Risk Assessment S. Haugen & M.
Rausand Risk Risk assessment Study object Accident categories Legislation Decisionmaking Stakeholders
Risk Assessment
Chapter 1
Introduction
Stein Haugen
stein.haugen@ntnu.no
Marvin Rausand
marvin.rausand@ntnu.no
RAMS Group Department of Production and Quality Engineering NTNU
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What is risk?
To dene risk is not an easy task
The words of risk analysis have been and continue to be a problem . . . . When our Society for Risk Analysis was brand new, one of the rst things it did was to establish a committee to dene the word risk. This committee labored for 4 years and then gave up, saying in its nal report that maybe its better not to dene risk
Stan Kaplan: The words of risk analysis. Risk Analysis, 17(4):407-417
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Risk
What is risk in our context?
Related to what can happen in the future. At present, let us dene risk as the answer to these three questions:
What can go wrong? What is the likelihood of that happening? 3 What are the consequences?
1 2
Risk analysis is our tool to answer these questions. Associated with accidentsand mainly accidents that have severe consequences and happen not very often (often called major accidents).
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Risk analysis
Understanding how accidents can happen and what the consequences will be
A basis for prevention and preparation
Born within military and space applications. Grown to be used within almost all types of business, and especially where the consequences of accidents can be large, such as nuclear power plants, chemical and process industry, oil and gas industry, transport industry, and so on. A rapidly growing need for risk analysis (new applications, new requirements)
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Conceptual model
The bow-tie model
Hazards / Threats
Legislation Decisionmaking Stakeholders
Hazardous event
Proactive barriers
Reactive barriers
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Consequences
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Accident categories
Risk Assessment S. Haugen & M. Rausand Risk Risk assessment
Objectives
of this course
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Study object Accident categories Legislation Decisionmaking Stakeholders
Present and discuss terminology Dene how risk can be quantied and how these metrics may be used to evaluate tolerability of risk Present methods for risk assessment and discuss applicability, pros and cons for each method. Present and discuss some problem areas related to risk assessment (e.g., human errors, dependent failures). Describe how risk assessment may be carried out in practice and illustrate some application areas.
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Focus
Technical and/or sociotechnical systems Future events Unwanted (negative) consequences Assets or values that we want to protect Accidents (sudden, unexpectednegative consequences) Mostly on severe accidents (but not limited to this) Providing information for decision-making, not decision-making in itself
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Risk analysis
Z Risk analysis: Systematic use of available information
to identify hazards and to estimate the risk to individuals, property, and the environment. Three main steps:
1 2 3
Hazard identication Frequency analysis Consequence analysis
The risk analysis may be qualitative, quantitative, or semi-quantitative.
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Types of risk analysis
Hazard source Assets
Humans The environment Material / financial Humans 1 4 7 The environment 2 5 8 Technology / materials 3 6 9
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Risk evaluation
Z Risk evaluation: Process in which judgments are made on the tolerability of the risk on the basis of a risk analysis and taking into account factors such as socioeconomic and environmental aspects.
Sometimes: Comparing results from risk analysis with risk acceptance criteria.
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Risk assessment
Z Risk assessment: Overall process of risk analysis and
risk evaluation.
Risk management Risk assessment
Decisionmaking Stakeholders
Risk analysis
- Identify hazards and threats - Identify hazardous events - Determine frequencies and consequences - Establish risk picture
Risk evaluation
- Evaluate risk (against risk acceptance criteria) - Propose risk-reducing measures - Assess alternative riskreducing measures
Risk control
- Make decisions related to risk-reducing measures - Implement measures - Monitor effects - Communicate risk
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Risk management
Z Risk management: A continuous management process with the objective to identify, analyze, and assess potential hazards in a system or related to an activity, and to identify and introduce risk control measures to eliminate or reduce potential harms to people, the environment, or other assets.
ntro Co
I de
nt i
fy
Communicate and Document
Track
Ana ly z
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Study object
Z Study object: Composite entity, at any level of
complexity, of personnel, procedures, materials, tools, equipment, facilities, and software. The elements of this composite entity are used together in the intended operational or support environment to perform a given task to achieve a specic objective.
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Sociotechnical system
E Environment M System organization and management H Hardware S Software
L Liveware (humans)
MTO = man, technology, and organization
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SHEL model
S Software
H Hardware
L Liveware
L Liveware
E Environment
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Accident categories
Adapted from Rasmussen (1997)
1
Frequency (log scale) Occupational accidents Traffic accidents
High risk
2
Airplane accidents Railway accidents
Low risk
3
Nuclear power accidents
Consequence (log scale)
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Accident categories
James Reason:
Organizational accidents vs. individual accidents
Process industry:
Process safety accidents vs. individual accidents
Offshore industry in Norway:
Major accidents vs. occupational accidents
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Increasing risk
Technological change, complex relationships between humans and automation Increasing scale of industrial installations Rapid development of ICT Aggressive and competitive marketplace Demand for speed (faster cars, trains, ships, . . . ) The increased likelihood of sabotage and terrorism The increasing use of multicultural workforces The emerging climate changes
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Legislation
EU Seveso II directive
Control of major accident hazards
EU Machinery directive
Safety aspects of a wide range of machinery
Health and safety at work act, UK Offshore installations (safety case) regulations, UK US Maritime transportation security act Offshore safety regulations, Noeway
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Risk and decision-making
Decisions may related to:
Should the activity be permitted? Are additional safety barriers or improvements necessary? Which options should be preferred? How much should be invested to reduce risk?
Requires an answer to the question what is safe enough?
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Model for decision-making
Adapted from Aven (2003)
Constraints
Study object Accident categories Legislation Decisionmaking Stakeholders
- Laws and regulations - Cost - Time
Stakeholders
- Preferences - Objectives - Criteria
Risk analysis Decision problem Other analyses - Decision alternatives
Managerial review and judgment
Decision
Decision analysis
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Decision-making
Deterministic: Decisions without consideration of the likelihood of possible outcome. Risk-based decision-making (RBDM): A process that uses quantication of risks, costs, and benets to evaluate and compare decision options competing for limited resources. Risk-informed decision-making (RIDM): An approach to decision-making representing a philosophy whereby risk insights are considered together with other factors to establish requirements that better focus the attention on design and operational issues commensurate with their importance to health and safety.
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Stakeholders
Z Stakeholder: Person or organization that can affect, be
affected by, or perceive themselves to be affected by a decision or activity. Stakeholders may be classied in different ways:
People who are affected directly. People who are interested, want to become involved in the process, and seek an opportunity to provide input. People who are generally interested and seek information. People who are affected but are unaware of it or do not participate in the stakeholder process.
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