Off-site consequence analysis

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. 

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. 

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. 

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. 

I met with DHS S T representatives several times early in the study process to discuss the statement of task, data availability, and the departments objectives in commissioning this study. Based on these discussions and from discussions with DHS representatives at the committee s first meeting, it was agreed that this study should complement and not attempt to duplicate other ongoing activities such as the DHS Risk Analysis and Management for Critical Asset Protection (RAMCAP) and Environmental Protection Agency s (EPA s) Off-Site Consequence Analysis. Thus, the committee did not attempt to assess the effectiveness of current protective measures although called for in the statement of task this was a part of the DHS RAMCAP effort, which DHS representatives made clear should not be duplicated. As the statement of task indicates, the focus of this review is on the vulnerabilities of the supply chain as a whole rather than the vulnerability of individual chemical plants. 

Off-site consequence analysis (OCA) 5- Five-year accident history... 

RMP Comp an electronic tool used to perform the off-site consequence analysis required under the Risk Management Program rule (currently available in draft form). 

Only chemicals that are considered relevant within the scenario of the proficiency test are to be reported to avoid irrelevant chemicals being reported, in real off-site sample analysis, confidential information on the facility under inspection is revealed (e.g. information on an industrial production process that is not relevant to the implementation of the CWC). This requirement is a consequence of Paragraph C.17 of the Confidentiality Annex of the CWC, l1. The reporting of irrelevant chemicals is penalized with immediate failure of the test see Section 6.1. 

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. 

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... 

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... 

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 ... 

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. 

Source term analysis and assessment of off-site consequences. 

A critical consideration is identifying an off-site waste processor who is able and willing to receive the carbon filter material from the VOC treatment step. A waste processor will certainly require that VOCs be stripped from the hydrolysate only after agent destruction has been confirmed by chemical analysis. Consequently, the spent activated carbon used to recover VOCs should be agent free and can be treated like any other commercially produced spent filter material. If the spent activated carbon cannot be certified as agent free, it will have to be managed in the same manner as spent activated carbon that is known or likely to be agent contaminated. 

Table 17.1 shows the aspects of process safety for which actions are required by OSHA in Title 29 of the Code of Federal Regulations, Part 1910, Section 119 (29 CFR 1910.119) [1] and by the EPA in Title 40 of the Code of Federal Regulations, Part 68 (40 CFR 68) [2]. This Chemical Process Safety section concentrates on the engineering aspects of Process Safety Information —on the consequences of failure of engineering and administrative controls and the qualitative evaluation of a range of the possible safety and health effects of failure of controls requirements of the OSHA and EPA Process Hazards Analysis and the Off-Site Hazard Assessment. ... 

An evaluation of the confinement functions in the HCF must consider the state of the confinement structures, and the potential flow and/or leakage paths that would result in dose consequences to either on-site or off-site personnel. Two outside evaluations of the seismic performance of HCF SSCs form the basis for this DBE analysis. The first, performed by Walla Engineering Ltd in December 1998, was an evaluation of the east shield wall of Zone 2A. This wall has the greatest potential for failure in a seismic event of ail of the basement concrete structural elements, since it is unrestrained at the top. The second evaluation is a qualitative assessment of several SSCs performed by Chavez-Grieves based on an on-sHe inspection, reported in memorandum format dated May 18,1999. 

The radiological consequence analysis was performed for conservative mass and energy releases to the environment through SDA(BRU-A). The analysis assumes that no operator actions are taken to terminate SI flow and conservatively high total mass and activity released to the environment in 2 hours was assumed. The off-site doses calculated are within foe dose acceptance criteria. 

The analysis of radiation consequences of beyond design basis accidents confirms that there will be no need for post-accident off-site emergency measures. 

Where required, this part of the SAR should provide a description in sufficient detail of the analysis performed to identify accidents that can lead to significant core damage and/or off-site releases of radioactive material (severe accidents). The challenges to the plant that such events represent and the extent to which the design may reasonably be expected to mitigate then-consequences should be considered, justified and referenced here. 

Risk associated with reactivity incidents usually is not the most dominant one. However, its consequences and little possibility of recovery before some fuel damage occurs make reactivity incidents an important concern. The slow dilution incidents are well understood and often experienced phenomena. The administrative and hardware improvements were made at many plants to prevent slow dilution. Rapid dilution, like introduction of a slug of unborated water in the core is potentially critical incident. Some analysis performed in Germany found that such an accident could lead to a pressure peak in the reactor. Hardware interlocks and administrative limitations were introduced to reduce the probability of such an event. In France, the charging flow to RCP is terminated during loss of off-site power, to prevent the formation of the slug of unborated water which would be transported to the core when the pump is restarted. 

Step 2 The safety classification of structures, systems and components reflects the internal postulated events and external events as set forth in the safety analysis of the plant (box (3) of Fig. 1). The definition of the defence in depth levels and barriers [2], the application of the single failure criterion and the assessment of the potential for common cause failures are identified in box (2) of Fig. 1 [19], bearing in mind the categorization of the facility. Next is the evaluation of the need for emergency procedures, both on and off the site. This is followed by identification of the internal events to be considered as a consequence of an external event or as contemporaneous to an external event, and therefore of the safety functions to be maintained in case of an external event (e.g. cooling of radioactive material, reactivity control, confinement). 

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