A Foundation for Root Cause Analysis-(2011.05.27) William R. Corcoran, Ph.D., P.E. Nuclear Safety...

A Foundation for Root Cause Analysis-(2011.05.27)

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.


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PECONUCLEARA Unit of PECO Energy

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YMP

Bill CorcoranAssisted Facilities

Designated by This Logo and Some

Others.

DNFSB

PORTSMOUTH

METROPOLIS

CHALK RIVER

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Bill CorcoranAssisted Units

Designated by This Logo and Some

Others.

Topics

• Background

• Facts

• Suggestion


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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.


A Purpose of RCA


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


“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 investigated first?


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.


Harmful Effects (Four Factor Essences)

Harmful Effect

ConditionDirect Factor(s)

BehaviorDirect Factor(s)

ActionDirect Factor(s)

InactionDirect Factor(s)

© 2011 W. R. Corcoran, NSRC Corp., [email protected]

Factor essences are not mutually exclusive.

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.”


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…)


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.”


Harmful Effects(Factor Building Block)

Harmful Effect

(Consequence or Factor)

Direct Factor 1

Direct Factor 2

Direct Factor …

Direct Factor 3

Direct Factor …


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.


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


Factor types are not mutually exclusive, but they all must be there.

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.


Harmful Effects (Four Factor Involvement Types)

Harmful Effect

Vulnerability(Set-up)

TriggerExacerbation Mitigation


A Barrier Model

Yet another legitimate perspective?

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


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.


Harmful Effects(Barrier Analysis Elements)

Harmful Effect

(Vulnerable) Target

Hazard/ Threat

No EffectiveBarriers

Co-location Simultaneity


“No Effective Barrier” Puzzlers

• How many missing and ineffective barriers make up the “no effective barrier?”

• Which missing and ineffective barriers should be included?

• Which missing and ineffective barriers should be investigated?

• Which missing and ineffective barriers should be investigated first?


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.”


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.


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.


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.


Fact Nine-Elaboration

• Allowing any non-robust mitigating factor to go unfortified is to predispose some future event.


Suggestion:

• Be the “building inspector” for your next root cause analysis.

• Check the foundation.

• If it is not sound the structure could collapse.


A Foundation for Root Cause Analysis-(2011.05.27) William R. Corcoran, Ph.D., P.E. Nuclear Safety...

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