Bayesian Statistical Analysis on the In-reactor Diametral Creep of Pressure Tubes in Wolsong Units

A CANDU unit measures dimensions of pressure tubes periodically, and examine the results of in-service inspection. In order to estimate the diameter expansion in a pressure tube, a mechanistic model was developed by Canadian researchers. The model is used in various CANDU units all over the world. Recently, the in-service inspection data has been accumulated substantially, and various statistical models are developed using the data. In this study, Bayesian statistics were applied to develop a statistical model for predicting the diametral creep of the pressure tubes in Korean CANDU reactors. Bayesian statistics is useful even when there is not enough data, and it can be applied to complex multilevel modeling. In our model, the bundle position effect was integrated within the existing statistical model. In this study, Bayesian statistical model for diametral expansion of pressure tubes CANDU units in Korea has been introduced. The channelbased model with bundle term calculated he predicted means and prediction intervals quantitatively, and it showed excellent prediction performance. The additional adjustment and improvement of the model is going to be conducted.