Reactor Core Components Development of Numerical Models for the Assessment of the AGR Graphite Reactor Core Containing Cracked Components

Understanding the behaviour of Advanced Gas-cooled Reactors graphite cores withmultiple cracked bricks is paramount to the assessment of structural integrity, safeoperation and life extension of the UK nuclear plants. With about 10,000 graphite components having a structural role, moderating the nuclear reaction and being the channels for control rods, extensive work is conducted to justify that these functions will remain fulfilled for the whole duration of the reactor life during normal operation and severe events such as earthquakes.

Models known as Cracked Brick Neighbourhood Arrays are being developed with the aim to enable engineers at EDF to assess the influence of a crack on the local deformation of the reactors. Such large scale industrial problems with contact mechanics, presence of cracks in components and complex aging behaviour laws, are challenging for finite elements software. In this article we take a look at the engineering analysis that is undertaken to predict the behaviour of the graphite components in the reactor core.

It must be noted that the cases presented in this article, and in particular the inspection data and the cracking scenarios, are not representative of the expected behavior of the reactors. Therefore, the results presented in the article are for demonstration only.