Conceptual design studies of Japanese commercialized Fast Breeder Reactor (abbreviated to FBR) are carried out. With the aim of reducing the construction cost, number and size of components are reduced. For example, Intermediate Heat Exchangers (abbreviated to IHXs) are integrated with primary pumps; number of main cooling loops is reduced from 3 to 2 and piping is shortened; the reactor vessel is simplified. Accompanying the reduction of cooling loops, Steam Generators (abbreviated to SGs) become larger, and semi-sphere perforated plates in 3-D structures are adopted for large sized steam generator to endure primary stress caused by pressurized steam. In “Design by Analysis” for these nuclear components, the stresses in these structures are classified into primary and secondary stresses. Conventional method of stress classification uses an evaluation section; however, it is difficult to define evaluation sections in 3-D structures. For this reason, an alternative evaluation method without evaluation sections, which can be easily applied to 3-D structures, is necessary. Primary stress is the so-called load controlled stress; this is decided as the stress in equilibrium with external loading and is independent of inelastic behavior of materials. Paying attention to above feature, there is an idea to obtain primary stress from a Re-distribution node (abbreviated to R-node), where stress is constant during stress re-distribution. One of concrete method is GLOSS (Generalized local Stress Strain) method proposed by R. Seshadri et al. [1–3]. To generate artificial stress re-distribution, this method needs to carry out two elastic analyses with different values of material constants. All stresses are different between two calculations except R-node and the stress at this point can be evaluated as the primary stress. This method adopts elastic analysis with special material constants that is determined from post-processing of stress distributions of the first elastic analysis due to the insufficient power of earlier computer. Recent progress of computer technologies reduces computational time and cost of inelastic calculation. Furthermore, it is not difficult for an elastic-plastic calculation to be carried out with classical constitutive equations provided by commercial codes. In this paper, an alternative method is proposed, which uses elastic-plastic analysis for artificial stress re-distribution instead of elastic analysis in GLOSS method. The proposed method is confirmed through the application to the example problem for a thick cylinder and the ability to be applied to actual structures is confirmed through the application to the example problem for a perforated plate.

This content is only available via PDF.
You do not currently have access to this content.