LBB assessment on ferrite piping structure of large-scale FBR

Yoo, Yeon-Sik

These days, this interest on LBB(Leak before Break) design becomes to be rising in the viewpoint of the cost reduction and structural inter-grity for the commercialization of FBR plants, LBB design enables pla-nts to be shut down safely before occuring unstable fracture by dete- cting the leak rates even if a crack initiates and penetrates a wall thickness. It is necessary to assess crack growth and penetration be- havior considering in-service conditions under operation temperature, leak retes considering detector capability and unstable fracture quan-titatively for LBB assessment. The governing service of FBR can be identified thermal expansion stress andthermal transient stress be- cause the operation temperature is higher than that of LWR and the li-quid metals contain higher heat transfer coefficient than water. On that reason, the use of 12Cr type ferrite steel in the primary cooling system is investigated for reducing stress in the design of large- scale FBR. This stud