Design of Startup Procedures with Both Thermal and Stability Considerations

6 Design of Startup Procedures with Both Thermal and Stability Considerations 

The startup curve for the sliding pressure startup scheme that is designed based on only the thermal considerations (Fig. 5.23) is redrawn taking the stability considerations into account as well. The constant pressure startup is not discussed here because the partial power operating conditions in the constant pressure startup are covered by the temperature increase phase and power increase phase of the sliding pressure startup. 

It is found that the thermal criterion (i.e., the MCST) is more limiting than the stability criteria, and hence, it dominates the available range of the power and flow rate at the pressurization phase. When the feedwater temperature and flow rate are kept as 280°C and 35% of the rated value, respectively, the available range of the core power is identified as shown in Fig. 5.19. The core power is also fixed as 20% of the rated value during pressurization that is within the available range. Both the thermal and stability criteria are satisfied as shown in Figs. 5.20, 5.37, and 5.54. The startup curve in the pressurization phase is not changed from that of Fig. 5.23. 

The partial power operating conditions at 25 MPa after the line switching are divided into the temperature increase phase and the power increase phase with only the thermal considerations as shown in Fig. 5.23. In the temperature increase phase, the power is gradually increased from 20 to 35% of the rated value, while the flow rate is fixed at 35% of the rated flow so that the core outlet temperature reaches the normal operating point (500°C). Then, both the power and flow rate are increased 

Maximum cladding surface temperature Thermal-hydraulic stability 

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