United States Nuclear Regulatory Commission - Protecting People and the Environment

Advanced Reactors Sub-Arena

Advanced reactors comprise one of four sub-arenas that the staff of the U.S. Nuclear Regulatory Commission (NRC) identified in considering which areas of the reactor safety arena to target for greater use of risk information. This page summarizes the following aspects of this sub-arena:

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Develop a coherent risk-informed and performance-based regulatory structure for design certification, licensing, and oversight of advanced reactors.

A coherent risk-informed and performance-based regulatory structure would offer significant improvements in effectiveness and efficiency (compared to the structure that has evolved for current-generation LWRs). For example, such coherence would ensure that the safety reviews conducted by the NRC consider design and operational aspects in an integrated manner. The bases for developing such a regulatory structure for licensing and oversight of advanced reactors are articulated in numerous Commission documents and policy statements. However, this guidance occurs largely in the context of existing and new LWRs and, consequently, needs to be adapted for advanced reactors.

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The bases for a coherent risk-informed and performance-based regulatory structure arise from the potential to realize benefits that are captured in the screening criteria that the NRC staff considers in undertaking regulatory improvement initiatives:

  • Effectiveness: One hallmark of effectiveness is the ability to model the tradeoffs that are involved in a complex safety review. Sometimes, such tradeoffs are represented as the ability to achieve desired outcomes in the licensing process. A risk-informed and performance-based regulatory structure is inherently better able to do this, especially if it is applied in the early phases of developing a new regulatory structure for advanced reactors.
  • Effective Communication: The explicit modeling of decision-making promotes transparency. Sometimes, the traditional prescriptive regulatory structure lacks transparency because it tends to emphasize compliance with a prescribed quantity, rather than focusing on the safety function.
  • Research: The NRC staff has conducted significant research into the models and methodologies for the risk-informed and performance-based regulatory structure and the products and expertise from this work are available for implementation. Particularly notable examples include NUREG-1860, NUREG/BR-0303, and SECY-05-0138. Specific details will need to be determined and guidance developed based on the particular technology and design aspects of the application.
  • Costs: The implementation of a coherent risk-informed and performance-based regulatory structure for advanced reactors will entail a combination of short- and long-term costs. The new regulatory approaches are likely to result in short-term costs. However, when considered in the context of implementing the Commission's strategic objectives, there are sound reasons to expect a significant reduction in the total cost to society.
  • Obstacles: There are no apparent factors (e.g., state-of-the-art, adverse stakeholder perception) that would preclude implementing a risk-informed and performance-based approach to the design certification, licensing, and oversight of advanced reactors once sufficient operating experience is available to provide input to the activities.

The NRC developed its strategic planning process as a result of considerable effort (beginning in the late-1990s) to improve the agency's regulatory structure in a forward-looking way, while preserving the gains that the agency had achieved in operating reactor safety. Using the most recent version of the Strategic Plan, development of a coherent risk-informed and performance-based regulatory structure for advanced reactors will involve implementing the strategies that the Commission articulated in the goal of "Safety". Under "Safety" strategies, the Commission directed the staff to "Use sound science and state-of-the-art methods to establish, where appropriate, risk-informed and performance-based regulations." This element continues to be part of the Strategic Plan for the Fiscal Year (FY) 2008–2013.

The basic infrastructure for the implementation of a risk-informed and performance-based approach exists at a high-level in Commission documents, such as the "White Paper on Risk-Informed and Performance-Based Regulation." The staff has also developed some specific guidance, including the risk-informed process for implementing the single-failure criterion (SECY-05-0138), but more may need to be developed. In many instances, the high-level documents superficially apply only to existing LWRs; however, more thorough study reveals considerable applicability to all reactor technologies. For example, the Reactor Oversight Process (SECY-99-007 and SECY-99-007A, as well as related staff requirements memorandum) provides a risk-informed and performance-based structure, although it is overlaid on top of existing LWR requirements.

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The staff's risk-informed and performance-based goals for advanced reactors relate to the following activities:

  • Ensure advanced reactor applicants use risk-informed safety insights to select among alternative features, operational strategies, and design options to reduce or eliminate the significant risk contributors of existing operating plants.
  • Ensure that the risk associated with advanced reactor designs compare favorably with the Commission's goals of less than 1E-04/year for core damage frequency and less than 1E-06/year for large release frequency

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List of Risk-Informed and Performance-Based Activities

This list shows the ongoing licensing initiatives, projects, and activities that the staff of the U.S. Nuclear Regulatory Commission (NRC) has targeted for greater use of risk information in the Advanced Reactors Sub-Arena within the Reactor Safety Arena:

Risk-Informed Review of Small Modular Reactor (SMR) Designs

Summary Description

In the Staff Requirements Memorandum (SRM) COMGBJ-10-0004/COMGEA-10-0001, "Use of Risk Insights to Enhance the Safety Focus of Small Modular Reactor Reviews," dated August 31, 2010, the Commission provided direction to the NRC staff on the preparation for, and review of, small modular reactor (SMR) applications, with a near-term focus on integral pressurized-water reactor designs. The Commission directed the NRC staff to more fully integrate the use of risk insights into pre-application activities and the review of applications and, consistent with regulatory requirements and Commission policy statements, to align the review focus and resources to risk-significant structures, systems, and components (SSCs) and other aspects of the design that contribute most to safety in order to enhance the effectiveness and efficiency of the review process. The Commission directed the NRC staff to develop a design-specific, risk-informed review plan for each SMR design to address pre-application and application review activities. One aspect of this review plan is the Design Specific Review Standards (DSRSs).

FY 2015 Status

The DSRS for the NuScale design has been drafted to provide guidance to the NRC technical staff for review of the NuScale Design Certification Application (DCA). In the Federal Register Notice of June 30, 2015, the NRC solicited public comment on the DSRS and Safety Review Matrix for the NuScale design. The comment period ended on August 31, 2015 and the staff continued to evaluate the comments received.


The final version of the NuScale DSRS was published on August 5, 2016. A working group was organized to develop tools for conducting the safety review of the NuScale DCA. The staff developed a SSC review tool to assist the technical reviewers in their review. The staff briefed the ACRS on the technical review process on August 16, 2016.


The staff applied the SSC review tool concepts including risk insights to enhance the safety focus of the NuScale DCA. The staff developed graded review approaches for each technical review areas. Senior managers presented these review approaches to their peers for feedback and to achieve a common management understanding of the proposed scope and depth of review in the various technical disciplines. The staff also briefed the ACRS on the staff's review approaches on May 3, 2017. The staff continues to monitor the implementation of the graded review for the NuScale DCA.

Risk-Informed Basis

This activity uses risk insights to prioritize staff review efforts on the more safety significant aspects of the NuScale design for a more effective and efficient review.

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Non-Light Water Reactor Licensing Modernization

Summary Description

The NRC is supporting risk-informed activities related to the Licensing Modernization Project (LMP) being led by Southern Company, coordinated by NEI, and cost-shared by DOE. The LMP's objective is to assist the NRC to develop technology-inclusive, risk-informed, and performance based regulatory guidance for licensing non-LWRs.

FY 2017 Status

The staff completed its review of two LMP white papers, "Modernization of Technical Requirements for Licensing of Advanced Non-Light Water Reactors - Selection of Licensing Basis Events (Draft Report)," and "Modernization of Technical Requirements for Licensing of Advanced Non-Light Water Reactors - Probabilistic Risk Assessment Approach (Draft Report)." The staff provided written comments to the LMP and the staff discussed the issues in public stakeholder meetings. The staff is currently reviewing one LMP white paper, "Modernization of Technical Requirements for Licensing of Advanced Non-Light Water Reactors - Safety System Classification." An additional LMP white paper on defense-in-depth is expected to be submitted in calendar year 2017. The staff is discussing the LMP project with industry and other interested stakeholders during a series of public meetings on non-light water reactor licensing issues.

Risk-Informed Basis

This activity supports risk-informing the licensing process for non-light water reactors.

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Staff Review of NuScale Emergency Planning Zone Licensing Topical Review

Summary Description

The purpose of this licensing topical report (LTR) is to provide a methodology to establish the technical basis for plume exposure emergency planning zone (EPZ) sizing, for the NuScale small modular reactor (SMR) plant design. Nuclear power plant emergency planning regulatory requirements are codified under 10 CFR and in coordination with FEMA. The current regulatory plume exposure EPZ for power reactors is ten miles but there is a provision for a different EPZ size for reactors with a thermal power of 250 MWt or less on a case-by-case basis. As the NuScale small modular reactor is a passive, 160 MWt (50 MWe) per module reactor, NuScale submitted a methodology to establish the technical basis for EPZ sizing with calculated results to illustrate its usability.

FY 2017 Status

The staff initiated the review of this LTR in December 2016.

Risk-Informed Basis

This activity will determine the acceptability of the risk-informed methodology to establish the EPZ sizing for the NuScale plant.

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Page Last Reviewed/Updated Wednesday, May 09, 2018