Shakedown and limit analyses of a pressurised water reactor vessel nozzle under cyclic thermo-mechanical loadings

This paper has investigated cyclic plasticity of a reactor pressure vessel (RPV) nozzle subjected to cyclic thermo-mechanical loads thoroughly: cyclic thermal loads, cyclic bending moments, and cyclic internal pressures. By utilising an advanced direct numerical method known as the Linear Matching Method, elastic shakedown limit boundaries of the RPV nozzle are constructed to evaluate the effects of different load combinations on the cyclic plasticity behaviours. In additions, limit load boundaries of the RPV nozzle are constructed to confirm whether alternative plasticity or ratchetting response appear under the same loading combinations. Through comprehensive numerical studies, the effects of geometric parameters of the nozzle geometries on the cyclic plastic behaviour are identified and the parametric study results are formulated as semi-empirical equations to predict both limit load and elastic shakedown limit boundaries. Ultimately, this research provides reactor design engineer insight into the design of the RPV nozzle in consideration of cyclic plasticity.