Release source models

Source models for throttling releases require detailed information on the physical structure of the leak they are not considered here. Free expansion release source models require only the diameter of the leak. 

Once the scenario has been identified, a source model is used to determine the quantitative effect of an accident. This includes either the release rate of material, if it is a continuous release, or the total amount of material released, if it is an instantaneous release. Eor instance, if the scenario is the mpture of a 10-cm pipe, the source model would describe the rate of flow of material from the broken pipe. 

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. 

Develop an appropriate source model to calculate the release rate or total quantity released based on the specified scenario (see Discharge Rates from Punctured Lines and Vessels). 

A version of the Gifford-Hanna model was evaluated (50) using 1969 data for 113 monitoring stahons for particulate matter and 75 stations for SO2 in the New York metropolitan area. This version differed from Eq. (20-19) in considering major point source contributions and the stack height of emission release. This model produced results (Table 20-2) comparable to those of the much more complicated COM model (51). 

Source models describe tlie release rate of material from tlie process equipment into tlie external enviromiient, and tlie rate of release of spilled vapors and volatile liquids into the atmosphere. 

Source models are constructed from fundamental or empirical equations representing the physicochemical processes occurring during the release of materials. For a reasonably complex... 

Chlorine is used in a particular chemical process. A source model study indicates that for a particular accident scenario 1.0 kg of chlorine will be released instantaneously. The release will occur at ground level. A residential area is 500 m away from the chlorine source. Determine... 

The release mitigation procedure is part of the consequence modeling procedure shown in Figure 4-1. After selection of a release incident, a source model is used to determine either the release rate or the total quantity released. This is coupled to a dispersion model and subsequent models for fires or explosions. Finally, an effect model is used to estimate the impact of the release, which is a measure of the consequence. 

The relief sizing calculation procedure involves, first, using an appropriate source model to determine the rate of material release through the relief device (see chapter 4) and, second, using an appropriate equation based on fundamental hydrodynamic principles to determine the relief device vent area. 

When using the semi-quantitative method, the quantity of the release is estimated using source models, and the consequences are characterized with a category, as shown in Table 11-2. This is an easy method to use compared with QRA. 

Virtual sources As indicated above, the gaussian model was formulated for an idealized point source, and such an approach may be unnecessarily conservative (predict an unrealistically large concentration) for a real release. There are formulations for area sources, but such models are more cumbersome than the point source models above. For point source models, methods using a virtual source have been proposed in the past which essentially use the maximum concentration of the real source to determine the location of an equivalent upwind point source that would give the same maximum concentration at the real source. Such an approach will tend to overcompensate and unrealistically reduce the predicted concentration because a real source has lateral and along-wind extent (not a maximum concentration at a point). Consequently, the modeled concentration can be assumed to be bounded above, using the point source formulas in Eq. (23-78) or (23-79), and bounded below by concentrations predicted by using a virtual source approach. 

Point source model—A thermal energy model based on representing the total heat release as a point source. 

Keywords. Chlorinated paraffins, Polychlorinated n-alkanes, Short chain chlorinated paraffins, Releases, Sources, Environmental fate, Environmental distribution, Biodegradation, Physical properties, Environmental fate modelling... 

The purpose of atmospheric dispersion modeling is to provide, if all the input data are known, the observed concentrations downwind of the source of release. The source information, GIS data, and meteorological conditions are required to solve an atmospheric dispersion problem. For the problem we re interested in, we have concentration data from sensor, GIS information, and meteorological condition. Thus, we need a system to get us the source model from the concentration data. 

No additional examples of intense heat sources or actual fires released within model forest or simulated urban environments are known to this author. 

The concentrations of SCCPs in the environment are estimated in the local areas around release sources, in Kanto region, and the whole of Japan using the FUSES [16]. The quantities used as inputs in the model are the total amount released in the Kanto region and across Japan. Details of the parameters for land use are shown in Table 7. The average temperature and the amount of rainfall are identified as 15°C and 1,500 mm per year, respectively [17]. 

The concentrations of SCCPs in the environment estimated by the multimedia model are shown in Tables 7 and 8. The environmental concentrations in Kanto region are higher than the average concentrations in Japan. Further, as shown in Table 3, SCCP concentrations in water and sediments around release sources are higher than those in Kanto region, suggesting that SCCPs remain locally and affect... 

The General Structure of Multiple-Source Plume Models Multiple-source plume (and particularly Gaussian plume) models (Calder 1977) are commonly used for predicting concentrations of inert pollutants over urban areas. Although there are many special-puipose computational algorithms currently in use, the basic element that is common to most is the single-point-source release. The spatial concentration distribution from such a source is the underlying component and the multiple-source model is then developed by simple superposition of the individual plumes from each of the sources. 

Methods to estimate dose resulting from release of the source term are based on a database of airborne dose versus distance calculations for single isotope releases from TA-V facilities (Naegeli 1999). The database was developed using the Melcor Accident Consequence Code System Version 2 (MACCS2) computer model with a standard input for each single isotope calculation. Combining doses for individual isotopes provides the dose from the released source term. 

This document summarizes the efforts of the Source Term Working Group to complete the tasked objectives under the lASAP. It presents a detailed discussion of the fission product, actinide, and activation product inventories at each Kara Sea disposal site and a detailed description, with assumptions, of the models used to predict potential release of the radionuclides into the Kara Sea. Results of the release scenario models, reliability of the model input parameters, and an analysis of the sensitivity of the results to changes in the protective barrier lifetimes and SNF corrosion rates are then presented. The potential for recriticality of the SNF bearing cores and considerations for potential remedial measures are next addressed. Finally, conclusions are drawn with respect to the radionuclide releases at each Kara Sea disposal site from the SNF and activated components. 

The source modeling for the above situations should consider the thermodynamics and dynamics of what happens inside the vessel and to the released material once it is outside containment, the heat transfer between the vessel and its surroundings, and the heat transfer between the released material and its surroundings, along with the appropriate chemical/ physical reactions and mass balances. 

FIGURE 27.1 Schematic presentation showing modeling of releases, source terms, atmospheric dispersion and effects for various conceivable accident scenarios. Source David Webber, Integral Science and Software, U.K.)... 

A road tanker carrying approximately 19 tons of anhydrous ammonia crashed through a barrier at an elevated section of motorway near Houston, Texas (Pedersen and Selig, 1989 Kaiser and Walker, 1978). The pressurized tank burst on hitting the roadway below. Five people were killed and 178 people injured. High concentrations of ammonia were confined to within a few hundred meters of the source of the accident. AU the fatalities and permanent injuries were within 70 m of the release source. The concentration contours predicted from calculations and models to account for the fatalities and injuries are shown in Table 32.8. 

Evaluate the incident outcomes (consequences). Incident outcomes might include the total quantity of material released, a downwind vapor concentration, radiant heat fltix, or an explosion overpressure. Source models (Chapter 2) and fire and e q>losion models (Chapter 3) are the major methods used to determine these outcomes. 

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