Recommendations for linearization procedure in pressure Vessel-Nozzle intersections

Abstract

The pressure vessel design is a fundamental step during the construction of new pressurized water reactors (PWRs). In these facilities, several safety requirements are necessary to guarantee the protection of workers, community and environment against the release of radioactive materials. The current version of the ASME Code for vessel pressure presents two types of procedures for structural analysis: Design by Standard and Design by Analysis. The Design by Analysis is a more complex procedure and it requires more rigorous analysis and classification of all types of stresses and loading conditions, in order to incorporate smaller safety coefficients. However, precise rules for achieving the various stress categories have not been implemented in the code. For this reason, this work presents a methodology for the stress linearization in nozzle vessel intersections. The used recommendation is that the line constructed for the linearization should be taken out of transitions elements. So a pressure vessel nozzle intersection was modeling, analyzed and verified then a discussion of how to perform the Code verifications was presented, as well as a mapping of stress. The lines that were constructed in pressure vessel between transition and structural elements in the longitudinal plane (0º) and lines in structural elements in the nozzle in the transversal plane (90º) presents higher stresses.