海洋条件下堆芯补水箱热分层特性实验研究

Background]: The Core Makeup Tank (CMT) is a passive safety injection technology that could maintain the same pressure as Reactor Coolant System (RCS) at all times, and it has been widely used in large commercial pressurized water reactors and small modular reactors. During the injection process of CMT, a significant thermal stratification phenomenon will form inside, which directly changes the driving force of CMT injection and has an important impact on the transient injection flow rate. [Purpose]: Based on the experimental facility of the core makeup tank, the characteristics of thermal stratification phenomenon and its influencing factors within CMT were investigated under typical ocean motion conditions such as heaving, inclining, and rolling. [Methods]: The CMT test setup was designed and constructed according to the principle of similarity, and the whole setup was placed on a six-axis platform used to simulate ocean motion. Temperature data were obtained through the multi-layer measurement points arranged axially and radically inside the CMT. Then the evolution of thermal stratification under different ocean conditions was compared and analyzed to obtain the characteristics of thermal stratification under ocean conditions and its influencing factors. [Results]: The test results show that the thermal stratification is affected by different ocean conditions to different degrees, the effect of heave motion on thermal stratification phenomena depends on the relative magnitude of the heave acceleration to the gravitational acceleration. The tilting motion is a kind of static condition, which will not enhance the mixing of hot and cold fluids, and both of them do not have a significant influence on the thermal stratification within the CMT. The rolling motion increases the mixing degree of hot and cold fluids inside the CMT, accelerates the energy transfer inside the thermal stratification, and significantly changes the axial temperature distribution inside the CMT. The rolling motion causes a significant thickening of the thermally stratified region, which has a relatively fixed range under static conditions, and a decreasing axial temperature gradient, which ultimately transforms most of the fluid region within the CMT into an obliquely heated region. [Conclusions]: Rolling motion has a large effect on thermal stratification. Under the rolling condition, a decrease in the period or an increase in the maximum Angle will lead to an enhancement of the mixed diffusion effect of the cold and hot fluids, eventually causing the entire internal area of the CMT to transform into the oblique temperature zone.