During the lifetime of an Advanced Gas-Cooled Reactor (AGR) the graphite components of the core are subject to irradiation induced deformations which lead to a build up of internal stresses in those components. The build up of internal stresses may eventually lead to crack initiation in some components which then has implications for the integrity of the core. Therefore it is important to have reliable predictions of both the deformations and stress state of the graphite components together with timings of when crack initiation may occur. This paper describes the methods used to predict stresses and deformations in graphite components with an emphasis on the graphite moderator bricks that form the bulk of the core of the AGRs. The paper describes the requirements of the predictions, the data needed for the assessments, the important features and properties of the components that need to be considered and methods of validating the predictions. The paper also considers how the assessments have advanced in recent years, particularly with the development of simple statistical methods that provide predictions of expected ranges of timings and deformations. Finally, current developments in modelling arrays of components and in the modelling of crack propagation are also briefly summarised.
展开▼
