The research and application of LBB boundary analysis curve

Since the use of LBB technology shall enhance safety level of NPP by way of simplification of maintenance of the systems of normal operation and safety systems under rejection of use of massive support restraints, LBB (Leak Before Break) technology is widely used for main coolant pipeline and other high energy pipelines inside containment of NPP worldwide. Since the successful LBB application on the main coolant loop of PC Project I, Snerdi continues its effort on expanding the LBB application on other high energy pipelines inside containment, and a principle which is called LBB boundary analysis curve and shows the relationship between the normal operation pipe stress and extreme pipe stress for a kind of pipe geometry and material properties of which pipe can meet the LBB requirements has been verified and exploited. Further application of the LBB boundary analysis curve on assisting in high energy piping LBB design and several factors which influence the characters of LBB boundary analysis curve have been discussed. A program has been achieved to generate the LBB boundary analysis curve. Several elements which influence the possibility of application of LBB technology have been discussed, such as the difference between normal operation pipe stress and extreme pipe stress, pipe thickness, the percentage of pipe bending stress, and the piping minimum allowable normal operation stress. (author)