PNNL-SA-108973
Risk-Informed Decision-Making:
Basic Concepts
Presentation to the
State Energy Risk Assessment Workshop
April 28-29, 2015
Presented by Steve Unwin, Ph.D.
Pacific Northwest National Laboratory
1
Business Sensitive
Outline
Risk Decisions
Risk Models
Risk Management
Risk Perception
Risk Guidance
First Steps
2
Business Sensitive
Risk-Informed Decision-Making
Decisions that take into account:
Uncertain future events
The impacts of those events
The likelihoods of those events
Structuring data, judgment, and system logic in a
coherent framework for decision-making
Risk-Informed versus Risk-Based decisions
The reality of accounting for risk
3
Business Sensitive
Modeling Risk
Hazard
condition that poses threat: presence of flammables or toxics,
natural phenomena, potential for market upsets, threat of
malevolent acts, presence of physical energies, ...
Scenario
specific hypothetical sequence of events that would result in
adverse consequences
Risk
a combination of the adverse consequences and likelihoods of a
scenario set
4
Business Sensitive
Risk Models – What varies between them?
Scope
natural phenomena? terrorism? human factors? system
boundaries? impact region of concern? ...
Depth
model resolution: e.g., industries vs. facilities vs. systems vs.
components (how far into the weeds?)
Precision
full quantitative vs. order of magnitude vs. qualitative
Risk types
safety, environmental, production/outage, business, schedule,
budget, public perception
5
Business Sensitive
Risk Type: Business – Risk (probabilityweighted production loss) associated with
forced outage of refinery units
HYDROGEN PLANT
SULFUR RECOVERY
SOUR WATER STRIPPING
VAPOR RECOVERY/GAS TREAT
ALKYLATION
OLEFIN TREATING
FLUIDIC CAT CRACKING
REFORMING
GAS OIL HYDROTREATING
DISTILLATE HYDROTREATING
NAPHTHA HYDROTREATING
DELAYED COKING
VACUUM DISTILLATION
CRUDE UNIT
CRUDE BLENDING
0
6
200,000
400,000
600,000
800,000
1,000,000 1,200,000 1,400,000
Downtime
$ risk per quarter
Business Sensitive
5/1/2015
Risk Type: Safety & Health – Frequency vs. number of
individuals exceeding ERPG2 exposure due to presence
of a selective catalytic reduction unit at a fossil plant
7
Business Sensitive
5/1/2015
Broadly Risk-Oriented: Representation of
bulk power system interruption
NERC, 2010
8
Business Sensitive
Structure of a Risk Model
Models
Mechanistic models
natural phenomena
engineered system behavior
Logic models (event trees, fault trees, networks)
logical relationships between events
Evidence/likelihood models
probabilistic
other
Consequence models
health, exposure, financial, reputation, ...
Input
Hard data/statistical models
Informed judgment
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Business Sensitive
Example: Event tree that models fire risk
in a research facility – Systematically
defines scenarios
Ignition
Failure to
immediately
extinguish
Ignition occurs
Personnel unable to
extinguish
immediately or no
extinguishers present
P1: Annual Frequency
P2: Probability (Yes)
Yes
Ignition was in a
Cluster area
No fire suppression
system (sprinkler) in
place, failure to actuate
locally, or system
ineffective
P3: Probability (Yes)
Yes
Failure to prevent
propagation beyond
room/cluster
High combustibles /
flammables load in
adjacent rooms
P4: Indicator
Yes
END STATE
Failure of other fire
isolation system (fire
wall)
Failure of
emergency response
organization to
respond effectively
P5: Probability (Yes)
No fire suppression
(sprinkler) system in
place, or failure to
actuate globally, or
system ineffective
P6: Probability (Yes)
P7: Probability (Yes)
P8: Probability (Yes)
Yes
Yes
Yes
Yes
1. Building Cluster Damage
No
2. Local Cluster Damage
3. Local Cluster Damage
No
4. Local Cluster Damage
No
5. Local Cluster Damage
No
No
Yes
Yes
Yes
No
No
No
No
6. Building Cluster Damage
No
OK
OK
OK
OK
Yes
7. Local Water Damage
No
OK
OK
No
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Yes
Business Sensitive
Risk Management
Doing what needs to be done to
continually and economically reduce risks.
Once we know where the greatest risks lie,
effectively manage them.
Where can resources be most effectively spent to reduce risk?
Where might expenditures be reduced without significantly affecting risk?
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Business Sensitive
The Elements of Risk Management
Analysis
Determining risks and
uncertainties
Identifying risk and
Evaluation
Control
Research
Reducing and controlling the
risks
Reducing the uncertainties
Communication
Monitoring
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uncertainty drivers.
Assessing risk and
uncertainty-reduction
options
Communicating risks and
their management to
stakeholders
Ongoing
confirmation/revision of
assumptions about risk
Business Sensitive
Risk-Informed Decision Portfolio
Risk tolerance criteria/goals, limits/objectives
numerical risk acceptance levels
Risk-based prioritization/allocation
risk importance metrics
Cost/benefit analysis
ALARP
as low as reasonably practicable
risk-based cost-benefit analysis
13
Business Sensitive
Risk objectives and limits. Risk acceptance
criteria for public radiation exposure
UK Health and Safety Executive Dose Tolerance
1.0E+01
Annual Exceedence Frequency
1.0E+00
1.0E-01
Basic safety limit
1.0E-02
Targeted risk
level
1.0E-03
1.0E-04
Basic safety objective
1.0E-05
1.0E-06
1.0E-01 1.0E+00 1.0E+01 1.0E+02 1.0E+03 1.0E+04
Maxim um Individual Public Dose (mSv)
14
Greatest
tolerable risk
level
Business Sensitive
Risk-ranking for explosion damage in
chemical process facility
STRUCTURE
Vulnerable
Structures
Explosion
Sources
15
6
3
2
5
4
7
10
9
8
1
RANK
Fermentation Building
Process 95 Building
Control Room A
Extraction Building
Laboratory Area
Maintenance Building
Guard Shack
Stores
Warehouse
Administration Offices
SOURCE
2.8
2.9
2.9
3.0
3.1
3.3
3.4
6.2
6.9
X
High rank =
high
protection
priority
RANK
Fermentation Area VCE
Process 95 PVE
Extraction Area PVE
Process 95 VCE
Extraction Area VCE
Main Storage PVE
Tank Farm B BLEVE
Main Storage BLEVE
Tank Farm B PVE
Business Sensitive
2.3
2.9
3.3
3.8
6.2
6.2
6.4
7.1
8.0
High rank =
high
prevention
priority
Cost-Benefit Criteria: Risk reduction / cost
tradeoff
USNRC:
US$ 2,000/person-rem (radiological dose)
averted
UK HSE:
UK£ 0.75 M per fatality averted
Range inferred from a variety of organizations (1990s):
$20K - $100M per fatality averted
Assessing
a riskreduction
option:
RiskReduction
Cost-beneficial
expenditure
Unwarranted
expenditure
Cost
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Cost-benefit acceptance
threshold
Business Sensitive
ALARP:
As Low (A Risk) As Reasonably Practicable
Reduce Risk
Regardless of Cost
Risk Intolerable
Follow Good
Practice
Consider Cost
of RiskReduction
Tolerable if ALARP
De
Minimis
Risk
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Business Sensitive
Risk Tolerable
Risk Perception
Perceived versus calculated
Factors driving risk perception
Personal controllability of exposure
Dreadedness of potential consequences
“Visibility” of exposure
Fairness of risk and benefit distribution
Peter Sandman’s Equation
Risk = Hazard + Outrage
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Business Sensitive
Risk Perception Factors
Not Observable
Unknown to Those Exposed
Effect Delayed
New Risk
Risk Unknown to Science
Factor 2
Unknown risk
Laetrile
Microwave Ovens
Water Fluoridation
Saccharin
Water Chlorination
Coal Tar Hairdyes
Oral Contraceptives
Valium
Nitrates
Hexachlorophene
Polyvinyl
Chloride
Diagnostic
X-Rays
IUD
Darvon Antibiotics
Rubber
Mfg.
Auto Lead
Lead Paint
Caffeine
Aspirin
DNA Technology
Electric Fields
DES
Nitrogen Fertilizers
Uncontrollable
Dread
Global Catastrophic
Consequences Fatal
Not Equitable
Catastrophic
High Risk to Future
Generations
Not Easily Reduced
Risk Increasing
Involuntary
SST
Radioactive Waste
2,4,5-T
Trichloroethylene
Nuclear Reactor
Accidents
Pesticides
Uranium Mining
Nuclear Weapons
PCBs
Asbestos
Fallout
Insulation
Satellite Crashes
DDT
Mercury Fossil Fuels
Coal Burning (Pollution)
Factor
Mirex
Cadmium Usage
1
Dread risk
Vaccines
Skateboards
Smoking (Disease)
Power Mowers
Snowmobiles
Trampolines
Tractors
Alcohol
Chainsaws
Auto Exhaust (CO)
LNG Storage &
Transport
D-CON
Coal Mining (Disease)
Nerve Gas Accidents
Large Dams
SkyScraper Fires
Nuclear Weapons (War)
Underwater
Elevators
Home Swimming Pools
Construction
Coal Mining Accidents
Electric Wir & Appl (Fires)
Downhill Skiing
Sport Parachutes
Smoking
Recreational Boating
General Aviation
Motorcycles
Electric Wir & Appl (Shock)
High Construction
Bicycles
Railroad Collisions
Bridges
Alcohol
Commercial Aviation
Fireworks
Accidents
Auto Racing
Auto Accidents
Handguns
Dynamite
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Business Sensitive
From:
Slovic, P. (1987). Perception
of risk. Science, 236, 280285.
Risk Standards / Methodology Guides / Risk
Acceptance Criteria / Review Guides
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Business Sensitive
Risk reading: A few starting points Quantifying and Controlling Catastrophic Risks, by B.
John Garrick (Academic Press, 2008)
U.S. Nuclear Regulatory Commission, A Proposed Risk
Management Regulatory Framework, NUREG-2150,
2012
Guidelines for Chemical Process Quantitative Risk
Analysis (American Institute of Chemical Engineers, 2nd
Ed., 1999)
NASA, Risk-Informed Decision Making Handbook,
NASA/SP-2010-576, 2010
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Business Sensitive
First Steps
Objectives/Drivers?
strategy selection, design support, optimizing operations, public
communications, ...
Hazard space?
incidents/accidents
natural phenomena
malevolent acts
market events
etc.
Risk space?
financial
environmental
production
safety
security
public perception
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Business Sensitive