ml120600599 - overview of u.s. nrc pra
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Overview of U.S. NRC PRA
Kevin CoyneProbabilistic Risk Assessment Branch
Office of Nuclear Regulatory Research
US Nuclear Regulatory Commission
13thAnnual Meeting of WGRisk
March 7-9, 2012
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Presentation Outline
Overview of Key Research Projects
Emerging Focus Areas
Fukushima Res onse
Recent Publications
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Overall PRA Research Goals
Support the reactor oversight and operating
experience programs.
Using risk-informed approaches to improve the
effectiveness and efficiency of regulation.
Expand PRA infrastructure to encompass new
and advanced reactor concepts and designs.
Support continuous advancement in PRA state-of-the-art and state-of-practice.
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Supporting Reactor Oversight
SPAR Focus Areas in the Coming Year
Other hazard and NFPA-805 fire models.
Support system initiating events.
Inte rated ca abilities model.
One SPAR model with all modes/hazards/levels that SPARcurrently covers.
Confirmatory success criteria analysis 4-loop Westinghouse plant.
Resolution of ASME peer review findings and
observations.
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Supporting Reactor Oversight
(cont.)
Common-Cause Failures (CCF) in Event
Assessment Draft NUREG-XXXX, Common-Cause Failure
Analysis in Event and Condition Assessment:
,
(ML111890290).
Topics treated in the NUREG include: Treatment of CCF potential conditioned upon an observed
component failure. Limitations of current CCF modeling and issues with alpha-factor
estimates.
Future research needed for data collection, parameter estimation
and casual models.
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Improving Effectiveness: PRA
Standards
PRA standards under development:
Level 1 (CDF) and LERF for low power and shutdownconditions addressing both internal and external hazards for
operating LWRs.
Level 1 (CDF) and LERF for at-power conditions addressing
both internal and external hazards for LWRs in design stage(pre-operational).
Level 2 for at-power conditions addressing both internal and
external hazards for operating and advanced LWRs.
Level 3 for all operating modes, all hazards, and both lightwater and non-light water reactors.
Level 1 and Level 2 for all operating modes addressing both
internal and external hazards for non-light water reactors.
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Improving Effectiveness: PRA
Standards (cont.)
NEI has develop/developing peer review guidance NEI 00-02/NEI 05-04 addresses Level 1/LERF for at-power
conditions for operating LWRs for internal events and internalflood.
NEI 07-12 address Level 1/LERF for at-power conditions for
o eratin LWRs for internal fires.
NEI developing guidance for seismic PRA for Level 1/LERF forat-power conditions.
PRA Standards and peer review guidance
endorsed in RG 1.200. NRC issuing Interim Staff Guidance documents providing
interim staff endorsement on updates to the standard until next
revision.
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Improving Effectiveness: Fire
Research Fire PRA and HRA
NFPA-805 Support - NRC/EPRI Training (2 classes/year):
July 1620, 2012 (Washington DC Area).
September 2428, 2012 (Washington DC Area).
NUREG-1921, Fire HRA, Summer 2012.
Fire Modeling
- , uc ear ower an re o e ng pp ca on u e, ummer .
Fire and Electrical Systems Circuit Analysis
NUREG/CR-7100, Direct Current Electrical Shorting in Response to Exposure Fire
(DESIREE-Fire): Test Results, Summer 2012.
Electrical Circuit Phenomena PIRT in progress.
Fire Testing
NUREG/CR-7115, Performance of Metal and Polymeric O-Ring Seals in Beyond-Design-
Basis Temperature Excursions, in publication; expected in April.
NUREG/CR-7010, Cable Heat Release, Ignition, and Spread in Tray Installations During
Fire (CHRISTIFIRE), Spring 2012.
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Emerging Focus Areas
Investigate risk-informed Emergency Action
Levels (NUREG Report under development).
Support spent fuel pool limited-scope
consequence study.
Continued work in dynamic event tree Level 1
and Level 2 PRA.
Evaluating options for more holistic risk-informed, performance-based regulatory
approach (February 11, 2011 Tasking Memo).
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Spent Fuel Pool Scoping Study
Focus: reexamination of the potential
advantages associated with moving older fuel
stored in the SFP to dry cask storage in an
expedited manner.
deliberations and external stakeholder interest. The project isusing:
Available information/methods.
A representative operating cycle for a BWR Mark I.
Past studies to narrow scope.
Plan finalized in July 2011.
Study to be completed by Summer 2012.
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Site Level 3 PRA
Commission directed the staff to perform a full-
scope comprehensive site Level 3 PRA for an
operating plant. Staff engaged nuclear industry; Vogtle, Units 1 and 2,
volunteered for study (4-Loop Westinghouse PWR).
Objectives: Reflect technical advances in PRA modeling and improvements
in plant operations, safety, and security.
Enhance PRA scope and capability. Extract new insights to enhance regulatory decision-making.
Evaluate feasibility and cost of Level 3 PRAs.
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Site Level 3 PRA (cont.)
In general, based on current state of practice.
Scope includes main site radiological sources, allinternal and external initiating events, and all
modes of operation.
e s u y w e or a s ng e mu -un s e og e,Units 1 and 2).
Study to be completed over a 4-year period.
Currently developing project plans, securingcontractor support, collecting and assessing
information on current state-of-practice.
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Fukushima Follow-Up: Key
Documents SECY-11-0093 (July 12th) and SRM (August 19th), Near-Term Report
and Recommendations for Agency Actions Following the Events in
Japan.
SECY-11-0117 (August 26th) and SRM (October 19th) Proposed Charter
for the Longer-Term Review of Lessons Learned from the March 11, 2011,
Japanese Earthquake and Tsunami.
SECY-11-0124 (September 9th) and SRM (October 18th),
Recommended Actions to be Taken Without Delay from the Near-Term
Task Force Report a.k.a. the 21 day paper.
SECY-11-0137, October 3rd, Prioritization of Recommended Actions to
be Taken in Response to Fukushima Lessons Learned a.k.a. the 45
day paper.
SECY-12-0025, Proposed Orders and Requests for Information in
Response to Lessons Learned from Japan's March 11, 2011, Great
Tohoku Earthquake and Tsunami.
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Fukushima Follow-Up
SECY-11-0137 contains staffs prioritization of
the NTTF recommendations. Tier 1 Start without delay.
Tier 2 Start in the near term.
Tier 3 Longer term actions.
SECY-12-0025 contains draft orders and
response to previous Fukushima items. Draft orders on Mitigating Strategies for Beyond-Design-Basis
External Events, Hardened and Filtered Vents (Mark I and IIBWRs), and Spent Fuel Pool Instrumentation.
Draft 50.54(f) letter - External Hazards Reevaluation.
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Recently-Issued Reports
NRC Staff Reports
NUREG-1935, State-of-the-Art Reactor ConsequenceAnalyses (SOARCA) Report, Draft for Comment
(comment period ended March 1, 2012).
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Analysis to Support Specific Success Criteria in the
Standardized Plant Analysis Risk ModelsSurry and
Peach Bottom, September 2011.
NUREG-2115, Central and Eastern United StatesSeismic Source Characterization for Nuclear Facilities,
January 2012.
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Recently-Issued Reports (cont.)
NRC Contractor Reports NUREG/CR-7004, Technical Basis for Regulatory Guidance on Design-Basis
Hurricane-Borne Missile Speeds for Nuclear Power Plants, November 2011.
NUREG/CR-7005, Technical Basis for Regulatory Guidance on Design-Basis
Hurricane Wind Speeds for Nuclear Power Plants, November 2011.
- , a e-o - e- r eac or onsequence na yses ro ec ,
January 2012.
NUREG/CR-7114, Methodology for Low Power/Shutdown Fire PRA, Draft for
Comment (comment period ended March 1, 2012).
NUREG/CR-7039, Systems Analysis Programs for Hands-on Integrated
Reliability Evaluations (SAPHIRE) Version 8: Technical Reference, June 2011.
NUREG/CR-7046, Design-Basis Flood Estimation for Site Characterization at
Nuclear Power Plants in the United States of America, November 2011.
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Recently Issued Regulatory Guides
RG 1.174, An Approach For Using Probabilistic Risk
Assessment In Risk-Informed Decisions On Plant Specific
Changes To The Licensing Basis, May 2011.
RG 1.177, An Approach For Plant-specific, Risk-informed
Decision-Making: Technical Specifications, May 2011.
RG 1.221, Design-Basis Hurricane and Hurricane Missilesfor Nuclear Power Plants, October 2011.
DG-1278, proposed Revision 3 to RG 1.160, Monitoring the
Effectiveness of Maintenance at Nuclear Power Plants,issued in September 2011, comment period closed, soon to
be issued as final.
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