Materials, 1963. 9(2): p. 197-210.
- Martin, W.H. and J.E. Brocklehurst, The thermal expansion behaviour of pyrolytic graphitebromine residue compounds. Carbon, 1964. 1(2): p. 133-134, IN3, 135-141.
- Brocklehurst, J.E., Dimensional Changes in Graphite: The Relationship Between Those Produced by Absorption of Bromine and Those Produced by Thermal Expansion and by Fast Neutron Irradiation. 1966, University of Manchester: Manchester. p. 49.
- Hall, G., et al., The relationship between irradiation induced dimensional change and the coefficient of thermal expansion: a modified Simmons relationship. Nuclear Engineering and Design, 2003. 222(2-3): p. 319.
- Hall, G., B.J. Marsden, and S.L. Fok, The microstructural modelling of nuclear grade graphite. Journal of Nuclear Materials, 2006. 353(1-2): p. 12-18.
- Preston, S.D. and B.J. Marsden, Changes in the coefficient of thermal expansion in stressed Gilsocarbon graphite. Carbon, 2006. 44(7): p. 1250-1257.