ML19011A440

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Lecture 8-3 Fire Protection 2019-01-22
ML19011A440
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Issue date: 01/16/2019
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Office of Nuclear Regulatory Research
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Nathan Siu 415-0744
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Risk-Informed Fire Protection Lecture 8-3 1

Overview Key Topics

  • Browns Ferry fire
  • Fire PRA history
  • Risk-informed fire protection
  • Current controversies 2

Overview Resources

  • U.S. Nuclear Regulatory Commission, The Browns Ferry Nuclear Plant Fire of 1975 Knowledge Management Digest, NUREG/KM-0002, Rev. 1, February 2014.
  • S.P. Nowlen, M. Kazarians, and F. Wyant, Risk Methods Insights Gained From Fire Incidents, NUREG/CR-6738, September 2001.
  • N. Siu, N. Melly, S. P. Nowlen, and M. Kazarians, Fire Risk Assessment for Nuclear Power Plants, The SFPE Handbook of Fire Protection Engineering, 5th Edition, Springer-Verlag, New York, 2016.
  • Nuclear Energy Agency, CSNI Technical Opinion: Fire Probabilistic Safety Safety Assessment for Nuclear Power Plants: 2019 Update, Boulogne-Billancourt, France, in publication.
  • N. Siu, K. Coyne, and N. Melly, Fire PRA maturity and realism: a technical technical evaluation, U.S. Nuclear Regulatory Commission, March 2017.

(ADAMS ML17089A537) 3

Overview Other References

  • U.S. Code of Federal Regulations, Fire Protection, 10 CFR 50.48, June 16, 2004, last amended Aug. 28, 2007.
  • National Fire Protection Association, Performance-Based Standard for Fire Protection for Light Water Reactor Electric Generating Plants, NFPA 805, 2001 Edition, Quincy, MA, 2001. (Available through the NFPA Online Catalog at www.nfpa.org)
  • Electric Power Research Institute and U.S. Nuclear Regulatory Commission Office of Nuclear Regulatory Research, EPRI/NRC-RES Fire PRA Methodology for Nuclear Power Facilities, EPRI 1011989 and NUREG/CR-6850, Electric Power Research Institute (EPRI), Palo Alto, CA and U.S. Nuclear Regulatory Commission, Washington, DC, 2005.

4

Overview Other References (cont.)

  • M. Kazarians, N. Siu, and G. Apostolakis, Fire risk analysis for nuclear power plants:

methodological developments and applications, Risk Analysis, 5, 33-51, 1985.

  • N. Siu, J.T. Chen, and E. Chelliah, Research Needs in Fire Risk Assessment, NUREG/CP-0162, Vol. 2, 25th Water Reactor Safety Information Meeting Bethesda, MD, October 20-22, 1997.
  • U.S. Nuclear Regulatory Commission, Perspectives Gained from the Individual Plant Examination of External Events (IPEEE) Program, NUREG-1742, April 2002.
  • Nuclear Energy Agency, International Workshop on Fire PRA: Workshop Proceedings, NEA/CSNI/R(2015)12, Boulogne-Billancourt, France, 2015. (Available from:

http://www.oecd-nea.org/nsd/docs/indexcsni.html)

  • B. McGrattan, et al., Fire Protection and Fire Research Knowledge Management Digest, 2013, NUREG/KM-0003, 2013.
  • N. Siu, Fire Risk Assessment for Nuclear Power Plants, FPE 580R - Fire Risk Assessment and Policy, Worcester Polytechnic Institute, December 2, 2015. (ADAMS ML15301A832)
  • N. Siu, PSA Heterogeneity: Implications for Risk Aggregation, IAEA Consultancy Meeting on Development of a Methodology for Aggregation of Various Risk Contributors for Nuclear Facilities, International Atomic Energy Agency, Vienna, Austria, April 10-13, 2017. (ADAMS ML17093A744) 5

Risk-Informed Regulations 6

Browns Ferry Fire How it started Adapted from NUREG-0050

  • Browns Ferry Nuclear Power Plant (3/22/75)
  • Candle initiated cable tray fire; 11.5m 8.5m water suppression delayed; complicated shutdown
  • Second-most challenging event in U.S. nuclear power plant 3m operating history
  • Spurred changes in requirements and analysis 7

Browns Ferry Fire Browns Ferry (March 22, 1975) 8

Browns Ferry Fire Fire Protection After Browns Ferry

- 20 feet separation with detectors and auto suppression, OR hour fire barrier with detectors and auto suppression

  • Concerns

- Equivalence of protection methods:

whats best?

foot criterion: how protective?

- Possible to make win-win trade-offs?

- License by exemption?

From Cline, D.D., et al., Investigation of Twenty-Foot Separation Distance as a Fire Protection Method as Specified in 10 CFR 50, Appendix R, NUREG/CR-3192, 1983.

9

Fire PRA/RIDM History Early Fire PRAs

  • Early cable spreading room analyses

- WASH-1400

- HTGR PRA

  • NRC-sponsored, post-Browns Ferry R&D at UCLA => fire PRA methodology

- Physical model for fire-induced damage

- Incorporation in PRA via competing processes model (growth vs.

Professor George Apostolakis, UCLA suppression) (UCLA School of Engineering)

  • Used and refined in Zion and Indian Point PRAs

Fire PRA/RIDM History Early Results - Fire Can Be Important Or Even Dominant Contributor to CDF 11

Fire PRA/RIDM History Near Misses - Empirical Support for Results Event Summary Description*

Browns Ferry Multi-unit cable fire; multiple systems lost, spurious component and system (BWR, 1975) operations; makeup from CRD pump Electrical cable fire; station blackout (SBO), loss of all normal core cooling for 5 Greifswald hours, loss of coolant through valve; recovered through low pressure pumps and (VVER, 1975) cross-tie with Unit 2 Turbine lube oil fire , collapsed turbine building roof, propagated into control Beloyarsk (LWGR, building, main control room (MCR) damage, secondary fires; extinguished in 22 1978) hours; damage to multiple safety systems and instrumentation.

Electrical cable fire (multiple locations), smoke spread to Unit 1 MCR, secondary Armenia explosions and fire; SBO (hose streams), loss of instrumentation and reactor (VVER, 1982) control; temporary cable from emergency diesel generator to high pressure pump Chernobyl (RBMK, Turbine failure and fire, turbine building roof collapsed; loss of generators, loss of 1991) feedwater (direct and indirect causes); makeup from seal water supply Narora Turbine failure, explosion and fire, smoke forced abandonment of shared MCR; (PHWR, 1993) SBO, loss of instrumentation; shutdown cooling pump energized 17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br /> later

Fire PRA/RIDM History Risk-Informed Fire Protection (NFPA 805)

  • Difficulties with deterministic compliance with Appendix R => exemptions
  • Risk-informed approach

- Alternative method for regulatory compliance

- Additional benefits: improved understanding of sources of fire risk, 10 CFR 50.48(c)(3)

  • Risk-informed, performance-based fire protection (10 CFR 50.48(c), NFPA 805) Making Sausage Standard and regulatory approach

- Voluntary alternative to Appendix R development

- Deterministic and performance-based

  • Consensus process elements
  • Multiple stakeholders, diverse views (incl. strong PRA critics)

- Changes can be made without prior

  • Good enough for immediate approval; risk must be acceptable problem 13

Fire PRA/RIDM History Fire PRA R&D

  • Restarted in 1997

- Better understanding of fire risk

- Improved support of regulatory activities

- Methods and tools

  • Near- and long-term issues, e.g.,

- Multiple spurious operations

- Lessons from operational events

  • Fire risk requantification task (to assess impact of methodological improvements) => guidance development (joint with EPRI) to support NFPA 805 NUREG/CR-6850/EPRI TR1011989
  • Major disruption: 9/11 14

Fire PRA/RIDM History Fire R&D: The Laundry List (c. 1998) 15

Fire PRA/RIDM History Fire PRAs - More Recent Results 16

Fire PRA/RIDM History Fire PRAs - Risk Contributors From: K. Voelsing, EPRI Fire PRA Research Plan, U.S. Nuclear Regulatory Commission Regulatory Information Conference, March 15, 2018. 17

Fire PRA/RIDM History Recap: Fire PRA/RIDM in the U.S.

Industry Full-Scope PRAs IPEEEs NFPA 805 LARs Browns Ferry fire NFPA 805, 10 CFR 50.48(c),

RG 1.205, NEI 04-02, EPRI 1011989/NUREG/CR-6850, NUREG-1150/RMIEP (WASH-1400 analysis)

Fire PRA R&D 1975 1980 1985 1990 1995 2000 2005 2010 2015 18

Current Challenges A Heated Debate

  • Is fire PRA mature? Are the results overly conservative?
  • Industry concerns

- Expense of detailed analyses

- Realism of specific sub-models

- Flexibility in making plant changes

- Implications for other risk-informed applications

  • NRC concerns

- Technical basis for alternative models RG 1.174, Revision 3

- Implications for other risk-informed applications 19

Current Challenges Common View: The Need for Realism

  • Excessive conservatism or optimism can

- Inappropriately focus decision maker attention

- Lead to wasteful or even problematic solutions

- Mask opportunities for other improvements

- Damage stakeholder confidence

?

20

Current Challenges Current Issues - An Example

  • High Energy Arcing Faults (HEAF) in cabinets
  • Operational events, e.g.,

- Maanshan (2001)

- Robinson (2010)

- Onagawa (2011)

  • Potentially important contributor to fire risk
  • Multi-national experimental program 21

Current Challenges Where are we now?

  • Completed transitions to NFPA 805 (> 1/3 fleet)
  • Use of fire PRA methods by international organizations
  • Cooperative data collection and R&D to address some issues
  • Debates over appropriate R&D for others
  • Debates over proper aggregation of results from heterogeneous analyses 22

Current Challenges On Aggregation

  • Heterogeneity sources in a practical PRA:

- Multiple technical disciplines

  • Different states of knowledge
  • Different views on what needs to be and what can be reasonably modeled
  • Different views on acceptable modeling approaches
  • Different views on treatment of uncertainty

- Limited project resources

  • Numerical results need to be provided in context 23

Comments

  • Multiple technical cultures with varying/divergent views on appropriate use of risk information + need for expediency =>

- Compromise solutions that might not be good enough for other applications

- Different solutions for different technical domains (and technical cultures)

  • Personal concern: myopic tactics can have short-term success but also social impacts that hurt fundamental, long-term acceptance (let alone support) of PRA and RIDM

- Sound-bite characterization of issues

- Goal-directed R&D (reducing conservatism vs. improving realism)

- Marginalization of stakeholders 24

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