The instrumentation and control (I&C) equipment in nuclear power plants gradually ages and becomes obsolete with increased operation time. Its performance deteriorates, and the probability of its failure also increases gradually. The failure of I&C equipment may directly lead to the degradation of the control or protection functions, reducing the reliability and safety margin required by the design. This will hurt the safety and stable operation of nuclear power plants. Therefore, an aging I&C management/replacement strategy is necessary to control and minimize this problem.

In this regard, this paper establishes a module lifetime evaluation model described by a composite probability density function for modules composed of multiple components. On this basis, we have developed a multi-objective aging replacement optimization model aimed at high reliability, economy, and feasibility, and propose an equipment aging replacement optimization calculation method based on the linear-weighted discrete state transition algorithm. The procedure is verified by the application of data from nuclear power engineering. The results show that the proposed aging replacement strategy and method can significantly reduce computational difficulty, improve equipment reliability, and lower aging replacement costs.