Risk-informed performance-based emergency preparedness for advanced reactors

The U.S. Department of Energy’s Argonne National Laboratory and the Nuclear Energy Institute worked together to create new guidance on emergency planning for small modular and advanced reactors. Their guidance, NEI 24-05, provides a methodology for using modern risk insights to develop emergency planning zones and emergency plans that match the actual characteristics and risk of each facility and site.

The work builds on the U.S. Nuclear Regulatory Commission’s (NRC) 2023 emergency preparedness rule for small modular reactors, non-light-water reactors and certain non-power facilities, such as medical isotope plants. This rule established a risk-informed, performance-based, and consequence-based emergency preparedness framework, which is considered necessary given the breadth of proposed new reactor technologies. 

A key part of the guidance is a step-by-step process to determine the size of the plume exposure pathway emergency planning zone, or EPZ. The EPZ is the area around a facility where special planning and resources might be needed to protect the public from radioactive material during an accident. The approach leverages the Licensing Modernization Project framework, which identifies Licensing Basis Events — a full spectrum of credible accident scenarios with estimated likelihood of occurrence and radiological releases.

For each event with a possible release of radioactive material, analysts calculate the potential radiation dose to the public based on the distance from the plant. After reviewing all identified Licensing Basis Events, they examine the total likelihood that a member of the public might receive more than one rem of radiation dose over 96 hours, which is the threshold tied to federal protective action guides for taking protective actions. In addition to potential radiation dose, the method also considers the characteristics of the event, such as the timing of the release of radioactive material, to examine the necessity and effectiveness of different protective action approaches. 

Importantly, the NRC rule and guidance recognize that, for some advanced designs, it may be possible to show that no offsite EPZ is needed, or in other words, the EPZ does not extend beyond the plant site boundary. In those cases, the plant must still have robust plans for protecting workers and any members of the public on site, in addition to capabilities to coordinate with offsite response organizations, as necessary.

The guidance also explains how the site emergency plan can leverage risk insights to aid in the determination of emergency classification levels, staffing, resources, and radiation monitoring. That alignment should make emergency planning more transparent, cost-effective, and better matched to each technology, while maintaining reasonable assurance of public health and safety.

NEI 24-05 has been reviewed by the NRC, which issued a letter in April indicating acceptability of the methodology, with plans for formal endorsement in the coming months. Reactor vendors can now leverage the guidance and the NRC approval to implement the approach within their reactor license applications. 

This effort was funded by the DOE Office of Nuclear Energy, Regulatory Development Program, which works to accelerate the safe and timely deployment of nuclear technologies through modernization of regulatory frameworks, tools, and guidance.