| Abstract: | The distribution of stresses in the cylindrical section of a reactor pressure vessel is evaluated for transient temperature and pressure loads. The calculation takes particularly into account the thermoplastic stresses of the cladding and the transition zone to the base material.The considered load history comprises stress-relief annealing, pressure test, start-up and shut-down of the reactor, followed by start-up, pressure drop with subsequent thermal shock.The stresses and strains are determined by the Prandtl-Reuss equations and the v. Mises flow condition depending on temperature. Creep effects are additionally included for stress-relief annealing.The problem is approximated by a second order time step method and the resulting changes in stress and strain are calculated using a shooting method. The results of the elastoplastic calculation for thermal shock differ from the linear calculation particularly in the cladding layer and its immediate vicinity. |
