ML19011A438
| ML19011A438 | |
| Person / Time | |
|---|---|
| Issue date: | 01/16/2019 |
| From: | Office of Nuclear Regulatory Research |
| To: | |
| Nathan Siu 415-0744 | |
| Shared Package | |
| ML19011A416 | List:
|
| References | |
| Download: ML19011A438 (19) | |
Text
Risk-Informed Regulatory Applications Lecture 8-1 1
Overview Key Topics U.S. applications - general and more examples*
- Regulations and guidance
- Licensing
- Oversight
- Operational experience
- See also Lecture 1-2 2
Overview Resources
- N. Siu, et al., Probabilistic Risk Assessment and Regulatory Decisionmaking: Some Frequently Asked Questions, NUREG-2201, U.S. Nuclear Regulatory Commission, September 2016.
- Coyne, K.A., Risk-Informed Regulation at the U.S. Nuclear Regulatory Commission, April 14, 2016. (ADAMS ML16105A427)
- U.S. Nuclear Regulatory Commission, Risk-Informed Activities https://www.nrc.gov/about-nrc/regulatory/risk-informed/rpp.html 3
Overview Other References
- G. Apostolakis, et al., A Proposed Risk Management Regulatory Framework, NUREG-2150, U.S Nuclear Regulatory Commission, April 2012.
- C. Miller, et al., Recommendations for Enhancing Reactor Safety in the 21st Century: The Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident, July 12, 2011. (ADAMS ML111861807)
- U.S. Nuclear Regulatory Commission, A Review of NRC Staff Uses of Probabilistic Risk Assessment, NUREG-1489, March 1994.
- Jackson, S.A., Transitioning to Risk-Informed Regulation: The Role of Research, NRC Commissioner Speech S-98-26, 26th Annual Water Reactor Safety Meeting, October 26, 1998. (ADAMS ML003711267)
- P.K. Samanta, et al, Handbook of Methods for Risk-Based Analyses of Technical Specifications NUREG/CR-6141, December 1994.
- U.S. Nuclear Regulatory Commission, Generic Environmental Impact Statement for License Renewal of Nuclear PlantsFinal Report, NUREG-1437, Revision 1, June 2013.
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Overview Other References (cont.)
Training Course P111: PRA Technology and Regulatory Perspectives, Module S, U.S. Nuclear Regulatory Commission. (ADAMS M12160A497)
- U.S. Nuclear Regulatory Commission, Notices of Enforcement Discretion, Inspection Manual Chapter 0410, October 4, 2012. (ADAMS ML12263A456)
- U.S. Nuclear Regulatory Commission, Significance Determination Process, Inspection Manual Chapter 0609, June 2, 2011. (ADAMS ML101400479)
- U.S. Nuclear Regulatory Commission, Integrated Risk-Informed Decision-Making Process for Emergent Issues, Office of Nuclear Reactor Regulation Office Instruction LIC-504, Revision 4, June 2, 2014. (ADAMS ML14035A143)
- U.S. Nuclear Regulatory Commission, Generic Issues Program, Management Directive 6.4, January 15, 2015. (ADAMS ML14245A048)
- U.S. Nuclear Regulatory Commission, Resolution of Generic Safety Issues:
Introduction, NUREG-0933, Main Report with Supplements 1-34, latest version available from http://nureg.nrc.gov/sr0933/Introduction/Introductions.html, December 2011.
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Risk-Informed Regulation All Functions, All Arenas 6
Risk-Informed Regulation Regulatory Approach Standard* Principles**
- Independence Reasonable assurance
- Openness of adequate protection
- Efficiency
- Clarity
- Reliability
- When granting, suspending, revoking, or amending licenses or construction permits.
(Atomic Energy Act of 1954, as amended - see NUREG-0980, v1, n7, 2005)
- NRC Strategic Plan (NUREG-1614, v6, 2014) 7
Regulations and Guidance Risk-Informed Regulation
- Risk information used to strengthen For each rulemaking, requirements, relax requirements, provide regulatory guide, or generic flexibility in meeting requirements (as long letter we issue, the as adequate protection is ensured).
Commission conducts a
- Numerous rules: regulatory analysis to
- 10 CFR 50.44 (Combustible Gas Control) weigh the costs associated
- 10 CFR 50.48 (NFPA 805) with the action against the
- 10 CFR 50.61a (PTS Rule) risk reduction and safety
- 10 CFR 50.63 (Station Blackout Rule)
- 10 CFR 50.65 (Maintenance Rule) enhancement to be
- 10 CFR 50.69 (Special Treatment) achieved.
- 10 CFR 50.109 (Backfit Rule) - S.A. Jackson (1998)
- 10 CFR 52.47 (New Reactor Certification and Licensing)
- Guidance documents support each application. (See Lecture 8-2) 8
Regulations and Guidance In the Future?
- Post-Fukushima Near-Term Task Force: recommended restructuring patchwork of regulatory requirements and other safety initiatives
- NUREG-2150 (initiated pre-Fukushima): proposal to increase use of risk information
- Concerns with resources, disruption during agency response 9
Licensing Changes in Plant Licensing Basis (RG 1.174)
- Voluntary changes:
licensee requests, NRC reviews
- Small risk increases might be acceptable
- Change requests may be combined
- Decisions are risk-informed 10
Licensing Risk-Informed Technical Specifications
- An early application of PRA technology [See Bickel (1983), Samanta et al. (1994)]
- Completion times (aka Allowed Outage Times)
Proposed completion time Currently allowed completion time Unavailability (and risk) increases with AOT and with
- Surveillance frequencies (aka Surveillance Test STI. Why might Intervals) the proposed Proposed STI changes be Currently allowed STI acceptable?
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Licensing Plant License Renewal
- Environmental reviews consider potentially cost-beneficial severe accident mitigation alternatives (SAMA)
- Plant-specific PRAs not required but typically used to support evaluations
- NRC reviews (supplements to NUREG-1437) often have information on risk contributors, sometimes have history of PRA model 12
Oversight Oversight Activities DCDF < 1E-6
- Reactor Oversight Program* DLERF < 1E-7
- Inspections
- Performance indicators (including 1E-6 < DCDF < 1E-5 Mitigating Systems Performance Index) 1E-7 < DLERF < 1E-6
- Significance Determination Process -
SDP 1E-5 < DCDF < 1E-4 1E-6 < DLERF < 1E-5
- Incident Investigation (Management Directive 8.3)*
DCDF > 1E-4
- Notice of Enforcement Discretion DLERF > 1E-5 (NOED)
CDF = Core damage frequency LERF = Large early release frequency
- See Lectures 1-2, 7-1 13
Operational Experience Operational Experience
- Accident Sequence Precursor (ASP) Program (Lecture 7-1)
- Emergent Issues (LIC-504)
- Generic Issues 14
Operational Experience Emergent Issues LIC-504 15
Operational Experience Generic Issues Program
- Addresses multi-facility issues affecting public health and safety, the common defense and security, or the environment (with respect to radiological health and safety
- Required by Congress; status and resolutions reported to Congress and the public
- Issues can be raised by public or by staff
- Three stages https://www.nrc.gov/about-nrc/regulatory/gen-issues/dashboard.html#genericIssue/genericIssueDetails/3
- Screening
- Assessment (including consideration of risk)
- Regulatory Office Implementation 16
Decision Support Decision Support
- R&D and other technical support (see Lecture 8-2)
- Near-term regulatory application
- Longer-term anticipated need
- Risk-informed R&D prioritization: coming soon?
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Positive Outcomes from PRA*
- Actionable safety insights and lessons
- SLOCA > LLOCA => protecting against worst case design basis accident (DBA) doesnt mean risk has been minimized
- Importance of SBO, auxiliary feedwater, human error, CCF, fires and external hazards
- Plant-specific nature of risk
- Changes that improved plant responses to actual events
- Improved plant performance
- Improved equipment reliability and plant performance under Maintenance Rule
- Reduced outage durations increased capacity factors
- Reduced worker doses (risk-informed in-service inspections)
- Increased objectivity of regulatory oversight (ROP)
- Not all resulting from regulatory activities 18
Thought Exercises Risk-Informed Technical Specifications
- The pre-outage unavailability growth curves look linear. Under what conditions is this reasonable?
- The computed risk increases from extending an AOT or STI is often very small. Why shouldnt indefinite extensions be allowed?
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