Experiences From Structural Dynamic Analysis Projects of BWR Plants Within the Scope of Power Uprate Projects Using FEA

During recent years, power-uprate projects have been executed at several BWR-units in Sweden. As part of these projects, structural verification of the safety-related buildings as well as the new and old internal parts of the reactor pressure vessel, RPV, has been performed. In this document, some experiences will be presented from structural dynamic verification, using finite element analysis, FEA, within the scope of these power uprate projects. From this work, a number of conclusions can be drawn. Global models with dense meshes can successfully be used for a broad range of applications. Today, large FEA-models can be used efficiently, e.g. in global vibration and structural verification analyses, if suitable dynamic analysis methods are used. There can be strong dynamic interactions between the containment, fluids, the RPV and RPV-internals. Stress calculation and evaluation can be executed efficiently on large models. The structural models can with advantage be re-utilized in future projects.