A computing system has been developed at VTT Energy for making efficient leak-before-break (LBB) evaluations of piping components. The system consists of fracture mechanics and leak rate analysis modules which are linked via an interactive user interface LBBCAL. The system enables quick tentative analysis of standard geometric and loading situations by means of fracture mechanics estimation schemes such as the R6, FAD, EPRI J, Battelle, plastic limit load and moments methods. Complex situations are handled with a separate in-house made finite-element code EPFM3D which uses 20-noded isoparametric solid elements, automatic mesh generators and advanced color graphics. Analytical formulas and numerical procedures are available for leak area evaluation. A novel contribution for leak rate analysis is the CRAFLO code which is based on a nonequilibrium two-phase flow model with phase slip. Its predictions are essentially comparable with those of the well known SQUIRT2 code; additionally it provides outputs for temperature, pressure and velocity distributions in the crack depth direction. An illustrative application to a circumferentially cracked elbow indicates expectedly that a small margin relative to the saturation temperature of the coolant reduces the leak rate and is likely to influence the LBB implementation to intermediate diameter (300 mm) primary circuit piping of BWR plants.
|Seminar||Seminar on Leak Before Break in Reactor Piping and Vessels|
|Period||9/10/95 → 11/10/95|