Accident, defined

The high-level system hazards that might be derived from the accidents defined for the NASA thermal tile processing robot in section 7.1 might be ... 

Indemnity Case Rate, which is a negative metric providing the rate of all workers compensation cases that involve lost time payments per 100 full time employees per year. It may be indicative of the company s basic prevention and reduction efforts in minimizing more serious lost time case incidence and severity. It relates closely to OSHA s DART or rate of injuries and illnesses resulting in days away from work, restricted work activity, and/or job transfer. According to Italian National Standards UNI 7249 (UNI 2007) further index rates are introduced, like incidence index of occurred accidents, defined as rate of occurred accidents per 1.000 workers, frequency index (rate of occurred accidents per 1.000.000 hours worked), severity index of accidents, which represents 1000 times total number of lost days per hours worked. 

Sentinel Event. A sentinel event is a category of medical accident defined by the Joint Commission on Accreditation of Healthcare Organizations to include the following ... 

Safety assignment focuses on loss of containment, etc. so it can be slightly modified to include uncontrolled event, and accident can be caused by a sudden occurrence (an uncontrolled event) causing serious danger or harm to relevant person(s), at any risk community, property or environment immediately or at a later time. This derived from major hazardous facility (MHF) regulation. Here occurrence includes escape, spillage, leakage, implosion, explosion, and fire. This is further to major accident defined in Clause 3.1.2. 

Accident - defined by the Health and Safety Executive as any unplanned event that results in injury or ill health of people, or damage or loss to property, plant, materials or the environment or a loss of a business opportunity . Other authorities define an accident more narrowly by excluding events that do not involve injury or ill-health. This book will always use the Health and Safety Executive definition. 

Analyses of radiation impacts in beyond design basis accidents define the control area around the nuclear cogeneration plant as coinciding with the site territory, while the planning area for post-accident measures was defined as 3 km. No post-accident measures planning the mandatory evacuation of population is required. 

Without proper control of hazards, a sequence of events (scenario) occurs which results ia an accident. A hazard is defined as anything which could result ia an accident, ie, an unplaimed sequence of events which results ia iajury or loss of life, damage to the environment, loss of capital equipment, or loss of production or inventory. 

Accidents in chemical plants make headline news, especially when there is loss of hfe or the general public is affected in even the slightest way. This increases the public s concern and may lead to government action. The terms hazard and risk are defined as follows ... 

The frequency analysis step involves estimating the likelihood of occurrence of each of the undesired situations defined in the hazard identification step. Sometimes you can do this through direct comparison with experience or extrapolation from historical accident data. While this method may be of great assistance in determining accident frequencies, most accidents analyzed by QRA are so rare that the frequencies must be synthesized using frequency estimation methods and models. 

Frequency Phase 1 Perform Qualitative Study, Typically Using HAZOP, FMEA, or What-if Analysis. To perform a qualitative study you should first (1) define the consequences of interest, (2) identify the initiating events and accident scenarios that could lead to the consequences of interest, and (3) identify the equipment failure modes and human errors that could contribute to the accident... 

While the F-N curve is a cumulative illustration, the risk profile shows the expected frequency of accidents of a particular category or level of consequence. The diagonal line is a line of constant risk defined such that the product of expected frequency and consequence is a constant at each point along the line. " As the consequences of accidents go up, the expected frequency should go down in order for the risk to remain constant. As the example illustrates, if a portion of the histogram sticks its head up above the line (i.e., a particular type of accident contributes more than its fair share of the risk), then that risk is inconsistent with the risk presented by other accident types. (Note There is no requirement that you use a line of constant risk other more appropriate risk criteria for your application can be easily defined and displayed on the graph.)... 

Risk is defined as the combination of the expected frequency and consequence of accidents that could occur as a result of an activity. Risk analysis is a formal process of increasing one s understanding of the risk associated with an activity. The process of risk analysis includes answering three questions ... 

Regulate the design and operation of defined major hazard installations. All necessary measures are required to prevent and limit the consequences of major accidents. Operators of upper-tier sites must produce a detailed Safety Report those of lower-tier sites must prepare a Major Accident Prevention Policy. 

A risk assessment analyses systems at two levels. The first level defines the functions the system must perform to respond successfully to an accident. The second level identifies the hardware for the systems use. The hardware identification (in the top event statement) describes minimum system operability and system boundaries (interfaces). Experience shows that the interfaces between a frontline system and its support systems are important to the system cs aluaiion and require a formal search to document the interactions. Such is facilitated by a failure modes and effect analysis (FMEA). Table S.4.4-2 is an example of an interaction FMEA for the interlace and support requirements for system operation. 

Since this text is not solely devoted to HRA, the above process is by necessity simplified. A more defined interaction is shown in Figure 4.5-2. Here HRA interacts with the development of the system models and feeds into not only the accident sequences but also the physical analysis of the inplant and explant accident progress,... 

At this point, following the chapters, the objectives have been defined, the effect of government regulations and standards are known, accidents have been identified and analyzed by various methods to determine the probability of an accident, and the accident consequences have been calculated. These parts must be assembled to present the risk and the analysis of the risk according to its various contributors. 

The initiating event task was a detailed and systematic search for accident initiators that fail barriers to radioactive material release using dendograms (hierarchical trees). Dendograms define barriers and their failure modes in terms of J phenomena (e.g., melt,... 

Accident Sequence Modeling using a logic model for the facility was developed. The model included all initiators of potential accidents and the response of the installation to these initiators. Specific accident sequences are defined in event trees consisting of an initiating... 

Risk is often defined as the likelihood of a certain event times a measure of the severity of its consequences. Most risk assessment studies concentrate on estimating the likelihood of certain events. They often concern the release of chemicals, or accidents in engineering projects and the project outcome. In thi.s section, the subject of accidents is not covered. Risk assessment (RA), as a technique, has been adopted by various national governments, by EU, and by OECD.-... 

You can quickly identify these plant sections by reviewing process flow diagrams and valving arrangements. Isolation points are defined by control valves or powered block valves that can be remotely activated. Process hazard analysis techniques help you identify the maximum credible accident scenarios. (Note that manual valves should not be considered reliable isolation points unless they are located to be accessible following a major accident. However, remotely-activated valves can only be considered reliable isolation points if there are adequate reliability engineering and maintenance programs in place.)... 

The analysis of accidents and disasters in real systems makes it clear that it is not sufficient to consider error and its effects purely from the perspective of individual human failures. Major accidents are almost always the result of multiple errors or combinations of single errors with preexisting vulnerable conditions (Wagenaar et al., 1990). Another perspective from which to define errors is in terms of when in the system life cycle they occur. In the following discussion of the definitions of human error, the initial focus will be from the engineering and the accident analysis perspective. More detailed consideration of the definitions of error will be deferred to later sections in this chapter where the various error models will be described in detail (see Sections 5 and 6). 

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