The purpose of the present study was to examine effects of driver, vehicle, and environment characteristics on Collision Warning System (CWS) design. One hypothesis was made that the capability of collision avoidance would not be same among a driver, vehicle, and environment group with different characteristics. Accident analysis and quantitative analysis was used to examine this hypothesis in terms of ‘risk’ and ‘safety margin’ respectively. Rear-end collision had a stronger focus in the present study. As a result of accident analysis, heavy truck showed a higher susceptibility of the fatal rear-end accidents than car and light truck. Also, dry road surface compared to wet or snow, dark condition compared to daylight condition, straight road compared to curved road, level road compared to grade, crest or sag, roadway having more than 5 travel lanes compared to roadway having 2, 3 or 4 travel lanes showed a higher susceptibility of the fatal rear-end accidents. Relative rear-end accidents involvement proportion compared to the other types of collision was used as a measure of susceptibility. As a result of quantitative analysis, a significant difference in terms of Required Minimum Warning Distance (RMWD) was made among a different vehicle type and braking system group. However, relatively small difference was made among a different age, gender group in terms of RMWD. Based on the result, breaking performance of vehicle should be regarded as an input variable in the design of CWS, specifically warning timing criteria, was concluded.

Dans le cadre des études visant à garantir l'intégrité de la gaine du crayon combustible, EDF est amené à caractériser la ductilité de la gaine après un Accident de Perte de Réfrigérant Primaire (APRP). La thèse porte sur la caractérisation du comportement à rupture des gaines en Zircaloy-4 détendu pour lesquels les conditions d'APRP ont été simulées en laboratoire par une oxydation à haute température suivie d'un refroidissement. L'oxydation est effectuée à 1100°C et à 1200°C pour différentes durées ce qui conduit à des niveaux d'oxydation de 3% à 30% d'ECR (Equivalent Cladding Reacted). Deux types de refroidissement sont mis en oeuvre : la trempe à l'eau et le refroidissement à l'air. Les gaines oxydées comportent deux couches fragiles, la couche de zircone externe ZrO2 et la couche α(O), et une couche présentant une ductilité résiduelle, la couche ex-β.Les gaines oxydées ont fait l'objet de caractérisations en microscope optique, par analyse à la microsonde et par nano-indentation. Une corrélation entre la teneur en oxygène et la nano-dureté et le module d'Young a été proposée.L'essai Expansion due à la Compression (EDC) a été développé avec une instrumentation par stéréo-corrélation d'images puis a été utilisé pour caractériser le comportement mécanique des gaines oxydées. Le comportement des gaines oxydées a été étudié à partir de l'analyse des courbes macroscopiques de l'essai EDC et à partir des observations des échantillons rompus ou pré-déformés.Un scénario de rupture des gaines oxydées a été proposé. Ce scénario a été validé d'une part par la réalisation d'essais sur gaines sablées ne comportant que la couche ex-β et d'autre part par la modélisation de l'essai par la méthode des éléments finis. Un critère de rupture des gaines oxydées a par ailleurs été établi. La modélisation du comportement et le critère de rupture proposés ont été validés par la modélisation des essais de compression d'anneau.

The purpose of this study is to find out if the Swedish Air Force and the military aviation industry, Saab Aerosystems, use an HTO perspective in incident investigations. The research objectives are to explore existing organizational and accident models, analyze the reporting system using the models, and suggest possible improvements to the existing incident investigation system. Fishman’s (1999) model for pragmatic studies was used to describe the study’s theoretical approach. Triangulation by literary review, case study and interviews were used to ensure validity and reliability. Three models were chosen: Rollenhagen’s HTO model (1997), Leveson’s STAMP (2002), and Shappell and Wiegmann’s HFACS (2000). The models were further tested in the case study, revealing that their usefulness depends on type of incident, and that they leave a lot up to the investigator. Interviews were conducted with key individuals at Saab Aerosystems as well as at the Swedish Armed Forces’ Headquarters. The interviews showed that the incident reporting system in question is a well functioning one, mainly due to the blame-free culture, multidisciplinary investigative teams, good feedback and a generally good knowledge of the HTO concept. Difficulties within the organizations exist due to organizational boundaries between the manufacturer and the operator, and recurring structural reorganizations within the Swedish Armed Forces. Saab acknowledges the emphasis on technical issues. The Flight Safety department at the headquarters is currently working with implementing HFACS into the Flight Safety Database. Our recommendations for Saab Aerosystems and the Air Force include: For Saab Aerosystems: Evaluate and learn from existing HTO work within the organization, and incorporate the results into existing processes and instructions for incident investigations. Make use of the theoretical models, where applicable, in the processes as well. Focus on HFACS in order to synchronize with the Air Force. Consider employing an HTO specialist. For the Air Force: Consider influences from other HTO models, like Rollenhagen’s or Leveson’s models, while still in the development phase of implementing HFACS. Perform risk analyses regarding the effects on flight safety when doing reorganizations. For both Saab Aerosystems and the Air Force we recommend: Use Leveson’s model STAMP for complex and serious incidents, comprising of organizational, human and technical aspects. / Denna studie har som syfte att ta reda på om det svenska Flygvapnet och den militära flygindustrin, Saab Aerosystems, använder ett MTO-perspektiv vid incidentutredningar. Forskningsmålen är att utforska befintliga organisations- och olycksmodeller, att analysera rapporteringssystemet med hjälp av modellerna, samt att föreslå möjliga förbättringar på det existerande incidentrapporterings- och utredningssystemet. Fishmans (1999) modell för pragmatiska studier användes som teoretisk utgångspunkt. För att säkerställa validitet och reliabilitet användes triangulering, bestående av litteraturstudie, fallstudie, samt intervjuer. Tre modeller valdes ut: Rollenhagens MTO-modell (1997), Levesons STAMP (2002) och Shappell och Wiegmanns HFACS (2000). Modellerna användes i fallstudien, med resultatet att modellernas användbarhet bedömdes variera beroende på typ av incident, samt att de lämnar mycket åt utredarens erfarenhet. Intervjuer genomfördes med nyckelpersoner på Saab Aerosystems och på Försvarsmaktens Högkvarter. Intervjuerna visade att rapporteringssystemet i fråga är väl fungerande, främst tack vare rapporteringskulturen, de multidisciplinära utredningsgrupperna, god återkoppling och en generellt sett god kännedom om MTO-konceptet. Organisatoriska svårigheter är dels gränsdragningen mellan tillverkare och användare, dels återkommande omstruktureringar inom Försvarsmakten. Saab medger också att deras fokus ligger främst på det tekniska. Flygsäkerhetsavdelningen på Högkvarteret arbetar med att införa HFACS i flyg­säker­hetsdatabasen. Våra rekommendationer till Saab Aerosystems och till Flygvapnet inkluderar: Till Saab Aerosystems: Utvärdera och drag lärdom av befintligt MTO-arbete inom organisationen, inkludera dessa resultat i befintliga processer och instruktioner för incidentutredningar. Utnyttja fler teoretiska modeller i processen, där så är lämpligt. Fokusera på HFACS för att synkronisera med Flygvapnet. Fundera på att anställa en MTO-specialist. Till Flygvapnet: Fundera på att också införa delar av andra MTO-modeller, som Rollenhagens eller Levesons modeller, under implementeringsfasen av HFACS. Genomför riskanalyser av påverkan på flygsäkerhet vid omorganisationer. Till både Saab Aerosystems och Flygvapnet rekommenderar vi: använd Levesons modell STAMP vid mer komplexa och allvarliga incidenter som innefattar organisatoriska, mänskliga och tekniska aspekter.

Traffic safety is an important problem in today&rsquo / s world with increasing number of fatalities and injuries in traffic accidents. For the solution of this problem, determination of accident prone locations on a network and reasons behind is an essential step, which is studied to some extend via different traffic accident analyses in the literature. While major factors affecting accident risk, such as speed, congestion, infrastructural aspects are known, it is still very difficult to figure out the interaction among these factors, due to complexity in the spatial and temporal distribution of the aforementioned factors and traffic network characteristics. While the case of accident analysis on highways is simpler, in case of urban roads, it requires more effort due to more complex traffic networks with quite a number of conflict points and varying flow characteristics. To investigate possible relationships between speed and accident occurrence on urban arterials, a Geographic Information Systems based accident analysis methodology (GIS-TAAM) is developed in this study. This methodology uses time-dependent average link speeds (calculated from GPS-based data) and accident history of links, and three safety measures in thematic accident maps: i) total number of accident, ii) a severity index based on number of fatality and injury accidents, and iii) an alternative severity index based on total number of fatalities and injuries. The implementation of the proposed methodology and its deliverables are discussed over a pilot study on in&ouml / n&uuml / Boulevard &ndash / EskiSehir Road, Ankara.

Die vorliegende Arbeit leistet einen Beitrag zur Identifizierung von Einflussgrößen und Fehlerursachen auf Verkehrsunfälle. Diese können als Grundlage für Hinweise für den Einsatz und die Gestaltung von Fahrerassistenzsystemen genutzt werden. Dafür wurden insgesamt 506 Unfälle umfassend (in depth) untersucht. Zur Analyse der Pre-Crash-Phase der Unfälle wurden die Ergebnisse einer psychologischen Befragung mit Angaben aus der polizeilichen Verkehrsunfallanzeige, Informationen zur Unfallstelle, medizinischen Berichten sowie Informationen aus der technischen Rekonstruktion integriert. Anschließend wurde eine Fehleranalyse unter Betrachtung der Teilsysteme Fahrer, Umwelt und Fahrzeug durchgeführt. Um den bestmöglichen Befragungszeitpunkt herauszufinden, wurden in einer Vorstudie jeweils 15 Interviews am Unfallort sowie telefonische Interviews ein bis 14 Tage bzw. 15 bis 90 Tage nach dem Unfall bezüglich der Anzahl ihrer Genauigkeits- und Glaubhaftigkeitsmerkmale, der Motivation zur Interviewteilnahme sowie möglicher Vergessenseffekte verglichen. Im Ergebnis konnten keine Nachteile nachträglicher telefonischer Befragungen im Vergleich zu Befragungen an der Unfallstelle gefunden werden. Zur Fehleranalyse wurde ein verkehrspsychologisches Fehlerklassifikationsschema auf der Basis der verhütungsbezogenen Klassifikation von Fehlhandlungsursachen (Hacker, 1998) erstellt. Mit dessen Hilfe wurden insgesamt 696 Unfalleinflussfaktoren für die Unfallverursacher (n=343) ermittelt. Im Ergebnis wurde so bei allen Unfalltypengruppen ein hoher Anteil von Fehlern infolge von Ablenkung sowie Aktivierungsmängeln festgestellt (jeweils zwischen 28 % und 47%). Des Weiteren gab es bei Kreuzungsunfällen zahlreiche Fehler infolge von Sichtverdeckungen (40%), Fokusfehlern (30%), Reizmaskierungen (26%) und Verstößen gen die Verkehrsregeln (11%). Unfälle durch Abkommen von der Fahrbahn traten zudem häufig infolge von Erwartungsfehlern (35%), Reizmaskierungen (26%), Verstößen gegen die Verkehrsregeln (24%) sowie Zielsetzungs- bzw. Handlungsfehler (23%) auf. Unfälle im Längsverkehr passierten des Weiteren durch Erwartungsfehler (36%), Zielsetzungs- und Handlungsfehler (36%) sowie durch Setzen eines falschen Aufmerksamkeitsfokus (24%) auf. Anhand dieser Studienergebnisse ist das Sicherheitspotential für Fahrerassistenzsysteme, welche den Fahrer bei der Informationsaufnahme unterstützen und ihm helfen Ablenkungen und Aktivierungsdefizite zu vermeiden, als hoch einzuschätzen. So könnten insgesamt über zwei Drittel der erfassten Fehlhandlungen vermieden werden. Darüber hinaus münden die Studienergebnisse in ein Klassifikationsschema zur Erfassung von Unfalleinflussfaktoren, welches im Rahmen der Unfallforschung dauerhaft eingesetzt werden sollte.

Considering the late in-vessel phase of an unlikely core melt down scenario in a light water reactor (LWR) with the formation of a corium pool in the lower head of the re-actor pressure vessel (RPV) the possible failure modes of the RPV and the time to failure have to be investigated to assess the possible loadings on the containment. In this work, an integral model was developed to describe the processes in the lower plenum of the RPV. Two principal model domains have to be distinguished: The temperature field within the melt and RPV is calculated with a thermodynamic model, while a mechanical model is used for the structural analysis of the vessel wall. In the introducing chapters a description is given of the considered accident scenario and the relevant analytical, experimental, and numerical investigations are discussed which were performed worldwide during the last three decades. Following, the occur-ring physical phenomena are analysed and the scaling differences are evaluated between the FOREVER-experiments and a prototypical scenario. The thermodynamic and the mechanical model can be coupled recursively to take into account the mutual influence. This approach not only allows to consider the tem-perature dependence of the material parameters and the thermally induced stress in the mechanical model, it also takes into account the response of the temperature field itself upon the changing vessel geometry. New approaches are applied in this work for the simulation of creep and damage. Using a creep data base, the application of single creep laws could be avoided which is especially advantageous if large temperature, stress, and strain ranges have to be covered. Based on experimental investigations, the creep data base has been de-veloped for an RPV-steel and has been validated against creep tests with different scalings and geometries. It can be stated, that the coupled model is able to exactly describe and predict the vessel deformation in the scaled integral FOREVER-tests. There are uncertainties concerning the time to failure which are related to inexactly known material parame-ters and boundary conditions. The main results of this work can be summarised as follows: Due to the thermody-namic behaviour of the large melt pool with internal heat sources, the upper third of the lower RPV head is exposed to the highest thermo-mechanical loads. This region is called hot focus. Contrary to that, the pole part of the lower head has a higher strength and therefore relocates almost vertically downwards under the combined thermal, weight and internal pressure load of the RPV. On the one hand, it will be possible by external flooding to retain the corium within the RPV even at increased pressures and even in reactors with high power (as e.g. KONVOI). On the other hand, there is no chance for melt retention in the considered scenario if neither internal nor external flooding of the RPV can be achieved. Two patents have been derived from the gained insights. Both are related to pas-sively working devices for accident mitigation: The first one is a support of the RPV lower head pole part. It reduces the maximum mechanical load in the highly stressed area of the hot focus. In this way, it can prevent failure or at least extend the time to failure of the vessel. The second device implements a passive accident mitigation measure by making use of the downward movement of the lower head. Through this, a valve or a flap can be opened to flood the reactor pit with water from a storage res-ervoir located at a higher position in the reactor building. With regard to future plant designs it can be stated - differing from former presump-tions - that an In-Vessel-Retention (IVR) of a molten core is possible within the reac-tor pressure vessel even for reactors with higher power.

Es wurde ein Modell zur realistischen Beschreibung der Kühlmittelvermischung innerhalb des Reaktordruckbehälters von Druckwasserreaktoren in den gekoppelten Programmkomplex DYN3D/ATHLET implementiert. Diese Modell basiert auf dem Prinzip der linearen Superposition Dirac-Impuls-ähnlicher Störungen und kann für die Modellierung der Vermischung von Kühlmittel unterschiedlicher Temperatur und/oder unterschiedlicher Borsäurekonzentration eingesetzt werden. Der um das Vermischungsmodell erweiterte Programmkomplex DYN3D/ATHLET wurde für Analyse von Borverdünnungsstörfällen und Frischdampflecks angewandt. Für den Fall "Start der ersten Hauptkühlmittelpumpe bei Vorhandensein eines minderborierten Pfropfens im kalten Strang" zeigten die Ergebnisse der durchgeführten Parameterstudie, dass es selbst bei Annahme des maximal möglichen Pfropfenvolumens nicht zu einer Schädigung des Brennstoffes kommt. Mit den Analysen zu einem generischen Frischdampfleckszenario wurde die Anwendbarkeit des Programmkomplexes DYN3D/ATHLET auf die zweite Störfallklasse, in der die Kühlmittelvermischung eine wichtige Rollen spielt, demonstriert. Im Rahmen der Arbeiten zum Projekt wurde außerdem gezeigt, dass der Einfluss der turbulenten Schwankungen des Geschwindigkeitsfeldes innerhalb des Reaktordruckbehälters auf neutronenkinetische Parameter im Nominalbetrieb und unter Störfallbedingungen nicht zu vernachlässigen ist. A model for the realistic description of the coolant mixing inside the pressure vessel of pressurized water reactors was implemented into the coupled code complex DYN3D/ATHLET. This model is based on the linear superposition Dirac-pulse-like perturbations. The model can be applied to the mixing of coolant of different temperature and/or boron concentration. The coupled code complex DYN3D/ATHLET with the newly implemented model was applied to the analysis of boron dilution and steam line break accidents. The results of a parameter study for the case "Start-up of the first main coolant pump with a slug of lower borated water in the cold leg" have shown, that even under the conditions of the maximum slug volume there is no fuel damage. The applicability to the second class of accidents, where the coolant mixing has to be considered, was demonstrated by the analysis of a generic main steam line break scenario. Further it was shown, that the influence of turbulent fluctuations of the velocity inside the reactor pressure vessel during nominal and accident conditions on neutron-kinetic parameters cannot be neglected.

Benchmark calculations for the validation of the coupled neutron kinetics/thermohydraulic code complex DYN3D-ATHLET are described. Two benchmark problems concerning hypothetical accident scenarios with leaks in the steam system for a VVER-440 type reactor and the TMI-1 PWR have been solved. The first benchmark task has been defined by FZR in the frame of the international association "Atomic Energy Research" (AER), the second exercise has been organised under the auspices of the OECD. While in the first benchmark the break of the main steam collector in the sub-critical hot zero power state of the reactor was considered, the break of one of the two main steam lines at full reactor power was assumed in the OECD benchmark. Therefore, in this exercise the mixing of the coolant from the intact and the defect loops had to be considered, while in the AER benchmark the steam collector break causes a homogeneous overcooling of the primary circuit. In the AER benchmark, each participant had to use its own macroscopic cross section libraries. In the OECD benchmark, the cross sections were given in the benchmark definition. The main task of both benchmark problems was to analyse the re-criticality of the scrammed reactor due to the overcooling. For both benchmark problems, a good agreement of the DYN3D-ATHLET solution with the results of other codes was achieved. Differences in the time of re-criticality and the height of the power peak between various solutions of the AER benchmark can be explained by the use of different cross section data. Significant differences in the thermohydraulic parameters (coolant temperature, pressure) occurred only at the late stage of the transient during the emergency injection of highly borated water. In the OECD benchmark, a broader scattering of the thermohydraulic results can be observed, while a good agreement between the various 3D reactor core calculations with given thermohydraulic boundary conditions was achieved. Reasons for the differences in the thermohydraulics were assumed in the difficult modelling of the vertical once-through steam generator with steam superheating. Sensitivity analyses which considered the influence of the nodalisation and the impact of the coolant mixing model were performed for the DYN3D-ATHLET solution of the OECD benchmark. The solution of the benchmarks essentially contributed to the qualification of the code complex DYN3D-ATHLET as an advanced tool for the accident analysis for both VVER type reactors and Western PWRs.

<p>The purpose of the present study was to examine effects of driver, vehicle, and environment characteristics on Collision Warning System (CWS) design. One hypothesis was made that the capability of collision avoidance would not be same among a driver, vehicle, and environment group with different characteristics. Accident analysis and quantitative analysis was used to examine this hypothesis in terms of ‘risk’ and ‘safety margin’ respectively. Rear-end collision had a stronger focus in the present study. </p><p>As a result of accident analysis, heavy truck showed a higher susceptibility of the fatal rear-end accidents than car and light truck. Also, dry road surface compared to wet or snow, dark condition compared to daylight condition, straight road compared to curved road, level road compared to grade, crest or sag, roadway having more than 5 travel lanes compared to roadway having 2, 3 or 4 travel lanes showed a higher susceptibility of the fatal rear-end accidents. Relative rear-end accidents involvement proportion compared to the other types of collision was used as a measure of susceptibility. </p><p>As a result of quantitative analysis, a significant difference in terms of Required Minimum Warning Distance (RMWD) was made among a different vehicle type and braking system group. However, relatively small difference was made among a different age, gender group in terms of RMWD. Based on the result, breaking performance of vehicle should be regarded as an input variable in the design of CWS, specifically warning timing criteria, was concluded.</p>

Abstract Background An analysis of Accident Compensation Corporation claims shows “inconsistent and inadequate diagnoses” by health care providers. Diagnostic performance is a result of two independent parameters, namely discrimination (accuracy) and decision (bias). Bias is related to the medical practitioner’s perception of the costs and benefits of making one choice over another. Bias may be statistical, sociological, political, biological or psychological in nature. This study investigated the factors that potentially bias diagnostic decision-making by general practitioners and the subjective value placed on these factors by different stakeholder groups in society. Methods Phase 1 of the study used focus groups of standard setters for general practitioners to identify factors that influenced diagnostic decision-making in general practice. These factors were evaluated for importance and desirability using standard Delphi methodology and Rasch analysis. Phase 2 of the study evaluated the importance and desirability of the factors identified in Phase 1 for influencing decision making as judged by significant health care stakeholder groups in New Zealand. Participant response was via questionnaire analysed by the Rasch Model. Results Thirty-nine factors were identified that potentially biased diagnostic decision-making in general practice. The measurements of, particularly, desirability have high reproducibility across stakeholder groups and high positive loading for the first principal component consistent with construct validity. No stakeholder group identifies factors consistent with Bayes’ theorem of diagnostic reasoning as being the only desirable influence on diagnosis. There is considerable categorical homogeneity between the stakeholder groups GP, GPACC, P, RACCSLT and RACCSST. Conclusions The findings of this and other studies challenge the current biomedical paradigm, indicating a less than Bayesian approach to medical decision-making. A social constructivist model, incorporating non-Bayesian factors into the definition of “illness” versus “disease”, may be more representative of reality. A social constructivist model of medicine is incompatible with the current legislatory and administrative framework within which the Accident Compensation Corporation and a number of other medical organisations operate. / Accident Compensation Corporation of New Zealand