Nuclear fission
Download 1 Mb.
|
- Navigate this page:
- Table 3 : CPQRA hazards, event sequences, incident outcomes, and consequences [11]
- Process hazards
- Intermediate events
- Extreme physical conditions
- Management systems failure
3.4Consequence AnalysisAn important step of the hazard definition is the consequence analysis. The size of exposed area, is the first parameter that has to be estimated, and such estimation depends on the following factors: physical-chemical properties of the hazardous material and its volume, design and characteristics of the container, pressure and temperature of the substance, conditions during accident and release mechanism and ambient meteorological conditions (wind direction and strength, temperature, humidity). Various scenarios should be analysed, depending on the dangerous material – the most important ones are: fire, BLEVE (Boiling liquid expanding vapour explosion), VCE (Vapour cloud explosion), explosions, flammable vapour cloud, asphyxiating cloud, chemical, biological or radioactive contamination. Event tree methodology can be applied to characterize the events leading to the accident, and finally to determine probabilities of the releases resulting in potentially high consequences. These consequences stand as the basis for further analysis for translating hazard into initiating event of NPP. Therefore consequence analysis of transportation accident have to be performed carefully taking into account all possible release mechanisms and scenario developments. In case of fire and flammability hazards, the ignition of the material can lead to the formation of pool fire, flash fire or jet fire. This depends on the properties of the material and conditions during the release. In order to determine the impact of thermal radiation for objects and people, a number of parameters have to be known as: quantity released, physical-chemical properties of the substance, flame surface, meteorological conditions, distance to exposed objects and possibility of sheltering. The area of a pool fire depends on whether the spill is confined or not. In the first case, it is naturally limited, while in the second case it depends on the volume of the liquid and its burning rate. When pressurized material is released and ignited at once, typically a jet fire is formed. Instantaneous release with immediate ignition can lead to fireball, while delayed ignition of pressure flammable material leads to flash fire or explosion. The latter case is related to VCE (vapour cloud expansion), which is the effect of rapid combustion with flame speed close to the sonic velocity. In consequence a blast wave can be produced. The combustion energy and the energy of the ignition source are the parameters determining the potential explosion. The characteristic of the material is a deciding factor for calculating how big the fraction of combustion energy is converted to the explosive one. In order to produce blast overpressure the turbulence is required, otherwise the flame front will not be accelerated enough, and finally hazard will be limited to thermal radiation caused by a burning cloud. The turbulence is usually due to the interaction between the flame front and obstacles; hence the localization plays an important role. Thus, the effects depend on flame speed, location and the type of the material – in this respect it should be mentioned that highly reactive substances are more likely to lead to VCE than the ones having lower reactivity. While the consequences of fire and explosion can be significant for objects, in case of the release of toxic substances, essentially people are exposed. Inhalation, skin burn, blindness and also carcinogenic hazards are the main types, but the latter one can have negative effects only later in life. The most important are immediate incapacitating effects. In order to determine toxic dispersion zones the following parameters should be known:
As far as the meteorological data are considered, in the consequence analysis it is important to provide a series of calculations with different sets of parameters. Often a conservative approach is applied, for example, stable conditions of the atmosphere are used, resulting in an increased zone. Chemical Process Quantitative Risk Analysis (CPQRA) is probably one of the most adequate methods that can be applied to risk analysis [7] [8]. Analogous methodology has been proposed by TNO [9], [10]. The Dutch guidelines based on these reports include a computer program, mandatory to use for all hazardous activities. Table 3 below contains the summary of CPQRA hazards, event sequences, incident outcomes, and consequences. It is related both to stationary and transportation accidents with dangerous chemicals. Table 3 : CPQRA hazards, event sequences, incident outcomes, and consequences [11]
The results of CPQRA are usually presented depending on applied risk measure (risk indices, individual risk or societal risk) in the form of risk contours, F-N curves or similar graphs (as this is a case of mandatory Dutch QRA program). Directory: wp-content -> uploads -> 2016 2016 -> 2017 afoCo Landmark Scholarship Program 2016 -> Instructions for the Preparation of Camera-Ready Contributions to the Conference Proceedings 2016 -> Step student Scholarships for Year 10-13 2016 -> The united church of canada 2016 -> Idan raichel biography – May 2016 Brief Producer, keyboardist, Lyricist, composer and Performer Idan Raichel 2016 -> An introduction to centre’s interventions expanding access to justice 2016 -> Sanchar Shakti 2016 -> Unit analysis should help here. We want number of bananas 2016 -> The Autobiography of Elder Joseph Bates 2016 -> The Great Heat and the Rhode Island Deep Water Bay Scallop (Argopecten irradians) Fishery 1875-1905 Download 1 Mb. Share with your friends:
| |||||||||||||