Numerical study on capacitive metal rod position detector in double-layer medium

Position signals of control rods are important parameters that should be measured during the operation of nuclear reactors. The performance of capacitive detectors for measuring control rod positions in a double-layer medium is numerically studied in this paper. According to the experimental results of concave electrodes capacitive detectors, the numerical model is verified. The mathematical expression of the detector signal is derived as a function of rod position and liquid level. The error characteristics of the capacitive detectors for measuring the eccentric metal rod are revealed. The method for evaluating measuring errors of capacitive detectors in double-layer medium is constructed. The relation between flare angles of electrodes and measuring errors is studied, and the optimization method of the flare angles is discussed. The design of the integrated capacitive metal rod position detector (CMRPD) is proposed. Measuring errors and performance of the detector are evaluated.