科研之友
微信
新浪微博
Facebook
分享链接
摘要
If a station blackout (SBO) occurs in a fast breeder reactor, heat removal by natural circulation is expected, because the height between the heat source and the sink was considered in the plant design to provide the potential for natural circulation. Therefore, many studies about heat removal by natural convection have been reported to date. In these studies, it was determined that the thermal hydraulics for natural circulation depend on the plant structure, cooling system, and component positions, unlike in the case of forced circulation. Thus, the heat removal ability by natural circulation differs in each system and each plant. For the fast breeder reactor (FBR) "MONJU" during normal operation, the ex-vessel fuel storage system (EVSS), which uses a natural circulation flow inside the ex-vessel fuel storage tank (EVST), and the EVST sodium cooling system rely on forced convection with an electromagnetic pump. The decay heat can be removed by air coolers and blowers. If an SBO occurs in this EVSS, all pumps and blowers would be stopped. However, the plant dynamics of the EVSS in the time after all the pumps and the blowers were tripped has not yet been evaluated. Therefore, in this study, a plant dynamics analysis model was developed using a flow network to calculate the entire dynamics of the EVSS in the event of an SBO. The Super-COPD program, which has been validated for models of the reactor and the main cooling system using several tests including the plant trip test and the natural circulation test, was used. A model of the EVSS was developed by considering the design information, and the modeling technique was based on specific analytical models for the reactor and the main cooling system, because there was no sufficient data to confirm the behavior of the sodium temperature and flow in this EVSS. For the model to simulate natural circulation, the heat capacity of the coolant plenum of the EVST, geometrical information such as the height of the components, and the heat transfer characteristics of the cooling coils were considered. Based on a comparison to experimental data, it was confirmed that the calculated the behavior of the sodium temperature and flow of the EVST sodium cooling system in an SBO is accurate. The thermal center of the heat transfer area of only the helical coils decreased to approximately 21% in comparison with that under normal operation, and the flow rate in the EVST decreased by approximately 20%. The natural convection force depends on the differences in the densities and the thermal centers of the heat transfer areas between each component. The calculation results based on the theory were almost equivalent to the analysis results. It is estimated that the developed model correctly considered the heat transfer characteristics of each component and can accurately calculate the natural convection force. From these results, it is concluded that the developed model for the EVSS is effective for calculating the temperature and flow behavior of the entire system under natural circulation conditions like those expected during an SBO. In the future, these models will be validated using a 3D fluid dynamics analysis and additional test results.
- 出版日期2013-3
