Improvement of ATWS Protective Signal and Mitigation System for CPR1000 Nuclear Power Plant

At the event of loss of normal feedwater-anticipated transient without scram (LOFW-ATWS) in CPR1000 nuclear power plant, the primary loop overpressure risk may exist when the regulation functions of temperature regulation (R) rods and power regulation (G) rods cannot work timely or have lost. In order to reduce the peak value of primary pressure and avoid the overpressure risk in this transient process, an improvement scheme of ATWS protective signal and mitigation system by adding shutdown action of coolant pumps was proposed in this paper, and then THEMIS program was adopted to verify this scheme. The verification results indicate that the improvement scheme can effectively reduce the peak value of primary pressure and eliminate overpressure risk in LOFW-ATWS event.