Response Current Delay-Effect Elimination for SPND in PWR-Core

Self-powered neutron detectors (SPND) are widely employed by third-generation pressurized water reactors (PWRs) to monitor the neutron flux behavior within the nuclear reactor core. However, the response current of the delayed-type SPNDs suffers from the delay effect. During the transient operating processes of the reactor core, the response current cannot accurately and promptly reflect the changes of the local power. Consequently, it is hard for the online core monitoring software to detect transient changes in the core based on SPND signals. Although some methods have been developed to address this effect, issues such as lack of real-time performance, imprecision, and instability remain in practical applications. Moreover, no method has been established to directly and analytically separate the delayed and prompt components of the response current. Thus, this study proposed a new algorithm to eliminate the delay effect. First, the response characteristic parameters of SPNDs in the reactor core are obtained using a core physics analysis software. Then, by directly separating the prompt and delayed components of the SPND response current transmitted from the core in real time, the real-time neutron flux density is obtained, eliminating the impact of delay effects. Under various typical operating conditions, the accuracy and response time of the new method is verified by using the response current values as the input and the neutron flux values at the detector location as the reference. Both the response current and the neutron flux were calculated by using the core physics analysis software NECP-Bamboo, which is equipped with the response current simulation function. The results confirm the validity and high computational efficiency of the proposed algorithm.