Leak Flow Rate from a Through-Wall Crack in a Pipe

This paper presents an evaluation of the leak flow rate from a circumferential through-wall fatigue crack in a pipe under the fluid conditions of high-pressure saturated water of a boiling water reactor (BWR), related to the leak-before-break (LBB) concept which is considered to be applicable to nuclear power plants. The following three items are discussed and clarified ; (1) examination of the leak flow path and surface roughness of a circumferential through-wall fatigue crack which was obtained in a fatigue growth test using a STS 42 carbon steel pipe, (2) analytical estimation methods of the leak rate as two-phase critical flow, which are greatly influenced by the crack opening displacement, the ratio of flow path length to hydraulic diameter L/D, surface roughness and the exit tot the stagnation area ratio of the leak flow path, (3) experimental evaluation of the leak flow rate using artificial slits simulating the through-wall crack.