A Proposal of high temperature design method for tubesheet structures

Kasahara, Naoto; Iwata, Koji; Imazu, Akira; Horikiri, Morito; Tokura, Sunao*

Tubesheet structures are one of the most critical portions in the LMFBR components, and also have complicated configurations. Consequently, the specialized evaluation methods are required for design of tubesheets. In the case of structural design of the prototype LMFBR "Monju", the tentative design evaluation method had been suggested. It is the purpose of this study to propose the advanced method, that can be applied to designs of condenced tubesheets and of higher temperature operating ones, which are required in the demonstration LMFBR. As a conventional design method, ASME Sec. III A-8000 is basicaly adopted in the world. A-8000, however, is the elastic design method for LWR where main loading is inner pressure. For a design of tubesheets in LMFBR, It is necessary to make A-8000 adopted to thermal stress and to develop inelastic strain calculation methods. In this study we clarified the application range of A-8000 and proposed the improved method to calculate thermal stresses. The elastic design method based on perforated palate models without A-8000 is also developed. To evaluate inelastic responses of material, the relation between inelastic strain amplifications around holes of tubesheets and ligament efficiencies is obtained in the view point of dependence of inelastic behavior on ligament efficiencies. As the results, we developed the inelastic strain concentration factor which have consistency with the general purpose high temperature design code.