A Simple Iterative Method for Compensating the Response Delay of a Self-Powered Neutron Detector

The self-powered neutron detector (SPND) is popularly used as an in-core neutron flux monitor in reactors due to its simple structure, self-powered feature. However, its response delay needs compensation to obtain the actual real-time neutron flux for reactor control and protection. In this paper, a simple iterative method for compensating SPND response delay is proposed as well as noise filtering. Two favorable noise filtering methods were compared, and then, the moving average filter was chosen. The governing differential equations were established according to decay mechanism, and then, iterative compensation relations for delay compensation were established by discretization with simplicity and flexibility. The test result shows that the compensated response delay for a prompt jump of neutron flux is only 0.9 s, indicating its effectiveness. Furthermore, the dependence on initial conditions and sampling time interval was also studied, indicating that two initial condition determination modes for two typical detector start-up situations can be chosen correspondingly for delay minimization and critical sampling with a time interval of about 0.7 s, which shows consistency with the Von Neumann stability analysis. Finally, our method has been compared with the Z-transform method and verified with measured current, which showed its better performance.