Accidents contributing

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.)... 

Determining the cause of the accident, contributing factors, direct and indirect causes, getting information from people, conducting successful interviews, and filling out accident reports. 

Another known accident contributing to marine contamination was the burn-up of a US satellite (SNAP 9A) above the Mozambique channel in 1964 which released 0.63 PBq Pu and 0.48 TBq Pu 73% was eventually deposited in the southern hemisphere. 

Often, ironically, our successful efforts to eliminate or reduce accidents contribute to the march toward higher risk. Perception of the risk associated with an activity often decreases over a period of time when no losses occur even though the real risk has not changed at all. This misperception leads to reducing the very factors that are preventing accidents because they are seen as no longer needed and available to trade off with other needs. The result is that risk increases until a major loss occurs. This vicious cycle needs to be broken to prevent accidents. In STAMP terms, the weakening of the safety control structure over time needs to be prevented or detected before the conditions occur that lead to a loss. 

Figure 1 (quoted from Lind 2009) describes a schema of maintenance operations, including the development of the need for maintenance (on the left) with possible unwanted consequences. These can be environmental emissions and/or impaired safety. The right side of the schema summarizes the main stages of a maintenance operation. Other main components in the schema are the direction of the analyses in the event of an occurred accident the analysis has to be top-down (e.g. fault tree analysis). In order to identify possible accident contributing factors beforehand, the analysis can be started from the unwanted outcome and then the model chain of contributing events leading to the accident (Lind 2009). 

Procedural problems are frequently cited as the cause of major accidents, contributing to some of the world s worst incidents, such as Bhopal. Piper Alpha and Clapham Junction. In the major hazard industries, fit-for-purpose procedures are essential to minimise errors, and to protect against loss of operating knowledge (eg when experienced personnel leave). 

Contributing causes are events or conditions that collectively with other causes increased the likelihood of an accident but that individually did not cause the accident. Contributing causes may be longstanding conditions or a series of prior events that, alone, were not sufficient to cause the accident, but were necessary for it to occur. Contributing causes are the events and conditions that set the stage for the event and, if allowed to persist or recur, increase the probability of future events or accidents. 

Cause of accident Contributing factor or root cause. 

Accidents/ Incidents indirect (retrospective) existing analysis of accident contributing factors damage incident analysis... 

Subjects to be interviewed are workers, supervisors, management, and safety-experts. They are recognized as subject matter experts. The evaluation of accident contributing factors and the proposals for improvement serve as key issues in the planning of safety activities. 

Inadequate communications practices during the accident contributed to its severity by hindering the timely flow of information to control room operators (EPA/OSHA 1998). 

Procedures are written to ensure that activities are performed in a systematic way. Accident investigation shows that the majority of accidents occur because procedures are not followed, and this contributes mostly to the base of the safety triangle introduced at the end of Section 4.1. 

Eault tree analysis (ETA) is a widely used computer-aided tool for plant and process safety analysis (69). One of the primary strengths of the method is the systematic, logical development of the many contributing factors that might result ia an accident. This type of analysis requires that the analyst have a complete understanding of the system and plant operations and the various equipment failure modes. 

ETA breaks down an accident iato its contributing equipment failures and human errors (70). The method therefore is a reverse-thinking technique, ie, the analyst begias with an accident or undesirable event that is to be avoided and identifies the immediate cause of that event. Each of the immediate causes is examined ia turn until the analyst has identified the basic causes of each event. The fault tree is a diagram that displays the logical iaterrelationships between these basic causes and the accident. 

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... 

A valuable QRA result is the importance of various components, human errors, and accident scenarios contributing to the total risk. The risk importance values highlight the major sources of risk and give the decision maker a clear target(s) for redesign or other loss prevention efforts. For example, two accident scenarios may contribute 90% of the total risk once you realize that, it is obvious that you should first focus... 

The models you use to portray failures that lead to accidents, and the models you use to propagate their effects, are attempts to approximate reality. Models of accident sequences (although mathematically rigorous) cannot be demonstrated to be exact because you can never precisely identify all of the factors that contribute to an accident of interest. Likewise, most consequence models are at best correlations derived from limited experimental evidence. Even if the models are validated through field experiments for some specific situations, you can never validate them for all possibilities, and the question of model appropriateness will always exist. 

In most cases, physical hazards are easy to identify. Let s consider housekeeping items. These items can contribute to slip, trip, and fall hazards. Most people are comfortable in observing and fixing these types of hazards, especially after an accident occurs. After all, you can easily see these types of hazards. The accident occurrence is also easy to envision. 

After having studied the peer comments about some important classes of initiating events, we remain unconvinced of the WASH-1400 conclusion that they contribute negligibly to the overall risk. Examples include fires, earthquakes, and human accident initiation. 

Humans control all chemical and nuclear processes, and to some extent all accidents result from human error, if not directly in the accident then in the process design and in the process inadequate design to prevent human error. Some automatic systems such used in nuclear power reactors because the response time required is too short for human decisions. Even in these, human error can contribute to failure by inhibiting the systems. 

Human error contributed to about 50% of the accident sequences m the RSS but none of the human error data came from the nuclear power industry. Furthermore, very high failure rates 0.5 to 0.1/action) were predicted but are not supported by the plant... 

The ingestion dose contributes very little to the dose from a severe reactor accident and is usually not computed. However, the food pathway is a major determinant of bow the exposed area must be treated in the months and years following the accident. If the ground concentration is high, the land may be interdicted from agricultural u.se or grazing. 

Uncertainly estimates are made for the total CDF by assigning probability distributions to basic events and propagating the distributions through a simplified model. Uncertainties are assumed to be either log-normal or "maximum entropy" distributions. Chi-squared confidence interval tests are used at 50% and 95% of these distributions. The simplified CDF model includes the dominant cutsets from all five contributing classes of accidents, and is within 97% of the CDF calculated with the full Level 1 model. 

N Reactor accidents are expected at lower fuel temperatures than LWR accidents. The large thermal capacity of the graphite moderator stack, the low melting point of the fuel (1,407"K) and the GSCS contribute to lower accident temperatures which retains heavy metals in the fuel. 

The five types of accidents significantly contributing to the risk are failure and their mean frequency ai c ... 

Humans seek and want thermal comfort, even at work in industrial settings. Clothing, activities, posture, location, and shelter are chosen, adjusted, altered, and sought consciously and unconsciously to reduce discomforts and enable us to focus more on the other tasks of life. Discomfort can contribute to mistakes, productivity decreases, and industrial accidents. " Thermal discomfort results from the physiological strain of thermoregulation. The strain can be in the form of altered body temperatures, sweating and excessive skin moisture, muscle tension and stiffness, shivering, and loss of dexterity. A small... 

At Bhopal, there had been changes in staff and reductions in manning, and the new recruits may not have been as experienced as the original team. However, I do not think that this contributed significantly to the cause of the accident. The errors that were made, such as taking protective equipment out of commission, were basic ones that cannot be blamed on inexperience of a particular plant. 

A liquefied propane tank truck whose volume is 6000 U.S. gallons (22.7 m ) is involved in a traffic accident, and the tank truck is engulfed by fire from burning gasoline. The tank is 90% filled with propane. Assume that all of the propane will contribute to the fireball. Radiation effects are calculated below blast and fragmentation effects for this problem will be calculated in Sections 9.2 and 9.3, respectively. 

This accident was therefore a typical example of "system-induced error." The poor design of the information display and the inaccessible steam valve created preconditions that were likely to contribute to the likelihood of an error at some time. 

Many data collection systems place the primary emphasis on the technical causes of accidents. There is usually a very detailed description of the chemical process in which the accident occurred, together with an in-depth analysis of the technical failures that are seen as the major causes. The human or system failures that may have contributed to the accident are usually treated in a cursory manner. Technically oriented reporting systems are very common in the CPI, where engineers who may be unfamiliar with human factors princi-... 

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