Abstract: The rod position system is used to monitor and display the position of the control rod in the reactor in real time. The rod position measurement is an important guarantee for the safe operation of the reactor. The rod position system is not used to generate protection or control signals. If the rod position is abnormal in more than 25% of the measured rod positions, the reactor will cause the reactor to withdraw from the power operation state to the hot shutdown state, which will affect the economic benefits of the unit. Aiming at the problems of measuring rod position display caused by the debugging and operation of domestic rod position system of unit 3 and 4 of Fuqing nuclear power plant, combining with the working principle of the card, Multisim software is used to simulate and analyze the causes of the problems, and corresponding improvement measures are formulated. Through the test and verification, the abnormal situations of measuring rod position display are effectively solved, the reliability of the card work is improved, and the stable operation of the reactor is guaranteed.

Key words: electronic technique; rod position system; measuring rod position; main current controller; gray code processor