For more than two decades, the NRC and industry have worked independently and together to assess the viability of scalable emergency planning zones (EPZs) for small modular reactors (SMRs) and other advanced reactor designs. In a preliminary finding made public last week in an Advanced Safety Evaluation, the NRC Staff agreed with the Tennessee Valley Authority’s (TVA) request for exemptions related to emergency planning, submitted as part of TVA’s Clinch River Early Site Permit application (ESPA). That conclusion included exemptions from the 10-mile EPZ requirement. This event marks the first time that the NRC Staff has concluded that a plume exposure pathway (PEP) EPZ with a radius of less than 10 miles may be appropriate for a commercial nuclear power plant utilizing an SMR design. This development suggests that the NRC Staff is willing to consider less expansive EPZs when licensing SMRs, and presumably other advanced reactors, when the applicant has provided sufficient analysis and technical bases for doing so.
The NRC’s regulations on emergency planning at nuclear power plants are codified at 10 CFR 50.47. Among other requirements, those regulations generally provide for a PEP EPZ and an ingestion exposure pathway EPZ. These EPZs generally consist of areas with about a 10-mile and 50-mile radius, respectively. 10 CFR 50.47(c)(2). Licensees establish protective action plans for these EPZs that are designed to avoid or reduce dose from potential exposure to radioactive materials.
Recognizing that the NRC’s regulations primarily have focused on large light water reactors and that the safety and performance attributes of SMRs might differ from those of large light water reactors, the NRC and industry have worked for more than two decades to assess the viability of scalable EPZs—EPZs with radii of less than 10 and 50 miles—for small modular reactors and other advanced reactor designs.
In May 2016, TVA submitted its ESPA to approve certain siting attributes for a potential nuclear plant consisting of several possible SMR designs at TVA’s Clinch River Nuclear Site in Tennessee. The ESPA provides a detailed analysis of the unique safety and performance attributes of these SMRs, and requests that the NRC grant exemptions related to the 10-mile PEP EPZ requirement, authorizing instead either a site-boundary PEP EPZ (in which the PEP EPZ is defined as the site) or a two-mile PEP EPZ (in which the PEP EPZ consists of an area with a two-mile radius). The specific size of the PEP EPZ would be determined by the SMR design ultimately selected for the site. Based on TVA’s analysis, the NRC Staff agreed with TVA’s exemption requests for a PEP EPZ consisting of an area with a radius of less than 10 miles.
This development will be of interest to SMR and advanced reactor designers. First, the NRC Staff’s agreement with TVA’s exemption request shows that, where public health and safety is protected, the NRC Staff is willing to consider exemptions from requirements related to emergency planning. Second, the contents of TVA’s ESPA provide a framework that future applicants can consider in preparing similar exemption requests. Third, the NRC Staff’s agreement with this exemption is the most recent example of a larger recognition that the enhanced safety features of small and advanced reactors might warrant a revised—and potentially simpler—licensing process.