Basic Plant Dynamics of the Super FR

The plant dynamics of the Super FR toward perturbations as assumed in Chap. 4 are analyzed first without a control system in order to understand the basic 

A positive reactivity ( 0.1) is inserted stepwise by withdrawing the CRs. The feedwater pump speed and the turbine control valve stroke are kept constant. The results are shown in Fig. 7.68 [31]. The reactor power increases about 10% almost stepwise due to the prompt jump and then gradually decreases due to the reactivity feedbacks from the fuel temperature and coolant density. This behavior implies that the Super FR also has inherent self controllability of the reactor power despite the much smaller density reactivity coefficient compared to that of the Super LWR. The main steam temperature increases, which leads to an increase in the main steam and core pressures because the specific volume of the main steam increases. The increase in the core pressure leads to a decrease in the feedwater and core flow rates, which increases the main steam temperature further. As a result, the maximum increase in the main steam temperature is nearly 40°C while that in the Super LWR is only 9°C (see Fig. 4.10). 

The turbine cmitrol valve s close slightly, and the main steam flow rate decreases by 5%. The CR position and the feedwater pump speed are kept constant. 

The results are shown in Fig. 7.69 [31]. The main steam pressure increases. The core coolant flow rate decreases with the main steam flow rate, which increases the main steam temperature. The increase in the main steam temperature is nearly 20° C while that in the Super LWR is 12°C. 

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