• Jung, Jae-Cheon (NSSS Engineering and Development Division, Korea Power Engineering Company) ;
  • Chang, Hoon-Sun (NSSS Engineering and Development Division, Korea Power Engineering Company) ;
  • Kim, Hang-Bae (NSSS Engineering and Development Division, Korea Power Engineering Company)
  • Published : 2009.02.28


The "3+3 Process" for safety critical software for nuclear power plants' I&C (Instrumentation and Control system) has been developed in this work. The main idea of the "3+3 Process" is both to simplify the software development and safety analysis in three steps to fulfill the requirements of a software safety plan [1]. The "3-Step" software development process consists of formal modeling and simulation, automated code generation and coverage analysis between the model and the generated source codes. The "3-Step" safety analysis consists of HAZOP (hazard and operability analysis), FTA (fault tree analysis), and DV (design validation). Put together, these steps are called the "3+3 Process". This scheme of development and safety analysis minimizes the V&V work while increasing the safety and reliability of the software product. For assessment of this process, validation has been done through prototyping of the SDS (safety shut-down system) #1 for PHWR (Pressurized Heavy Water Reactor).


  1. IEEE Std. 1228-1994, “IEEE Standards for Software Safety Plans”, IEEE, Aug. 1994
  2. Debra S. Herrmann, “Software Safety and Reliability”, IEEE Computer Society, 1999, pp. 28-32, 48-54
  3. Standish Group International, Inc., “Extreme Chaos”, 2001
  4. Jean-Louis Camus, Bernard Dion, “Efficient Development of Airborne Software with Scade SuiteTM”, Esterel Technologies white-paper, 2003
  5. NUREG/CR-6430, “Software Safety Hazard Analysis”, U.S. Nuclear Regulatory Commission, Feb. 1996
  6. Regulatory guide 1.173, “Developing Software Life Cycle Processes for Digital Computer Software used in Safety System of NPPs”, U.S. Nuclear Regulatory Commission, Sep. 1997
  7. Elizabeth Hull, Ken Jackson and Jeremy Dick, “Requirements Engineering”, Springer, 2005
  8. Korea Institute of Nuclear Science, “Development of Safety Requirements and Guides for Digital Based I&C System Important to Safety in NPPs”, KINS/RR-106, Mar. 2002
  9. IEEE Std. 1012-2004, “IEEE Standard for Software Verification and Validation”, IEEE, June 2005
  10. IEC Std. 61508-5, “Functional Safety of Electrical/Electronics/ Programmable/Electronics Safety-related Systems - Part 5: Examples of Methods for the Determination of Safety Integrity Levels”, IEC, 1998
  11. IEEE Std. 1074-1995, “IEEE Standards for Software Life Cycle Processes”, IEEE, Sep. 1995
  12. Neil Storey, “Safety-Critical Computer Systems”, Addison- Wesley Publishing Company, 1996
  13. Francois Pilarski, “Cost Effectiveness of Formal Methods in the Development of Avionics System at Aerospace”, $17^{th}$ Digital Avionics Conference, WA, Nov. 1998
  14. Wolfram Hohmann “Supporting Model based Development with Unambiguous Specifications, Formal Verification and Correct-by-construction Embedded Software”, Society of Automotive Engineers, SAE international, 2004
  15. Felix Redmill, Morris Chudleigh, and James Catmur, “System Safety: HAZOP and Software HAZOP,” John Wiley & Sons, 1999, pp. 25–26