An Investigation of Turbine Blade Ejection Frequency Considering Common Cause Failure in Nuclear Power Plants

공통원인고장을 고려한 원전 터빈블레이드 비산빈도계산

  • Oh, Ji-Yong (Central Research Institute, Korea Hydro & Nuclear Power Co., Ltd.) ;
  • Chi, Moon-Goo (Central Research Institute, Korea Hydro & Nuclear Power Co., Ltd.) ;
  • Hwang, Seok-Won (Central Research Institute, Korea Hydro & Nuclear Power Co., Ltd.)
  • 오지용 (한국수력원자력 중앙연구원) ;
  • 지문구 (한국수력원자력 중앙연구원) ;
  • 황석원 (한국수력원자력 중앙연구원)
  • Received : 2011.02.21
  • Accepted : 2012.02.08
  • Published : 2012.04.01


The objective of this research is to examine the probabilistic approach to evaluating turbine ejection frequency considering common-cause failure. This paper identifies basic turbine ejection mechanisms under high and low speeds and presents a detailed probabilistic methodology (fault tree) for assessing ejection frequency. The alpha factor methodology is applied to common-cause failure evaluations. The frequencies under different test schemes are compared and the propagation of uncertainty through the fault tree model is evaluated. The following conclusions were reached: (1) the turbine blade ejection frequency due to ductile failure under high speed is around 8.005E-7/yr; (2) if common-cause failure is considered, the frequency will be increased by 11% and 33% depending on the test scheme; and (3) if the parameter uncertainties are considered, the frequency is estimated to be in the range of 9.35E-7 to 1.13E 6, with 90% confidence.


Turbine;Ejection;Missile;Fault Tree;Uncertainty;Staggered;Non-Staggered


  1. KHNP, Kori units 3&4 Turbine-Generator System P&ID.
  2. KHNP, 2004, Kori units 3&4 Final Probabilistic Safety Assessment Report.
  3. Spencer H. Bush, 1973, "Probability of Damage to Nuclear Components Due to Turbine Failure," Nuclear Safety.
  4. Rosario, D., 2001, "Technical Approach to Turbine Missile Probability Assessment," EPRI TR 10006451.
  5. PRA Procedures Guide, 1982, NUREG/CR-2300, ANS and IEEE.
  6. Park, C.K. and Ha, J.J., 2003, "Probabilistic Safety Assessment," KAERI.
  7. Oh, J.Y. and Kim, O.G., 2010, "Test Interval Extension of Kori 3&4 Turbine Overspeed Protection System Valve," NETEC.
  8. Mosleh, A., 1998, "Guidelines on Modeling Common Cause Failures in Proabilistic Risk Assessment," NUREG/CR-5485.
  9. 2007, "CCF Parameter Estimations 2007," updating data for NUREG/CR-5485, NRC.
  10. Ang, A. and Tang, W., 1975, "Probability Concepts in Engineering Planning and Design," Wiley & Sons.
  11. Modarres, M., 1999, "Reliability Engineering and Risk Analysis," Marcel Dekker.
  12. Shooman, M., 1968, "Probabilistic Reliability of Engineering Approach," McGraw-Hill.