This chapter examines potential attack vectors that exist in a nuclear power plant and correlates the likelihood of an attack from each vector. The focus is on the boron monitoring system, which directly affects the reactivity in the core; cyber attacks on this system can lead to increased core wear, unsafe reactivity levels and poor power performance. A mockup model is developed using open-source software and hardware, which is tested to evaluate the potential of cyber attacks. A man-inthe-middle attack is implemented to demonstrate a cyber attack and its potential effects. Additionally, a redundancy-based cyber attack mitigation method is implemented using a hardware device that compares the input/output values of multiple programmable logic controllers. The approach for modeling general attack and defense steps is applicable to industrial control systems in the energy sector.