Effect of parametric sensitivity on stability boundary of Chinshan NPP

Boiling water reactors are susceptible to instabilities under certain condition and require stability boundary to prevent instability. On this stability boundary, any perturbation or oscillation may easily induce unstable events. All of the parameters that may dominate global mode instability must be analyzed and evaluated. In each core reload design, a decay ratio analysis must be conducted to ensure system stability. LAPUR5.2 and SIMULATE-3 codes were employed to establish a process to conduct such analysis. This investigation contributes to the parametric sensitivity effect, which is a variation of the decay ratio with power/flow operating points along the stability boundary. The results indicate that fractional changes of decay ratios with variation in certain important parameters under different power/flow points. The density reactivity coefficient, gap conductance, recirculation loop gain and system pressure, at the points of high power/flow, all are associate with larger fractional changes in the decay ratio than the points of low power/flow.