Thermo-economic performance comparison between two steam source schemes in the auxiliary steam system in nuclear power plants

Two steam source schemes in the auxiliary steam system of nuclear power plants, which are the main steam directly desuperheated and decompressed scheme and the main steam as heat-emission medium forming a integrate steam-water circulation transformation scheme, have been presented. The indices of each scheme, such as exergy consumption coefficient, unit thermo-economic cost, cost difference and exergy economic coefficient, have been calculated and analyzed by thermo-economics analysis method. The results show that the cost of the steam source obtained by the main steam directly desuperheated and decompressed scheme is lower than the main steam's steam-water circulation transformation scheme in either energy cost or non-energy expenditure, and in the secondary one, the vulnerable spots in energy utilization mainly are the auxiliary de-aerator and the feed-water pump, the reasons of which are the higher heat exchange temperature difference in de-aerator and higher delivery head of feed-water pump.