Explosions models

The next part of the procedure involves risk assessment. This includes a deterrnination of the accident probabiUty and the consequence of the accident and is done for each of the scenarios identified in the previous step. The probabiUty is deterrnined using a number of statistical models generally used to represent failures. The consequence is deterrnined using mostiy fundamentally based models, called source models, to describe how material is ejected from process equipment. These source models are coupled with a suitable dispersion model and/or an explosion model to estimate the area affected and predict the damage. The consequence is thus determined. 

Once the source modeling is complete, the quantitative result is used in a consequence analysis to determine the impact of the release. This typically includes dispersion modeling to describe the movement of materials through the air, or a fire and explosion model to describe the consequences of a fire or explosion. Other consequence models are available to describe the spread of material through rivers and lakes, groundwater, and other media. 

An explosion model is used to predict the overpressure resulting from the explosion of a given mass of material. The overpressure is the pressure wave emanating from a explosion. The pressure wave creates most of the damage. The overpressure is calculated using a TNT equivalency technique. The result is dependent on the mass of material and the distance away from the explosion. Suitable correlations are available (2). A detailed discussion of source and consequence models may be found in References 2, 8, and 9. 

Hjertager, B. H. 1989. Simulation of gas explosions. Modeling Ident Contr. 10 227-247. 

Fire and explosion models describe the magnitude and physical effects (heat radiation, explosion overpressure) resulting from a fire or e.xplosion. 

Effect models describe the impact of the physical effects of a fire, e.xplosion, or toxic gas release on exposed people, the environment or property, based on the results of tlie source, dispersion, and fire and explosion models. 

Cause-consequence analysis serx es to characterize tlie physical effects resulting from a specific incident and the impact of these physical effects on people, the environment, and property. Some consequence models or equations used to estimate tlie potential for damage or injury are as follows Source Models, Dispersion Models, Fire Explosion Models, and Effect Models. Likelihood estimation (frequency estimation), cliaractcrizcs the probability of occurrence for each potential incident considered in tlie analysis. The major tools used for likelihood estimation are as follows Historical Data, Failure sequence modeling techniques, and Expert Judgment. 

Anderson, R. P., and D. R. Armstrong, 1973, Comparison between Vapor Explosion Models and Recent Experimental Results, AIChE Preprint 16, 14th Natl. Heat Transfer Conf., Atlanta, GA. (2)... 

Additional models and software are identified in A Guide to Quantitative Risk Assessment for Offshore Installations (Spouge, 1999) which address offshore risk analysis, explosion modeling, evacuation and rescue analysis, reliability analysis, accident databases, event tree analysis, and safety management. 

The conceptually simplest way of forming a black hole at the heart of a massive star, thereby setting up the conditions of the hypernova model, is to begin by repudiating the traditional explosion model detonated by neutrinos. The iron core then collapses without remission in the space of one second. A black hole prospers, pulling down the rest of the stellar edifice. This may be a common occurrence for stars of 35 to 40 Mq. However, uncertainties remain concerning convection, mass loss and mixing due to rotation, not to mention the explosion mechanism itself. 

In Belgium, at first explosives modelled on the French ones were used, but later they were replaced by others containing cooling ingredients, such as ammonium chloride, sulphate, or oxalate or sodium chloride. The safety explosives used initially in Belgium included mixtures with ammonium perchlorate, of the Yonckite type. Examples of these explosives for rock and coal work are given in Table 95. 

Cambrite—an ammonium nitrate explosive modelled on the German Car-bonits (see Table 124). It contained a small quantity of nitroglycerine, potassium or sodium nitrate and a considerable amount of carbonaceous material (e.g. wood meal, charcoal etc.). This material was added to prevent the complete combustion of the carbon included in the explosive (to carbon monoxide only), to reduce the heat of explosion and, in consequence, the temperature of the explosion. 

The discussion in this paper shows that we in the future can expect the understanding of the stellar nucleosynthesis from observations of supernovae to be considerably improved. Most of the physics in connection with the thermalization of the y-rays is well understood, as well as most of the atomic data going into the calculations. There are, however, in this area some uncertain processes, most importantly the charge transfer reactions between the various ions, like O II + Na I O I + Na II. Also the ionization of the trace elements, Na I, Mg I and Si I, may be sensitive to the treatment of the UV radiation field. However, these problems are likely to be solved in the near future. Therefore, from a given explosion model of the density and abundance structure one can predict what the late spectrum should be, and compare this with the observations. Especially the line profiles are important, since they provide a test of the probably most uncertain part of the explosion calculations. 

Additional details and references for explosion modeling maybe found in Baker et al. (1978), Baker et al. (1983), CCPS (1994) Lees (1980) Strehlow (1980), and Wiekema (1979). 

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