Catastrophe definition

Absolute risk estimates can be difficult to use when there is no apparent human experience against which to calibrate them. By definition, there never exists enough experience about catastrophic rare events (fortunately) with which to calibrate the thinking about their significance. If there were enough data, you would not have elected to do the QRA in the first place. So, now thatyou have a bottom line estimate... 

To meet this requirement, a company must define an incident in specific terms for their facility. This includes an operational definition that indicates the number of pounds of the substance used in a particular process that would qualify as a catastrophic event . Defining an incident in site-specific terms also includes defining the terms "could reasonably have resulted in . Appendix C of the regulation provides guidelines for clarifying this point. It includes definitions of "near misses in which a catastrophic failure occurred, but a chemical release did not occur. Clear guidelines should be established that provide the employee with a quantifiable means of defining those incidents that require a violation report. 

There is also a certain amount of statistical information available on the failures of process system components. Arulanantham and Lees (1981) have studied pressure vessel and fired heater failures in process plants such as olefins plants. They define failure as a condition in which a crack, leak or other defect has developed in the equipment to the extent that repair or replacement is required, a definition which includes some of the potentially dangerous as well as all catastrophic failures. The failure rates of equipment are related to some extent to the safety of process items. If a piece of equipment has a long history of failures, it may cause safety problems in the future. Therefore it would be better to consider another equipment instead. It should be remembered that all reliability or failure information does not express safety directly, since all failures are not dangerous and not all accidents are due to failures of equipment. 

Failure occurs when the component ceases to perform its required function. In the case of catastrophic failure, such as the rupture of a pipe or electrical breakdown of an insulator, this is obvious, but in many cases there is no such clear end of life. For example, is the end point when a small amount of environmental stress cracking has occurred, or when cracks have reached 5 mm in length Broadly, the definition of end point is that a property has reached a level at which safety, performance or market acceptance dictate that the component or product can no longer be used. 

For the inhabitants of the exclusion zone, situated in a forested region without well-developed economic and social infrastructures, it is of interest to estimate the relative contributions to internal exposure of forest food (berries and mushrooms) and conventional agricultural food (potatoes and milk). Some specialist studies have assumed that forest food represents only a small part of the diet of inhabitants of the exclusion zone, but we would suggest that in fact, it plays a major role. Typically, the consumption of forest food contributes 50% of the internal exposure dose, while for some critical population groups, it can exceed 80%. The definition of the spatial variation in pollution, the prevailing ecological conditions, and the diet should allow a scientifically-based prediction to be made of the internal exposure dose to the local population, and will help to identify the major risk factors within a certain time period following the Chernobyl catastrophe. 

It is somewhat confusing that the term critical diameter is also used by those interested in the potential of an energetic material to undergo thermal runaway. Because, by definition, the energetic material releases heat when it decomposes, it has the potential to increase its local environmental temperature. Depending on the decomposition kinetics of the material, at some critical dimension the charge can self-heat to catastrophic reaction. This can be referred to in terms of the critical diameter or, more often, in terms of the initial environmental temperature that allows this scenario, the critical temperature . 

Each incident is unique. One working definition of Process Safety Incidents is incidents which—in the judgment of responsible, informed, in-plant administrators (such as the shift superintendent or any second-level supervisor)—could reasonably have resulted or actually had resulted in a catastrophic release of highly hazardous chemicals. A catastrophic release for these purposes is a major uncontrolled emission, fire, or explosion, involving one or more highly hazardous chemicals, that presents serious danger to employees in the workplace. 

We here summarize the results of Bader et a/.118 which are concerned with the definition of molecular structure and with the extension of this concept, together with the associated concept of a bond, to the dynamic case. A precise description and physical interpretation of the making and breaking of chemical bonds is presented by these workers in a quantitative analysis of the evolution of molecular structure. The topological analysis of the dynamic system, as pointed out by Collard and Hall,119 falls naturally into the realm of an existing and elegant mathematical theory, the catastrophe theory of Thom.120... 

As discussed above and illustrated in Fig. 3.4, the partitioning of nuclear configuration space obtained as a result of the definition of molecular structure leads to the concept of a structure diagram. The space R is partitioned into a finite number of structural regions with their boundaries, as defined by the catastrophe set, denoting the configurations of unstable structures. This information constitutes a system s structure diagram, a... 

In order to state the conditions under which one will observe a catastrophe of the conflict type, it is necessary to introduce a number of definitions and the notion of a transversal or stable interseetion of two submanifolds of three-dimensional space. 

The number of elementary catastrophe types depends upon q. It has been shown that only for values of g < 5 is the number of catastrophe types finite. Thom has classified these types by their co-rank k and co-dimension q for values of g < 4. The concept of an unfolding and the accompanying definitions are illustrated first in terms of the simplest of all catastrophe types, the so-called fold catastrophe for which both the co-rank and co-dimension equal one. 

This definition of a geochemical cycle demonstrates that recognizing the appropriate scale of the cycle is vital. Particularly important is the timescale. It is clear that on short timescales catastrophic transfers may take place between reservoirs which on a longer timescale would be "smoothed out." As has already been noted, the appropriate choice of timescale is particularly pertinent to a consideration of the carbon cycle (see Kump et al., 1999), for whether or not the sedimentary rock... 

Figure 2.5 shows also the concentration dependence of the inverse Kauzmann temperature T (entropy catastrophe temperature). For the pure metal, T is much higher than the temperature T0 as discussed. The 77-line should also decrease with increasing concentration and end in the triple point(C, 7 )[2.21] as follows from its definition (AS = 0). It is interesting to note that at this point the real Kauzmann temperature and the inverse Kauzmann temperature meet. But in real systems, the amorphous phase has an excess entropy (small fraction of the entropy of fusion) when compared to the corresponding crystal, the exact amount determined from the kinetics and timescale of the glass transformation. Therefore, another glass transition temperature line with finite excess entropy must be considered, which will be parallel to the Tg-line (above it) and cross the T0- and 77-lines not exactly in the triple point. 

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