Investigation of the importance of site-specific fauna in environmental risk assessment for routine atmospheric radionuclidesreleases

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UDINEE: Evaluation of multiple models with data from the JU2003 puff releases in Oklahoma City. Part II: Simulation of puff parameters

The capabilities of nine atmospheric dispersion models (ADMs) in predicting near-field dispersion from puff releases in an urban environment have been addressed under the Urban Dispersion INternational Evaluation Exercise (UDINEE) project. The models’ results have been evaluated using tracer observations from the Joint Urban 2003 (JU2003) experiment where neutrally buoyant puffs were released in the downtown of Oklahoma City. Sulphur hexafluoride (SF6) concentration time series measured at ten sampling locations during four daytime and four nighttime puff releases were used in this paper to evaluate how the models simulate the puff passage at the measurement locations. The neutrally buoyant puff releases in JU2003 are the closest scenario to Radiological Dispersal Device (RDD) releases in urban areas, and therefore, UDINEE is a first step towards the better emergency response to an RDD event in urban environments. We have investigated for each puff and sampler the models’ capability of simulating the peak concentration; the peak and puff arrival times; and time duration, defined as the time period over which concentrations exceeds the 10 % of the peak concentration. As expected, due to the highly transient nature associated with puff releases, this quantitative comparison has pointed out differences among the individual model performances on simulating the puff dispersion. The results have also shown that the characteristics of the release site can impact the modelling of the initial puff size and the initial along downwind spread of the puff.JRC.G.10-Knowledge for Nuclear Security and Safet

UDINEE: Evaluation of multiple models with data from the JU2003 puff releases in Oklahoma City. Part I: Comparison of observed and predicted concentrations

In a complex environment, such as an urban area, accurate predictions of the atmospheric dispersion of airborne harmful materials, like radioactive substances, are necessary for establishing response actions and assessing risk or damage. Given the variety of urban atmospheric dispersion models (ADMs) available, evaluation and inter-comparison exercises are vital to assess quantitatively and qualitatively their capabilities and differences. To that end, the European Commission/Directorate General Joint Research Centre (EC/DG JRC) in support to EC/DG-Migration and Home Affairs (HOME), and with the contribution of the U.S. Defense Threat Reduction Agency (U.S DTRA), launched the Urban Dispersion INternational Evaluation Exercise (UDINEE) project. Within UDINEE, nine ADMs have been evaluated and inter-compared. Sulphur hexafluoride (SF6) concentrations from puff released near the ground during the Joint Urban 2003 (JU2003) field experiment are used in UDINEE to evaluate ADMs. JU2003 was chosen because UDINEE aims at better understanding of modelling capabilities for Radiological Dispersal Device (RDD) in urban areas, and the neutrally buoyant puff releases performed in JU2003 are the closest scenario to this purpose. The simulation of the dispersion of puffs is particularly challenging. The results of UDINEE could therefore constitute a benchmark against which future model developments could be compared. The present study evaluates the models’ capability to simulate the presence and concentration levels of the tracer at sampling locations. The simulation of the time-integrated concentrations for each puff and sampler is also evaluated, as it is representative of a dose estimate, which is among the most important impact parameters for population protection.JRC.G.10-Knowledge for Nuclear Security and Safet