Digital Instrumentation and Control (I&C) systems in critical energy infrastructure, including nuclear power plants, raise cybersecurity concerns. Cyber-attack campaigns have targeted digital Programmable Logic Controllers (PLCs) used for monitoring and autonomous control. This paper describes the Nuclear Instrumentation and Control Simulation (NICSim) platform for emulating PLCs and investigating potential vulnerabilities of the I&C systems in nuclear power plants. It is being developed at the University of New Mexico’s Institute for Space and Nuclear Power Studies (UNM-ISNPS), in collaboration with Sandia National Laboratories (SNL), with high fidelity emulytics and modeling capabilities of a physics-based, dynamic model of a PWR nuclear power plant. The NICSim platform would be linked to the SCEPTRE framework at SNL to emulate the response of the plant digital I&C systems during nominal operation and while under cyber-attack.