Modelling mitigation measures

Consequence modeling can be used to evaluate the impact of post-release mitigation measures and determine the relative effectiveness of techniques, or combinations of techniques. Release scenarios are described in Chapter 2, and mitigation techniques are presented in Chapters 3 through 6. 

In the analysis it was assumed that the water-spray curtain was activated within one minute of the start of the incident and that 86% of the HF vapor from the evaporating pool that reached it was removed. The balance of the HF not removed by the water sprays became the material that formed the reduced hazard zone and the input for the dispersion modeling. For the F/l meteorological conditions the mitigated hazard zone for the centerline concentration of 20 ppm was 750 m. The effectiveness of water spray as postrelease mitigation measure is shown in Table 7.6. 

Wauchope, R.D., Pesticides in runoff measurement, modeling, and mitigation, J. Environ. Sci. Health 31, Part B Pesticides, Food Contaminants, and Agricultural Wastes, 31, pp. 337-344, 1996. 

Whereas Step 1 is very conservative and nearly no compound fulfils the relevant requirements when using these PEC-values (Predicted Environmental Concentration), calculations with Step 2 tools lead to a more realistic exposure assessment. However, often even more realistic model calculations are needed for the 10 representative surface water scenarios of Step 3 to come to safe use within EU. Whereas in the first two steps, a 30-cm deep static waterbody is used, a few additional types are covered in Step 3. Usually only one PEC is calculated for one use and all relevant exposure routes together. In Step 4, even more specific scenarios have recently been made available which are also useful in connection with the setting of risk mitigation measures [5]. However, currently it is not... 

The degree of health damage caused by coal dust has been significantly cut down since coal mines have taken mitigating measures to cut down on coal dust in the air. This model can be used to evaluate the merits after these measures have been taken. 

Abhishek, Tiwary, and Jeremy Colls, Air Pollution Measurement, Modeling, and Mitigation, 3rd ed., Routledge, Lxjndon, 2010. 

Development of accident sequence models for SLP PSA requires a close co-operation between plant personnel who are familiar with an outage and PSA analysts to assure that the all possible scenarios are appropriately modelled. Available accident mitigation measures may be much broader that for the power PSAs. The systems and the plant features which have been credited in power PSA may not be available for shutdown mode (as an example, heat removal using steam generators). The development of sequences should be an iterative process to adequately model sequences which represent actual plant configuration. 

In order to assess the effectiveness of such an impact mitigation measure, proper numerical simulations and parametric studies are needed, considering various types and configurations of structures under different dynamic excitations. Nevertheless, the behavior of rubber shock absorbers under impact loading must be sufficiently well modeled. Undoubtedly, the most precise modeling can be achieved with the development of a detailed finite element model using special elements and material laws to... 

It has been suggested that a sensitive test of the diffusion model would be found in the evolution of the eh yield (Schwarz, 1969). Early measurements by Hunt and Thomas (1967) and by Thomas and Bensasson (1967) revealed -6% decay within the first 10 ns and 15% decay in 50 ns. The diffusion theory of Schwarz predicts a very substantial decay ( 30%) in the first nanoseconds for instantaneous energy deposition. Schwarz (1969) tried to mitigate the situation by first integrating over pulse duration (-4.2 ns) and then over the detector response time (-1.2 ns). This improved the agreement between theory and experiment somewhat, but a hypothesis of no decay in this time scale would also agree with experiment. Thus, it was decided that a crucial test of the diffusion theory would... 

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. 

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