Advertisement

Fire Technology

, Volume 53, Issue 3, pp 1249–1271 | Cite as

Statistical Characterization of Heat Release Rates from Electrical Enclosure Fires for Nuclear Power Plant Applications

Article

Abstract

Since the publication of NUREG/CR-6850/EPRI 1011989 in 2005, the US nuclear industry has sought to re-evaluate the default peak heat release rates (HRRs) for electrical enclosure fires typically used as fire modeling inputs to support fire probabilistic risk assessments (PRAs), considering them too conservative. HRRs are an integral part of the fire phenomenological modeling phase of a fire PRA, which consists of identifying fire scenarios which can damage equipment or hinder human actions necessary to prevent core damage. Fire ignition frequency, fire growth and propagation, fire detection and suppression, and mitigating equipment and actions to prevent core damage in the event fire damage still occurred are all parts of a fire PRA. The fire growth and propagation phase incorporates fire phenomenological modeling where HRRs have a key effect. A major effort by the Electric Power Research Institute and Science Applications International Corporation in 2012 was not endorsed by the US Nuclear Regulatory Commission (NRC) for use in risk-informed, regulatory applications. Subsequently the NRC, in conjunction with the National Institute of Standards and Technology, conducted a series of tests for representative nuclear power plant electrical enclosure fires designed to definitively establish more realistic peak HRRs for these often important contributors to fire risk. The results from these tests are statistically analyzed to develop two probabilistic distributions for peak HRR per unit mass of fuel that refine the values from NUREG/CR-6850, thereby providing a fairly simple means by which to estimate peak HRRs from electrical enclosure fires for fire modeling in support of fire PRA. Unlike NUREG/CR-6850, where five different distributions are provided, or NUREG-2178, which now provides 31, the peak HRRs for electrical enclosure fires can be characterized by only two distributions. These distributions depend only on the type of cable, namely qualified versus unqualified, for which the mean peak HRR per unit mass is 11.3 and 23.2 kW/kg, respectively, essentially a factor of two difference. Two-sided, 90th percentile confidence bounds are 0.0915 to 41.2 kW/kg for qualified cables, and 0.0272 to 95.9 kW/kg for unqualified cables. From the mean (~70th percentile) upward, the peak HRR/kg for unqualified cables is roughly twice that for qualified, increasing slightly with higher percentile, an expected phenomenological trend. Simulations using variable fuel loadings are performed to demonstrate how the results from this analysis may be used for nuclear power plant applications.

Keywords

Electrical enclosures Cable fires Heat release rates Fire modeling Nuclear power plants 

Notes

Acknowledgements

The authors wish to thank Dr. Marc Janssens and Osvaldo Pensado of the Center for Nuclear Waste Regulatory Analyses at the Southwest Research Institute for their comments and suggestions that improved this paper.

References

  1. 1.
    USNRC/EPRI, EPRI/NRC-RES (Office of Nuclear Regulatory Research) (2005) Fire PRA methodology for nuclear power facilities, NUREG/CR-6850/EPRI 1011989Google Scholar
  2. 2.
    USNRC (1987) An experimental investigation of internally ignited fires in nuclear power plant control cabinets: part 1—cabinet effects tests, NUREG/CR-4527/1.Google Scholar
  3. 3.
    USNRC (1987) An experimental investigation of internally ignited fires in nuclear power plant control cabinets: part 2—room effects tests, NUREG/CR-4527/2Google Scholar
  4. 4.
    Mangs J, Keski-Rahkonen O (1994) Full-scale fire experiments on electronic cabinets, Technical Research Centre of Finland, VTT Publications 186, EspooGoogle Scholar
  5. 5.
    Mangs J, Keski-Rahkonen O (1996) Full-scale fire experiments on electronic cabinets II. Technical Research Centre of Finland, VTT Publications 269, EspooGoogle Scholar
  6. 6.
    EPRI (2012) Evaluation of peak heat release rates in electrical cabinet fires (Reanalysis of Table G-1 of NUREG/CR-6850 and EPRI 1011989), EPRI 1022993Google Scholar
  7. 7.
    Mangs J, Paananen J, Keski-Rahkonen O (2003) Calorimetric fire experiments on electronic cabinets. Fire Saf J 38:165–186Google Scholar
  8. 8.
    Melis S, Rigollet L, Such JM, Casselman C (2004) Modelling of electrical cabinet fires based on the CARMELA experimental program. Eurosafe ForumGoogle Scholar
  9. 9.
    USNRC (2012) Recent fire PRA Methods Review Panel Decisions and EPRI 1022993, ‘Evaluation of Peak Heat Release Rates in Electrical Cabinet Fires’,” Letter from Joseph Giitter, Director, Division of Risk Assessment, Office of Nuclear Reactor Regulation, NRC, to Biff Bradley, Director, Risk Assessment, NEI, June 21, 2012 (ADAMS Accession No. ML12172A406)Google Scholar
  10. 10.
    USNRC (2015) Refining and characterizing heat release rates from electrical enclosures during fire (RACHELLE-FIRE)—volume 1: peak heat release rates and effect of obstructed plume, NUREG-2178Google Scholar
  11. 11.
    IEEE (2015) 383-2015, IEEE standard for qualifying electric cables and splices for nuclear facilitiesGoogle Scholar
  12. 12.
    USNRC (2012) Cable heat release, ignition, and spread in tray installations during fire (CHRISTI-FIRE), NUREG/CR-7010, vol 1Google Scholar
  13. 13.
    USNRC (2015) Heat release rates of electrical enclosure fires (HELEN-FIRE), NUREG/CR-7197Google Scholar
  14. 14.
    USNRC/EPRI (2014) Nuclear power plant fire ignition frequency and non-suppression probability estimation using the updated fire events database, NUREG 2169/EPRI 3002002936Google Scholar
  15. 15.
    Worrell C, Rochon C (2016) Fire probabilistic risk assessment and its applications in the nuclear power industry. Fire Technol 52(2):443–467Google Scholar
  16. 16.
    Gallucci RHV (2009) Thirty-three years of regulating fire protection at commercial U.S. nuclear power plants: dousing the flames of controversy. Fire Technol 45(4):355–380Google Scholar
  17. 17.
    Gallucci RHV (2016) Statistical characterization of cable electrical failure temperatures due to fire for nuclear power plant risk applications. Fire Technol 1–12. doi: 10.1007/s10694-016-0616-0
  18. 18.
    McGrattan K, Peacock R, Overholt K (2016) Validity of fire models applied to nuclear power plant safety. Fire Technol 52(1): 5–24 (2016)Google Scholar

Copyright information

© Springer Science+Business Media New York (outside the USA) 2016

Authors and Affiliations

  1. 1.U.S. Nuclear Regulatory Commission (USNRC)WashingtonUSA

Personalised recommendations