Accident process

Inherently safer strategies can impact the accident process at any of the three stages. The most effective strategies will prevent initiation of the accident. Inherently safer design can also reduce the potential for propagating an accident, or provide an early termination of the accident sequence before there are major impacts on people, property, or the environment. 

This section reflects on the limitations of the PSA process and draws extensively from NUREG-1050. These subjects are discussed as plant modeling and evaluation, data, human errors, accident processes, containment, fission product transport, consequence analysis, external events, and a perspective on the meaning of risk. 

Typically, the first phase of a comprehensive accident investigation process will involve describing the way in which the hardware, the chemical process, individual operators and operating teams are involved in the accident process. This is the domain of the structural analysis techniques and the technical analysis of the chemical process which gave rise to the accident. Analyses of human error will primarily address the interactions between hardware systems and individuals or operating teams (the first two layers... 

These questions tmd otliers are answered and analyzed. Changes are Uicn made to reduce the risk of an accident. Process checklists are updated and audited at reguhir inter als. 

The article select 100 coal mine accident cases from all the accidents happened in 2001-2009 according to the reason type of coal mine accidents, including mine roof accident, gas accident, water disaster accident, transportation accident, mechanical and electrical accident, explosion accident, fire accident and other accidents. Though analysis the accidents process, acquainting accident investigation and handling, the accident reasons were found out. The reason of coal mine accidents in our country mainly includes the following four areas ... 

That the theory coal mine accidents human error model proposed in the paper mainly reflects that human error is the ultimate reason lead to accident. The model contains two parts, that is, inside and out the red line region. Part of outside red line region embodies the relationship from the macroscopic among human error, object misconduct and environmental degradation, and the accident mechanism and consequences Part of inside red region describes the different accident processes from the microscopic. As shown in the model diagram, object misconduct and environmental degradation are... 

It should be noted that the problem of sodium circuit hydraulic resistance is of vital importance due to some features of accident processes. Accidental pressure in the sodium volume in the vicinity of large water leak into sodium depends not only on the leak rate but also on the hydraulic "compliance" of the sodium circuit. The experience shows that, in view of the above circumstances, sodium circuit pressure drop within the boundaries of "SG-expansion gas volume inlet" section should not exceed 0.3 MPa value. 

Because the safety control structure and the behavior of the individuals in it, like any physical or social system, changes over time, accidents must be viewed as dynamic processes. Looking only at the time of the proximal loss events distorts and omits from view the most important aspects of the larger accident process that are needed to prevent reoccurrences of losses from the same causes in the future. Without that view, we see and fix only the symptoms, that is, the results of the flawed processes and inadequate safety control structure without getting to the sources of those symptoms. 

An accident analysis technique should provide a framework or process to assist in understanding the entire accident process and identifying the most important systemic causal factors involved. This chapter describes an approach to accident analysis, based on STAMP, called CAST (Causal Analysis based on STAMP). CAST can be used to identify the questions that need to be answered to fully understand why the accident occurred. It provides the basis for maximizing learning from the events. 

In STAMP, an accident is regarded as involving a complex process, not just individual events. Accident analysis in CAST then entails understanding the dynamic process that led to the loss. That accident process is documented by showing the sociotechnical safety control structure for the system involved and the safety constraints that were violated at each level of this control structure and why. The analysis results in multiple views of the accident, depending on the perspective and level from which the loss is being viewed. 

The goal of the accident analysis should instead be to determine how to change or reengineer the entire safety-control structure in the most cost-effective and practical way to prevent similar accident processes in the future. Once the STAMP analysis has been completed, generating recommendations is relatively simple and follows directly from the analysis results. 

One consequence of the completeness of a STAMP analysis is that many possible recommendations may result—in some cases, too many to be practical to include in the final accident report. A determination of the relative importance of the potential recommendations may be required in terms of having the greatest impact on the largest number of potential future accidents. There is no algorithm for identifying these recommendations, nor can there be. Political and situational factors will always be involved in such decisions. Understanding the entire accident process and the overall safety control structure should help with this identification, however. 

One general thing to note in this accident is that there were a large number of redundancies in each part of the process to prevent the loss, but they were not effective. Sometimes (as in this case), built-in redundanqr itself causes complacenqr and overconfidence and is a critical factor in the accident process. The use of redundanqr... 

While the accident report was more thorough than most, information that would have been helpful in understanding the entire accident process and generating more complete recommendations, was omitted. A STAMP-based accident analysis process provides assistance in determining what questions should be asked during the incident or accident investigation. 

Because accidents are composed of sets of individual events, all of which are interrelated, each event affects one or more actors and what they do next, changing their state. The first event in the accident process is a perturbation or an undesired or nnplanned change in someone or something within the planned process. That first dismptive event initiates a sort of cascading effect, culminating in some harm or loss [p. 31]. 

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