In recent years, traffic accidents have been the ninth cause of fatalities in the world and the second in Iran (after heart diseases). Many individuals suffer financially from traffic accidents or lose their lives every year. Traffic accident analysis, as a powerful tool, can give valuable data regarding the cause of accidents and appropriate solutions. Such analysis would be possible at two levels; the "project" and the "network". In this paper, the analysis has been carried out at "network" (provinces) level to achieve a proper approach to increase the macro management abilities for the presentation of classified approaches appropriate to the conditions of each district. Because every province is unique, regarding driver behavior, infrastructure conditions, precautionary measures before and relief measures after an accident, classification of similar provinces for the purpose prioritization of safety measures and necessary decision making to reduce the number of fatalities in accidents deems necessary. Also, group study of similar condition provinces helps decision makers to provide similar measures for the solution of safety problems. "Cluster Analysis" is a method used for the purpose of classification. In this study, cluster analysis, using six methods, has been carried out for all provinces, on the basis of accidents data in 2004, obtained from Legal Medicine Organization (LMO). Necessary variables required for the cluster analysis, were obtained through the study of accidents data epidemiology and contain eight major groups called number of fatalities, gender, age, education, occupation, place of death, user situation and final death cause (totally 64 variables). The analysis was done in 4 clusters and the results were validated with help of "Chernoff Faces Method". The results obtained reveal that some provinces maybe classified under one group, but some other provinces, like Isfahan, need special studies.

Cities are constantly exposed to new hazards and hazards due to their constant changes and dynamics, which require appropriate methods and patterns to deal with and manage these disasters. In fact, cities need to reach a resilient level in their various dimensions and it is very necessary to examine them in the institutional dimension. The purpose of this article is to investigate the institutional resilience in the management of urban accidents in the country. The type of paper is descriptive-analytical and it is applied in terms of purpose. In this study, dematel technique was used for analysis. The results show that among the components, the most influential and performance indicators are the most effective indicators. On the other hand, among the indicators of infrastructure, the status of infrastructure in urban disaster management and improvement of the most effective index and standard zoning and construction of the most effective index, among the indicators of relationships, continuity and sustainability index of operational plans except the most effective and the level of coordination of institutions is the most effective and finally. Among the performance indicators, the extent to which organizations and institutions address the needs of citizens at the time of urban disasters are the most influential and finally the success rate of the performance of organizations in the urban disasters are the most influential indicators.

Tehran Research Reactor (T.R.R.) is a pool-type, 5 MW thermal research reactor. One probable event is that if some external objects or debris fall down into the reactor core and cause obstruction of the coolant flow through one of the fuel assemblies, decreasing the surface flow area, ceases the coolant flow, and also raises the fuel and sheaths temperature. Thermal hydraulic analysis of this event has been studied using RELAP5 system code. This report is related to the partial and total obstruction of a single Fuel Element (F.E.) and cooling channel of 27 F.E. equilibrium core of the T.R.R. Such event may lead to severe accident for such type of research reactors, since it may cause a local dry out and eventually loss of the F.E. integrity. Two scenarios are analysed in order to emphasize the severity of the mentioned accident. The first is a partial blockage of hot F.E. which is considered for four different obstruction levels of the nominal flow area: 25%, 50%, 75% and 93%. The second is related to an extreme case which consists of the total blockage of the same F.E. The reactor power is derived through the kinetic point calculation in the RELAP5 code. The point kinetic feedbacks including the fuel temperature (Doppler coefficient) and the coolant density coefficient have been considered through the applied model. The main results obtained from the RELAP5 calculations are as follows: 1. In case when the flow blockage is under 93% of the nominal flow area of an average F.E., only the increase of the coolant and clad temperatures are observed with no integrity of the F.E. consequences. The mass flow rate remains sufficient enough and cools the clad safely 2. In the case of a total obstruction in the nominal flow area, it is seen that the severe accident is due to dryout conditions and reaches promptly, while melting of the cladding occurs.