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Operating Reactors Sub-Arena

The Nation's fleet of operating reactors comprises 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 the Operating Reactors Sub-Arena:

Objective

Make continuing, incremental improvements in rulemaking, licensing, and oversight of operating reactors, while focusing on implementing existing risk-informed and performance based activities.

This objective focuses on activities that are already in progress to risk-inform the operating reactor subarena, including completed rulemaking activities, guidance documents, and implementation of some initiatives.

The NRC will revisit and update this objective (as appropriate) once the industry has implemented the currently planned activities and feedback becomes available.

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Basis

The risk-informed initiatives currently in progress were originally selected using screening criteria similar to those presented in the RPP. Consequently, the five activities (listed below) that support the goals for this subarena satisfy the following screening criteria:

  • The risk-informed initiatives that are currently underway help to improve the effectiveness and efficiency of the NRC’s regulatory process, including improved safety and reduction of unnecessary regulatory burden.
  • Information and analytical models of operating reactors, particularly for at-power operations, exist and are fairly mature.
  • The cost-beneficial nature of several of the risk-informed initiatives is evidenced by their voluntary adoption by licensees.
  • No factors have been identified to date that would motivate changing the regulatory approach in the areas where risk-informed activities are already underway. Stakeholder feedback substantiates that there is no immediate need to initiate any new risk-informed initiatives, and that the NRC should focus on completing currently identified activities and allowing the industry time to implement those activities.
  • Goals and activities to meet the objective for this subarena will be performance-based, to the extent that they meet the following four criteria:
    1. measurable parameters to monitor performance
    2. objective criteria to assess performance
    3. flexibility to allow licensees to determine how to meet the performance criteria
    4. no immediate safety concern as a result of failure to meet the performance criteria

Risk-informed activities for operating reactors occur in five broad categories:

  • applicable regulations
  • licensing process
  • revised oversight process
  • regulatory guidance
  • risk analysis tools, methods, and data

The activities in these categories are derived from the Commission’s policy statements and guidance, and include revisions to technical requirements in the regulations; risk-informed technical specifications; a new framework for inspection, assessment, and enforcement actions; guidance on other risk-informed applications (e.g., in-service inspections); and improved standardized plant analysis risk models.

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Goals

The following goals are derived from the Commission’s policy statements and guidance, which reflect the current phase of NRC and industry development, as well as the current implementation of risk-informed activities:

  • Finish the development of current risk-informed regulations (e.g., 10 CFR 50.46a rulemaking) and associated regulatory/staff guidance.
  • Implement existing NRC risk-informed activities [e.g., risk-informed technical specifications and pilots for 10 CFR 50.69 and the National Fire Protection Association (NFPA) Standard 805].
  • Encourage the industry to implement risk-informed rules and approved/endorsed activities.
  • Continue making incremental improvements to the established licensing, rulemaking, and oversight activities.
  • Modify/update established activities to account for lessons learned.

Risk-Informed and Performance-Based Activities

The following tables specify the ongoing programs and projects that the staff of the U.S. Nuclear Regulatory Commission (NRC) has targeted for greater use of risk information in the Operating Reactors Sub-Arena within the Reactor Safety Arena.

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Rulemaking Function for Operating Reactors

Initiative, Program or Project Project Description and Major Activities Status
Oct 2012
Emergency Core Cooling System (ECCS) Requirements: Re-definition of Loss-of-Coolant Accidents (LOCAs)

Make risk-informed changes to LOCA-related technical requirements (10 CFR 50.46a).

  • Issue final rule (revised 10 CFR 50.46) to redefine large LOCA.
 More Information
Emergency Core Cooling System (ECCS) Requirements: LOCA-Loss of Offsite Power (LOOP)

Remove the requirement to consider a LOOP in conjunction with a large LOCA.

  • Complete safety evaluation of the LOCA-LOOP topical report promulgated by the Boiling-Water Reactor Owners' Group (BWROG).
  • Issue final rule to remove LOCA-LOOP requirement.
 More Information

Licensing Function for Operating Reactors

Initiative, Program or Project Project Description and Major Activities Status
Oct 2012
Revise Regulatory Guide 1.201

Guidelines for Categorizing Structures, Systems, and Components (SSCs) in Nuclear Power Plants (NPPs) According to Their Safety Significance

  • Conduct pilot application of Title 10, Section 50.69, of the Code of Federal Regulations (10 CFR 50.69).
 More Information
Update Regulatory Guide 1.174 As directed in SRM-SECY-11-0014, Regulatory Guide 1.174 and related regulatory guides (i.e., RGs 1.175, 1.177, and 1.178) were updated to clarify language describing defense-in-depth and the draft regulatory guides (DGs 1285, 1286, 1287, and 1288) are available for public review and comment.
Out for public review and comment.
Develop risk-informed improvements to the standard technical specifications (STS) Initiative 1 - Define the preferred end-state for technical specification actions [usually hot-shutdown for pressurized-water reactors (PWRs)]. More Information
Initiative 4b - Modify the current system of fixed completion times to allow reliance on a configuration risk management program (CRMP) to determine risk-informed completion times.
Initiative 5 - Optimize surveillance frequencies.
Initiative 6 - Modify actions associated with Limiting Condition for Operation (LCO) 3.0.3 to allow a risk-informed evaluation to extend operating time prior to shutdown.
Initiative 8 - Risk-inform the scope of 10 CFR 50.36.
National Fire Protection Association (NFPA) Standard 805 Review the implementation of NFPA 805, "Performance-Based Standard for Fire Protection for Light-Water Reactor Electric Generating Plants." More Information
Risk-Informed, Performance-Based Implementation and Improvements in Fire PRA and related activities More Information
Digital Systems Probabilistic Risk Assessment (PRA)

Development of methods, tools, and guidance for (1) including digital system models in nuclear power plant (NPP) PRAs and (2) incorporating digital systems into the NRC’s risk-informed licensing and oversight activities

  • Software failure quantification (proof-of-concept studies); address other areas where enhancement in the state-of-the-art for PRA modeling of digital systems is needed (e.g., modeling of self-diagnostics, reconfiguration, and surveillance; software common-cause failure; and data for hardware failures of digital components)
 More Information

Oversight Function for Operating Reactors

Initiative, Program or Project Project Description and Major Activities Status
Oct 2012
Consequential Steam Generator Tube Rupture (C-SGTR) Develop an enhanced risk-assessment procedure for C-SGTR by closing technical gaps. More Information
Development of Standardized Plant Analysis Risk (SPAR) Models

Develop Standardized Plant Analysis Risk (SPAR) models for each unique plant-specific design (as applicable), and maintain models to support user needs.

  • Enhance/Update Level 1 SPAR Models.
  • Develop External Event SPAR Models.
  • Develop Low-Power/Shutdown Models.
  • Develop Level 2/Large Early Release Frequency (LERF) Models.
 SECY-12-0133
Maintenance and development of the Systems Analysis Programs for Hands-on Analysis Integrated Reliability Evaluations (SAPHIRE) Code Maintain and update the SAPHIRE software and documentation. More Information
Event and Condition Assessment: Technical Guidance

Provide guidelines for analysis of events, and maintain guidelines in support of revised methods and user needs.

  • Provide an integrated handbook for the analysis of internal, external, and low-power/shutdown events.
  • Document Methods for estimating common-cause failure (CCF), equipment unavailability, independent failure probability, and initiating event frequency.
 More Information
Event and Condition Assessment: Technical Support

Maintain analysis methods to support user needs, and provide on-call technical assistance to senior reactor analysts and NRR.

  • Provide event-specific methods and SPAR model modifications (MD 8.3, ROP, ASP).
  • Provide Significance Determination Process (SDP) analysis reviews, as requested.
  • Provide support (methods and models) to the Risk Assessment Standardization Project (RASP) help desk.
NRC Risk Network A structured assessment to define, prioritize, and implement enhancements to risk tools. More Information
Risk-related Generic Issues (GI) from the Generic Issues Program (GIP)

Several active GIs are heavily relying on risk analysis for their resolution.

GI-191: Assessment of Debris Accumulation on PWR Sump Performance.
GI-199: Implications of Updated Probabilistic Seismic Hazard Estimates in Central and Eastern US on Existing Plants.
GI-204: Flooding of Nuclear Power Plant Sites Following Upstream Dam Failure.

 More Information
Implementing Lessons Learned from Fukushima Following the accident at the Fukushima Dai-ichi nuclear plant in Japan, the NRC initiated actions to evaluate lessons learned and to implement appropriate changes in nuclear power plant designs and procedures. Initial recommendations were included in the Near Term Task Force (NTTF) report entitled “Recommendations for Enhancing Reactor Safety in the 21st Century.” Several of the items (e.g., Recommendation 1 regarding improving the regulatory framework and Recommendation 2.1 on re-evaluating seismic and flooding hazards) include incorporation of risk-informed, performance-based approaches into NRC activities. The status and program plans for items identified for longer term evaluations were reported to the Commission in SECY 12-0095.
More Information
Full-scope site Level 3 Probabilistic Risk Assessment (PRA) Develop a Level 3 PRA, generally based on current state-of-practice methods, tools, and data, that (1) reflects technical advances in PRA and related fields, as well as plant modifications, that have occurred since the NUREG-1150 studies were published in 1990, and (2) addresses scope considerations that were not considered in NUREG-1150 (e.g., low power and shutdown, multiunit risk, and spent fuel storage). More Information
Improvement of Human Reliability Analysis (HRA) methods and practices

HRA efforts address the suitability of an individual method to a regulatory application; consistency among HRA practitioners in use of methods; the absence of guidance on the rigor needed for quantifying human reliability; and the scarcity of empirical data to evaluate human performance.

  • International HRA Empirical Study for benchmarking HRA methods.
  • NRC/EPRI collaborative effort to address HRA model differences (SRM-M061020).
  • Develop HRA methodology for risk analyses of shutdown operational events.
 More Information

Data collection for HRA

  • Implement MOU with the South Texas Project Nuclear Operation Company (STPNOC) to use STPNOC's crew and simulator for data collection.
 More Information
Risk Informing Emergency Preparedness Oversight: Proof of Concept Examine feasibility of risk informing EP regulatory structure.  As a first step, select accident scenarios and explore use for significance determination More Information
Risk Informing Emergency Preparedness Oversight: Performance Based Offsite Response Organization Evaluation Study feasibility of using performance based evaluation techniques for emergency response programs More Information
Risk Informing Emergency Preparedness Oversight: Risk Inform Emergency Action Levels (EALs) Apply SPAR models to calculate the conditional core damage probabilities (CCDPs) of different event scenarios for each EAL at different emergency classification levels (ECLs).  Determine if there is any new risk-informed insight that can be applied to update the EALs in each plant.  Results will be published in a NUREG/CR by December 2012. More Information
Risk Informing Security Workshop The staff plans to conduct a workshop on risk-informing security as a follow-on to the September 2010 workshop conducted at Sandia National Laboratories. More Information

To request additional information, Contact Us About Risk-Informed, Performance-Based Regulation.

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Page Last Reviewed/Updated Tuesday, June 18, 2013