This glossary explains the most important risk terminology used in this report. References are supplied to specific sections within the report where these contain a more detailed explanation.
| Term |
Explanation |
| Accident |
Undesired event leading to a loss. |
| Accident scenario |
A number of events leading to an accident. An accident scenario starts with an initiating event and ends with the final consequence. |
| ALARA (As Low As Reasonably Achievable) |
The principle that all safety measures reasonable from a technical and economic perspective must be implemented. ALARA arose in the area of radiation protection, but is also used for process safety, as for example in Environment Project 112 |
| ALARP (As Low As Reasonably Practicable) |
In the United Kingdom and in the offshore industry, the term ALARP is used instead of ALARA. ALARP involves a higher degree of quantitative cost-benefit analysis (i.e. analysis of whether the safety gain exceeds the cost of the measures). Risk is ‘ALARP’ when further risk reduction involves ‘grossly disproportionate’ expense in relation to the safety gain achieved. |
| Barrier point |
Scale for safety barrier reliability. Each point corresponds to a square root of 10 reduction in failure rate (section 2.1.2). |
| Consequence |
The results of an accident, such as personal injury or death, or damage to material assets or the environment (section 1.2). |
| Consequence distance |
The distance from the hazard, within which damage or injury can be expected (to life, health, the environment, or assets) due to the accident (section 1.2.2). |
| Consequence-based risk assessment |
See Deterministic risk assessment (section 3.1.1.1). |
| Consistency |
Decisions are consistent when comparable decisions are made in comparable situations (section 3.1). |
| Deterministic risk assessment |
Risk assessment based on analysis of the consequence distance of each accident, without taking into account its probability (section 3.1.1.1). |
| End point value |
Exposure level (for a toxic substance, heat radiation or shockwave) that causes a particular effect.s |
| Expected loss |
The expected frequency for an accident multiplied by its consequences (section 1.2). |
| F-N curve |
Curve showing the cumulative probability (F) for accidents involving more than a certain number of fatalities (N). Used to illustrate societal risk (see below) in a quantitative way (see Figure 2 for further explanation). |
| Frequency (expected -) |
Probability of which an event may take place within a particular time period, such as a year. |
| Group risk |
See societal risk (synonym) |
| Hazard |
Situation or state that can lead to damage or injury (section 1.2). |
| Hybrid risk assessment |
Risk assessment method combining elements from quantitative and qualitative methods (section 3.1.1.4). |
| Individual risk |
The expected frequency at which a person may be injured or dies (due to an accident). This report favours the term ‘location-based (individual) risk’ (section 1.2.3). |
| Initiating event |
Event initiating a process that could lead to an accident. |
| Irreversible damage |
Damage that cannot be repaired. |
| Iso-risk curve |
Curve connecting points with the same location-based risk (see Figure 1). |
| Location-based risk (originally a Dutch term) |
The total risk of a person who is continually present and unprotected in a given location in an accident (section 1.2.3). |
| Maximum consequence distance |
Consequence distance for the worst case accident (section 1.2.2). |
| Potential Loss of Life PLL |
The total sum of the individual risk (of death) for exposed persons. Can be calculated by multiplying location-based risk by the number of people exposed to this risk (section 1.2.5). |
| Probabilistic |
A probabilistic analysis leads to the probability that a statement is true or false, whereas a deterministic analysis leads to statements that are either true or false. |
| Probabilistic Risk Assessment (PRA) |
Risk assessment calculating the probability for an event with a particular consequence occurring, in contrast to deterministic risk assessment. See also quantitative risk assessment (section 1.3.2.1). |
| Qualitative risk assessment |
Risk assessment whereby the risk analysis only involves qualitative description of risks, without quantifying frequencies (section 1.3.2.2). |
| Quantitative Risk Assessment (QRA) |
Risk assessment whereby risk analysis involves both a description and a quantification of risk (section 1.3.2.1).s |
| Reference accident scenario |
Accident scenario, the consequence distance for which is used as the safety distance. See also worst credible accident (section 1.3.2.2). |
| Risk |
A combination of the frequency of an undesired event and the extent of the consequences (section 1.2). |
| Risk acceptance criteria |
Qualitative or quantitative expression placing limits on the acceptable risk for a given establishment. |
| Risk analysis |
Method for systematically reviewing an activity involving risk, with the aim of identifying, classifying, and determining the risks linked to the activity (section 1.3.2). |
| Risk assessment |
Risk analysis, followed by comparison of the results with acceptance criteria or other decision parameters. |
| Risk aversion |
The perception that few major accidents are more serious than several minor accidents, even if the total number of victims is the same (section 4.3.2).s |
| Risk matrix |
A table used to classify an accident scenario using frequency and consequence classes (see Table 1, section 1.2.1).s |
| Risk zone |
Area within the safety distance (note that the risk is higher inside the risk zone, while it is safe outside the zone). |
| Risk-based risk assessment |
Risk assessment taking into account both the consequences and frequency of accidents. Quantitative risk assessment is a form of risk-based assessment (section 3.1.1.2). |
| Safety barrier |
Safety measure that can prevent an accident, or mitigate its consequences.s |
| Safety distance |
The distance within which restrictions are placed on the presence of the public (section 1.3.1). |
| Safety-barrier diagram |
Diagram illustrating the safety barriers in place (section 2.1.2). |
| Societal risk |
The probability that a certain number of people are simultaneously exposed to injury from a single accident (section 1.2.4). |
| Vulnerable objects |
Individuals and objects such as buildings, land and natural reserves susceptible to injury or damage in the event of an accident. The term is often used to refer to objects or members of the public who require special consideration or are particularly vulnerable to the consequences of an accident (children, the aged, sick or disabled people, and objects of particular relevance to the community, such as water supply infrastructure, etc). |
| Worst case accident |
The largest theoretically possible accident, based on the given hazards and accident potential (section 1.3.2.2). |
| Worst credible accident |
The largest accident considered to be not improbable following assessment. See also reference accident (section 1.3.2.2). |