Societal risk

The NRC safety goal can be evaluated by comparison to the risks from accidents incurred from other human activities (Eig. 2) (29). The safety goal and the safety record of the nuclear power industry indicate much lower societal risks from commercial nuclear power than from a wide range of other common human activities. 

Risk Estimation There are a number of risk measures which can be estimated. The specific risk measures chosen are generally related to the study objective and depth of study, and any preferences or requirements established by the decision makers. Generally, risk measures can be broken down into three categories risk indices, individual risk measures, and societal risk measures. 

A common form of societal risk measure is an F-N curve, which is normally presented as a cumulative distribution plot of frequency F... 

Both individual and societal risks may be presented on an absolute basis compared to a specific risk target or criterion. Or, they may be presented on a relative basis to avoid arguments regarding the adequacy of the absolute numbers while preserving the salient differences between alternatives. The end results of the risk presentation may be a single number (or a range of numbers if an uncertainty analysis was performed) or one or more graphs. 

Figures 12 and 13 illustrate two of the more commonly used methods for displaying societal risk results (1) an F-N curve and (2) a risk profile. The F-N curve plots the cumulative frequencies of events causing N or more impacts, with the number of impacts (N) shown on the horizontal axis. With the F-N curve you can easily see the expected frequency of accidents that could harm greater than a specified number of people. F-N curve plots are almost always presented on logarithmic scales because of...

General societal risk data. It is important to consider the context of societal risk data. Some particularly important factors include whether or not the risk is voluntary, and whether persons exposed to the risk derive any benefit from the activity that generates the risk. Covello, Sandman, and Slovic, Slovic, and Wilson and CroLich provide examples of general societal risk data and discuss risk comparison and perception. 

Average societal risk for onsite workers in occupied buildings (API 752)... 

A graphical illustration of the cumulative frequency (F) of accidents resulting in a consequence of greater than or equal to N impacts. A way of illustrating societal risk... 

Ways of combining information on likelihood with the magnitude of loss or injury (e.g., risk indices, individual risk measures, and societal risk measures)... 

Societal risks to life and health from nuclear power plant operation should be comparable to or less than the risks of generating electricity by viable competing technologies and should not be a significant addition to other societal risks. ... 

Erdmann, R. C. et al., 1976, ATWS A Reappraisal Part If Evaluation of Societal Risks Due to Reactor Protection System Failure Vol IIBWR Risk Analysis EPRINP-265,. ugust. 

Kdly, J. E. et al 1976, ATWS, A Reappraisal Part II, Evaluation of Societal Risks due to Reactor Protection System Failure Vol.3 PWR Risk Analysis, EPRINP 265, August. 

Okrent, D 1980, Comment on Societal Risk Science 208, pp 372-375, April. 

This study investigated risks to the public from serious accidents which could occur at the industrial facilities in this part of Essex, U.K. Results are expressed as risk to an individual and societal risk from both existing and proposed installations. Risk indices were also determined for modified versions of the facilities to quantify the risk reduction from recommendations in the report. Nine industrial plants were analyzed along with hazardous material transport by water, road, rail and pipeline. The potential toxic, fire and explosion hazards were assessed for flammable liquids, ammonia, LPG, LNG, and hydrogen fluoride (HE). The 24 appendices to the report cover various aspects of the risk analysis. These include causes and effects of unconfined... 

The purpose of this analysis was to assess the risk of operating Limerick Station, specifically with regard to its location near a high population density area. These risks were evaluated to determine whether they represent a disproportionately high segment of the total societal risk from postulated nuclear reactor incidents. 

Societal Risk - This represents a measure of the risk to a group of people, including tlie risk of incidents potentially affecting more tlian one person. Individual risk (see above) is generally not significantly affected by the number of people involved in an incident. The risk to a person at a particular location depends on tlie probability of occurrence of the luizardous event, and on the probability of an adverse imptict at that location should the event occur. 

Briefly describe the differences between individual and societal risks. 

Risk characterization estimates tlie healtli risk associated with tlie process under investigation. The result of tliis cliaracterization is a number tliat represents tlie probability of adverse healtli effects from tliat process or from a substance released in tliat process. Tlie major types of risk include Individual Risk, Maximum Individual Risk (MIR), Population Risk (PR), Societal Risk, and Risk Indices. 

Risk can be measured and expressed in a number of ways. CCPS s Guidelines for Chemical Process Quantitative Risk Analysis (Ref. 4) identifies three main categories of risk measure Risk Indices, Individual Risk, and Societal Risk. 

Figure 4.3 Acceptability criteria for societal risk—The Netherlands (Ref. 50). 

Societal Risk measures the potential for incidents to affect many people. It has historically been applied as a measure of risk to the general public exposed to the same event or events. Societal risk is often presented as a frequency distribution of multiple-casualty events, called an F-N curve, showing the frequency of events F) leading to N or more fatalities. 

While societal risk is generally applied to events that can impact the public, major accidents in chemical processing plants may also have the potential to affect large numbers of people. In particular, a single major event could affect multiple buildings and many individuals inside each building. Thus, the concept of societal risk can be applied to on-site risk evaluations as well as off-site evaluations. 

As will be shown in Section 4.2, published data are available on the application of societal risk measures, including the development of risk tolerability limits for F-N curves. However, much of this guidance has been developed for characterizing risks to the general public and would not normally be considered as a basis for assessing risks to on-site personnel. It is appropriate, therefore, to suggest another risk measure, similar in concept to societal risk, for on-site applications to process plant buildings ... 

Aggregate risk is used to measure the collective risk to people in a facility who could be exposed to an event or events. It indicates the frequency that a specified number of people will suffer a specific level of harm (e.g., death). Just as is the case with societal risk, aggregate risk can be expressed in terms of the frequency distribution of multiple-casualty events. 

Aggregate risk A measure of the risk to personnel within a building or buildings or within a facility who are impacted by the same events, taking into account the total time spent in the building(s) or facility. (Aggregate risk is "societal risk" applied to a specific group of people within a facility.)... 

Atmospheric releases of flammable gases such as hydrogen may lead to major fires with extensive effects on the surroundings. In activities where hazards are associated with cloud fires, there is the need of societal risk assessment that involves the estimation of hazardous zones due to the resulting thermal radiation. However, till now only limited work has been done on modeling the effects of flash fires, in a way that available techniques may be judged insufficient [47],... 

Island/Thurrock Area, HMSO, London, 1978. Rasmussen, Reactor Safety Study An Assessment of Accident Risk in U. S. Commercial Nuclear Power Plants, WASH-1400 NUREG 75/014, Washington, D.C., 1975. Rijnmond Public Authority, A Risk Analysis of 6 Potentially Hazardous Industrial Objects in the Rijnmond Area—A Pilot Study, D. Reidel, Boston, 1982. Considine, The Assessment of Individual and Societal Risks, SRD Report R-310, Safety and Reliability Directorate, UKAEA, Warrington, 1984. Baybutt, Uncertainty in Risk Analysis, Conference on Mathematics in Major Accident Risk Assessment, University of Oxford, U.K., 1986. 

FIG. 23-29 Example of a societal risk F-N curve. (AIChE-CCPS, 1989, p. 4.4.)... 

The outputs of an event tree from a post-release frequency analysis are a number of outcomes ranging from more to less hazardous. An event tree highlights failure routes for which no protective system can intervene and where additional protective systems/mitigative action may be contemplated. The quantitative output is the frequency of each event outcome. These outcomes (which might specify BLEVE, flash fire, pool fire, jet fire) are used to determine individual and societal risk. 

Knowledge of the distribution and density of people is necessary to assess the impact of radiant heat and smoke from fires. This allows an estimate to be made of the risk to which the population in and around the facility may be exposed. Extensive population data is necessary where an estimate of societal risk is required. Where only an estimate of individual risk is desired, extensive population data may not be required. However, it is still necessary to determine the location of the people whose individual risk is being estimated. 

There are three commonly used ways of calculating risk estimates risk indices, individual risk, and societal risk. 

Risk indices are single numbers or a tabulation of numbers that are correlated to the magnitude of the risk to people. Some risk indices are relative values with no specific units. The limitations on the use of indices are that they may not be an absolute criteria for accepting or rejecting the risk. Risk indices also do not communicate the same information as individual or societal risk measures. An example of risk indices is a risk ranking matrix. Table 6-4 (modified from CCPS, 1992) shows how severity and likelihood are combined to obtain risk indices. An example risk matrix is shown in Figure 6-3 (RRS, 2002). 

Societal risks are single number measures, tabular sets of numbers, or graphical summaries that estimate risk to a group of people located in the effected zone of an incident. Since major incidents have the potential to affect many people, societal risk is a measure of risk to a group of people. It is most often expressed in terms of the frequency distribution of multiple casualty events, such as the F-N curve shown in Figure 6-5. The calculation of societal risk requires the same frequency and consequence information as individual risk. Additionally,... 

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