Can the Nuclear Regulatory Commission Match Regulation to Risk?

The Proposed Part 57 Licensing Framework Is a Start

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On May 1, the Nuclear Regulatory Commission (NRC) released a proposed new licensing framework—Part 57—for microreactors and other designs with very low potential offsite consequences.

The proposed rule closely follows the release of the final Part 53 rule that establishes a technology-inclusive licensing framework aligned with advanced reactor technology and modern risk analysis. Part 53 represents a transition away from purely deterministic regulation—such as earlier licensing frameworks like Part 50 and 52 that regulated the construction of large reactors—but is not a risk-informed, performance-based approach.

Part 57 differs from existing NRC rules because it works as a pathway for reactors that first satisfy restrictive entry criteria. The rule is built around the idea that some reactors are small enough, simple enough, and low-consequence enough that applying the licensing structure developed for large commercial power reactors may add cost and delay without adding commensurate safety value.

But Part 57 would not be a universal shortcut for new reactors. Proposed reactors must clear two gates before accessing streamlined licensing. First, applicants must show, with reasonable assurance, that an individual in the unrestricted area following an accident would not receive more than 1 rem total effective dose equivalent for the duration of the accident. Second, the reactor must have a total inventory of thorium, uranium, and plutonium—i.e. nuclear fuel—less than 10 metric tons.

The proposed rule could represent the first attempt by the NRC to create a licensing framework proportional to the safety risk of a proposed reactor. Proportional regulation is the right goal for the NRC, but Part 57 can only achieve that if the Commission can justify its entry criteria, explain its operational assumptions, and make its framework internally coherent.