CPR1000堆型机组运行1～3a出现了主蒸汽压力持续降低现象,与大亚湾M310堆型机组投运初期主蒸汽压力上升或维持现象不同.从核岛蒸汽发生器热力性能、核岛热功率变化、汽轮机热力性能等方面,分析引起主蒸汽压力降低的潜在原因.通过收集某在役核电机组运行数据,分析主蒸汽压力持续降低对热力系统与设备、再热系统及机组功率的影响.经分析,CPR1000堆型机组主汽压力持续降低的主要原因是蒸汽发生器热力性能降低,主蒸汽压力在一定范围内降低对常规岛二回路热力系统及设备、机组功率基本没有影响,若超过规定范围,会影响汽轮机的安全运行.“,”Different from the phenomena that the main steam pressure of the M310 reactor type unit in Daya Bay Nuclear Power Plant went up or remained unchanged in the initial stage when it was first put into operation,the main steam pressure of the CPR1000 reactor type unit owned by Shenzhen Engineering Design Co.Ltd.all along wend down continuously in the time period of first one to three years after putting into operation.From such aspects as thermodynamic performance of the steam generators,changes of the thermal power and thermal performance of the steam turbine in the nuclear island etc.,analyzed were the potential causes for dropping of the main steam pressure.Through collecting the operation data of a unit in a nuclear power plant,an analysis was performed of the influence of the continuous dropping of the main steam pressure on the thermal systems and equipment items,reheat systems and output power of the unit.It has been found that the main causes for such a continuous drop in the main steam pressure of the CPR1000 reactor type unit lie in the degradation of the thermal performance of the steam generators.A drop of the main steam pressure in a certain range will basically have no influence on the thermal systems and equipment items as well as output power of the unit in the secondary circuits of the conventional island.If such a drop is beyond the range stipulated,it will affect the safe operation of the steam turbine units.