Abstract Leak-before-break analyses on tube microcracks are beneficial for preventing small loss of coolant accident in nuclear power plants. Specially, the tube leakage of steam generator may lead to steam generator tube rupture. Currently, experimental investigations on leak flow rate characteristics of normal temperature water and high pressure subcooled water through axial and circumferential microcracks of steam generator tubes were carried out, respectively. Cold Test results indicate that leak flow rates of circumferential microcracks for 0.13 ≤ W ≤ 0.16 mm and 3.6 ≤ δ/Dh ≤ 4.4 increase with a decreasing back pressure (Pout) first and then can be regarded as a constant value for a given working pressure in steam generator tubes (Pin). Additionally, each of Pin has a critical differential pressure between Pin and Pout (ΔPc). The ratio of ΔPc to Pin is equal to 0.55, which is smaller than 0.64 for axial microcracks. Hot Test results show that leak flow rates decrease significantly with an increasing working fluid temperature (Tf, in) when Tf, in is larger than a certain value due to the flashing of subcooled water near exits of microcracks. Besides, discharge coefficients of high pressure subcooled water through axial and circumferential microcracks under various back pressure conditions decreases with an increasing Pin for a given subcooled temperature. In general, new correlations were developed to give excellent predictions for the leak flow rate data of normal temperature water and high pressure subcooled water through axial and circumferential microcracks of steam generator tubes under various back pressure conditions with a maximum deviation of ±6%.

中文翻译：

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高背压条件下高压过冷水通过蒸汽发生器管轴向和周向微裂纹泄漏流量特性的实验研究

摘要 管子微裂纹断前泄漏分析有利于防止核电厂冷却剂小损失事故的发生。特别是蒸汽发生器管道泄漏可能导致蒸汽发生器管道破裂。目前，分别对常温水和高压过冷水通过蒸汽发生器管轴向和周向微裂纹的泄漏流量特性进行了实验研究。冷试验结果表明，0.13 ≤ W ≤ 0.16 mm 和 3.6 ≤ δ/Dh ≤ 4.4 的周向微裂纹泄漏流量随着背压 (Pout) 的降低先增加，然后可以视为给定工作压力下的恒定值在蒸汽发生器管（销）中。此外，每个 Pin 在 Pin 和 Pout 之间都有一个临界压差 (ΔPc)。ΔPc 与 Pin 的比值等于 0.55，对于轴向微裂纹小于 0.64。Hot Test结果表明，当Tf,in大于一定值时，由于微裂纹出口处过冷水的闪蒸，泄漏流量随着工质温度(Tf,in)的升高而显着降低。此外，对于给定的过冷温度，高压过冷水在各种背压条件下通过轴向和周向微裂纹的排放系数随着Pin的增加而减小。总的来说，开发了新的相关性，以对在各种背​​压条件下通过蒸汽发生器管的轴向和周向微裂纹的常温水和高压过冷水的泄漏流量数据提供出色的预测，最大偏差为 ±6%。