**1. Introduction**

Instrumentation and control system (I&C) plays a vital role in the field of the nuclear industry. Nowadays I&C systems are embedded into the nuclear power plant (NPP) operation and reliability. Each component of NPP, such as transformers, valves, circuit breakers, heat exchangers. is equipped with digital I&C system whose reliability plays a vital role to avoid any accidents. Because these components are safety-critical systems (SCS) whose failure may cause huge losses in the form of economic loss, human resource damage, and environmental loss. As instrumentation and control systems are the important and first layer of safety, reliability, and stability in the NPP [1] that is the reason, it is essential to ensure the reliability of such a safety system. With, the introduction of digital control systems in the last few decades where the reliability of digital I&C must not be degraded. Therefore, researchers are rigorously working to address the dependability of the system. The dependability includes reliability, safety analysis, performance, and availability attributes that are ultimately related to security. The model checking may be used to various issues, which can lead to spurious actuation of the I&C system [2]. The transformation from analog to digital I&C safety systems added new challenges for researchers as well as software developers to deliver correct software reliability [3]. Based on this software experts could take essential steps early in the design phase of software by avoiding failures in I&C of NPP. The cyberattack occurred in the I&C system in the Iranian Bushehr nuclear power plant, where configure was destroyed by malicious code [4]. Therefore, it is essential to I&C systems required having secure and reliable to avoid any kind of attacks causing major accidents. Many researchers have put efforts to address the reliability analysis on such systems using various techniques, such as fault tree analysis (FTA), reliability block diagram (RBD), Bayesian network, etc.

This work proposes the reliability analysis of instrumentation and control system (I&C) of NPP using stochastic Petri net (SPN).

The organization of this paper is as follows. In Section 2, our focus is on the related work of the proposed work. In Section 3, we discuss the background and mathematical fundamentals. In Section 4, proposes the framework of the proposed method. In Section 5, the case study of the proposed work. In Section 6, reliability analysis of the proposed work. In Section 7, the validation part is covered. In Section 8, the conclusion is made with future work.
