The use of multiscale materials modelling within the UK nuclear industry

The continued safe operation of high integrity structures and components in the nuclear industry is assured by using arguments which are usually based upon deterministic methodologies. These require theoretical models to provide the input parameters or the necessary mechanistic understanding of the mechanical or physical properties. Consideration is given to modelling that has been used for one class of reactor type power stations, Magnox. Modelling to provide key parameters for input to the safety cases is discussed. The models adopted span many orders of magnitude from the atomic scale to those providing a description of aspects of complete engineering structures. At the atomic scale these provide an insight to the production of point defect damage in steels as a result of exposure to a neutron spectrum containing fast and thermalised neutrons and the subsequent effects of both temperature and neutron dose. In addition equilibrium and non-equilibrium segregation of alloying and impurity atom species to grain boundaries is modelled. Both are necessary for understanding the changes in fracture and mechanical properties for these steels after extended periods of service. At the microstructural level models are adopted to develop insights into the fracture processes and the prediction of the changes in mechanical properties. The benefits of these models to the arguments developed within safety cases which underwrite safe continued operation of these power stations are considered.