DOI QR코드

DOI QR Code

Comparison of event tree/fault tree and convolution approaches in calculating station blackout risk in a nuclear power plant

  • Man Cheol Kim (School of Energy Systems Engineering, Chung-Ang University)
  • Received : 2023.02.06
  • Accepted : 2023.09.13
  • Published : 2024.01.25

Abstract

Station blackout (SBO) risk is one of the most significant contributors to nuclear power plant risk. In this paper, the sequence probability formulas derived by the convolution approach are compared with those derived by the conventional event tree/fault tree (ET/FT) approach for the SBO situation in which emergency diesel generators fail to start. The comparison identifies what makes the ET/FT approach more conservative and raises the issue regarding the mission time of a turbine-driven auxiliary feedwater pump (TDP), which suggests a possible modeling improvement in the ET/FT approach. Monte Carlo simulations with up-to-date component reliability data validate the convolution approach. The sequence probability of an alternative alternating current diesel generator (AAC DG) failing to start and the TDP failing to operate owing to battery depletion contributes most to the SBO risk. The probability overestimation of the scenario in which the AAC DG fails to run and the TDP fails to operate owing to battery depletion contributes most to the SBO risk overestimation determined by the ET/FT approach. The modification of the TDP mission time renders the sequence probabilities determined by the ET/FT approach more consistent with those determined by the convolution approach.

Keywords

Acknowledgement

This work was supported by the Nuclear Safety Research Program of the Korea Foundation of Nuclear Safety funded by the Korean Government's Nuclear Safety and Security Commission [grant number 2203027-0122-CG100, 2104028-0222-SB120].

References

  1. Office of the Federal Register, Station Blackout (10 CFR 50.63), Code of federal regulations, June 1988. 
  2. USNRC, Station Blackout (Regulatory Guide 1.155), United States Nuclear Regulatory Commission, Washington, DC, 1988. August. 
  3. R.E. Battle, D.J. Campbell, Reliability of Emergency AC Power Systems at Nuclear Power Plants (NUREG/CR-2989), United States Nuclear Regulatory Commission, Washington, DC, 1983. 
  4. A.M. Kolaczkowski, A.C. Payne Jr., Station Blackout Accident Analyses (NUREG/CR-3226), United States Nuclear Regulatory Commission, Washington, DC, 1983. 
  5. P.W. Baranowsky, Evaluation of Station Blackout Accidents at Nuclear Power Plants (NUREG-1032), United States Nuclear Regulatory Commission, Washington, DC, 1988. 
  6. S.A. Eide, C.D. Gentillon, T.E. Wierman, D.M. Rasmuson, Reevaluation of Station Blackout Risk at Nuclear Power Plants (NUREG/CR-6890), United States Nuclear Regulatory Commission, Washington, DC, 2005. 
  7. IAEA, Case Study on the Use of PSA Methods: Station Blackout Risk at Millstone Unit 3, International Atomic Energy Agency, Vienna, Austria, 1991 (IAEA-TECDOC-593). 
  8. J.A. Schroeder, R.F. Buell, Proposed SPAR Modeling Method for Quantifying Time Dependent Station Blackout Cut Sets, 10th International Probabilistic Safety Assessment & Management Conference (PSAM10), 2010. 
  9. P.J. Rodi, Algorithms for Incorporation of Dynamic Recovery in Estimating Frequency of Critical Station Blackout, Master of Science Thesis, Texas A&M University, May 2012. 
  10. J.K. Knudsen, T. Wood, S. Prescott, C. Smith, J.A. Schroeder, Convolution correction factor adjustments on static PRA models for event assessment, in: Proceedings of the International Topical Meeting on Probabilistic Safety Assessment and Analysis (PSA 2017), 2017, pp. 156-162. 
  11. M.M. Degonish, Practical Application of the loss of offsite power recovery analysis using the convolution methodology, PSA2019, in: Proceedings of the International Topical Meeting on Probabilistic Safety Assessment and Analysis, 2019. 
  12. M.C. Kim, Systematic approach and mathematical development for conditional core damage probabilities under station blackout of a nuclear power plant, Reliab. Eng. Syst. Saf. 217 (January 2022), 107969. 
  13. KEPCO and KHNP, APR1400 Design Control Document, Tier 2 (APR1400-K-X-FS-14002-NP), Revision 3, Korea Electric Power Corporation (KEPCO) and Korea Hydro & Nuclear Power Co, Ltd. (KHNP), 2018. 
  14. S.A. Eide, T.E. Wierman, C.D. Gentillon, D.M. Rasmuson, C.L. Atwood, Industry-average Performance for Components and Initiating Events at U.S. Commercial Nuclear Power Plants (NUREG/CR-6928), United States Nuclear Regulatory Commission, Washington, DC, 2007. 
  15. Z. Ma, T.E. Wierman, K.J. Kvarfordt, Industry-average Performance for Components and Initiating Events at U.S. Commercial Nuclear Power Plants: 2020 Update (INL/EXT-21-65055), Idaho National Laboratory, Idaho Falls, Idaho, 2021. 
  16. S.A. Eide, C.D. Gentillon, T.E. Wierman, D.M. Rasmuson, Reevaluation of Station Blackout Risk at Nuclear Power Plants - Analysis of Loss of Offsite Power Events: 1986-2004 (NUREG/CR-6890), United States Nuclear Regulatory Commission, Washington, DC, 2005. 
  17. N. Johnson, Z. Ma, Analysis of Loss-Of-Offsite-Power Events 2020 Update (INL/EXT-21-64151), Idaho Falls, Idaho National Laboratory, Idaho, 2021.