Dissertations / Theses: 'Accident modelling'

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ANNA, RICARDO E. SILVA DE SANT. "ROTOR ACCIDENT ANALYSIS: MODELLING AND SIMULATION." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2007. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=11885@1.

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A Dissertação aqui apresentada descreve um acidente em um rotor de máquina de grande porte (compressor de ar) de uma fábrica de fertilizante cujas conseqüências foram perdas financeiras de alta monta tanto para a empresa quanto para o Estado, pela importância econômica onde a fábrica é situada. O objetivo da Dissertação foi simular matematicamente o acidente ocorrido e esclarecer o mesmo. Para se chegar ao diagnóstico do problema se modelou o rotor e o discretizou pelo Método de Elementos Finitos. As técnicas de investigação do problema e a sua seqüência de investigação podem ser tomadas como base em investigação de eventuais acidentes envolvendo rotores futuramente. O capítulo relativo a Análise Modal será extraído como base de apostila para curso envolvendo pessoal da área de Manutenção Mecânica.
A problem related with an air compressor gave birth to the MSc Thesis. Problems related with rotative machines are usual in the industrial field. Difficulties come from the data gathering in order to analyze, and propose a theory of failure in order to explain and avoid the recurrence of such problem. Modelling a rotor with a Timoshenko beam element and the discretization by finite element method permit the dynamical analysis and the modal analysis of the rotor considering its interaction with the radial and thrust bearings (assuming stiffness and rigidity). The work is divided in seven chapters: chapter one introduces the work and gives the overview of it; chapter two describes the industrial problem; chapter three is a brief explanation of bearing types and the fundamental principle of lubrication; chapter four introduces vibration theory and modal analysis; chapter five introduces the finite element method; chapter six is the simulation of the problem, using tailor-made MATLABr programs to reconstruct the problem and to compare the test field results with the here mentioned formulation; chapter seven discusses the results and proposes future works. Appendix shows the kinetic theory and the beam deformation model used in the program and the Laval simple rotor as a limited description of the dynamic of a rotor with distributed mass, rigidity and stiffness. The aim of this work is to help understand and avoid the recurrence of the failure described and to easy the understanding of modal analysis for new engineers and technicians which will deal with rotor dynamics.

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While, David Thomas. "Statistical modelling and analysis of accident data." Thesis, University of Southampton, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315104.

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Imprialou, Maria-Ioanna. "Developing accident-speed relationships using a new modelling approach." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/19604.

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Changing speed limit leads to proportional changes in average speeds which may affect the number of traffic accident occurrences. It is however critical and challenging to evaluate the impact of a speed limit alteration on the number and severity of accidents due primarily to the unavailability of adequate data and the inherent limitations of existing approaches. Although speed is regarded as one of the main contributory factors in traffic accident occurrences, research findings are inconsistent. Independent of the robustness of their statistical approaches, accident frequency models typically use accident grouping concepts based on spatial criteria (e.g. accident counts by link termed as a link-based approach). In the link-based approach, the variability of accidents is explained by highly aggregated average measures of explanatory variables that may be inappropriate, especially for time-varying variables such as speed and volume. This thesis re-examines accident-speed relationships by developing a new accident data aggregation method that enables improved representation of the road conditions just before accident occurrences in order to evaluate the impact of a potential speed limit increase on the UK motorways (e.g. from 70 mph to 80 mph). In this work, accidents are aggregated according to the similarity of their pre-accident traffic and geometric conditions, forming an alternative accident count dataset termed as the condition-based approach. Accident-speed relationships are separately developed and compared for both approaches (i.e. link-based and condition-based) by employing the reported annual accidents that occurred on the Strategic Road Network of England in 2012 along with traffic and geometric variables. Accident locations were refined using a fuzzy-logic-based algorithm designed for the study area with 98.9% estimated accuracy. The datasets were modelled by injury severity (i.e. fatal and serious or slight) and by number of vehicles involved (i.e. single-vehicle and multiple-vehicle) using the multivariate Poisson lognormal regression, with spatial effects for the link-based model under a full Bayesian inference method. The results of the condition-based models imply that single-vehicle accidents of all severities and multiple-vehicle accidents with fatal or serious injuries increase at higher speed conditions, particularly when these are combined with lower volumes. Multiple-vehicle slight injury accidents were not found to be related with higher speeds, but instead with congested traffic. The outcomes of the link-based model were almost the opposite; suggesting that the speed-accident relationship is negative. The differences between the results reveal that data aggregation may be crucial, yet so far overlooked in the methodological aspect of accident data analyses. By employing the speed elasticity of motorway accidents that was derived from the calibrated condition-based models it has been found that a 10 mph increase in UK motorway speed limit (i.e. from 70 mph to 80 mph) would result in a 6-12% increase in fatal and serious injury accidents and 1-3% increase in slight injury accidents.

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Chaisan, Kittisak. "Modelling the environmental transfers of radioactivity following the Fukushima accident." Thesis, University of Portsmouth, 2015. https://researchportal.port.ac.uk/portal/en/theses/modelling-the-environmental-transfers-of-radioactivity-following-the-fukushima-accident(60b31ec7-b843-4878-b374-931c5234b90c).html.

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After the massive tsunami on 11 March 2011, the explosions at 4 reactors of the Fukushima Daiichi (I) Nuclear Power Stations (Fukushima I NPSs) in Japan led to a large radioactive cloud being ejected into the atmosphere. Radionuclides released to the atmosphere were washed out in rain causing an area of remarkably high deposition in the area to the northwest of the Fukushima I NPSs. Activity remaining in the atmosphere was dispersed further to other areas of Japan. At various times during the accident, plumes of contamination were transported from Japan to the Pacific Ocean, the North American continent, crossing the Atlantic Ocean to Europe, and eventually to Asia. Due to the lack of measurements in three major ecosystem compartments i.e. air, soil and surface water, information on the highest impact early-phase after fallout and the interpretation of long-term impacts is limited and unclear. The transfer of contaminated radionuclides to soil and air around the Fukushima I NPSs was studied using ratios of various radioisotopes to the long-lived nuclide 137Cs. It was found that ratios of three radionuclides i.e. 134,136Cs and 132Te were consistent with direction and distance in air and soil while the ratio 131I/137Cs was not. It was shown that, deposited 131I/137Cs had an inverse correlation with 137Cs activity in soil. These nuclides were key in forming the high-gamma dose rates in the early phase, particularly the high gamma energy of 132I from the 132Te/132I decay. The derived ratios of these key radionuclides in soil were used together with available measured gamma dose rates in the early phase (< 30 days) to develop a model to reconstruct and predict external gamma dose rate. Model “blind” tests showed that more than 95% of predictions were within a factor of two of measurements from 15 sites to the north, northwest and west of the power station. It is demonstrated that generic isotope ratios provide a sound basis for reconstruction of early-phase external dose rates in these most contaminated areas. For contamination in surface runoff water, lake water and fish, a previous model developed following the Chernobyl accident (AQUASCOPE) was applied to the Fukushima situation. It was shown that by adjusting for the stronger absorption of radiocaesium in soils in Japan (compared with European countries) the model could be used successfully to predict long-term contamination in aquatic systems affected by Fukushima fall out. The results of the model showed good agreement with measured data, in particular in the long-term period (around 0.5-2 years) after the accident.

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Nanopoulos, Dionysios. "Mechanistic modelling of swelling in the accident tolerant fuel candidate U3Si2." Thesis, KTH, Fysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-223218.

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Krystul, Jaroslav. "Modelling of stochastic hybrid systems with applications to accident risk assessment." Enschede : University of Twente [Host], 2006. http://doc.utwente.nl/57127.

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Eyre, Matthew. "The use of laser scanning and 3D modelling in accident investigations." Thesis, University of Exeter, 2015. http://hdl.handle.net/10871/18002.

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In order to prevent accidents we need to understand them, this is achieved through effective accident investigation. Accident investigation is a complex process of gathering and evaluating information to determine factors that may have implications on the final event. One of the fundamental aspects in the investigation process is to capture geospatial data of the incident, to document the scene in its current condition, providing the investigation team with a record for future reference. The production of plans have conventionally remained the same, with a surveyor tasked to illustrate a 3D scene with 2D representations. Recent developments in instrumentation have provided the geospatial industry with the means to capture vast amounts of 3D data directly using laser scanning. In addition, there have been considerable advancements in software applications which can be used to process the surveyed datasets. This research evaluates the use of the latest technology in respect of accident investigation applying the methodology to fire related incidents, industrial accidents and mining incidents. This is achieved by using a number of case studies that have been undertaken throughout the timeline of the project and whilst working with industry professionals in the field.

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Murali, Rajiv. "A rigorous approach to combining use case modelling and accident scenarios." Thesis, Heriot-Watt University, 2016. http://hdl.handle.net/10399/3119.

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Nearly all serious accidents, in the past twenty years, in which software has been involved can be traced to requirements flaws. Accidents related to or involving safety-critical systems often lead to significant damage to life, property, and environment in which the systems operate. This thesis explores an extension to use case modelling that allows safety concerns to be modelled early in the systems development process. This motivation comes from interaction with systems and safety engineers who routinely rely upon use case modelling during the early stages of defining and analysing system behaviour. The approach of embedded formal methods is adopted. That is, we use one discipline of use case modelling to guide the development of a formal model. This enables a greater precision and formal assurance when reasoning about concerns identified by system and safety engineers as well as the subsequent changes made at the level of use case modelling. The chosen formal method is Event-B, which is re nement based and has consequently enabled the approach to exploit a natural abstractions found within use case modelling. This abstraction of the problem found within use cases help introduce their behaviour into the Event-B model via step-wise re nement. The central ideas underlying this thesis are implemented in, UC-B, a tool support for modelling use cases on the Rodin platform (an eclipse-based development environment for Event-B). UC-B allows the specification of the use cases to be detailed with both informal and formal notation, and supports the automatic generation of an Event-B model given a formally specified use case. Several case studies of use cases with accident cases are provided, with their formalisation in Event-B supported by UC-B tool. An examination of the translation from use cases to Event-B model is discussed, along with the subsequent verification provided by Event-B to the use case model.

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Ham, Marnie Elizabeth Jean. "Dispersion modelling of radioactive aerosols released during a severe nuclear reactor accident." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq20646.pdf.

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Tunaru, Radu. "Statistical modelling of road accident data via graphical models and hierarchical Bayesian models." Thesis, Middlesex University, 1999. http://eprints.mdx.ac.uk/8030/.

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The objective of this thesis is to develop statistical models for multivariate road accident data. Two directions of research are followed: graphical modelling for contingency tables cross-classified by accident characteristics, and hierarchical Bayesian models for multiple accident frequencies of different types modelled jointly. Multi-dimensional tables are analysed and it is shown how to use collapsibility to reduce the dimensionality of the analysis without the problems of Simpson's paradox. It is revealed that accident severity and the number of casualties are associated, and that these variables are mainly influenced by the number of vehicles and speed limit. Graphical chain models allow causal hypotheses to be formulated and it is shown how they are valuable tools for empirical research about road accident characteristics. The hierarchical Bayesian models developed combine generalized linear models with random effects. The novelty of these models consists in the joint modelling of multiple response variables. The models account for overdispersion and they are used for accident prediction and for ranking hazardous sites. All models are fully Bayesian and are fitted using Markov Chain Monte Carlo methods. It is shown that multiple response variables models are superior to separate univariate response models. Some theoretical problems are examined regarding the maximum likelihood estimation process for the two parameters negative binomial distribution. A condition is given that is equivalent with unique maximum likelihood estimators. The two directions of research are connected by using graphs to describe the models. In addition, a new Bayesian model selection procedure for contingency tables is proposed. This is based on Gibbs sampling and avoids problems associated with asymptotic tests. The conclusions revealed here can help practitioners to design better safety policies and to spend money more wisely on sites that really are dangerous.

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Lloyd, Louise. "Modelling trends in road accident frequency : Bayesian inference for rates with uncertain exposure." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/358621/.

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Several thousand people die as a result of a road accident each year in Great Britain and the trend in the number of fatal accidents is monitored closely to understand increases and reductions in the number of deaths. Results from analysis of these data directly influence Government road safety policy and ensure theintroduction of effective safety interventions across the country. Overall accident numbers are important, but when disaggregating into various characteristics, accident risk (defined as the number of accidents relative to an exposure measure) is a better comparator. The exposure measure used most commonly for accident rate analysis is traffic flow which can be disaggregated into vehicle types, road type, and year. Here we want to assess the accident risk across different car types and car ages, and therefore alternative exposure sources are required. We disaggregate exposure to a further extent than possible with currently available data in order to take the increased variability within these new factors into account. Exposure data sources are mainly based on sample surveys and therefore have some associated uncertainty, however previous accident risk analysis has not, in general, taken this into account. For an explicit way to include this uncertainty we use a Bayesian analysis to combine three sources of exposure using a log-Normal model with model priors representing our uncertainty in each data source. Using further Bayesian models, we propagate this uncertainty through to accident rates and accident severity, determining important factors and inter- relationships between factors to identify key features affecting accident trends,and we make the first exploration of the effect of the recent recession on road accidents.

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Mooney, John. "Derivation of spatially structured population data in the context of major hazard accident modelling." Thesis, Staffordshire University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443298.

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Fletcher, Adrian. "Generic simulation modelling of accident and emergency patient flows in acute hospitals in England." Thesis, Lancaster University, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.606344.

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Accident and Emergency (A&E) departments deal with emergency patients in NHS acute hospitals in England. They have access to diagnostics facilities and inpatient beds. A previous government target was that 98% of A&E patients should be completed within four hours. The author was the analytical lead for emergency care in the Department of Health (DH) in 2003 and 2004, responsible for analytical support to ministers on issues faced by the NHS in managing A&E patient flow. A so-called 'generic' discrete event simulation model of A&E services was developed at this time. It described a 'typical' A&E de~artment and enabled detailed investigation and facilitated workshop discussions of potential interventions. It helped advise whether the target was achievable. The development and use of this model at national level is described. An opportunity is also described to use the model in hospital trusts where it was also found to be useful. The experiences with this model provided the motivation to investigate this area further. Simulation is widely used to model A&E services, but very few models are 'generic'- they are usually designed for specific trusts. Three particular research questions are investigated: 1 What are generic hospital simulation models? 2 How can generic hospital simulation models be built? 3 Can they be useful? This research uses a literature review and an informal survey of health OR academics and experienced DH modellers to generate two answers to question 1: a broad four level classification of model types, and a more detailed framework of typical characteristics of generic hospital simulation models. An improved 'generic' A&E patient flow simulation model was then developed to address the shortcomings of the first model, particularly through increased scope and detail. Experiences with,both the original DH model and this improved model provide answers to the second question in identifying different build techniques and important issues to consider when developing generic models. The improved model was used with DH on two case studies: possible NHS responses to a potential swine flu pandemic, and the impact of patient mix and resuscitation patients on A&E performance. This experience, and that with the first model, provide answers to the third question by examining the successes and failures of the use of the models at national and hospital trust level. Possible reasons for the relative levels of success are discussed

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Wong, Ka Yick. "The modelling of accident frequency using risk exposure data for the assessment of airport safety areas." Thesis, Loughborough University, 2007. https://dspace.lboro.ac.uk/2134/7964.

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This thesis makes significant contributions to improving the use of Airport Safety Areas (ASAs) as aviation accident risk mitigation measures by developing improved accident frequency models and risk assessment methodologies. In recent years, the adequacy of ASAs such as the Runway End Safety Area and Runway Safety Area has come under increasing scrutiny. The current research found flaws in the existing ASA regulations and airport risk assessment techniques that lead to the provision of inconsistent safety margins at airports and runways. The research was based on a comprehensive database of ASA-related accidents, which was matched by a representative sample of normal operations data, such that the exposure to a range of operational and meteorological risk factors between accident and normal flights could be compared. On this basis, the criticality of individual risk factors was quantified and accident frequency models were developed using logistic regression. These models have considerably better predictive power compared to models used by previous airport risk assessments. An improved risk assessment technique was developed coupling the accident frequency models with accident location data, yielding distributions that describe the frequency of accidents that reach specific distances beyond the runway end or centreline given the risk exposure profile of the particular runway. The application of the proposed methodology was demonstrated in two case studies. Specific recommendations on ASA dimensions were made for achieving consistent levels of safety on each side of the runway. Advances made in this study have implications on the overall assessment and management of risks at airports.

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Tusheva, Polina. "Modelling and analysis of severe accidents for VVER-1000 reactors." Forschungszentrum Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-124697.

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Accident conditions involving significant core degradation are termed severe accidents /IAEA: NS-G-2.15/. Despite the low probability of occurrence of such events, the investigation of severe accident scenarios is an important part of the nuclear safety research. Considering a hypothetical core melt down scenario in a VVER-1000 light water reactor, the early in-vessel phase focusing on the thermal-hydraulic phenomena, and the late in-vessel phase focusing on the melt relocation into the reactor pressure vessel (RPV) lower head, are investigated. The objective of this work is the assessment of severe accident management procedures for VVER-1000 reactors, i.e. the estimation of the maximum period of time available for taking appropriate measures and particular decisions by the plant personnel. During high pressure severe accident sequences it is of prime importance to depressurize the primary circuit in order to allow for effective injection from the emergency core cooling systems and to avoid reactor pressure vessel failure at high pressure that could cause direct containment heating and subsequent challenge to the containment structure. Therefore different accident management measures were investigated for the in-vessel phase of a hypothetical station blackout accident using the severe accident code ASTEC, the mechanistic code ATHLET and the multi-purpose code system ANSYS. The analyses performed on the PHEBUS ISP-46 experiment, as well as simulations of small break loss of coolant accident and station blackout scenarios were used to contribute to the validation and improvement of the integral severe accident code ASTEC. Investigations on the applicability and the effectiveness of accident management procedures in the preventive domain, as well as detailed analyses on the thermal-hydraulic phenomena during the early in-vessel phase of a station blackout accident have been performed with the mechanistic code ATHLET. The results of the simulations show, that the effectiveness of the procedures strongly depends on the ability of the passive safety systems to inject as much water as possible into the reactor coolant system. The results on the early in-vessel phase have shown potentially delayed RPV failure by depressurization of the primary side, as slowing the core damage gives more time and different possibilities for operator interventions to recover systems and to mitigate or terminate the accident. The ANSYS model for the description of the molten pool behaviour in the RPV lower plenum has been extended by a model considering a stratified molten pool configuration. Two different pool configurations were analysed: homogeneous and segregated. The possible failure modes of the RPV and the time to failure were investigated to assess the possible loadings on the containment. The main treated issues are: the temperature field within the corium pool and the RPV and the structure-mechanical behaviour of the vessel wall. The results of the ASTEC calculations of the melt pool configuration were applied as initial conditions for the ANSYS simulations, allowing a more detailed and more accurate modelling of the thermal and mechanical behaviour of the core melt and the RPV wall. Moreover, for the late in-vessel phase, retention of the corium in the RPV was investigated presuming external cooling of the vessel wall as mitigative severe accident management measure. The study was based on the finite element computer code ANSYS. The highest thermomechanical loads are observed in the transition zone between the elliptical and the vertical vessel wall for homogeneous pool and in the vertical part of the vessel wall, which is in contact with the molten metal in case of sub-oxidized pool. Assuming external flooding will retain the corium within the RPV. Without flooding, the vessel wall will fail, as the necessary temperature for a balanced heat release from the external surface via radiation is near to or above the melting point of the steel.

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Ramlakan, Alastair Justin. "Modelling of fission product release from TRISO fuel during accident conditions : benchmark code comparison / Ramlakan A." Thesis, North-West University, 2011. http://hdl.handle.net/10394/7299.

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This document gives an overview of the proposed MSc study. The main goal of the study is to model the cases listed in the code benchmark study of the International Atomic Energy Agency CRP–6 fuel performance study (Verfondern & Lee, 2005). The platform that will be employed is the GETTER code (Keshaw & van der Merwe, 2006). GETTER was used at PBMR for the release calculations of metallic and some non–metallic long–lived fission products. GETTER calculates the transport of fission products from their point of fission to release from the fuel surface taking into account gas precursors and activation products. Results show that for certain experiments the codes correspond very well with the experimental data whilst in others there are orders of magnitude differences. It can be seen that very similar behaviour is observed in all codes. Improvements are needed in updating the strontium diffusion coefficient and in understanding, on a deeper level, the transport of silver in TRISO particles and how it deviates from simple diffusion models.
Thesis (M.Sc. Engineering Sciences (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2012.

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Tusheva, Polina. "Modelling and analysis of severe accidents for VVER-1000 reactors." Helmholtz-Zentrum Dresden-Rossendorf, 2012. https://hzdr.qucosa.de/id/qucosa%3A22175.

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Accident conditions involving significant core degradation are termed severe accidents /IAEA: NS-G-2.15/. Despite the low probability of occurrence of such events, the investigation of severe accident scenarios is an important part of the nuclear safety research. Considering a hypothetical core melt down scenario in a VVER-1000 light water reactor, the early in-vessel phase focusing on the thermal-hydraulic phenomena, and the late in-vessel phase focusing on the melt relocation into the reactor pressure vessel (RPV) lower head, are investigated. The objective of this work is the assessment of severe accident management procedures for VVER-1000 reactors, i.e. the estimation of the maximum period of time available for taking appropriate measures and particular decisions by the plant personnel. During high pressure severe accident sequences it is of prime importance to depressurize the primary circuit in order to allow for effective injection from the emergency core cooling systems and to avoid reactor pressure vessel failure at high pressure that could cause direct containment heating and subsequent challenge to the containment structure. Therefore different accident management measures were investigated for the in-vessel phase of a hypothetical station blackout accident using the severe accident code ASTEC, the mechanistic code ATHLET and the multi-purpose code system ANSYS. The analyses performed on the PHEBUS ISP-46 experiment, as well as simulations of small break loss of coolant accident and station blackout scenarios were used to contribute to the validation and improvement of the integral severe accident code ASTEC. Investigations on the applicability and the effectiveness of accident management procedures in the preventive domain, as well as detailed analyses on the thermal-hydraulic phenomena during the early in-vessel phase of a station blackout accident have been performed with the mechanistic code ATHLET. The results of the simulations show, that the effectiveness of the procedures strongly depends on the ability of the passive safety systems to inject as much water as possible into the reactor coolant system. The results on the early in-vessel phase have shown potentially delayed RPV failure by depressurization of the primary side, as slowing the core damage gives more time and different possibilities for operator interventions to recover systems and to mitigate or terminate the accident. The ANSYS model for the description of the molten pool behaviour in the RPV lower plenum has been extended by a model considering a stratified molten pool configuration. Two different pool configurations were analysed: homogeneous and segregated. The possible failure modes of the RPV and the time to failure were investigated to assess the possible loadings on the containment. The main treated issues are: the temperature field within the corium pool and the RPV and the structure-mechanical behaviour of the vessel wall. The results of the ASTEC calculations of the melt pool configuration were applied as initial conditions for the ANSYS simulations, allowing a more detailed and more accurate modelling of the thermal and mechanical behaviour of the core melt and the RPV wall. Moreover, for the late in-vessel phase, retention of the corium in the RPV was investigated presuming external cooling of the vessel wall as mitigative severe accident management measure. The study was based on the finite element computer code ANSYS. The highest thermomechanical loads are observed in the transition zone between the elliptical and the vertical vessel wall for homogeneous pool and in the vertical part of the vessel wall, which is in contact with the molten metal in case of sub-oxidized pool. Assuming external flooding will retain the corium within the RPV. Without flooding, the vessel wall will fail, as the necessary temperature for a balanced heat release from the external surface via radiation is near to or above the melting point of the steel.

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Sehgal, Bal Raj, Eberhard Altstadt, Hans-Georg Willschuetz, and Frank-Peter Weiss. "Modelling of in-vessel retention after relocation of corium into the lower plenum." Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-28586.

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Considering the unlikely core melt down scenario for a light water reactor (LWR) a possible failure mode of the reactor pressure vessel (RPV) and its failure time has to be investigated for a determination of the loadings on the containment. Worldwide several experiments have been performed accompanied with material properties evaluation, theoretical, and numerical work. At the Institute of Safety Research of the FZR a finite element model has been de-veloped simulating the thermal processes and the viscoplastic behaviour of the ves-sel wall. An advanced model for creep and material damage has been established and has been validated using experimental data. The thermal and the mechanical calculations are sequentially and recursively coupled. The model is capable of evalu-ating fracture time and fracture position of a vessel with an internally heated melt pool. The model was applied to pre- and post test calculations for the FOREVER test se-ries representing the lower head RPV of a PWR in the geometrical scale of 1:10. These experiments were performed at the Royal Institute of Technology in Stock-holm. The results of the calculations can be summarised as follows: # The creeping process is caused by the simultaneous presence of high tem-perature (>600 °C) and pressure (>1 MPa) # The hot focus region is the most endangered zone exhibiting the highest creep strain rates. # The exact level of temperature and pressure has an influence on the vessel failure time but not on the failure position # The failure time can be predicted with an uncertainty of 20 to 25%. This uncer-tainty is caused by the large scatter and the high temperature sensitivity of the viscoplastic properties of the RPV steel. # Contrary to the hot focus region, the lower centre of the vessel head exhibits a higher strength because of the lower temperatures in this zone. The lower part moves down without significant deformation. Therefore it can be assumed, that the vessel failure can be retarded or prevented by supporting this range. # The development of a gap between melt crust and vessel wall could not be proofed. First calculations for a PWR geometry were performed to work out differences and commonalities between prototypic scenarios and scaled experiments. The results of the FOREVER-experiments cannot be transferred directly to PWR geometry. The geometrical, mechanical and thermal relations cannot be scaled in the same way. Because of the significantly higher temperature level, a partial ablation of the vessel wall has to be to expected in the PWR scenario, which is not the case in the FOREVER tests. But nevertheless the FOREVER tests are the only integral in-vessel retention experiments up to now and they led to a number of important insights about the behaviour of a vessel under the loading of a melt pool and pressure.

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Sehgal, Bal Raj, Eberhard Altstadt, Hans-Georg Willschuetz, and Frank-Peter Weiss. "Modelling of in-vessel retention after relocation of corium into the lower plenum." Forschungszentrum Rossendorf, 2005. https://hzdr.qucosa.de/id/qucosa%3A21686.

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Considering the unlikely core melt down scenario for a light water reactor (LWR) a possible failure mode of the reactor pressure vessel (RPV) and its failure time has to be investigated for a determination of the loadings on the containment. Worldwide several experiments have been performed accompanied with material properties evaluation, theoretical, and numerical work. At the Institute of Safety Research of the FZR a finite element model has been de-veloped simulating the thermal processes and the viscoplastic behaviour of the ves-sel wall. An advanced model for creep and material damage has been established and has been validated using experimental data. The thermal and the mechanical calculations are sequentially and recursively coupled. The model is capable of evalu-ating fracture time and fracture position of a vessel with an internally heated melt pool. The model was applied to pre- and post test calculations for the FOREVER test se-ries representing the lower head RPV of a PWR in the geometrical scale of 1:10. These experiments were performed at the Royal Institute of Technology in Stock-holm. The results of the calculations can be summarised as follows: # The creeping process is caused by the simultaneous presence of high tem-perature (>600 °C) and pressure (>1 MPa) # The hot focus region is the most endangered zone exhibiting the highest creep strain rates. # The exact level of temperature and pressure has an influence on the vessel failure time but not on the failure position # The failure time can be predicted with an uncertainty of 20 to 25%. This uncer-tainty is caused by the large scatter and the high temperature sensitivity of the viscoplastic properties of the RPV steel. # Contrary to the hot focus region, the lower centre of the vessel head exhibits a higher strength because of the lower temperatures in this zone. The lower part moves down without significant deformation. Therefore it can be assumed, that the vessel failure can be retarded or prevented by supporting this range. # The development of a gap between melt crust and vessel wall could not be proofed. First calculations for a PWR geometry were performed to work out differences and commonalities between prototypic scenarios and scaled experiments. The results of the FOREVER-experiments cannot be transferred directly to PWR geometry. The geometrical, mechanical and thermal relations cannot be scaled in the same way. Because of the significantly higher temperature level, a partial ablation of the vessel wall has to be to expected in the PWR scenario, which is not the case in the FOREVER tests. But nevertheless the FOREVER tests are the only integral in-vessel retention experiments up to now and they led to a number of important insights about the behaviour of a vessel under the loading of a melt pool and pressure.

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Ecay, Lionel. "Concrete transfer properties evolution and nuclear containment vessel tightness assessment during an accident." Thesis, Pau, 2018. http://www.theses.fr/2018PAUU3022/document.

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L’accident de Fukushima a démontré qu’aujourd’hui encore, malgré les progrès déjà réalisésdans le domaine de la sûreté nucléaire, une interruption prolongée du circuit de refroidissement primaire du réacteur (plusieurs semaines ici) était possible. La France s’est par conséquent vue contrainte de réévaluer le niveau de sûreté de ses centrales. Plus spécifiquement, le cas le plus défavorable qu’EDF considérait jusqu’alors, qui consistait en un arrêt total du système de refroidissement primaire de 24h, a été réévalué à deux semaines. Ce changement d’échelle temporelle a introduit des problématiques de fluage, d’évolution hygrométrique du béton ainsi que de flux de vapeur – celle-ci transportant les radionucléides – jusque-là laissées de côté. De ces considérations est né le projet ANR/RSNR MACENA (MAîtrise du Confinement d’une ENceinte en Accident), qui vise à évaluer le confinement d’une enceinte soumise à une température de 180°C et à une pression de 5 bar pendant deux semaines. Ce travail s’inscrit dans la lignée de celui entamé par Khaddour [2014] dans le but de parvenir à une meilleure prédiction des propriétés de transport des milieux poreux en se basant uniquement sur une caractérisation indirecte, la distribution des tailles de pore obtenue grâce à la technique de porosimétrie par intrusion de mercure. Si l’aptitude du modèle initial à estimer correctement les perméabilités intrinsèques a été confirmée sur des matériaux représentant une large gamme de perméabilités, il n’était pas, en l’état, capable de prédire les perméabilités relatives au gaz et au liquide. C’est pourquoi une approche dite redistributive a été développée, laquelle a montré de bons résultats sur diverses PSD. Enfin, un nouveau modèle a été développé pour essayer de s’affranchir de cette approche tout en améliorant la capacité à déterminer les perméabilités relatives. Bien qu’efficace sur des PSD monomodales, étroites ou larges, il a montré ses limites sur une PSD réelle bimodale. En parallèle, une étude de faisabilité a exhibé la possibilité de suivre un front de saturation à l’intérieur d’un matériau poreux, ce qui permettrait à terme de valider l’inclusion d’autres phénomènes dans le modèle, liés notamment à la pression de perçage
The Fukushima catastrophe that struck Japan in 2011 demonstrated that despite significant progress in the field of nuclear safety a prolonged reactor primary cooling circuit breakdown was possible (several weeks in this specific case). With 4 nuclear power plants located on its shoreline, France therefore needed to reassess the safety level of its facilities. More specifically, the worst case scenario considered up until that point by EdF — which consisted in a 24h breakdown of the primary cooling system — was revised up to two weeks. This time-scale shift induced creep, drying and vapour flow problems previously left aside. Thus came to be the ANR/RSNR MACENA (MAîtrise du Confinement d’une ENceinte en Accident) project, which aims at bettering the tightness assessment of a nuclear containment vessel submitted to a temperature of 180°C and to a pressure of 5 bar for two weeks. This work falls in line with that initiated by Khaddour [2014], who set out to better predict porous materials’ transport properties based solely on an indirect characterisation of their topology, namely Pore Size Distribution (PSD) which is obtained via an experimental technique called Mercury Intrusion Porosimetry (MIP). The initial model’s ability to correctly estimate intrinsic permeabilities was confirmed on several different materials whose intrinsic permeabilities span several orders of magnitude. However, it was not fit to accurately account for gas and liquid relative permeabilities. This led to the introduction of a so-called redistributive approach, which yielded better results on various PSD and corresponding experimental datasets. Finally, a new model was developed to try and avoid said approach while bettering relative permeability predictions. Although it behaved well with monomodal pore size distributions, be they wide or narrow, it fell short when applied to a real bimodal PSD. In parallel, an experimental feasibility study demonstrated the possibility of tracking a saturation front within a porous material, which should ultimately allow for the implementation of several other phenomena into the model, linked among others to breakthrough capillary pressure

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21

Belharet, Mokrane. "Modélisation numérique du transfert du radiocésium dans les chaines trophiques pélagiques marines suite à l'accident nucléaire de Fukushima Dai-ichi (côte Pacifique du Japon)." Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30339/document.

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Une forte contamination radioactive du milieu marin, notamment par le 137Cs, s'est produite dans le Pacifique nord-ouest suite à l'accident nucléaire de Fukushima Dai-ichi survenu le 11 mars 2011. Deux sources majeures ont été à l'origine de cette contamination, les retombées atmosphériques (sèches et humides) et les rejets liquides directement en mer. Cette radioactivité a été transférée aux organismes marins conduisant à la contamination de plusieurs espèces pélagiques et benthiques. Dans le cadre de l'étude des conséquences de cet accident sur le milieu marin, une première modélisation de la dispersion du 137Cs dans les eaux de la côte Pacifique du Japon a été réalisée par le groupe SIROCCO, permettant ainsi d'estimer l'évolution spatio-temporelle de la concentration de ce radionucléide dans l'eau et de déterminer son terme source, c'est-à-dire sa quantité globale rejetée en mer sous forme liquide. Ce travail de thèse s'inscrit dans la même démarche et vise, par une approche de modélisation, à étudier le transfert du 137Cs aux chaines trophiques pélagiques de la côte Est du Japon, composées par les populations planctoniques, les poissons planctonivores, et les poissons carnivores. Le couplage d'un modèle radioécologique, spécifiquement développé pour cette étude, à un modèle de l'écosystème composé d'un modèle NPZD (Nutrients-Phytoplankto-Zooplankton-Detritus) et d'un modèle de circulation régionale, s'est imposé comme la méthode la plus adaptée à l'étude de la contamination des populations planctoniques dans des conditions post-accidentelles. Les résultats de cette étude ont montré des niveaux de contamination assez élevés de ces populations notamment aux alentours de la centrale où les concentrations estimées sont environ 4 ordres de grandeur supérieures à celles observées avant l'accident. En dépit de ces concentrations élevées, le débit maximal de la dose absorbée reste largement au-dessous du débit de référence à partir duquel les effets sur les populations sont ressentis. Cette étude a aussi mis en évidence la prédominance de la voie trophique dans les processus d'accumulation du césium par ces espèces, ainsi que la présence d'une légère bioamplification chez les classes de taille de zooplancton. Le modèle radioécologique développé pour étudier la contamination des espèces nectoniques est structuré en taille. Chaque espèce est composé d'un ensemble de cohortes dont le nombre est fonction de la durée de vie de l'espèce et de sa fréquence de reproduction. Contrairement aux modèles classiques, le taux d'ingestion de la nourriture par l'organisme ainsi que son régime alimentaire ne sont pas constants dans le temps mais généralement variables en fonction de la taille de l'organisme. Dans cette approche le processus de prédation est considéré comme étant totalement opportuniste. Les résultats sont généralement satisfaisants et le modèle a été validé dans les conditions d'équilibre pré-accidentelles ainsi que dans les conditions post-accidentelles. L'importance de la prise en compte des mouvements migratoires de certaines espèces dans ce type de modèle a été mis en évidence notamment dans les conditions accidentelles caractérisées par une forte variabilité spatiale de la concentration du radionucléide dans la colonne d'eau. Les niveaux de contamination estimés pour les différentes espèces sont largement supérieurs à ceux observés avant l'accident, avec une tendance à l'augmentation lorsque la taille de l'individu augmente
Huge amounts of radionuclides, espicially 137Cs, were released to the coastal northwestern Pacific ocean after the Fukushima nuclear power plant accident, that occurred on 11 March 2011. The resultant radiocesium contamination was quickly transferred to marine biota resulting in elevated cesium levels in various organisms. Using a modelling approach, this work aims to study the 137Cs transfer to the marine pelagic food chains, from plankton populations to the large piscivorous fishes. Coupling the radioecological model, developed in this study, with an ecosystem model comprising an NPZD biogeochemical model and a regional ocean circulation model, is appeared to be the most adapted tool for modelling of plankton populations contamination in this accidental situation. The results of this study showed high contamination levels in the plankton populations, especially in the vincity of the power plant, where the maximal concentrations are estimated to be about 4 orders of magnitude higher than those observed before the accident. In spite of these high contamination levels, the maximum 137Cs absorbed dose rates for phyto- and zooplankton populations were estimated to be well below the 10 Gy/h benchmark value, from which a measurable effect on the marine biota can be observed. This study has also highlighted the predominance of the cesium uptake from food and the presence of biomagnification potential at this trophic level. The radioecological model developed to study the nektonic species contamination is based on the individual size. In this approach, each species is represented by a set of cohorts. The number of these cohorts is a function of the species life span and reproduction frequency. Unlike traditional approaches, the organism ingestion rate and diet composition considered in this modelling approach are not constant, but vary over the time according to the size of the organism. The model results are in general satisfactory, and the validation is carried out in both equilibrium and accidental situations. This study highlighted the importance of the organism migratory movements in the radioecological modelling espicially in the accident situations caracterized by a very high spatial variability of radionuclides concentrations in the seawater. The detailed caracteristics of 137Cs concentration dynamics in the different species are discussed. The contamination levels estimated for the different species are significantly higher than those observed before the accident, with a clear tendency to increase with individual size

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22

Golizadeh, Hamed. "Adoption of building information modelling innovations to reduce occupational fatalities in the Australian construction industry." Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/133919/1/Hamed%20Golizadeh%20Thesis_Redacted.pdf.

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The potential uses of building information modelling (BIM) can drastically alter the occupational health and safety (OHS) practices in the construction industry. However, there is no established framework to employ BIM for construction OHS management. A mixed methods research design was adopted to address this research gap. Case study analysis, semi-structured interviews, and a questionnaire survey were conducted to develop the innovation adoption model of this research. The most significant contributions of this research are the identification of the critical areas in construction accidents, the effectiveness of BIM applications in these areas, and success factors for the adoption of BIM.

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23

Ozenne, Brice. "Modélisation statistique pour la prédiction du pronostic de patients atteints d’un Accident Vasculaire Cérébral." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10169/document.

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L’Accident Vasculaire Cérébral (AVC) est une maladie grave pour laquelle des critères très stricts encadrent l’administration du traitement curatif en phase aigüe. Ces critères limitent drastiquement l’accès à ce traitement : on estime que seuls 10% des patients atteints d’un AVC en bénéficient. L’objectif de ce travail est de proposer un modèle prédictif de l’évolution de l’AVC qui permette d’identifier le volume de tissu à risque de chaque patient. Ce volume, qui correspond au bénéfice potentiel du traitement, permettra de mieux orienter le médecin dans sa décision de traiter. Pour répondre à cet objectif nous nous intéressons aux problématiques d’évaluation de modèles prédictifs dans un contexte de faible prévalence, de modélisation prédictive sur données spatiales, de prédiction volumique en fonction de l’option de traitement et de segmentation d’images en présence d’artefacts. Les outils développés ont été rassemblés au sein d’une librairie de fonctions du logiciel R nommée MRIaggr
Stroke is a serious disease that needs emergency health care. Due to potential side effects, the patients must fulfil very restrictive criteria for eligibility to the curative treatment. These criteria limit drastically the accessibility to treatment : currently, an estimated 10% of stroke patients are treated. The purpose of this work was to develop a statistical framework for stroke predictive models. We deal with assessing predictive models in a low-prevalence context, building predictive models for spatial data, making volumic predictions depending on the treatement option, and performing image segmentation in presence of image artefacts. Tools developed in this thesis have been collected in an R package named MRIaggr

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Bearfield, George Joseph. "Using Bayesian networks to represent parameterised risk models for the UK railways." Thesis, Queen Mary, University of London, 2009. http://qmro.qmul.ac.uk/xmlui/handle/123456789/28163.

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The techniques currently used to model risk and manage the safety of the UK railway network are not aligned to the mechanism by which catastrophic accidents occur in this industry. In this thesis, a new risk modelling method is proposed to resolve this problem. Catastrophic accidents can occur as the result of multiple failures occurring to all of the various defences put in place to prevent them. The UK railway industry is prone to this mechanism of accident occurrence, as many different technical, operational and organizational defences are used to prevent accidents. The railway network exists over a wide geographic area, with similar accidents possible at many different locations. The risk from these accidents is extremely variable and depends on the underlying conditions at each particular location, such as the state of assets or the speed of trains. When unfavourable conditions coincide the probability of multiple failures of planned defences increases and a 'risk hotspot' arises. Ideal requirements for modelling risk are proposed, taking account of the need to manage multiple defences of conceptually different type and the existence of risk hotspots. The requirements are not met by current risk modelling techniques although some of the requirements have been addressed experimentally, and in other industries and countries. It is proposed to meet these requirements using Bayesian Networks to supplement and extend fault and event tree analysis, the traditional techniques used for risk modelling in the UK railway industry. Application of the method is demonstrated using a case study: the building of a model of derailment risk on the UK railway network. The proposed method provides a means of better integrating industry wide analysis and risk modelling with the safety management tasks and safety related decisions that are undertaken by safety managers in the industry.

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25

Greening, Philip. "The influence of market structure, collaboration and price competition on supply network disruptions in open and closed markets." Thesis, Cranfield University, 2013. http://dspace.lib.cranfield.ac.uk/handle/1826/8473.

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The relaxation of international boundaries has enabled the globalisation of markets making available an ever increasing number of specialised suppliers and markets. Inevitably this results in supply chains sharing suppliers and customers reflected in a network of relationships. Within this context firms buyers configure their supply relationships based on their perception of supply risk. Risk is managed by either increasing trust or commitment or by increasing the number of suppliers. Increasing trust and commitment facilitates collaboration and reduces the propensity for a supplier to exit the relationship. Conversely, increasing the number of suppliers reduces dependency and increases the ease of making alternative supply arrangements. The emergent network of relationships is dynamic and complex, and due in no small part to the influence of inventory management practices, tightly coupled. This critical organization of the network describes a system that contrary to existing supply chain conceptualisation exists far from equilibrium, requiring a different more appropriate theoretical lens through which to view them. This thesis adopts a Complex Adaptive Systems (CAS) perspective to position supply networks as tightly coupled complex systems which according to Normal Accident Theory (NAT) are vulnerable to disruptions as a consequence of normal operations. The consequential boundless and emergent nature of supply networks makes them difficult to research using traditional empirical methods, instead this research builds a generalised supply network agent based computer model, allowing network constituents (agents) to take autonomous parallel action reflecting the true emergent nature of supply networks. This thesis uses the results from a series of carefully designed computer experiments to elucidate how supply networks respond to a variety of market structures and permitted agent behaviours. Market structures define the vertical (between tier) and horizontal (within tier) levels of price differentiation. Within each structure agents are permitted to autonomously modify their prices (constrained by market structure) and collaborate by sharing demand information. By examining how supply networks respond to different permitted agent behaviours in a range of market structures this thesis makes 4 contributions. Firstly, it extends NAT by incorporating the adaptive nature of supply network constituents. Secondly it extends supply chain management by specifying supply networks as dynamic not static phenomena. Thirdly it extends supply chain risk management through developing an understanding of the impact different permitted behaviour combinations on the networks vulnerability to disruptions in the context of normal operations. Finally by developing the understanding how normal operations impact a supply networks vulnerability to disruptions it informs the practice of supply chain risk management.

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Unver, Ozge. "A Modelling Study For The Health Risk Posed By Nuclear Power Plant In Bulgaria At Different Parts Of Turkey." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/729053/index.pdf.

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In this study, following a severe accident at Kozloduy nuclear plant in Bulgaria how Turkey would be affected was investigated. The severe accident refers to core meltdown accident with catastrophic failure of containment. The model used is HySPLIT model developed in America. The worst day was predicted considering deposition of radionuclides. For initial runs, accidental release of I-131 and Cs-137 radionuclides was modeled for each day of year 2000 to find the worst day, seen to result from release beginning on April 7th 2000. After modeling release of all radionuclides for the worst day, radiation dose at different receptors, 12 most populated cities over Turkey has been calculated via different pathways. Late effects, fatal cancer, non-fatal cancer and hereditary risks, has been investigated for these receptors. The mostly affected part of Turkey was Marmara region and fatal cancer risk therein was 7x10-2 %. The collective health risk throughout Turkey was approximately 20 600 people. The same approach was then applied for investigating health risk of proposed nuclear reactor at Akkuyu, Turkey. In this case, the worst day was resulted from release beginning on 21st of February 2000. The worst affected part was the narrow strip in Central Anatolia extending to the north-eastern cost and fatal cancer risk in this region was 3.4x10-1 %. The collective health risk over Turkey was approximately 30 600 people. The results showed that Kozloduy nuclear plant has dominating effect throughout Turkey, but proposed Akkuyu reactor affects very limited region.

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Molinaro, Matteo. "Geometry and kinematics of the SE Zagros Mountains (Iran) : structural geology and geophysical modelling in a young collisional fold-thrust belt." Paris 11, 2004. http://www.theses.fr/2004PA112177.

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L'objectif de cette thèse est l'étude de la structure et la cinématique du Zagros oriental (Iran) et de la zone de transition avec le prisme du Makran appelée syntaxe de Bandar Abbas. Une étude structurale de terrain a permis de mettre en évidence le contrôle exercé par la stratigraphie mécanique - et donc les conditions paleogéographiques - sur le style structural d'un côté à l'autre de la syntaxe. La restauration de la première coupe équilibrée à travers le sud-est de la ceinture du Zagros permet de montrer que le Zagros plissé a subi deux phases téctoniques majeures, une première impliquant uniquement la couverture suivie par une deuxième impliquant le socle. Le raccourcissement accommodé dans la section depuis le Miocène moyen est d'au moins 45 km. La présence d'une puissante série évaporitique à la base de la couverture a favorisé le developpement de grands plis de décollement. L'analyse d'exemples de terrain dans la région d'étude ainsi que de profils sismiques dans le Zagros Central permet de discuter la cinématique de ces plis ainsi que les facteurs contrôlant leur style, notamment la mobilité du sel, l'existence de multiples décollements et le rôle tardif des failles de socle. Enfin, une modélisation géophysique de la structure lithosphérique du Zagros permet de discuter les facteurs fondamentaux qui ont guidé l'évolution récente de l'orogène. On met en évidence une amincissement lithosphérique qui pourrait être lié à un détachement récent du slab plongeant. Ce processus pourrait expliquer la transition récente d'une tectonique de couverture à une tectonique de socle
This thesis focuses on the structure and kinematics of the south-eastern Zagros Mountains (Iran) and the transitional structures with the adjacent Makran accretionary prism, known as the Bandar Abbas syntaxis. The structural style, as evidenced by a field-based structural study, is strongly controlled by changing mechanical stratigraphy and therefore paleogeographic conditions from one side to the other of the syntaxis. Restoration of the first complete balanced cross-section through the south-eastern Zagros fold-thrust belt shows that the external part of the orogen (a) underwent two main phases of deformation, i. E. A thin-skinned phase of deformation followed and partly overprinted by a thick-skinned phase, and (b) absorbed at least 45 km of shortening since middle Miocene times. The presence of an exceptionally thick layer of salt at the base of the cover allowed the development of huge detachment anticlines. Field examples from our study area and seismic profiles from Central Zagros allow us to discuss the still poorly understood kinematics of these folds as well as examine the various factors controlling the style of folding, essentially salt mobility, multiple decollement levels and late basement faulting. Finally, geophysical modelling of the deep lithospheric structure of Zagros brings new insight on the fundamental factors controlling the recent orogenic kinematics. In particular, a previously undocumented thinning of the lithosphere beneath Zagros could be attributed to recent slab break-off and is thought to have controlled the recent switch from thin-skinned to thick-skinned tectonics

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Novák, Jan. "Analýza návrhových prvků okružních křižovatek v závislosti na nehodovost." Doctoral thesis, Vysoké učení technické v Brně. Fakulta stavební, 2018. http://www.nusl.cz/ntk/nusl-390280.

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The dissertation deals with the analysis of roundabout design elements and their impact on accidents. The analysis objective was to identify the important elements of roundabouts that have impact on accidents. In order to achieve this goal, the multifactorial statistical safety assessment method was used on the basis of a representative sample of data, by developing several safety performance functions, verifying them and interpreting the result. Several design elements, which from the point of view of the traffic accident mechanism belong to the infrastructure factor, have been identified: AADT, average diameter, entrance width, entry angle, direct passage angle, location and many others. The original sample contained about 1200 roundabouts, which were reduced to 200 based on data availability. Accident frequencies were monitored between 2009 and 2016, i.e. for eight years, resulting in total 2674 roundabouts accidents. The result is an accident prediction model, developer based on roundabout approach design elements, and map of critical roundabouts, identified based on empirical Bayes estimate of accident frequency. Following approach parameters were identified: AADT, entry angle, distance between collision points, deviation of angles between approaches, presence of apron, presence of bypass, entry type, presence of pedestrian crossing and surrounding area type.

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29

Zarimpas, N. "Modelling in-plant aspects of nuclear reactor accidents." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37909.

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30

Liu, Yilin. "Bayesian modelling of the spatial distribution of road accidents." Thesis, Middlesex University, 2008. http://eprints.mdx.ac.uk/13419/.

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This research aims to develop Hierarchical Bayesian models for road accident counts that take account of the spatial dependency in the neighbouring areas or sites. The Poisson log-linear model is extended by introducing a second level of random variation that includes a conditional autoregressive (CAR) component. Both models for accidents at the area level and models for accidents on a road network are developed. Areal models are fitted using data for counties and districts in England covering two different periods and data for wards in the West Midlands region in 200l. Network models are fitted to link data for the MI motorway and to junction data for the city of Coventry. Results show that, in most cases, adding a spatial (CAR) component to conventional models produces better estimates of the expected number of accidents in an area or at a site. Signs of the coefficients for explanatory variables, including level of traffic and road characteristics, are consistent with expectation. Levels of the spatial effects in a CAR model reflect the relative influence of the unknown or unmeasurable explanatory variables on the expected number of accidents. Results from models at the local authority level in the 2000s show that spatial effects are positive in London boroughs and are negative in most metropolitan districts. For accidents at the ward level in the West Midlands, the performance of the CAR model is similar to that of the non-CAR model which includes log-normal random effects and metropolitan county effects. For models of accidents on the MI, several links are identified to have positive and fairly large spatial effects. For Coventry junction accidents, the CAR model does not perform better than the non-CAR model. Approaches to including temporal effects in spatial models when data cover two or more periods and jointly modelling different types of accidents are also proposed and examined. Two applications of the CAR models developed in this research are introduced. The first application is about predicting the number of accidents in a local authority in a new year based on previous years' data. One advantage of using the CAR model is that it produces more precise predictions than the non-CAR model. The second application of the CAR model is a new approach for site ranking. The sites selected by such a criterion are those with high risks caused by some unknown or unmeasured factors for instance, curvature or gradient of roads) which are spatially correlated. Further on-site investigation will be needed to identify such factors.

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Poudel, Minesh. "Aircraft emergency evacuation : analysis, modelling and simulation." Toulouse 2, 2008. http://www.theses.fr/2008TOU20026.

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Cette thèse s’intéresse à l’évacuation d’urgence des avions et plus particulièrement à la conception d’un simulateur numérique capable de représenter de façon réaliste ce processus afin de contribuer à la certification de configurations et de procédures d’évacuation d’urgence pour les avions gros porteurs. Cette thèse est composée de deux grandes parties. Dans la première partie, il s’est agi d’identifier le problème, de réaliser un état de l’art et de caractériser le comportement des passagers pendant l’évacuation. Dans la deuxième partie de la thèse il s’est agi de concevoir les élément constitutifs d’un simulateur d’évacuation d’urgence des aéronefs. Après avoir analysé les modèles existants et revu les méthodes de modélisation des systèmes dynamiques cellulaires, le schéma conceptuel d’un tel simulateur a été développé. Le simulateur d’évacuation d’urgence a été conçu via UML en langage Java. En conclusion, les perspectives concernant la poursuite de cette étude sont présentées
This thesis is about aircraft emergency evacuation and its principal objective is to establish a computational model able to simulate realistically it. This will contribute to the certification process of new aircraft emergency evacuation layouts and egress procedures for large capacity airliners. This thesis is composed of two main parts. In the first one, the main problem issues are identified, a state of the art in emergency evacuation from aircraft is realized and human behaviours during such an event are described. In the second part of this work, the elements of the emergency evacuation model are identified. After analysing existing models and different models of dynamic cellular systems, the conceptual model of this simulator is proposed. Its framework has been designed using UML and the routines are written in Java. Finally future research directions are given

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Tavares, Richard António Martins. "Accidental release of hazardous gases: modelling and assessing risk." Doctoral thesis, Universidade de Aveiro, 2011. http://hdl.handle.net/10773/7629.

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Doutoramento em Ciências Aplicadas ao Ambiente
The renewed concern in assessing risks and consequences from technological hazards in industrial and urban areas continues emphasizing the development of local-scale consequence analysis (CA) modelling tools able to predict shortterm pollution episodes and exposure effects on humans and the environment in case of accident with hazardous gases (hazmat). In this context, the main objective of this thesis is the development and validation of the EFfects of Released Hazardous gAses (EFRHA) model. This modelling tool is designed to simulate the outflow and atmospheric dispersion of heavy and passive hazmat gases in complex and build-up areas, and to estimate the exposure consequences of short-term pollution episodes in accordance to regulatory/safety threshold limits. Five main modules comprising up-to-date methods constitute the model: meteorological, terrain, source term, dispersion, and effects modules. Different initial physical states accident scenarios can be examined. Considered the main core of the developed tool, the dispersion module comprises a shallow layer modelling approach capable to account the main influence of obstacles during the hazmat gas dispersion phenomena. Model validation includes qualitative and quantitative analyses of main outputs by the comparison of modelled results against measurements and/or modelled databases. The preliminary analysis of meteorological and source term modules against modelled outputs from extensively validated models shows the consistent description of ambient conditions and the variation of the hazmat gas release. Dispersion is compared against measurements observations in obstructed and unobstructed areas for different release and dispersion scenarios. From the performance validation exercise, acceptable agreement was obtained, showing the reasonable numerical representation of measured features. In general, quality metrics are within or close to the acceptance limits recommended for ‘non-CFD models’, demonstrating its capability to reasonably predict hazmat gases accidental release and atmospheric dispersion in industrial and urban areas. EFRHA model was also applied to a particular case study, the Estarreja Chemical Complex (ECC), for a set of accidental release scenarios within a CA scope. The results show the magnitude of potential effects on the surrounding populated area and influence of the type of accident and the environment on the main outputs. Overall the present thesis shows that EFRHA model can be used as a straightforward tool to support CA studies in the scope of training and planning, but also, to support decision and emergency response in case of hazmat gases accidental release in industrial and built-up areas.
A renovada preocupação na avaliação dos riscos e consequências dos perigos tecnológicos em zonas industriais e urbanas continua a enfatizar o desenvolvimento de modelos de análise de consequências (AC) à escala local, capazes de simular episódios de poluição de curto prazo e seus efeitos na saúde humana e ambiente resultantes da exposição em situação de acidentes com substâncias perigosas. Neste sentido, o principal objecto desta tese é o desenvolvimento e validação do modelo Efects of Released Hazardous gAses (EFRHA). Esta ferramenta foi desenvolvida para simular a libertação e dispersão atmosférica de gases perigosos pesados e passivos em ambientes de topografia complexa e edificados, bem como, estimar as consequências da exposição a episódios de poluição de curta duração de acordo com limites de segurança e controlo. O modelo é constituído por cinco módulos principais: meteorológico, fontes, terreno, dispersão e efeitos. Diferentes estados físicos e tipos de acidente podem ser analisados. Considerado o elemento principal da ferramenta, o módulo de dispersão é baseado na modelação ‘shallow layer’, que permite considerar a influência de obstáculos na dispersão de gases perigosos. A validação do modelo inclui métodos de análise qualitativa e quantitativa através da comparação dos principais outputs com bases de dados medidos ou simulados. A análise preliminar dos módulos meteorológica e fontes baseada na comparação com resultados de modelos também validados demonstra a correcta descrição das condições ambientais e da variação das características da fonte ao longo da libertação. O módulo de dispersão é comparado com resultados de medições experimentais considerando diferentes condições de libertação e dispersão atmosférica. Em geral, os critérios de qualidade estimados encontram-se dentro dos limites de aceitação para modelos ‘non-CFD’, demonstrando a capacidade para simular razoavelmente a libertação e dispersão atmosférica de gases pesados perigosos em ambientes industriais e urbanos. O modelo EFRHA também foi aplicado a um caso de estudo, o Complexo Químico de Estarreja (ECC), com base num conjunto de cenários de libertação acidental, no âmbito de um estudo de AC. Os resultados demonstram a potencial magnitude dos efeitos na área envolvente ao ECC, bem como a influência das condições meteorológicas e tipo de acidente. De um modo geral, a presente tese demonstra a aplicabilidade do modelo como ferramenta para estudos de CA, bem como no suporte à decisão e preparação de resposta de emergência em situação de libertação acidental em zonas urbanas e industriais.

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Ladi, Hj Supry Hj Ag. "Geographical information systems coupled prediction modelling of road traffic accidents in Brunei." Thesis, University of East London, 2006. http://roar.uel.ac.uk/3402/.

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The analysis of road accident data has led to the development of a number of prediction models to allow testing of road improvement schemes. However, the advances in Information Technology and particularly within the field of Geographical Information Systems (GIS) has enabled it to be linked with applied sciences such as Fluid Mechanics, Highway Design and Traffic Engineering to create a "loosely" to "tightly coupled" GISbased system. Such a system allows correction and simulation tasks to be performed whenever necessary. This approach has been applied to the problem in Brunei where they are at the initial stage towards realising the importance of road-safety research. This work has been proved to contribute tangible benefits for the Brunei road safety authorities. ArcGIS software was used to produce clusters of road accidents along a road and create a road accident database linked with the Brunei road network which form the initial stage of this research. The research develops a new 'Modified Voronoi Process' (MVP) for the identification of accident hotspots along a road. This technique uses a combination of GIS functionalities with Microsoft Excel software. The establishment of a Hotspot Zone dimension (HZD) within the MVP is creative and is very beneficial for Brunei road safety authorities and other researchers. The technique incorporates Brunei road accident hotspot definition established by the author. The final outcome of this research is the development of a GIS-based Road Accident Prediction System and is an innovation and enhancement to the world of road accident prediction system and particularly in Brunei. The system incorporates an external prediction model, which is "tightly coupled" or integrated with a GIS. The coupling enables the prediction to be carried out on a single platform for easy input and computation. The system was tested using accident data acquired from manually recorded 24-hour police reports and statistical software used to analyse the sensitivity of accident locations. The system was also used for a sensitivity analysis of the application of the United States Federal Highway Agency (USFHA) prediction model on a segment of road in Brunei.

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Memon, A. Q. "Modelling road accidents from national datasets : a case study of Great Britain." Thesis, University College London (University of London), 2012. http://discovery.ucl.ac.uk/1354623/.

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This study investigates the occurrence of road traffic accidents in Great Britain at a national scale. STATS 19 data for road accidents, vehicles involved in road accidents and casualties occurring over several years were analysed and modelled using various statistical techniques. The main aims of this research were to investigate the use of different statistical model formulations and to investigate the numbers of road accidents, casualties, and vehicles involved that occur on each day. Generalized linear model (GLM), generalized estimation equation (GEE), and hierarchical generalized linear model (HGLM) formulations were investigated for this purpose. The variables of weekday 3 (weekday, Saturday, Sunday), seasons (Spring, Summer, Autumn, Winter), month, time, Public holidays, Christmas holidays, new-year holidays, road type and vehicle class, together with certain interactions between them, were found to be important in developing models of risk per unit of distance travel. Additional variables of distance travelled per vehicle, vehicles per head of population, population density, meteorological factors were also investigated, and population, age group and gender were used to develop models of casualty rate per person-year. The GLM model structure with log link function was found to fit data for the occurrence of road accidents reasonably well when the negative binomial distribution was adopted to accommodate over-dispersion beyond Poisson levels. The GEE with negative binomial error together with autoregressive (AR1) structure was preferred over the GLM as it can also accommodate serial correlation that was found to be present in the data due to the natural order of the observations. The coefficients and significance levels of some variables were found to change significantly if the presence of serial correlation is not respected. Finally HGLM with Poisson-gamma errors and log link function was used to estimate the number of casualties involved in road accidents on each day. The advantage of HGLM over GLM and GEE is that it can account for variability within and between clusters using both random effects and dispersion modelling: this was found to be substantial. However, unlike GEE, HGLM cannot accommodate time series structure so that the coefficients and the associated standard errors of some of the variables should be viewed with caution. From the model results, it is found that distance travelled provided a good measure of exposure to risk in most cases, and that each of distance travelled per vehicle, population density and rain is associated with greater risk for road accident per unit of travel whereas risk diminishes with increase in each of numbers of vehicles per person and mean minimum monthly temperature. The risk per unit of travel was also estimated for each of 5 classes of vehicles on each of 5 different kinds of roads. Finally the age and gender specific rate of casualty per person-year was estimated for each combination of age group and gender. The results obtained from this study will lead to the promotion of safe usage of road and vehicle class combinations by raising travellers’ awareness. On the other hand the casualty rates estimated for each of the 8 age groups and two gender groups by vehicle class will help to identify those that need more attention. These results will help various educational, planning, and rescue agencies to identify target groups for education and engineering initiatives to improve road safety.

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Abdalla, Ibrahim Mohamed. "Statistical investigation and modelling of relationships between road accidents and social characteristics." Thesis, Edinburgh Napier University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.682566.

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Al, Kaabi Abdulla Mohammed Saeed Khalaf. "Modelling traffic accidents using duration analysis techniques : a case study of Abu Dhabi." Thesis, University of Newcastle upon Tyne, 2013. http://hdl.handle.net/10443/2171.

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One of the main aims of Traffic Incident Management (TIM) is to reduce the duration of the disruption to traffic caused by an accident. Several approaches have been applied in the past in order to analyse and predict this. Incident duration can be broken down into four time intervals: reporting, response, clearance and recovery. Accurate models of each interval allow traffic controllers to deploy resources efficiently, thereby minimising an accident’s effect on traffic flow and congestion. This may, in turn, lead to a reduction in other adverse impacts of traffic accidents such as air pollution, fuel consumption and secondary crashes. A new approach to this problem, based on the accidents’ characteristics, was developed using a fully parametric hazard based modelling technique to predict accident durations. The road network around Abu Dhabi, capital of the UAE, was used as a case study. Data was obtained from the UAE Federal Traffic Statistics System (FTSS) and the Abu Dhabi Serious Collision Investigation Section (ASCIS). These data included the start and end of each time interval, the total accident duration, temporal, geographical, environmental and other accident characteristics. To analyse the total duration, the analysis was conducted using three time intervals. Accordingly, fully parametric Accelerated Failure Time (AFT) models were created for the purpose of reporting time, response time, and clearance time (all urban roads) and response time (rural freeways), depending on the data available. Analysis showed that the time intervals had different distributions. In addition, there was no similarity in the variable that affected each interval. The results also revealed that weaknesses exist in the current practices of TIM in Abu Dhabi. The results of the analysis were used to create decision trees to aid traffic controllers with decisions regarding traffic diversion and disseminating traffic information to travellers.

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Sun, Yu. "Risk-based framework for freight movement analysis." Thesis, Queensland University of Technology, 2002.

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Decision-making models have, m the recent years, been developed to provide systematic and comprehensive tools to analyse, evaluate and manage freight movement. Freight transport models developed thus far have not precisely defined risk agents brought by travelling vehicles, which lead to indistinct risk types. Instead, most of the models developed discussed the risks mainly related to direct impacts by traffic accidents. On the other hand, transport efficiency, which is of more and more concern, has not been sufficiently emphasised in the previous models. This thesis studies the factors in relation to not only safety issues, but efficiency issues. And the risks due to freight movement have been classified into categories in accordance with their distinct natures and typically, affected population groups including human, environment and economic infrastructure. Two new theories, risk agent and risk response factor, have been introduced to the framework to precisely define and evaluate various risk types. Vehicle travelling on a specific route may encounter various situations combined by road characteristics, traffic flow and weather conditions, etc. In order to assist in analysing freight movement in a systematic manner, freight movement behaviours, which pose negative impacts to nearby population, are divided into different modes, which have been interpreted as "risk-producing activities" in the Risk-based Framework for Freight Movement Analysis (RBF-FMA) in order to identify the characteristics of the risk agents. It is important to differentiate the segments with significant changes in the travel risk producing conditions. This study divides travel route into segments and each segment is assessed separately and differentiates among three segment types: travel segment, intersection, and roundabout according to their different contributing factors. The framework developed in this study also considers the availability of emergency response facilities and support system as a major risk-reducing factor. When applied and compared with the risk rating results estimated by the Queensland Transport Department (QTD) using their risk-rating model, the RBF-FMA gave highly comparable results. In the evaluation, both the QTD and RBF-FMA models were applied to assess the risk associated with the release of hazardous mate1ials at 25 segments identified as having high risk by the QTD. The RBF-FMA was also successfully applied to compare two routes between two common points and the results were generally consistent with the concentration of human population, enviromnental population and economic activity and infrastructure along the two routes. The basic data that was needed to conduct the RBF-FMA was easily generated using site visits and from available data basis. While the RBF-FMA presents a logical framework that is based on the risk assessment and management methodology, the process of assigning scores (ranks) and weights to the various factors and sub-factors is basically subjective and reflects the education, values, judgement and understanding of the model by the user. It is recognised that this subjectivity can lead to viability in the results. The contribution of this study is significant in that it translates the basic risk assessment model used in the public health field into a framework suitable for rating the risk associated with freight movement. In addition, the effort presented a basic modelling approach that can be modified or built on by other researchers in this field. The framework formulated in this study is worthy of further research and development as it can be used as a useful system for making decisions related to moving freight along selected routes. Further work could include development of a GIS-based computer program which is able to contain huge amount of risk assessment data associated with freight movement and provide a visual operation of the risk analysis.

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Irumba, Richard. "Modelling of Construction Safety Performance and Housing Markets in Kampala, Uganda." Doctoral thesis, KTH, Bygg- och fastighetsekonomi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-166816.

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The construction industry in Uganda is characterized by a high incidence rate of accidents. During the late 1990s, an annual average of 49 accidents were reported in the construction industry while during the period 2001 to 2005, the annual average for this sector was 103 cases. Between 2006 and 2010, more construction accidents were registered with a total of 49 fatalities reported in Kampala metropolitan area alone. This trend has continued up to the present date. Meanwhile, the demand for housing in Uganda exceeds supply resulting into a huge housing deficit. Rapid population growth without matching housing facilities has been cited as the main cause of the housing deficit. Land holding in Uganda is characterized by multiple rights of ownership, and high social costs including land conflicts and violent evictions. Reportedly, these developments are affecting the performance of the housing sector. Given the above background, the aim of this thesis is to propose policies and strategies for improvement of construction safety performance and the housing sector in Uganda. The thesis is based on two broad themes i.e. construction safety performance and housing markets. Although the research themes are unique in their own right, they both address pertinent issues concerning the construction industry in Uganda. Whereas the first theme investigates accidents as events that affect the production of construction infrastructure (including housing), the second theme handles topical issues which affect the demand and supply for housing in Uganda. The study area is Kampala, the capital city of Uganda. In addition to the overview chapter, this thesis contains four research papers. The first two papers relate to theme on construction safety performance whereas the last two papers relate to theme on housing markets. The first paper investigates the causes of construction accidents in Kampala, establishes the prevailing injury and fatality rates, examines spatial patterns in occurrence of accidents and thereafter, proposes strategies of mitigating accidents. The second paper investigates how undiscovered rework (defined as unnecessary effort of redoing a process or activity that is incorrectly implemented the first time) leads to accidents, develops a computer based model for simulating occurrence of accidents on projects and thereafter, proposes strategies of reducing rework related accidents. Evidently, the first paper is explorative investigating construction safety issues at industry level, whereas the second paper is more specific studying safety dynamics at project level. The third paper investigates how the choice of land tenure system affects housing values and thereafter, proposes strategies of mitigating the negative effects of land tenure on the housing market. Finally, the fourth paper examines how population changes affect the housing needs of a city, develops a computer based model for simulating the city population and housing needs, and experiments a plethora of housing policy proposals. Overall, findings of this thesis such as the concept of spatial dependence in occurrence of construction accidents, where accidents at one location were found to be associated with those which occur in the neighborhood; the phenomenon of congestion, defined in this thesis as the existence of high building density amidst many fulltime workers on site, and its significant association with accidents occurrence; and the uniqueness of private mailo land tenure system and the 12% premium it offers in housing values amidst high social costs, are unique contributions to the existing body of knowledge.

ISBN: 978-91-87111-05-01

QC 20150522

None

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39

Wong, C. W. "Numerical modelling of masonry panels subject to loading from gas explosions." Thesis, Middlesex University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337850.

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40

Moore, Craig Andrew. "In vitro modelling of dermal absorption of chemicals following environmental or accidental exposure." Thesis, University of Newcastle Upon Tyne, 2010. http://hdl.handle.net/10443/960.

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These studies were aimed at identifying potential surrogate compounds for dermal absorption of bioactive agents in vitro using flow through and static cell diffusion systems, and also to generate novel data on the effects of application vehicle on chemical absorption following low level exposure. For protection and risk assessment purposes, the influence of ‘everyday’ clothing, and skin surface decontamination on dermal chemical absorption was also assessed. The model compounds (caffeine and benzoic acid), and the surrogate compounds (chlorpyrifos, dichlorvos and phorate) were generally found to be poor marker chemicals for comparison with HD absorption through human and pig skin in vitro. However, benzoic acid absorption from a finite dose in IPA more closely matched the absorption profile of HD applied as a finite dose in IPA. Dichlorvos absorption was greatest from all vehicles compared with chlorpyrifos and HD absorption in vitro. Dermal absorption of chlorpyrifos was enhanced when applied in PG compared with absorption from IPA or IPM. No differences were observed between absorption of neat HD and HD in IPA in terms of percentage of applied dose absorbed at 24 hours. Absorption of HD through full thickness pig skin more closely matched absorption through full thickness human skin, split thickness pig skin overestimated absorption of HD in vitro in comparison. ‘Everyday’ clothing (cotton shirt) significantly reduced absorption of dichlorvos, chlorpyrifos and HD through human skin. Chemicals were applied to clothed skin in IPA to mimic finite exposure, and left in contact for 30 minutes (dichlorvos), 4 hours (chlorpyrifos), and 1 hour (HD). For all chemicals, removal of clothing followed by immediate skin surface decontamination with 0.5% (v/v) soap solution further reduced absorption compared with removal of clothing alone. Despite these differences not being significant, in terms or civilian exposure, it would be recommended to remove clothing and decontaminate as early as possible postexposure to minimise the potential for dermal absorption and localised toxicity within the skin. In conclusion, the organophosphate compounds used in these studies (chlorpyrifos and dichlorvos) could potentially be useful surrogates for organophosphate agents such as VX or sarin, however, further work is needed to make these comparisons. The vehicle in which a chemical is applied to the skin can have a profound effect on dermal absorption, and this knowledge is important for risk assessment for exposure to a range of chemicals. Cotton shirt material significantly reduced dermal absorption of all chemicals used compared with 24 hour exposure. Despite this clothing not being designed for protective purposes, this may have a significant impact for reducing dermal absorption and toxicity in vivo as a result of chemical exposure. Further investigation is needed to assess absorption of a wider range of chemicals and application vehicles for risk assessment purposes, and to identify chemicals that more closely mimic dermal absorption of bioactive agents in vitro for extrapolation to in vivo exposure scenarios

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Abdelrahman, Hany Nabil Mohamed Amin. "Modelling the liquid breakup and vapour generation during accidental releases of liquid fuels." Thesis, University of Sheffield, 2015. http://etheses.whiterose.ac.uk/10017/.

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42

Cardon, Clément. "Modélisation de la diffusion multi-composants dans un bain de corium diphasique oxyde-métal par une méthode d'interface diffuse." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLX096/document.

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Ce travail de thèse porte sur la modélisation de la cinétique de stratification des phases liquides oxyde et métallique dans un bain de corium (système U-O-Zr-acier) du point de vue de la diffusion multi-composants et multiphasique. Cette démarche de recherche s’inscrit dans le cadre du développement d’une modélisation « fine » du comportement d’un bain de corium basée sur une approche CFD (« Computational Fluid Dynamics ») de la thermo-hydraulique. Elle vise à améliorer la compréhension des phénomènes mis en jeu et construire des lois de fermetures adéquates pour des modèles macroscopiques intégraux.Pour ce faire, la méthode du champ de phase couplée avec une fonctionnelle d’énergie utilisant la méthode CALPHAD se révèle être un outil pertinent.Dans une première partie, nous nous sommes intéressés au système binaire U-O. Nous avons développé un modèle à interface diffuse (basé sur une équation de Cahn-Hilliard) pour décrire la diffusion dans ce système. Nous avons procédé à la mise en place du couplage entre ce modèle et une base de données thermodynamiques CALPHAD, ainsi qu’au paramétrage d’un tel modèle avec en particulier une procédure d’élargissement de l’interface.Ensuite, dans le cadre d’une modélisation sur le système ternaire U-O-Zr nous avons proposé une généralisation du modèle à interface diffuse par le biais d’une hypothèse d’équilibre local des mécanismes d’oxydo-réduction. Nous avons porté une attention particulière à l’analyse de ce modèle par le biais de simulations numériques 1D en nous intéressant notamment à l’état stationnaire et aux profils de composition obtenus.Finalement, nous avons montré l’application de ce modèle au système U-O-Zr-Fe. Pour cela, nous avons considéré une configuration similaire aux essais expérimentaux à « petite échelle » relatifs à l’étude de la stratification d’un bain oxyde-métal
This Ph.D. topic is focused on the modelling of stratification kinetics for an oxide-metal corium pool (U-O-Zr-steel system) in terms of multicomponent and multiphase diffusion. This work is part of a larger research effort for the development of a detailed corium pool modelling based on a CFD approach (“Computational Fluid Dynamics”) for thermal-hydraulics. The overall goal is to improve the understanding of the involved phenomena and obtain closure laws for integral macroscopic models.The phase-field method coupled with an energy functional using the CALPHAD method appears to be relevant for this purpose.In a first part, this works has been focused on the U-O binary system. We have developed a diffuse interface model (based on a Cahn-Hilliard equation) in order to describe the diffusion process in this system. This model has been coupled with a CALPHAD thermodynamic database and its parameterization has been developed with, in particular, an upscaling procedure related to the interface thickness.Then, within the framework of a modelling for the U-O-Zr ternary system, we have proposed a generalization of the diffuse interface model through an assumption of local equilibrium for redox mechanisms. A particular attention was paid to the model analysis by 1D numerical simulations with a special focus on the steady state composition profiles.Finally we have applied this model to the U-O-Zr-Fe system. For that purpose, we have considered a configuration close to small-scale experimental tests dedicated to the study of oxide-metal corium pool stratification

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Matteo, Laura. "Modélisation unidimensionnelle du comportement d’une pompe rotodynamique en fonctionnement normal et accidentel." Thesis, Paris, ENSAM, 2019. http://www.theses.fr/2019ENAM0038/document.

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La conversion de l’énergie mécanique en énergie de pression (transportée par un fluide) -ou inversement-, est nécessaire dans de nombreux domaines de l’industrie : transport, production d’électricité, ventilation... Pour cela, des machines tournantes sont très souvent utilisées. Dans le cas des pompes, elles sont constituées d’au moins une partie rotative contenant des aubes transmettant l’énergie au fluide (la roue), laquelle est liée à un arbre, lui-même mis en rotation par un moteur. La méthode de design de telles machines a évolué depuis le début du siècle dernier jusqu’à aujourd’hui. De nos jours, les composants sont optimisés par l’utilisation de calculs numériques à l’échelle locale de type Computational Flow Dynamics (CFD). La simulation à l’échelle locale apporte des informations sur l’écoulement à l’intérieur des éléments de la machine tournante en trois dimensions. Toutefois, la qualification locale des résultats de calcul à l’échelle CFD reste un challenge, notamment en termes de techniques de mesures expérimentales. Par ailleurs, les temps de calcul sont conséquents même à l’échelle de la machine seule, ce qui permet difficilement la simulation de scénarii transitoires accidentels longs à l’échelle d’un réacteur entier, lesquels sont étudiés dans le cadre de la sûreté nucléaire en particulier. Et d’autant plus s’il est nécessaire de réaliser un grand nombre de calculs (études de propagation d’incertitudes). Dans ce contexte, un modèle d’une échelle intermédiaire entre l’étude globale de la machine par les triangles des vitesses et la modélisation CFD a été développé au cours de cette thèse. L’approche choisie consiste à considérer une ligne de courant moyenne adoptée par l’écoulement dans chaque partie de la pompe et un maillage unidimensionnel (ie. 1D) le long de cette ligne. Il permet, par la description géométrique de la pompe, de prédire ses performances (pression produite, énergie transmise au fluide). Plusieurs machines tournantes ont pu être représentées avec le modèle 1D développé : des pompes centrifuges et hélico-centrifuges et un compresseur. Différents fluides ont été simulés (eau, sodium, air). Des régimes d’écoulement monophasiques et diphasiques dans ces machines ont été représentés lors de calculs permanents et transitoires. Le modèle est capable de prédire les performances de machines de géométries variées en conditions monophasiques quasi-stationnaires avec une erreur relative maximale de l’ordre de 15% sur une large gamme de débit. Le modèle permet également de détecter l’occurrence de la cavitation pour une pompe centrifuge à différentes conditions de débit. Il est capable de prédire la dynamique d’un transitoire de démarrage rapide d’une pompe centrifuge en conditions monophasiques. Il subsiste des difficultés numériques lors de la simulation d’un transitoire comparable où un régime de cavitation s’installe dans la roue de la pompe. Une pompe ainsi modélisée peut être intégrée à la modélisation d’une installation complexe telle qu’un réacteur nucléaire. Ceci ouvre des possibilités en termes d’études de transitoires accidentels dans le cadre d’études de sûreté. Les perspectives d’application du modèle envisagées sont la modélisation des turbines ou de machines multi-étagées et la simulation d’autres fluides
Conversion of mechanical energy into pressure inside a fluid -or inversely-, is necessary in numerous industries: transport, electricity production, air circulation... Rotating machineries are often used in these frames. They are constituted of at least one bladed rotating part giving energy to the fluid (the impeller) and connected to a shaft, which is entrained by a motor in the case of a pump. The design method of such turbomachines has evolved from the begining of the last century to these days. Nowadays Computational Flow Dynamics (CFD) local scale computations are used to optimize the pump components. Local simulation allows to obtain information on what is happening inside the machine in three dimensions. However, qualification of the local results of such simulations remains a challenge, mostly due to constraints on experimental technics. Additionally, computation cost of such local simulations is heavy even at the scale of the machine alone. That hardly allows the simulation of transient scenarii on whole and complex systems such as a reactor, which are studied in the frame of nuclear safety in particular. And even more when uncertainty propagation studies are intended, which involve a large number of simulations. In such a context, a model of an intermediate scale -between the global study of the machine using velocity triangles and local CFD computations- has been developed during this PhD thesis. The proposed approach consists in considering a mean stream line that is adopted by the flow inside each part of the machine, associated to a one-dimensional (1D) meshing. By defining main geometrical characteristics of the machine, it can predict its performances in terms of pressure rise and energy given to the fluid. Several turbomachines have been modelled using this 1D model: centrifugal pumps, mixed flow pumps and a radial compressor. Various working fluids have been simulated, such as water, liquid metal sodium and air non-condensable gas. Single-phase and two-phase flow regimes have been represented in those machines in steady and transient conditions. The model is able to predict performances of machines of various geometries in steady single-phase conditions with a relative error globally less than 15% for a large range of flow rates. The model allows also to detect the occurrence of cavitation for a centrifugal pump in various conditions of flow rate. It catches also pump fast startup transient dynamics in single-phase conditions. It subsists numerical difficulties when simulating the same transient in cavitating conditions. A pump modelled as described here can be included into the modelling of closed experimental loops or complex facilities such as nuclear reactors. This work opens up new possibilities to study accidental transient in the frame of safety analysis. Intented application prospects of the model are the modelling of turbines or multi-stage machines and the use of other fluids

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44

Grip, Jesper. "Metaanalys av förslag på åtgärder i kommunala olycksundersökningar." Thesis, Karlstads universitet, Institutionen för miljö- och livsvetenskaper, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-46924.

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This paper carry out a qualitative meta-analysis of 112 “proposals for action” identified in 30 of the approximately 630 accident investigations that are published on the Swedish Civil Contingencies Agency (MSB) website. Accident investigations have been carried out at the discretion of each municipality and then sent to the MSB, which in turn, after a secrecy review and an ethical review, publishes most of the investigations on the web page Kommunala olycksundersökningar. The accident investigations are split into a number of different categories by type of event and the categories analysed in this paper are “Automatic alarm - not fire” and “Fire - not in building”.The process of learning from accidents can be illustrated using the CHAIN model (Reporting - selection - Investigation - spread - implementation). This model attempts to show how the process of learning from accidents step by step and point out that every step must be followed and implemented for a lesson to be learned - from event to implemented lesson learned. Previous studies however have found that the steps in the CHAIN model are not followed from the beginning to the end in terms of learning from municipal accident investigations. A first problem is that some proposals listed can be unclearly formulated in terms of who is supposed to carry out the proposal, but above all, there are weaknesses in distribution and thus also the implementation of the proposals.Aim and method This paper seeks to compile, analyse and present the proposals for action contained in the selected accident investigations. The method used is a qualitative meta-analysis understood here as an "analysis of analyses" performed with the qualitative method content analysis, which may also contain quantitative elements.Findings Almost all of the proposals set out are alone in its kind. There is just two proposals contained more than once. Proposals for measures can be further divided into categories by thought, or stated, receivers and for similarities between the proposals. More than half of all proposals are targeted to Rescue services own work, either regarding the intervention itself, organizational or other planning or collaboration with other agencies or stakeholders. One group is aimed towards the operator and propose improvements in various parts of their systematic fire prevention (SBA). Two smaller groups of proposals suggests improvements for handling errors and to do changes in the products and that this information should be communicated to operators/retailers or producer. Some proposals do not fall within any of the other categories.It noted that, in principle, all suggestions are workable and implementable and that these proposals can be generalized beyond its original context into a larger one. And that this kind of qualitative meta-analysis can be a part of the CHAIN model's implementation.
I denna uppsats görs en kvalitativ metaanalys av 112 förslag på åtgärder vilka anges i 30 av de runt 630 kommunala olycksundersökningar som finns publicerade på Myndigheten för samhällsskydd och beredskaps (MSB) hemsida. Olycksundersökningarna har genomförts efter beslut i respektive kommun och därefter skickats in till MSB, vilka i sin tur, efter en sekretessprövning och en etisk prövning, publicerar de flesta på webbsidan Kommunala olycksundersökningar. Olycksundersökningarna delas upp på ett antal olika kategorier efter typ av händelse och de kategorier vilka analyseras i denna uppsats är Automatlarm – ej brand samt Brand – ej i byggnad.Processen att lära från olyckor kan åskådliggöras med hjälp av CHAIN-modellen (rapportering – urval – utredning – spridning – genomförande). Denna modell vill visa på hur processen med lärandet från olyckor går till steg för steg samt poängtera att varje steg måste följas och genomföras för att ett lärande ska komma i mål – från händelse till implementerad lärdom. Tidigare studier har dock funnit att CHAIN-modellens steg inte följs från början till slut vad gäller lärandet från kommunala olycksundersökningar. Ett första problem är att vissa förslag som anges kan vara otydligt formulerade vad gäller vem som ska genomföra förslaget, men framförallt finns det brister i spridningen och således också genomförandet av förslagen.Syfte och metod Denna uppsats syfte är att sammanställa, analysera och presentera de förslag på åtgärder som återfinns i de utvalda olycksundersökningarna, samt att värdera dessa utifrån generaliserbarhet. Metoden som använts är en kvalitativ metaanalys med vilket här avses en ”analys av analyser” utförd med den kvalitativa metoden innehållsanalys, vilken också kan innehålla kvantitativa inslag.Resultat Nästan alla de förslag på åtgärder som anges i olycksundersökningarna är ensamma i sitt slag, det är bara 2 förslag som återfinns mer än en gång. Detta beror troligen på att en utökad olycksundersökning görs först om utredningen bedöms kunna tillföra ny information. Förslagen på åtgärder kan vidare delas in i kategorier efter tänkt, eller angiven, mottagare samt efter likheter mellan förslagen. Men än hälften av alla förslag är riktade mot Räddningstjänstens eget arbete, antingen gällande själva insatsen, organisatoriskt eller annat planeringsarbete eller gällande samverkan med andra myndigheter eller aktörer. En grupp förslag riktar sig mot verksamhetsutövaren och föreslår förbättringar i olika delar av dessas Systematiska brandskyddsarbete. Två mindre grupper förslag ger förslag på förbättringar efter handhavandefel respektive på förändringar av produkter samt att denna information ska delges verksamhetsutövare/återförsäljare eller producent. Några förslag faller inte inom någon utav de övriga kategorierna.Konstateras görs också att i princip alla förslag är konkreta och genomförbara samt att dessa förslag kan generaliseras utanför sitt ursprungliga sammanhang till en större kontext. Samt att denna typ av kvalitativ metaanalys kan vara ett led i CHAIN-modellens genomförande.

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Colomer, Segura Carles [Verfasser]. "Reduced Order Modelling of Steel Beams and Columns for Analysis against Accidental Actions / Carles Colomer Segura." Aachen : Shaker, 2017. http://d-nb.info/1138179299/34.

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Meheust, Maxime. "Analyse et modélisation des indicateurs du risque routier : le modèle MIRR." Thesis, Paris 10, 2016. http://www.theses.fr/2016PA100034.

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Les enjeux humains liés à l’accidentologie routière et les coûts qu’ils font supporter à la collectivité sont tels qu'ils rendent obligatoire la mise à disposition d'une batterie d'outils la plus complète et complémentaire possible afin de comprendre au mieux la problématique du risque routier. L’enjeu de cette thèse est justement de proposer de nouveaux outils capables de mieux apprécier ce phénomène et, in fine, d'orienter et d'appuyer les décisions des pouvoirs publics en la matière. Ils ont été développés en modélisant successivement le kilométrage parcouru qui formalise l’exposition au risque, les nombres d’accidents corporels, de tués, de blessés ainsi que les taux de gravité associés en privilégiant une longue période d’analyse (janvier 1970-décembre 2013) et une fréquence mensuelle. Ceci en tenant compte, au niveau du panel des variables exogènes testées, de la très forte pluri-dimensionnalité (motifs de déplacement, météorologie, structure du parc automobile et de la population, environnement économique, facteurs comportementaux, etc… ) intrinsèque à cette problématique. En rupture avec les modèles conventionnels du risque routier, les outils proposés par le modèle MIRR sont matérialisés, pour toutes les variables analysées, par des équations économétriques de long terme couplées à des équations de court terme autorisant ainsi deux visions complémentaires liées au risque routier. Ce, au profit d’une meilleure compréhension de cette problématique et d’une perception améliorée des enjeux à venir
Human and social challenges related to the road safety including the costs for the society, are so important that they require a diversity of complementary analysis tools in order to better understand the road risk problem. The issue of this thesis aimed precisely at offering new tools to assess, in the best possible way, this phenomenon and to ultimately guide and support government decision-making in this field. These tools have been developed by modelling successively the mileage driven which formalizes the risk exposure, the injury accidents, the fatalities, the injuries and the two associated severity rates, using a long period and a monthly frequency. This was made by taking into consideration the multidimensional aspect, regarding the tested exogenous variables (motives for movement, meteorology, structure of the vehicle fleet and of the population, economic environment, behavioural factors, etc..), intrinsic to this issue. Breaking with conventional road accident models, the tools proposed by the MIRR model use, for every analysed variable, long-term econometric equations coupled with short-term ones. These approaches thus allow two complementary views of the road risk for a better understanding of this issue as well as an improved perception of future challenges

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Targa, Alexandre. "Development of multi-physics and multi-scale Best Effort Modelling of pressurized water reactor under accidental situations." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLX032/document.

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L’analyse de sûreté des réacteurs nucléaires nécessite la modélisation fine des phénomènes y survenant et plus spécifiquement ceux permettant d’assurer l’intégrité des barrières de confinement. Les outils de modélisation et codes actuels favorisent une analyse fine du système réacteur par discipline dédiée, et couplée avec des modèles simplifiés. Néanmoins, le développement depuis plusieurs années d’une approche dite « Best Estimate », basée sur des calculs multiphysiques et multi-échelle, est en cours de réalisation. Cette approche permettra d’accéder au suivi et à l’analyse détaillée de problèmes complexes tels que l’étude des Réacteurs nucléaires en situation standard et accidentelle. Dans cette approche, les phénomènes physiques sont simulés aussi précisément que possible (selon la connaissance actuelle) par les modèles couplés. Par exemple, des codes disciplinaires existent et permettent la modélisation précise de la neutronique, de la thermohydraulique du cœur du réacteur ou de la thermohydraulique sur l'ensemble du système, de la thermomécanique du combustible ou des structures. Une approche « Best Estimate » consiste à coupler ces modèles afin de réaliser une modélisation globale et précise du système de réacteur nucléaire. Cette approche nécessite de bien définir les modèles qui sont utilisés afin de préciser exactement leurs limites, et donc préciser les incertitudes des résultats des modèles couplés afin de les assumer et de les optimiser.C’est dans ce contexte de travail que s’inscrit cette thèse. Elle consiste dans le développement d'un couplage multiphysique et multi-échelle « Best Estimate » afin d'obtenir une analyse précise des Réacteurs à Eau Légère en situations normale et accidentelle. Elle a consisté principalement en l’analyse des modèles et de leurs interactions et à la mise en œuvre d'un algorithme de couplage multiphysique entre une neutronique et une thermohydraulique exprimées à l'échelle du réacteur, ainsi qu’avec une thermomécanique fine à l'échelle élémentaire du crayon combustible. En outre, un travail spécifique a été effectué afin de préparer ou d'améliorer l’accés à l'information physique locale nécessaire à la mise en œuvre de modélisations couplées multi-échelles, à l'échelle du combustible
The safety analysis of nuclear power plants requires a deep understanding of underlying key physical phenomena that determine the integrity of the physical containment barriers. At the present time, cutting edge models focus on a single aspect (discipline) of the physical system coupled with rough models of the other aspects needed to simulate the global system. But, safety analyses can be carried out based on Multiphysics and Multiscales modelling. This Best Effort approach would give a full and accurate (High Fidelity) comprehension of the reactor core under standard and accidental situations. In this approach, the physical phenomena are simulated as accurately as possible (according to present knowledge) by coupled models in the most efficient way. For example, codes exists that are accurate modellings of Neutronics, or modellings of thermal fluid mechanics inside the core, or modellings of thermal fluid mechanics over the whole system, or modellings of thermal mechanics of the fuel pin or over the whole device structure. A Best Estimate approach would couple these models in order to realize a global and accurate modelling of the Nuclear reactor. This approach requires to define well the models that are used in order to exactly specify their limits, and hence, specify uncertainties of the coupled model results in order to assume and optimize them.It is in this context that this PhD thesis work is being under taken. It consists in the development of a Multi-physics and multi-scale Best Estimate modelling in order to obtain an accurate analysis of Pressurized Water Reactor under standard and accidental operating situations. It mainly involves the understanding of each model and their interactions, followed by the implementation of multiphysics algorithms coupling Neutronics and Thermohydraulics at reactor scale to an accurate Thermomechanics at the elementary scale of the fuel pin. In addition, a work project has been carried out in order to prepare or improve the access to the local physical informations that are needed for the implementation of multiscale coupling scheme, at the elementary scale of the fuel pin

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Le, Hong Duc. "Modelling of nanoparticles laden jet from a conveying pipe leakage." Phd thesis, Toulouse, INPT, 2018. http://oatao.univ-toulouse.fr/21454/1/LE_Hong_Duc.pdf.

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Since a few years, nanomaterials are more and more used in industrial process. In order to protect the population and the environment from the consequences of an accidental release into the atmosphere, the risk assessment allowed to identify the accidental scenario in transport, manipulation and storage of those products. The accidental leakage of the conveying pipe may lead to a massive release of nanoparticles. In order to evaluate the consequences of this type of accident, our study focuses on the prediction of particles properties dispersed into the air, for example the particle number concentration and the particle diameter distribution. The first step of the study consists in the analyse of physical phenomena related to nanoparticles in order to choose the most predominant physical phenomena to model. The relevant physical phenomena in the present configuration are the agglomerate complex shape, the drag force on agglomerates, the agglomerate breakage by gas, the agglomerate collision and the agglomeration. After that, the modelling of physical phenomena chosen is developed in CFD tool Code\_Saturne. For each physical phenomenon, a simulation test case is realized in order to verify the development in CFD tool. A good agreement between CFD tool Code\_Saturne and 0D tool from Scilab and model in the literature is obtained. Also in the present study, new model for the collision probability of agglomerates is proposed. This new model is validated with the numerical experiment. After that, the numerical tool developed is applied in a simulation of an accidental pipe leakage. The field near the leakage is simulated by Code\_Saturne. The results from Code\_Saturne is used as the input data for ADMS tool, a simulation tool for the particle dispersion in large scale. The results show that the particles are dispersed more than 1 km from the release source, which is in agreement with the distance observed. In perspective, the influences of different parameters as the wind field and the particle properties, on the agglomerate size and number distribution can be tested. An experiment of the microparticle jet is realized at INERIS in order to be able to assess the nanoparticle jet experiment in the laboratory scale.

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Dartnall, James Edward. "Examining the effect of daylight on road accidents and investigating a state space time series approach to modelling zero inflated count data." Thesis, University of Southampton, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438672.

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Miradji, Faoulat. "Quantum modelling of Ruthenium chemistry in the field of nuclear power plant safety." Thesis, Lille 1, 2016. http://www.theses.fr/2016LIL10192/document.

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Lors d’un Accident Grave (AG) survenant à un réacteur nucléaire à eau pressurisée, sous atmosphère fortement oxydante, des relâchements importants de ruthénium, depuis le combustible dégradé, sont attendus du fait de la formation d’oxydes gazeux. Les composés de Ru représentent un risque sanitaire lié aux isotopes 103Ru et 106Ru, radio-contaminants à court et moyen terme. En outre l’oxyde RuO4, volatil à température ambiante, est susceptible d’être relâché à l’environnement via les fuites de l’enceinte de confinement. L’évaluation de ce rejet à l’environnement présente des incertitudes importantes, liées entre autres aux données thermochimiques des composés de ruthénium gazeux avec des disparités entre les valeurs de la littérature pour les oxydes. Concernant les oxyhydroxydes, les données sont très parcellaires et celles disponibles sont sujettes à caution. Une première étape de ces travaux de thèse a consisté au développement d’une méthodologie de calcul pour obtenir les données thermochimiques des oxydes de ruthénium gazeux en fonction de la température, via des outils de chimie quantique, avec la fonctionnelle TPSSh-5%HF pour l’optimisation de géométrie, suivi de la méthode CCSD(T) pour le calcul des énergies électroniques. Cette méthodologie fut ensuite étendue aux oxyhydroxydes. Des calculs de spéciation chimique ont été effectués afin de prédire les espèces gazeuses les plus stables lors d’un AG. A l’aide des propriétés thermochimiques des espèces d’intérêts et des méthodologies développées, une étude cinétique a été conduite afin de déterminer les chemins réactionnels conduisant à la formation d’oxydes de Ru, espèces gazeuses les plus stables en conditions AG
During a severe accident (SA) occurring to a pressurized water reactor (PWR), fission products (FPs) are released from the nuclear fuel and may reach the nuclear containment building. Among the FPs, ruthenium (Ru) is of particular interest due to its ability to form volatile oxide compounds in highly oxidizing conditions combined with its high radiotoxicity (103Ru and 106Ru isotopes) at middle term after the accident. Uncertainties concerning evaluation releases of Ru are important and some R&D efforts are led to get a better understanding of ruthenium chemistry in such conditions. The thermodynamic database on ruthenium species used to estimate these releases shows some discrepancies for most ruthenium oxides and for other species such as oxyhydroxides, data are scarce and not reliable, calling for quantum chemical calculations. The most suitable approach corresponds to TPSSh-5%HF for geometry optimization, followed by CCSD(T) for the calculation of the total electronic energies. The energetics are combined with statistical physics to obtain the thermochemical properties of ruthenium oxides and ruthenium oxyhydroxide species as the latter may play an important role on the transport of ruthenium in the primary circuit due to high steam content. The revised thermodynamic database is then used to predict which species are most stable in representative severe accident conditions. Next, kinetic calculations are also performed to obtain pathways of formations for ruthenium trioxide and tetraoxide gaseous compounds, which are the most stable Ru volatile species in steam/air atmospheres

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Dissertations / Theses on the topic 'Accident modelling'

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