Abstract:

The flushing scheme for secondary circuit thermal cycling was discussed in AP1000 nuclear power plant， in which condensate pump was used as a power source and single column heater was input one by one. At first， by means of the calculation of heat balance analysis， the usage amount of auxiliary steam before flushing was determined. Then， the mathematical model was built for heat dissipating capacity calculation with assumption that the temperature of flushing water was 60 ℃， the total heat dissipating capacity of small cycle and large cycle was calculated， as well as calculation results with the thermal power of single condensate pump were compared. The calculation results show that during the flushing process， the flushing water temperature can be slightly higher than 60 ℃ and reach the thermal equilibrium without auxiliary steam， and the thermal power of a single condensate pump can offset total heat dissipation. Finally， the change trend of water temperature in deaerator tank was presented through the calculation of heat release， and some measures for avoiding condenser over temperature were proposed.

Key words: AP1000 nuclear power plant, secondary circuit, thermal cycling, flushing