Accident Selection

Besides the analysis of nuclear fuel and of radioactive waste materials, the determination of contamination and enrichment of selected radioactive nuclides, e.g., which is one of the most important environmental indicators of nuclear accidents, Se, Tc, Np, Pu, °Pu and "Am at ultratrace concentration levels, is useful for environmental monitoring of fallout from nuclear weapons testing, nuclear power plants or nuclear accidents. ". Selected application fields for the determination of natural and artificial long-lived radionuclides (LLR) and radionuclides investigated by mass spectrometric techniques are summarized in Tables 9.36 and 9.37, respectively. 

This section summarizes the methods used to evaluate and quantify the consequences of operational accidents, natural phenomena events, and external events selected in Section 3.3.2.3.5, Accident Selection as DBAs. Consequences to the public and the environment stem from airborne releases of radioactive material since no liquid or solid radioactive material would be released in the selected accidents. The airborne pathway is of primary interest for releases from nonreactor nuclear facilities according to DOE-STD-1027-92 (DOE 1997). Exposure to direct or scattered radiation is a hazard only for workers due to the distance to the public. 

Section 3.3.2.3.5, Accident Selection, identified one beyond DBA as, Multiple simultaneous errors or events that affect multiple SCBs, resulting in release of the contents of multiple targets. Release of the fission products from multiple targets (six) in a single SCB has already been analyzed in two DBAs Spill of Process Materials in an SCB and Fire in a Process SCB. The source term and consequences of the Multiple simultaneous errors or events... beyond DBA are discussed in Section 3.4.3.1 and S.4.3.2 below. Two additional hazards are discussed in Sections 3.4.3.3 and 3.4.3.4 as beyond DBAs to provide a perspective of the residual risk associated with the operation of the facility. These beyond DBAs are 1) seismic events resulting in a release of radiological material and 2) dispersal of radiological material by an explosion in the HCF. 

All U.S. civil aviation accidents and certain public-use aircraft accidents Selected highway accidents... 

Functional group analysis relates to those reactions that polymers undergo, either intentionally or accidently. Selective degradation refers to those chemical reactions that a polymer undergoes which cut particular bonds. These may... 

The subsequent step is to identify the various scenarios which could cause loss of control of the hazard and result in an accident. This is perhaps the most difficult step in the procedure. Many accidents have been the result of improper characterization of the accident scenarios. For a reasonably complex chemical process, there might exist dozens, or even hundreds, of scenarios for each hazard. The essential part of the analysis is to select the scenarios which are deemed credible and worst case. 

Automotive and architectural laminates of PVB develop maximum impact strength near 20°C, as shown in Figure 2. This balance is obtained by the plasticizer-to-resin ratio and the molecular weight of the resins. It has been adjusted to this optimum temperature based on environmental conditions and automobile population at various ambient temperatures. The frequency and severity of vehicle occupant injuries vs temperature ranges at the accident location have been studied (5), and the results confirm the selection of the maximum performance temperature and decreasing penetration resistance at temperature extremes. 

The Center for Chemical Process Safety (CCPS), a directorate of AIChE, was established in 1985 to develop and disseminate technical information for use in the prevention of major chemical accidents. The CCPS is supported by a diverse group of industrial sponsors in the chemical process industry and related industries who provide the necessary funding and professional guidance for its projects. The CCPS Technical Steering Committee and the technical subcommittees oversee individual projects selected by CCPS. Professional representatives of the sponsoring companies staff the subcommittees, with a member of the CCPS staff coordinating the activities of the sub-committee. 

Layer of protection analysis (LOPA) is a simplified form of event tree analysis. Instead of analyzing all accident scenarios, LOPA selects a few specific scenarios as representative, or boundary, cases. LOPA uses order-of-magnitLide estimates, rather than specific data, for the frequency of initiating events and for the probability the various layers of protection will fail on demand. In many cases, the simplified results of a LOPA provide sufficient input for deciding whether additional protection is necessary to reduce the likelihood of a given accident type. LOPAs typically require only a small fraction of the effort required for detailed event tree or fault tree analysis. 

A simplified form of event tree analysis using selected accident scenarios and order-of-magnitude estimates to determine whether additional protection is needed... 

Liquids can also exert pressure due to thermal expansion. Table 4.15 provides an indication of pressure increases due to temperature increases for selected common liquids in full containers or pipes. Serious accidents can arise unless the design of rigid plant items such as pipework takes into account the changes in volume of liquids with temperature fluctuation by the following or combinations thereof ... 

To be effective, the creation of a task or modification of a task through the introduction of new processes or equipment should automatically require you to develop a new or revised JHA. Jobs with many steps are usually good candidates. As stated before, you should assign each job selected a priority based on the accident potential and the severity of associated potential injuries. 

After the hazard assessment has been conducted and the data has been collected, it should be organized in a logical outline that will estimate the potential for employee injury The organized data will help to decide the type of hazard(s) involved, the level of risk, and the seriousness of potential injury The appropriate levels of PPE are then selected based on the hazard determination and the availability of PPE. The user should be properly fitted for the specified PPE, and the employer should make sure that it is comfortable to wear. Hazard reassessments should be conducted as necessary based on the introduction of new or revised processes, equipment, and accident experience, to ensure the continued suitability of selection of the proper PPE. 

Selection of a PrHA methodology requires consideration of many factors including the availability of process information such as experience with the process, changes that have taken place, reliability, aging, maintenance, etc. If it is a new process, less reliance can be placed on experience and greater reliance must be placed on the analysis of possible accidents and accidents in similar or related processes. Size, complexity and hazard severity influences the dunce ot ihe most appropriate PrHA methodology. 

After the What-lf questions for a process step have been developed, the previously obtained Checklist is applied. Tlie team selects each Checklist item for accident potential and adds them to the What-lf list for evaluation. The checklist is reviewed for each area or step in the process. 

Step I - Select the combinations of systems that enter the analysis. (This is equivalent to finding accident sequences in event tree analysis.)... 

While event trees are not so common in chemical plant PSA they are extensively used to analyze nuclear accidents, but before beginning the analysis, preliminaries that are needed are plant tamiliarity and initiator selection... 

As the previous ehapter discussed nuelear power reactor operation and how to perform a PSA on it, this chapter attempts to apply a similar framework to chemical processing. The problem is the diversity of chemical processing that blurs the focus. This chapter begins by showing that accidents in the chemical process industry cost lives and dollars. Descriptions of deadly chemical accidents arc presented to show the chain of sequences that were involved to suggest how their PSA may be structured. Background on selected hazardous chemical process is presented followed by descriptions of how their PSA have structured. The chapter concludes by applying FTAPSUIT to a pressure vessel rupture analysis. 

The following is a list by major heading of processes in the Chemical Industry. While accidents can occur in any activity, the scope of the chemical process industry is so wide that processes are selected for description based on judged hazard. These are identified by the number of the section in which they are described. Process not identified by a three digit number are excluded on the basis of low perceived accident potential. 

Its unique design suggests several accident scenarios that could not occur at other reactors. For example, failure to supply ECC to 1/16 of the core due to the failure of an ECC inlet valve. On the other hand, some phenomena of concern to other types of reactors seem impossible (e.g., core-concrete interactions). The list of phenomena for consideration came from previous studies, comments of an external review group and from literature review. From this, came the issues selected for the accident progression event tree (APET) according to uncertainty and point estimates. 

One of my tasks was to pass on to design and operating staff details of accidents that had occurred and the lessons that should be learned. This book contains a selection of the reports I collected from many different companies. Although most have been published before, they were scattered among many different publications, some with small circulations. 

Selection of incidents described was based on the availability of information, the kind and amount of material involved, and severity of damage. Accidents occurring on public property generally produce better published documentation than those occurring on privately owned property. 

E)ocumentation of flash fires is scarce. In several accident descriptions of vapor cloud explosions, flash fires appear to have occurred as well, including those at Flixborough, Port Hudson, East St. Louis, and Ufa. The selection and descriptions of flash fires were based primarily on the availability of information. 

Chapter 2 discussed the possible influence of atmospheric dispersion on vapor cloud explosion or flash fire effects. Factors such as flammable cloud size, homogeneity, and location are largely determined by the manner of flammable material released and turbulent dispersion into the atmosphere following release. Several models for calculating release and dispersion effects have been developed. Hanna and Drivas (1987) provide clear guidance on model selection for various accident scenarios. 

The first perspective is the traditional safety engineering approach (Section 2.4). This stresses the individual factors that give rise to accidents and hence emphasizes selection, together with motivational and disciplinary approaches to accident and error reduction. The main emphasis here is on behavior modification, through persuasion (motivational campaigns) or pimishment. The main area of application of this approach has been to occupational safety, which focuses on hazards that affect the individual worker, rather than process safety, which emphasizes major systems failures that could cause major plant losses and impact to the environment as well as individual injury. 

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