Heat Load Operation Range of Plate Heat Exchanger of Component Cooling System for NPP at Extra-Low Temperature Site

The temperature of sea water at Hongyanhe nuclear power plant is too low that the temperature of Component Cooling System（RRI） might be lower than the limit, even the water might be frozen in the heat exchangers. It would cause the lost of final heat trap. Heat load subarea operation was performed to provide RRI from the low temperature. The edge of single subarea was calculated and the summation of total subareas were reckoned, based on the design limit, by the analysis of the input and boundary of both Essential Water System（SEC） hydrodynamic and RRI/SEC heat exchanging calculation. Designing of heat load subarea was the most important academic base of RRI heat exchanging design at Hongyanhe. This method informed a valuable example for the RRI heat exchanging design at low temperature sites.