This section discusses the development of NRC’s fire safety regulations, NRC’s adoption of risk-informed regulation, and the status of the nuclear industry’s adoption of the risk-informed fire safety approach. NRC’s deterministic fire safety approach and its risk-informed fire safety approach contain requirements that plants’ fire protection programs have defense-in-depth objectives in areas important to fire safety. Under both approaches, plants must meet the following objectives: (1) prevent fires from starting; (2) detect rapidly, control, and extinguish promptly those fires that do occur; and (3) provide protection for structures, systems, and components important to safety so that a fire that is not promptly extinguished by the fire suppression activities will not prevent the safe shutdown of the plant. The two approaches provide different methods for plants to demonstrate defense-in-depth capabilities. According to NRC officials and nuclear industry representatives, no fire since the Browns Ferry fire in 1975 has threatened a U.S. nuclear reactor’s ability to safely shut down. NRC’s deterministic fire safety approach requires that power plant operators ensure that at least one system of electric cables and equipment is available to safely shut down a reactor if a fire occurs. To meet requirements under the deterministic approach, these operators must, among other things, separate redundant systems, either by distance or fire resistant barriers, such as a fire resistant wall or floor, or by a material (fire wrap) that protects important cables and, in some cases, operators must install fire detection and automatic suppression systems. The requirements also specify the amount of space between redundant systems or how long fire barriers should be able to withstand For example, fire barriers must also be able to withstand fire for at fire. least 1 hour in areas with automatic fire suppression systems and fire detectors or for at least 3 hours where such features are not present. If these requirements are not met or if a redundant system required for shutdown could be damaged by fire suppression activities or operation of the fire suppression system, NRC requires an alternative dedicated shutdown capability. Figure 1 shows the process a plant operator uses to demonstrate fire safety compliance under the deterministic approach. Specifically, the deterministic fire safety approach requires nuclear reactors to have at least one redundant system of electric cables and equipment available to safely shut down the reactor. When two systems are in the same area of a nuclear reactor building, the regulations require that they be (1) separated horizontally by more than 20 feet with no intervening combustibles or fire hazards and for the area to have fire detectors and automatic fire suppression systems, or (2) separated by a fire barrier, such as a fireproof wall or floor, or by a material (fire wrap) that can withstand fire for 3 hours, or (3) enclosed by a fire barrier or material that can withstand fire for 1 hour and for the area to have fire detectors and an automatic fire suppression system. “Containment” refers to structures, systems, or components provided to prevent or mitigate the release of radioactive materials. A “radiant energy shield” is a device used to protect components from the effects of radiant heat generated by a fire. Over the years, NRC has approved exemptions or deviations from this deterministic approach for units that could not meet the fire safety requirements if the units could otherwise demonstrate the ability to safely shut down. Plants follow the following processes, as applicable: Exemption process. Under this process, plant operators could obtain an exemption from the deterministic requirements if they could demonstrate fire safety through methods or features other than those explicitly stated in the regulations. Deviation process. Some of the reactors that came online after NRC had defined the deterministic approach still could not meet the requirements. In such cases, NRC allowed operators to seek deviations from their licensing requirements if they could demonstrate an acceptable alternate approach to fire safety. In part because of variations among plant designs and different interpretations of fire safety regulations between industry and NRC, the agency continued to issue updated guidance related to the deterministic regulations, according to NRC and industry documents. However, in 2004, NRC reported that the processing of exemption and deviation requests had placed a “significant” burden on the resources of the agency and the nuclear industry. NRC also acknowledged that industry representatives and some members of the public described the deterministic requirements as an “unnecessary regulatory burden.” As of April 2012, NRC had granted more than 900 exemptions and deviations from the deterministic fire safety approach, according to NRC documents and officials. In response to charges that the processes for granting exemptions and deviations under the deterministic approach were burdensome, NRC issued a regulation in 2004 permitting plants to voluntarily transition to risk-informed fire protection requirements. Under this approach, a plant operator adopts performance goals, objectives, and criteria for fire safety that are defined by the fire protection standard issued by NFPA. The operator can use probabilistic risk assessments (PRA) and fire models, among other tools, to meet the performance criteria. A PRA is a systematic assessment of what can go wrong, its likelihood, and its potential consequences to determine quantitative estimates of a particular risk, such as a fire safety risk. Fire models are mathematical predictions of fire growth, environmental conditions, and potential effects on structures or systems. Figure 2 illustrates how a plant demonstrates fire safety compliance under the risk-informed approach. Nuclear power plant operators can choose to make a transition from using the deterministic approach to the risk-informed approach. In doing so, they can conduct a PRA that is subsequently reviewed by teams of experts from other plant operators and consulting firms that are not involved in developing the PRA under review. After the PRA is reviewed, the transitioning plant requests that NRC amend the plant’s operating license. NRC staff review the amendment request and, if necessary, request additional information from plant operators and conduct audits of transition documents to ensure that the plant has conducted the necessary tasks. If NRC approves the license amendment request, it will issue a final report evaluating the safety of the plant, after which the transition is considered complete. According to NRC documents and officials, the agency expects the approval process for each plant to take about 2 years after the plant submits its request for a license amendment. NRC’s change to a risk-informed approach to fire safety is part of a larger NRC effort to move toward accepting or adopting a risk-informed approach to nuclear safety in general. Examples are as follows. In 1995, NRC issued a policy statement encouraging the increased use of PRA in all regulatory matters to the extent supported by the state of the art in PRA methods and data and in a manner that complemented NRC’s existing deterministic approach and supported NRC’s defense-in-depth philosophy. In 2007, NRC issued regulations requiring applicants for combined licenses for new nuclear power reactors to submit a description and the results of a plant-specific PRA to NRC as part of their applications. NRC also began requiring recipients of combined licenses to develop, maintain, and periodically upgrade a plant- specific PRA. Among other things, NRC required the PRA to cover initiating events––that is, events that can lead to a reactor accident— for which there are NRC-endorsed consensus standards for PRA. In 2011, NRC commissioned a risk management task force to develop a strategic vision and options for adopting a more comprehensive risk- informed, performance-based regulatory approach. In its April 2012 report, the task force identified goals and objectives that could be the framework for NRC regulatory activities 10 to 15 years in the future and addressed changes that would be needed to ensure that the framework is implemented. The task force reported, “NRC has recognized that purely deterministic and prescriptive approaches can limit the flexibility of both the regulated industries and the NRC to respond to lessons learned from operating experience and support the adoption of improved designs or processes.” The task force went on to recommend, among other things, “the goal to adopt risk- informed and performance-based approaches, where practical, should continue and should be incorporated into the revised regulatory framework.” According to NRC documents, the 65 commercial nuclear power plants operating in the United States house 104 reactors that incorporate 80 different designs. Furthermore, operators for 47 of these reactors, located at 29 plants, plan to or are in the process of transitioning to the risk- informed approach to fire safety. NRC has adopted a staggered schedule for such plants to submit license amendment requests seeking approval to transition to the risk-informed approach. This schedule anticipates that the agency will receive amendment requests from all of the plants by 2014 and will decide on all of the requests by 2016. (Appendix III contains a list of transitioning plants and the dates they are scheduled to submit their license amendment requests to NRC.) According to NRC officials, the agency has implemented a discretionary enforcement policy under which inspection findings related to the transition will not automatically result in violations or penalties. The period of enforcement discretion is tied to each plant’s committed date for submitting its license amendment request and, according to NRC documents, provides incentive for plants to adhere to their transition schedule. Plants that elect not to complete the transition process must then seek exemptions or deviations or conduct the modifications necessary to comply with the deterministic approach. To assist the transition process, operators at two plants—including a plant with three reactors in South Carolina and a plant with one reactor in North Carolina—participated in a pilot program for the risk-informed approach. These plants began the transition in August 2005 and, by December 2010, both plants had completed it. In 2011, NRC issued a report on lessons learned from the pilot experience for other plant operators interested in making the transition. Figure 3 shows the location of the 65 power plants and identifies those with nuclear reactors that will transition to the risk-informed approach and those that remain under the deterministic approach.