A code was developed in this study to predict the leakage of the leak before break (LBB). Various stagnation conditions were considered, including the subcooled water, the two-phase fluid and the overheated steam. Moreover, both the critical and noncritical flow was studied. The Henry-Fauske critical flow model was revised by a new phase transition point and the pressure drop due to friction and turns were modified. The code was verified by the comparison with the experimental data on the leakage of conventional pipes, artificial cracks and naturally occurring cracks, which shows a good agreement and this code has a higher precision than the existing codes. The influence of crack morphologies on LBB leakage was discussed, including the local roughness, the global roughness, the crack open displacement (COD) and the number of the corners. Besides, the dependence of the LBB leakage on stagnation enthalpy and back pressure was also investigated.

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