General Trends Observed in Reactor Power Distribution Synthesis with a Response Function-Based Approach

Monitoring the power distribution in nuclear reactor cores is an essential part of nuclear power plant operations. The distribution of power throughout the core has direct implications for the distribution of heat and heat flow. Therefore, power distribution information can provide operators with assurance that the reactor is producing power within specified safety criteria. A variety of sensor types are used to enable the synthesis (i.e., reconstruction) of the power distribution, and in-core or ex-core sensors may be used to perform this process. A typical method by which synthesis is performed is through response functions that define contributions to sensor signals from various segments of the fuel in the core; these response functions inform the mathematics that allow for an updated back-calculation of the power distribution based on measured sensor responses. In this work, self-powered neutron detectors have been analyzed in simulations of a few different reactor types using a response function-based method, coined the point-based iterative method. These simulations have elucidated trends in the accuracy and convergence time associated with the synthesis as a function of certain parameters, such as core segmentation fidelity, the number of sensors in the core, sensor uncertainty, and fuel burnup. These trends are summarized to provide a quantitative and qualitative understanding of how a core monitoring system and synthesis method may be optimized to ensure that the power distribution is determined accurately in real time.