Plastic Analysis of a Reactor Pressure Vessel Support Pad With Different Methods From Appendix F, Faulted Conditions, Comparison of Allowable Loads

Abstract

The present paper shows the results of different plastic analysis methods stipulated in the ASME-code appendix F for faulted conditions. Results will be compared and differences with an elastic analysis are discussed. The analyzed structure is a support pad of the RPV (reactor pressure vessel) of a German PWR. There are four support pads equally distributed around the outer surface of the flange of the RPV. Under normal and faulted conditions these support pads serve as a link between the RPV and RPV support construction, which is in the German design a ring girder. A vertical force is applied onto the structure in an incremental manner until failure will occur. Real measured true stress strain curve is used. In the context of the European research project LISSAC [7] special attention is paid on local effects near holes or notches causing non-uniform stress and strain distributions. The chosen support pad provides such a hole. Allowable loads achieved with elastic analysis, plastic analysis, limit load or plastic analysis collapse load are compared. Details as well as problems of the numerical analysis were discussed. Another aspect is the strain distribution in a plastic analysis, especially near local discontinuities. As an outlook these plastic strains were compared with local failure strains found in the LISSAC project.