A new monitoring method for control rods position of small modular reactors (SMRs)-based coaxial capacitor.

• A new design of the capacitive control rods position indicator for SMRs is proposed in this paper. • The performance of the indicator is evaluated based on a theoretical model. • The maximum error of the indicator is ±0.05 mm. The position of control rods is one of the core parameters that can affect the power of nuclear reactors, and it is needed to be monitored by the position indicators. Based on the central shielding effect of the driving rod, the design of the coaxial capacitive position indicators is proposed in this paper. The theoretical rod position recognition model of the indicator is constructed by the conformal mapping, and it is verified by the numerical method. The results manifest that the performance of the indicator can be accurately analyzed by the theoretical model. The performance of the indicator is studied, and it is compared with that of the existing capacitive position indicator. The results show that compared with the existing design, the precision and the sensitivity of the new indicator can be enhanced by two orders of magnitude at the same time. [ABSTRACT FROM AUTHOR]