Critical channel power reduction due to pressure tube diametral creep

Pressure tube diametral expansion due to irradiation and thermal creep is one of the major aging mechanisms of CANDU-6 reactor. The characteristic design concept of pressure tube causes this CANDU-6 unique phenomenon. Increasing of pressure tube diameter due to irradiation creep reduces the hydraulic resistance in the channel, hence increases flows, but causes the coolant to preferentially bypass the interior sub-channels of the bundle, reducing the ability of fuel cooling, thereby reducing Critical Channel Power (CCP). With the prediction of creep rate, the quantitative assessment of CCP reduction is performed