Off-site consequences

The ha2ard assessment is to iaclude identification of a worst-case scenario and other more likely scenarios for release of a regulated substance, and analy2e the off-site consequences of such releases. The release and consequence assessment is to iaclude the rate, duration, and quantity of the release, the distances for exposure or damage (usiag atmospheric, called "F" stabiUty and a 1.5-m/s wiad, and most-often-occurriag conditions), populations that could be exposed, and environmental damage that could be expected. 

An off-site consequence analysis that evaluates specific potential release scenarios, including worst-case and alternative scenarios... 

One of the important elements of PSM and RMP regulations that the plant would be required to comply with is on-site and off-site consequence analysis or modeling to assess potential on-site/off-site exposures. 

Hazard assessment. A hazard assessment is required to assess the potential effects of an accidental (or intentional) release of a covered chemical/material. This RMP element generally includes performing an off-site consequence analysis (OCA) and the compilation of a five-year accident history. The OCA must include analysis of a least one worst-case scenario. It must also include one alternative release scenario for the flammables class as a whole also each covered toxic substance must have an alternative release scenario. USEPA has summarized some simplified consequence modeling... 

The off-site consequence analysis must be reviewed and updated every five years. However, if process changes might reasonably be expected to cause the worst-case scenario footprint or signature to increase or decrease by a factor of two or more, then the OCA must be revised and the risk management plan must be resubmitted to USEPA or designated authority within six months. 

Program 1. Requirements apply to processes for which a worst-case release, as evaluated in the hazard assessment, would not affect the public. These are sources or processes that have not had an accidental release that caused serious off-site consequences. Remotely located sources and processes using listed flammables are primarily those eligible for this program. Program 1 requirements are as follows ... 

The USEPA s requirement to protect the public requires the covered facility to conduct an off-site consequence analysis (OCA). In PSM, the employer is only required to investigate each incident that resulted in or could have resulted in a catastrophic release of a highly hazardous chemical in the workplace. 

Significant accidental release. Any release of a regulated substance that has caused or has the potential to cause off-site consequences such as death, injury, or adverse effects to human health or the environment, or to cause the public to shelter in place or be evacuated to avoid such consequences. 

Those who respond to a release are usually heading into an area from which everyone else is trying to escape. Well-designed postrelease mitigation measures can provide response personnel with safer access to the hazard zone. Off-site consequences can be significantly reduced, as well. 

The second factor to be considered is the target attractiveness. Terrorists tend to consider national monuments, major cultural, political, and sporting events, and the financial sector to be particularly attractive, as an attack on such a target is viewed as an attack on their enemy s entire way of life. Likewise, key infrastructure components such as key bridges, tunnels, highways, and railways are more attractive. Finally, the public s fear of chemical and petroleum facilities may make these more attractive targets, more so if materials in the facility have potential off-site consequences if released. 

The EPA standard does not require an off-site consequence analysis for pool fires unless the thermal-radiation endpoint (5 kilowatts/m ) is outside the property boundary, or unless there are locations within the property boundary to which the public has routine and unrestricted access during or outside business hours. If either of these situations could exist, the EPA standard recommends that the consequences of a pool fire be evaluated as an alternative scenario for a flammable-liquid release and be described in terms similar to those listed under Toxicity Hazards. 

This section presents a derivation of the HCF TSRs. Because of the hazard classification of the HCF (i.e., HC-2) and the results of the accident analysis, no safety-class structures, systems, or components (SSCs) have been identified. That is, there are no SSCs vt/hich are needed to maintain off-site consequences within the 25 rem off-site Evaluation Guideline. Therefore, the TSRs consist of Limiting Conditions for Operation, Surveillance Requirements, and Administrative Controls as shown in Table 5.3-1. 

By DOE-STD-1027 definition, the HCF radioactive material storage areas (RMSA), since they are limited to radiological material inventories less than Hazard Category 2 thresholds, do not, by themselves, have the potential for significant off-site consequences. However, the potential release of this inventory as a contributor to the overall release can be evaluated for a perspective of the overall risk. 

As an example, one might weigh dispersal of storage of highly hazardous chemicals rather than concentrate that storage in one potentially vulnerable location. That way, if there is a release of a smaller amount of material, the overall concentration would be less and the off-site consequence would smaller. 

No significant off-site consequences fw aiqr credible accident. 

The results of safety analysis taking into account single failure criteria demonstrated that for all design basis accidents (DBA) the ABV reactor safety was ensured without reliance on any operators actions. Practically no on - site and off - site consequences take place at the DBA... 

In addition, the results of the PSA should be compared with the probabilistic safety criteria when these have been defined for the plant. This should be done for all the probabilistic criteria defined for the plant, including those which address system reliability, core damage, releases of radioactive material, worker health effects, public health effects and off-site consequences such as land contamination and food bans. 

There are usually a large number of end points in the event tree analysis and these are normally grouped into release and/or source term categories which have similar radiological characteristics and off-site consequences. 

The analysis of the off-site consequences models the release of radionuclides from the nuclear power plant, their transfer through the environment and... 

Estimating the off-site consequences of releases of radioactive material from the plant. 

In 1995 the IAEA published a technical document on safety principle for the design of future nuclear power plants [5]. The report represents the conclusion of a long effort of many experts from different countries and different organizations (authorities, designers, utilities, etc) to formulate a proposal of safety objectives and principles for the design of the nuclear power plants. The proposed safety objective stresses the importance of the explicit consideration of severe accidents and the minimization of the off-site consequences, even in the case of severe accidents. 

Threat category I facilities can also have releases resulting in severe exposure and contamination off-site. Consequently plans should be in place to screen exposed people and assign them to hospitals and other faculties for treatment. Due to the very low probability of such an event, reliance should be placed on use of existing facilities that have made a minimum level of preparations to include some staff training. 

For events where higher accuracy is desirable, well-established quantitative techniques are available for improving the accuracy of the analysis. For such events (especially those with off-site consequences), the next steps are ... 

Off-site consequences >25 rem from operational accidents must be protected with Safety Class Structures, Systems, and Components (SSCs) independent of frequency. Follow DOE-STD-3009 for manmade external and natural phenomenon events. 

The references cited supersede the foUowiag IAEA safety standards Techniques and Decision Making in the Assessment of Off-site Consequences of an Accident in a Nuclear Facility, Safety Series No. 86, IAEA, Vienna (1987) Response to a Radioactive Materials Release Having a Transboundary Impact, Safety Series No. 94, IAEA, Vienna (1989) Emergency Planning and Preparedness for Accidents Involving Radioactive Materials Used in Medicine, Industry, Research and Teaching, Safety Series No. 91, IAEA, Vienna (1989). 

The methods and models [33,35] used to assess doses to members of the public from normal discharges are not appropriate for emergency situations, in which the maximum use needs to be made of the available information, from a limited number of measurements, to estimate off-site consequences promptly. These methods should include provisions to project off-site consequences that could arise as a result of the conditions at the facility (e.g. in the case of unmonitored or possible future releases). These projected off-site consequences could be precalculated doses for different accident conditions, as provided in Ref. [10], or computer models such as INTERRAS [10]. The dose projections should be as realistic as possible, and in any case doses for situations in which persons might be in danger of being harmed should not be underestimated. 

Garland, J.A., Pattenden, N.J. (1989). Resuspension following Chernobyl. Commission of the European Communities, Seminar on Methods and Code for Assessing the Off-Site Consequences of Nuclear Accidents, Athens (Greece), May 1990. 

Although this guidance focuses on the LOPA technique, other techniques such as fault tree analysis or detailed quantitative risk assessment, used separately, may be a more appropriate alternative under some circumstances. Quantified methods can also be used in support of data used in a LOPA study. It is common practice with many dutyholders to use detailed quantified risk assessment where multiple outcomes need to be evaluated to characterise the risk sufficiently, where there may be serious off-site consequences, where the Societal Risk of the site is to be evaluated, or where high levels of risk reduction are required. 

Adequate mapping to assist mitigation actlon(s) and reduce off-sIte consequences /Impact on off-sIte arrangements ... 

Owners and operators of facilities the produce, process, and store extremely hazardous substances must develop a risk management plan (RMP) including an executive summary, registration information, off-site consequence analysis, five-year accident history, prevention program, and emergency response program. 

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