Abstract: A description is presented of the debug method of C2 gate at nuclear power plants using sealed gas proportional counter as detector, including the analysis of the feasibility and necessity of performance optimization. To ensure the optimized detection efficiency, the high voltage value is to be determined. The lowest detectable limit of the equipment is calculated and the low background alarm threshold is set. Protective method for detector are provided.

Key words: Sealed gas proportional counter, C2 gate, Plateau curve, Detection limit