Pressurized Thermal Shock analysis of the reactor pressure vessel

PTS analysis is a substantial part of the technical analyses supporting the license application for operation beyond design life. Guidance for the analysis' concept is given by the Hungarian nuclear regulator which is in line with the relevant international rules. Involving technical support organizations and independent consultants as well as taking into account the changes in fuel management Paks NPP, Hungary, compiled a new PTS analysis. Subjects of the analysis were the RPV belt line region components as well as other circumferential welds of the RPV including nozzle region. Beyond the PTS initiating events selected on the basis of engineering judgment a PSA provided additional transients which showed a higher frequency than 10(-5)/year. Thermal-hydraulic calculations completed for each selected PTS initiating event provided the necessary input for the structural analysis. Based on core configurations end-of-life fluence were calculated. Neutron dosimetry surveillance results were used to verify the calculations. Temperature and stress field calculations were performed by solving the system of equations of elasticity. Underclad crack was postulated for fracture mechanics calculation. K-I was calculated at the crack tip and the boundary between the cladding and base / weld metal; K-Ic was calculated on the basis of the reference curve. Comparison of these two parameters (K-I <= K-Ic), i.e. evaluation of whether the postulated defect stability criteria was met, gave the result. (C) 2018 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ECF22 organizers.