Guidelines of elevated temperature structural design methods to realize compact reactor vessels

Main loadings of reactor vessels in fast reactor plants are thermal stresses induced by fluid temperature change at transient operation. Structures respond to them with elastic plastic creep deformation under high temperature conditions. It can induce incremental deformation and creep fatigue crack at critical portions around the sodium surface, thermal stratification layer and core support structures. Those phenomena are so complex that design evaluation becomes sometimes too conservative. In order to achieve precise high temperature design for realizing compact reactor vessels of fast reactor plants, next guidelines were proposed for thermal load modeling, structural analysis and strength evaluation. This paper gives the summary of these guidelines. (author)