Studies of Advanced Intermediate Heat Exchanger to replace 2^<nd> Na Loop of FBR

本课题的目的是为循环式快中子增殖反应堆先进中间换热器寻找合适的中间换热介质材料。我们之前已经开始了对液态金属镓的研究，也有了实验仪器，所以主要目的是对比铅铋合金与液态金属镓作为中间传热流体的适用性。快堆中的二次钠回路将一次钠的热能传递给蒸汽发生器，产生蒸汽和电力。这里24MPa的蒸汽条件远高于轻水反应堆，不能排除钠水反应。本研究拟引入不与水和钠发生反应的第三种介质，并将中间换热器（IHX）与SG组合，以减小装置规模。2000年，对实验设备进行了改造，以铅铋…More代替镓作为工作流体。随着这种流体的变化，工作温度从100摄氏度上升到300摄氏度，因此在铅铋回路和水回路之间插入了有机冷却剂的第三个冷却回路。进行了自然对流换热实验，发现铅铋比镓更容易通过自然对流循环，其体积膨胀系数更大。2001年进行了加电磁泵的强制对流实验。铅铋在材料表面具有非常不稳定的润湿性，这会导致电磁流量计指示不稳定等问题。由此，提出了一种基于温度波动的互相关测量流速的新方法。传热系数低于镓的传热系数，与Sabottines经验方程吻合较好。2002年，对铅铋液进行了气升强制循环测试。在水循环中建立了气举法，但在液态金属中几乎没有。用氩气使铅铋和镓循环。研究了流体密度为1、6和10时的气升特性，并进行了对比研究。结果表明，在低流量区域，经验公式与实验结果基本一致，但当滑差比接近3时，循环特性趋于饱和。作为总结；澄清了镓和铅铋液态金属流体的特性，揭示了许多新知识。这些结果可以为以重金属为工质的示范反应堆的概念设计提供参考。少

The purpose of the present project was to find out appropriate materials which could be used as an intermediate heat exchange medium in the Advanced Intermediate Heat Exchanger for loop type Fast Breeder Reactor. We had initiated studies on liquid metal gallium previously and had the experimental apparatus, so the main object was to see how the lead-bismuth alloy was suitable for intermediate heat transfer fluid in comparison with liquid metal gallium.The secondary sodium loop in the FBR transfers the heat energy to the steam generator from the primary sodium to generate steam and electricity. The steam condition there of 24MPa is much higher than that in the light water reactors and sodium water reaction could not be excluded. The present study intends to introduce the third medium which does not react with water nor sodium and combine the intermediate heat exchanger(IHX) with SG to reduce the plant size too.In 2000, the experimental equipments were modified so as to use lead-bismuth … More as a working fluid instead of gallium. With this fluid change the working temperature rose very much from 100 degree C to 300C, so the third cooling loop of an organic coolant was inserted between the loops of lead-bismuth and water. The heat transfer experiment at natural convection was carried out and found that the lead-bismuth could he circulated by natural convection easer than gallium owing to larger volume expansion coefficient.In 2001, the forced convection experiment was performed with adding an electro-magnetic pump. Lead-bismuth has a problem of very instable wettability on a material surface, and this causes problems such as instable indication of the electro-magneto flow meter. Thus, new method of flow velocity measurement from cross correlation in the temperature fluctuation was developed. The heat transfer coefficient was found to be lower than that in gallium and found to agree well with the Sabottines empirical equation.In 2002, the lead-bismuth fluid was tested by the air-lift forced circulation. The air lift method was established in water circulations but scarcely no in the liquid metals. Argon gas was used to circulate the lead-bismuth as well as gallium. The air lift characteristics were studied over fluid density from onity, six and ten, and were studied in comparison. The result showed that the empirical formula agreed with the experimental results over the low flow rate region but circulation property saturated as the slip ratio approached three.As a summary; characteristics of liquid metal fluid of gallium and lead-bismuth were clarified and many knowledge were revealed. These results could contribute to the conceptual design of the demo reactor which uses heavy liquid metals as working fluid. Less