Fire protection in US nuclear power plants was long regulated under a set of federal regulations called 10 CFR 50.48 Appendix R that prescribed fire protection measures. In 2001, the National Fire Protection Association issued NFPA 805, a performance based standard for fire protection at nuclear power plants. This standard, endorsed by the US Nuclear Regulatory Commission (NRC), allowed plants to transition from a prescriptive fire protection program to a performance based. Since the issue of NFPA 805, the NRC has issued additional rules allowing the use of risk assessment in support of maintenance and plant technical specifications. All of these applications require a detail risk model of the plant of which fire is a major contributor to overall risk. This presentation will give an overview of risk assessment at US nuclear power plants with a focus on fire risk assessment and the hierarchy of modeling tools used in support of the assessment.