The document outlines a foundation for conducting root cause analyses based on 9 key facts. The foundation establishes that (1) an event results from factors that can be traced through a hierarchical tree structure, (2) addressing any harmful factors can prevent recurrence, and (3) preserving mitigating factors can limit severity of future events. The suggestion is to use this foundational approach to thoroughly investigate root causes.

1. A Foundation for Root Cause Analysis William R. Corcoran, Ph.D., P.E. Nuclear Safety Review Concepts Corporation © 2011 W. R. Corcoran, NSRC Corporation, firebird.one@alum.MIT.edu

3. NSRC Experience PECO NUCLEAR A Unit of PECO Energy

4. YMP Bill Corcoran Assisted Facilities Designated by This Logo and Some Others. DNFSB PORTSMOUTH METROPOLIS CHALK RIVER

5. Bill Corcoran Assisted Units Designated by This Logo and Some Others.

7. Root Cause Analysis? Root Cause Analysis is any structured approach to identifying the factors that resulted in the nature, the magnitude, the location, and the timing of the consequences of one or more past events in order to identify what conditions, behaviors, actions, and/or inactions, need to be changed to prevent/reduce recurrence of similar consequences, when adverse, and to identify the lessons to be learned to promote the achievement of better consequences. COMMENT: A given root cause analysis can be successful or unsuccessful. It can be superficial or insightful. It can be honest or dishonest. As long as it is a structured approach with the intent given above it would be fairly classed with other root cause analyses. © 2011 W. R. Corcoran, NSRC Corporation, firebird.one@alum.MIT.edu

8. A Purpose of RCA © 2011 W. R. Corcoran, NSRC Corporation, firebird.one@alum.MIT.edu

9. What’s a Problem? A gap between what ought to be and what is.

10. Some Examples of “What is.” © 2011 W. R. Corcoran, NSRC Corporation, firebird.one@alum.MIT.edu BP Deepwater Hindenburg Bhopal Chernobyl Timing Location Magnitude Nature Nickname

16. Harmful Effects (Factor Building Block) © 2011 W. R. Corcoran, NSRC Corp., William.R.Corcoran@1959.USNA.com Harmful Effect (Consequence or Factor) Direct Factor 1 Direct Factor 2 Direct Factor … Direct Factor 3 Direct Factor …

18. Harmful Effects (Four Property-related Factors) © 2011 W. R. Corcoran, NSRC Corp., William.R.Corcoran@1959.USNA.com Factor types are not mutually exclusive. Harmful Effect Direct Factor(s) Affecting Nature of Effect Direct Factor(s) Affecting Magnitude of Effect Direct Factor(s) Affecting Location of Effect Direct Factor(s) Affecting Timing of Effect

20. Harmful Effects (Four Factor Involvement Types) © 2011 W. R. Corcoran, NSRC Corp., William.R.Corcoran@1959.USNA.com Harmful Effect Vulnerability (Set-up) Trigger Exacerbation Mitigation

21. © 2011 W. R. Corcoran, NSRC Corp., William.R.Corcoran@1959.USNA.com THREAT BARRIER THE BASICS OF BARRIER ANALYSIS BARRIER: Anything that has the effect of (or is intended to ) reduce the probability and/or consequences of the effect of a threat on a target. (Notice that a barrier is only defined with respect to both a threat and a target.) TARGET

23. Harmful Effects (Barrier Analysis Elements) © 2011 W. R. Corcoran, NSRC Corp., William.R.Corcoran@1959.USNA.com Harmful Effect (Vulnerable) Target Hazard/ Threat No Effective Barriers Co-location Simultaneity

25. Factor X Direct Factor Direct Factor Direct Factor Direct Factor Intermediate Factor Deeper Intermediate Factor Root Factor Factor Module for Factor X

32. Questions? For a free subscription to "The Firebird Forum" send me an e-mail. © 2011, William R. Corcoran, NSRC Corp., 860-285-8779, firebird.one@alum.mit.edu