Qualification of LMFBR piping systems for external and internal extreme loads by strain assessments

Liquid metal fast breeder reactors operate in a temperature range between 180/degree/C and 550/degree/C with relatively low internal pressure. This could lead to medium wall thicknesses, but thermal transient loads require sections with more flexibility. If the classical method assuming elastic behaviour with the yield strength criterion (force controlled) is used for the transient dynamic event loads with low numbers of cycles (earthquake, aircraft crash, and steam generator design accident), it could lead to stiff structures. An alternate method and criteria are herein proposed for dynamic load events. Strain estimation methods for these transient dynamic event loads were developed by Interatom. During the licensing procedure of the SNR 300 for the load cases of aircraft crash and steam generator accident, strain estimation methods based on energy control were used for the components' design. A more refined strain estimation method even for earthquake load is under development and it has to be verified. The comparison of two different shaker experiments (SAE-Experiment of KWU and high level dynamic test at HEDL) and the results of the Interatom estimation method showed always conservative numerical results. The overestimation of the strain range is about a factor of 1.0 to 2.0 for a structure. 9 refs., 5 figs