Any risk in safety-critical or control applications may lead to catastrophic disaster; hence, safety is a primary concern for such applications. The impact of risk varies from minor inconvenience and cost to personal injury, significant economic loss, and death. Therefore, a safety assessment process should be an inherent part of the system development process to make a system safe or to ensure that the effects from failures are minimized. This paper deals with a new probabilistic approach to quantify the safety of safety-critical systems (SCSs) and control systems based on probabilistic safety assessment to deal with the shortcomings of the existing techniques. The methodology has been tested on 29 operational data sets to validate its effectiveness. This paper demonstrates the methodology on the digital feedwater controller system of a nuclear power plant. The results indicate that the method can identify possible hazards and quantify such hazards of a SCS.