UNIGRAF: Understanding and Improving Graphite for Nuclear Fission

Graphite has been an important material used in nuclear energy since the first reactor at Oak Ridge Laboratory (ORNL) in the USA where it was used as a moderator to slow down neutrons and control the fission process. Graphite is also used in the existing gas-cooled reactors (AGRs) in the UK and is an important material for the next generation of nuclear reactors. However commercially produced graphite produced on a large scale for nuclear applications is not the perfect layered structure that is described in text books but has a complex microstructure which depends on the production process. It is not yet known which production process gives the 'best' type of graphite for nuclear applications as radiation damage depends critically on the type of microstructure. To understand how the different forms of graphite respond to radiation damage, a joint experimental and modelling programme will be undertaken. This will involve international project partners. Different forms of graphite will be produced by a chinese company, Sinosteel which will be irradiated with a neutron source at ORNL and analysed experimentally there, to avoid the problems of shipment of hot material to the UK. Samples of the graphite, produced by Sinosteel will also be irradiated in the UK using ion beams as a surrogate for neutrons and also at GSI Darmstadt in Germany using swift heavy ions. Various forms of experimental analysis will be undertaken at Loughborough, Oxford and Bristol to examine the microstructure and to determine the its effect on physical properties and thus the type of graphite that has the best radiation resistant properties. A complementary computer simulation investigation will help with the understanding of the basic science behind the radiation damage produced by individual collision cascades but will also examine radiation dose effects which have not been the focus so far of computational investigation.
The research will be of benefit to the UK both in terms of its application to existing AGRs but will also keep the UK in the loop for new reactor designs which are currently being planned internationally, where graphite is an essential component.

This research will also contribute to, and have impact on: the advancement of academic knowledge; the development of new graphite materials for Gen IV reactors; the understanding of the role of irradiated graphite in existing advanced gas-cooled reactors (AGR).
The primary industrial beneficiaries will be those companies involved in the commercial production of graphite. In our case Sinosteel are producing the graphite samples for our study but the results of our research will be open source and available to other companies involved in commercial graphite production.
Society as a whole will benefit since the knowledge gained will help improve the understanding of how nuclear graphite is affected by irradiation and hence make nuclear energy more safe which could potentially extend the life of existing reactors, thus helping with the UK's carbon emission targets.
Training three young researchers in this field will add to the nuclear expertise in the UK and, depending on energy policy, help provide a basis of knowledge for future new reactors that the UK may wish to design and build.
Impact will also occur through the collaboration with GSI who have a future application of graphite as a target wheel for the production of radioactive beams at the Facility for Antiproton and Ion Research (FAIR) to be built within the coming years.
Our co-I, James Marrow (Oxford) advises the UK ONR (Office of Nuclear Regulation) on graphite issues. The work will be of direct benefit to them.
The work will benefit the UK Advanced Gas Cooled reactors, aiding the interpretation by EDF Energy UK of the observed differences in the ageing behaviour of the different graphites within the fleet that were produced by different manufacturers over a period of time; improved understanding of the underlying mechanisms will allow better use to be made of the limited data obtained by core inspection.