<p>As one of the highest fatalities causes, traffic accidents and collisions always requires a large amounteffort to be reduced or prevented from occur. Traffic safety management routines therefore always needefficient and effective implementation due to the variations of traffic, especially from trafficengineering point of view apart from driver education.Traffic Accident Prediction Model, considered as one of the handy tool of traffic safety management,has become of well followed with interested. Although it is believed that traffic accidents are mostlycaused by human factors, these accident prediction models would help from traffic engineering point ofview to enlarge the traffic safety level of road segments. This thesis is aiming for providing a guidelineof the accident prediction model implementation in traffic safety management, regarding to trafficengineering field. Discussion about how this prediction models should merge into the existing routinesand how well these models would perform would be given. As well, cost benefit analysis of theimplementation would be at the end of this thesis. Meanwhile, a practical field study would bepresented in order to show the procedures of the implementation of traffic accident prediction model.The field study is about this commercial model set SafeNET, from TRL Limited UK, implemented inRoad Safety Audit procedures combined with microscopic simulation tool. Detailed processing andinput and output data will be given accompany with the countermeasures for accident frequencyreduction finalization.</p>

As one of the highest fatalities causes, traffic accidents and collisions always requires a large amounteffort to be reduced or prevented from occur. Traffic safety management routines therefore always needefficient and effective implementation due to the variations of traffic, especially from trafficengineering point of view apart from driver education.Traffic Accident Prediction Model, considered as one of the handy tool of traffic safety management,has become of well followed with interested. Although it is believed that traffic accidents are mostlycaused by human factors, these accident prediction models would help from traffic engineering point ofview to enlarge the traffic safety level of road segments. This thesis is aiming for providing a guidelineof the accident prediction model implementation in traffic safety management, regarding to trafficengineering field. Discussion about how this prediction models should merge into the existing routinesand how well these models would perform would be given. As well, cost benefit analysis of theimplementation would be at the end of this thesis. Meanwhile, a practical field study would bepresented in order to show the procedures of the implementation of traffic accident prediction model.The field study is about this commercial model set SafeNET, from TRL Limited UK, implemented inRoad Safety Audit procedures combined with microscopic simulation tool. Detailed processing andinput and output data will be given accompany with the countermeasures for accident frequencyreduction finalization.

Innerhalb des Vorhabens wurde ein ATHLET-CD-Eingabedatensatz für einen generischen deutschen DWR vom Typ KONVOI entwickelt. Das ATHLET-CD-Modell wurde für die Simulation schwerer Störfälle aus den Störfallkategorien Station Blackout (SBO) und Kühlmittelverluststörfällen mit kleinen Lecks (SBLOCA) eingesetzt. Dabei ist die vollständige Störfalltransiente für den Zeitbereich zwischen dem einleitenden Ereignis bis zum Versagen des Reaktordruckbehälters (RDB) abgedeckt und alle wesentli-chen Phänomene schwerer Störfällen werden abgebildet: Beginn der Kernaufheizung, Spaltproduktfrei-setzung, Aufschmelzen von Brennstoff- und Absorbermaterialien, Oxidationsprozesse mit Freisetzung von Wasserstoff, Verlagerung von geschmolzenem Material, Verlagerung in das untere Plenum, Schä-digung und Versagen des RDB. Das Modell wurde für die Analyse möglicher präventiver und mitigativer Notfallmaßnahmen für SBO und SBLOCA angewandt. Dafür wurden die Notfallmaßnahmen primärseitige Druckentlastung (PDE), primärseitiges Einspeisen mit mobilen Pumpensystemen sowie für SBLOCA das verzögerte Einspeisen der kaltseitigen Druckspeicher untersucht und die Eigenschaften und Einleitekriterien der Maßnahmen variiert. Es wurden die Zeitverläufe der Unfallszenarien analysiert und die verbleibenden Zeitspannen für die Einleitung zusätzlicher Maßnahmen ermittelt. Für ein SBO-Szenario mit PDE wurde für die Frühphase der Transiente (bis zum Beginn der Kernschmelze) eine Unsicherheits- und Sensititvitätsanalyse durchgeführt. Zusätzlich wurde für ein SBLOCA-Szenario ein Code-zu-Code-Vergleich zwischen ATHLET-CD und dem Störfallcode MELCOR erarbeitet.

Innerhalb des Vorhabens wurde ein ATHLET-CD-Eingabedatensatz für einen generischen deutschen DWR vom Typ KONVOI entwickelt. Das ATHLET-CD-Modell wurde für die Simulation schwerer Störfälle aus den Störfallkategorien Station Blackout (SBO) und Kühlmittelverluststörfällen mit kleinen Lecks (SBLOCA) eingesetzt. Dabei ist die vollständige Störfalltransiente für den Zeitbereich zwischen dem einleitenden Ereignis bis zum Versagen des Reaktordruckbehälters (RDB) abgedeckt und alle wesentli-chen Phänomene schwerer Störfällen werden abgebildet: Beginn der Kernaufheizung, Spaltproduktfrei-setzung, Aufschmelzen von Brennstoff- und Absorbermaterialien, Oxidationsprozesse mit Freisetzung von Wasserstoff, Verlagerung von geschmolzenem Material, Verlagerung in das untere Plenum, Schä-digung und Versagen des RDB. Das Modell wurde für die Analyse möglicher präventiver und mitigativer Notfallmaßnahmen für SBO und SBLOCA angewandt. Dafür wurden die Notfallmaßnahmen primärseitige Druckentlastung (PDE), primärseitiges Einspeisen mit mobilen Pumpensystemen sowie für SBLOCA das verzögerte Einspeisen der kaltseitigen Druckspeicher untersucht und die Eigenschaften und Einleitekriterien der Maßnahmen variiert. Es wurden die Zeitverläufe der Unfallszenarien analysiert und die verbleibenden Zeitspannen für die Einleitung zusätzlicher Maßnahmen ermittelt. Für ein SBO-Szenario mit PDE wurde für die Frühphase der Transiente (bis zum Beginn der Kernschmelze) eine Unsicherheits- und Sensititvitätsanalyse durchgeführt. Zusätzlich wurde für ein SBLOCA-Szenario ein Code-zu-Code-Vergleich zwischen ATHLET-CD und dem Störfallcode MELCOR erarbeitet.

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.

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2016-06-22T14:12:07Z No. of bitstreams: 0 / Made available in DSpace on 2016-06-22T14:12:07Z (GMT). No. of bitstreams: 0 / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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.

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2016-06-22T14:12:07Z No. of bitstreams: 0 / Made available in DSpace on 2016-06-22T14:12:07Z (GMT). No. of bitstreams: 0 / Após os acidentes nucleares ocorridos no mundo, critérios e requisitos extremamente rígidos para a operação das instalações nucleares foram determinados pelos órgãos internacionais que regulam essas instalações. A partir da ocorrência destes eventos, as operadoras de plantas nucleares necessitam simular alguns acidentes e transientes, por meio de programas computacionais específicos, para obter a licença de operação de uma planta nuclear. Com base neste cenário, algumas ferramentas computacionais sofisticadas têm sido utilizadas como o Reactor Excursion and Leak Analysis Program (RELAP5), que é o código mais utilizado para a análise de acidentes e transientes termo-hidráulicos em reatores nucleares no Brasil e no mundo. Uma das maiores dificuldades na simulação usando o código RELAP5 é a quantidade de informações geométricas da planta necessárias para a análise de acidentes e transientes termo-hidráulicos. Para a preparação de seus dados de entrada é necessário um grande número de operações matemáticas para calcular a geometria dos componentes. Assim, a fim de realizar estes cálculos e preparar dados de entrada para o RELAP5, um pré-processador matemático amigável foi desenvolvido, neste trabalho. O Visual Basic for Applications (VBA), combinado com o Microsoft Excel, foi utilizado e demonstrou ser um instrumento eficiente para executar uma série de tarefas no desenvolvimento desse pré-processador. A fim de atender as necessidades dos usuários do RELAP5, foi desenvolvido o Programa de Cálculo do RELAP5 PCRELAP5 onde foram codificados todos os componentes que constituem o código, neste caso, todos os cartões de entrada inclusive os opcionais de cada um deles foram programados. Adicionalmente, uma versão em inglês foi criada para PCRELAP5. Também um design amigável do PCRELAP5 foi desenvolvido com a finalidade de minimizar o tempo de preparação dos dados de entrada e diminuir os erros cometidos pelos usuários do código RELAP5. Nesse trabalho, a versão final desse pré-processador foi aplicada com sucesso para o Sistema de Injeção de Emergência (SIE) da usina Angra 2. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP