Graphite thermal expansion relationship for different temperature ranges

For practical reasons, the coefficient of thermal expansion (CTE) has to be measured over a particular temperature range, for example 20-120 °C, 20-400 °C or 500-700 °C. However, in many cases, engineers or scientists involved in the assessment of graphite components such as nuclear reactor moderator bricks, electrodes or moulds require CTE over temperature ranges other than that of the original measurement. This paper compares three different techniques used to convert CTE from one temperature range to another. The method used by the UK nuclear industry is compared with techniques proposed by two international companies. There was close agreement between two of the methods. However there was some divergence in the case of the third method. This may be related to the type of graphite (fine-grain) for which the third method was developed.