Coupled natural circulation systems

Abstract

Abstract Coupled loops are commonly used in nuclear reactor systems, especially for decay heat removal. Such systems are found in the Indian PFBR, PHWR-700, AHWR, and in ALWRs like AP-1000, APR-1400, and CPR-1000. Coupled natural circulation systems (NCSs) also find application in solar thermal power plants. Following the Fukushima accident, there has been a trend to design infinite mission time passive decay heat-removal systems. Such systems employ coupled NCSs with the ultimate heat sink as the atmosphere. Coupled NCSs can be classified as series, parallel-series, or series-parallel coupled systems. Besides providing a classification of coupled systems, their analysis methodology and applications are also briefly described in this chapter. In general coupled loops can be thermally coupled or both thermally and hydrodynamically coupled. Analysis procedures for both thermally and hydrodynamically coupled systems are presented. Simple problems involving series-coupled, parallel-coupled, and series-parallel coupled systems are solved to illustrate the analysis procedure. In the case of series-coupled loops, the overall heat transport capability is limited by the lowest heat transport capability loop in the series. Although transient and stability results are not presented in this chapter for simple coupled loops, they can be obtained using the methodology described in earlier chapters.