A Foundation For Root Cause Analysis 2011.05.25
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Transcript of A Foundation For Root Cause Analysis 2011.05.25
A Foundation for Root Cause Analysis
William R. Corcoran, Ph.D., P.E.
Nuclear Safety Review Concepts Corporation
© 2011 W. R. Corcoran, NSRC Corporation, [email protected]
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Anyone who obtains this may:
• Use this slideshow in whole or in part in any training activity in their organization.
• Adapt this slideshow for use in their organization
Provided that:
• It does not go outside their organization without the permission of NSRC Corporation.
• The source of the material is always indicated.• Any changes to it are shared with Bill Corcoran.
© 2011 W. R. Corcoran, NSRC Corporation, [email protected]
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PECONUCLEARA Unit of PECO Energy
4
YMP
Bill CorcoranAssisted Facilities
Designated by This Logo and Some
Others.
DNFSB
PORTSMOUTH
METROPOLIS
CHALK RIVER
5
Bill CorcoranAssisted Units
Designated by This Logo and Some
Others.
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Root Cause Analysis?Root Cause Analysis is any structured approach toidentifying 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 orunsuccessful. It can be superficial or insightful. It can be honestor dishonest. As long as it is a structured approach with the intent given above it would be fairly classed with other root causeanalyses.
© 2011 W. R. Corcoran, NSRC Corporation, [email protected]
A Purpose of RCA
© 2011 W. R. Corcoran, NSRC Corporation, [email protected]
What’s a Problem?
A gap between what ought to beand what is.
Some Examples of “What is.”
Nickname Nature Magnitude Location Timing
Chernobyl
Bhopal
Hindenburg
BP Deepwater
© 2011 W. R. Corcoran, NSRC Corporation, [email protected]
“What is” Puzzlers
• What are the relevant statements of “what is” for a given event?
• Which statements of “what is” should be investigated?
• Which “what is” should be investigate first?
© 2011 W. R. Corcoran, NSRC Corporation, [email protected]
Fact One: The “What is” resulted from factors
• The “What is” is an effect.• A synonym for “effect” is “phenomenon.”• A factor is something that affected an effect.• Factors include conditions, behaviors, actions,
and/or inactions. • If a condition, behavior, action, or inaction did
not affect any property of the effect, e.g., the “what is”, then it wasn’t a factor of the effect.
© 2011 W. R. Corcoran, NSRC Corporation, [email protected]
Fact One-Elaboration
• “The “ought to be” resulted from factors as well.
• One strategy for solving the problem, i.e., closing the gap, is to change the “ought to be.”
© 2011 W. R. Corcoran, NSRC Corporation, [email protected]
Fact Two: The “What is” has properties
• A “property” is a condition of reality.
• “Attribute” is a synonym for “property.”
• The properties of an effect include:– Nature– Magnitude (bigness, badness, spread…)– Location– Timing (beginning, end…)
© 2011 W. R. Corcoran, NSRC Corporation, [email protected]
Fact Three: The “What is” directly resulted from direct factors.
• A “direct factor” is a factor that affected the effect without any intervening factors.
• “Proximate” and “immediate” are synonyms for “direct.”
• “Intermediate Factor” is a synonym for “intervening factor.”
© 2011 W. R. Corcoran, NSRC Corporation, [email protected]
Harmful Effects(Factor Building Block)
Harmful Effect
(Consequence or Factor)
Direct Factor 1
Direct Factor 2
Direct Factor …
Direct Factor 3
Direct Factor …
© 2011 W. R. Corcoran, NSRC Corp., [email protected]
Fact Four: The direct factors explain all of the properties.
• The properties explained by the direct factors include the:– Nature– Magnitude (number, bigness, badness, intensity,
seriousness…)– Location– Timing (beginning, end…)
• If the identified direct factors do not explain the properties, then one or more direct factors are missing.
© 2011 W. R. Corcoran, NSRC Corporation, [email protected]
Harmful Effects (Four Property-related Factors)
Harmful Effect
Direct Factor(s) AffectingNature of Effect
Direct Factor(s) Affecting
Magnitude of Effect
Direct Factor(s) AffectingLocation of Effect
Direct Factor(s) AffectingTiming of
Effect
© 2011 W. R. Corcoran, NSRC Corp., [email protected]
Factor types are not mutually exclusive.
Fact Five: The direct factors include four types of “involvement” factors.
• The situation for the effect was set-up.
• The creation of the effect was triggered.
• The effect was as bad as it was.
• The effect was not any worse than it was.
© 2011 W. R. Corcoran, NSRC Corporation, [email protected]
Harmful Effects (Four Factor Involvement Types)
Harmful Effect
Vulnerability(Set-up)
TriggerExacerbation Mitigation
© 2011 W. R. Corcoran, NSRC Corp., [email protected]
THREAT BARRIER
THE BASICS OF BARRIER ANALYSIS
BARRIER:Anything that has the effect of (or is intended to ) reduce theprobability 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 atarget.)
TARGET
© 2011 W. R. Corcoran, NSRC Corp., [email protected]
Fact Six: The direct factors include the barrier analysis factors.
• There must have been something that could be harmed. (A “target.”)
• There must have been something that could harm the target. (A “hazard” aka “threat.”)
• The target and the hazard must have been in the same place.
• They must have been there at the same time.• There must have been no barrier that effectively
protected the target from the hazard.
© 2011 W. R. Corcoran, NSRC Corporation, [email protected]
Harmful Effects(Barrier Analysis Elements)
Harmful Effect
(Vulnerable) Target
Hazard/ Threat
No EffectiveBarriers
Co-location Simultaneity
© 2011 W. R. Corcoran, NSRC Corp., [email protected]
Fact Seven: As the investigation goes deeper each factor becomes a “what is” and the above apply.
• This implies a tightly linked, evidence-based, hierarchical factor-effect tree-like structure.
• That structure allows the deepest factors to be traced up to the highest “what is.”
© 2011 W. R. Corcoran, NSRC Corporation, [email protected]
Factor X
DirectFactor
DirectFactor
DirectFactor
DirectFactor
IntermediateFactor
DeeperIntermediate
Factor
RootFactor
© 2011, William R. Corcoran, NSRC Corp., 860-285-8779, [email protected]
Fact Eight: Favorably addressing any harmful factor favorably affects
everything above it.• “Favorably address” includes: ameliorate,
remove, improve, correct, contain, reduce, dilute, and the like.
• No matter how deep or shallow an investigation with this foundation goes it will reveal harmful factors that if favorably addressed will aid in preventing the recurrence of a problem and/or reducing the severity of its future recurrence.
© 2011 W. R. Corcoran, NSRC Corporation, [email protected]
Fact Eight-Elaboration
• The deeper an investigation with this foundation goes the more harmful factors it will reveal-- that if effectively addressed will aid in preventing the recurrence of a problem and/or reducing the severity of its future recurrence.
• Allowing any harmful factor to go unaddressed is to predispose some future event.
© 2011 W. R. Corcoran, NSRC Corporation, [email protected]
Fact Nine: Unfavorably addressing any mitigating factor allows adverse recurrence
of everything adverse above it.
• “Unfavorably address” includes: deteriorate, remove, weaken, de-institutionalize, release, reduce, dilute, and the like.
• Deeper investigations will reveal more mitigating factors that if preserved and/or improved will aid in preventing the recurrence of a problem and/or limiting the severity of its future recurrence.
© 2011 W. R. Corcoran, NSRC Corporation, [email protected]
Fact Nine-Elaboration
• Allowing any non-robust mitigating factor to go unfortified is to predispose some future event.
© 2011 W. R. Corcoran, NSRC Corporation, [email protected]
Suggestion:
• Be the “building inspector” for your next root cause analysis.
• Check the foundation.
• If it is not sound the structure could collapse.
© 2011 W. R. Corcoran, NSRC Corporation, [email protected]