In the second generation CPR nuclear power station, due to the limitations of design and equipment, it is not possible to generate or remove vapor space of pressurizer simultaneously with the temperature rise or fall of the primary loop coolant. But in the third generation HUALONG-1 nuclear power station, the obstacles on the equipment have been resolved and the foundation is already in place to solve the above technical problem. If we can improve the scheme appropriately, the primary loop coolant is heated or cooled while generating or removing vapor space of the pressurizer, which will be realized firstly. There are two main benefits: 1, It can reduce outage duration and improve economic efficiency. 2, It is conducive to decrease radioactive sources during the outage condition.