Dispersion and ground deposition of radioactive material according to airflow patterns for enhancing the preparedness to N/R emergencies

Role of modelling in monitoring soil and food during different stages of a nuclear emergency

In case of a nuclear accident, adequate protection of the public and the environment requires timely assessment of the short- and long-term radiological exposure. Measurements of the radiation dose and the radioactive contamination in the environment are essential for the optimization of radiation protection and the decision making process. In the early phase, however, such measurements are rarely available or sufficient.To compensate for the lack of monitoring data during nuclear emergencies, especially in the early phase of the emergency, mathematical models are frequently used to assess the temporal and spatial distribution of radioactive contamination. During the transition and recovery phase, models are typically used to optimise remediation strategies by assessing the cost-effectiveness of different countermeasures. A prerequisite of course is that these models are fit for purpose. Different models may be needed during different phases of the accident. In this paper, we discuss the role of radioecological models during a nuclear emergency, and give an outlook on the scientific challenges which need to be addressed to further improve our predictions of human and wildlife exposure.

Consequences of selecting different subsets of meteorological data to utilize in deterministic safety analysis

Atmospheric dispersion calculation of radiological releases can be done for different purposes such as deterministic or probabilistic safety analysis, environmental impact assessment, emergency preparedness and response. The characteristics of the weather conditions used in such assessments have a significant effect on the results, thus it is vital to select appropriate meteorological data for the calculation. In this paper, we conduct a study on deterministic safety analysis of radiological releases and investigate the effects of using different subsets of a meteorological database for such assessments. We demonstrate that conducting deterministic dose assessment with a large site specific dataset of meteorological measurements and the use of a dose percentile is more beneficial than using one set of meteorological parameters. This is because variations in the meteorological condition have considerable effect on the dose results when using one set of meteorological parameters (e.g. worst case scenario) and less when a large meteorological database is used. We show that there can be a significant difference in the maximum dose computed with a large (at least annual with hourly resolution) meteorological database when there is a lack of data points or conversion of the parameters is needed, thus the 100th dose percentile is not optimal for verification of safety criteria fulfillment. It is better to use a relatively high percentile (e.g. from 80th to 99th), partly because it behaves more robustly and also because the use of the maximum dose (100th percentile) would be overly conservative. In case of meteorological data not being available for a sufficient temporal domain (e.g. data available for only one year or less), a multiplication factor - determined based on conservative assumptions and extensive studies on the possible spread of meteorological conditions and their effect at a given location - can be used for the comparison of a selected dose percentile with the safety limit. A 5-years long meteorological database provided by a meteorological measurement system was used in this study as an example to demonstrate and calibrate the methodology on a real database. The methods presented in this work are universal, they can be used in deterministic safety analysis of other nuclear facilities, and the results can facilitate the development of optimal meteorological databases.

Key Points in Air Pollution Meteorology

Although emissions have a direct impact on air pollution, meteorological processes may influence inmission concentration, with the only way to control air pollution being through the rates emitted. This paper presents the close relationship between air pollution and meteorology following the scales of atmospheric motion. In macroscale, this review focuses on the synoptic pattern, since certain weather types are related to pollution episodes, with the determination of these weather types being the key point of these studies. The contrasting contribution of cold fronts is also presented, whilst mathematical models are seen to increase the analysis possibilities of pollution transport. In mesoscale, land-sea and mountain-valley breezes may reinforce certain pollution episodes, and recirculation processes are sometimes favoured by orographic features. The urban heat island is also considered, since the formation of mesovortices determines the entry of pollutants into the city. At the microscale, the influence of the boundary layer height and its evolution are evaluated; in particular, the contribution of the low-level jet to pollutant transport and dispersion. Local meteorological variables have a major influence on calculations with the Gaussian plume model, whilst some eddies are features exclusive to urban environments. Finally, the impact of air pollution on meteorology is briefly commented on.