Quantification of the uncertainty in the effect of irradiation on Charpy properties

The provision of material property values for use in safety assessments requires the use of statistical analysis techniques which can produce, for the deterministic approach, best estimate and confidence limit values and, for the full probabilistic method, probability distributions. In this paper a description is given of a robust and efficient method of analysis for deriving probability distributions which reflect the information in the data. As this novel approach adopts a Bayesian viewpoint for the analysis, the main aspects of this will first be presented before moving on to giving the details of the method. In order to illustrate the use of the various methods, results will be presented of an analysis of the effect of neutron irradiation dose on Charpy impact energy curves. On the basis of this analysis a model is derived with which it is possible to predict the form of the Charpy curve at any dose and for any probability level. Comparisons between the model predictions and the measured values are shown.