ATMOSPHERIC DISPERSION OF RADIOACTIVE DEBRIS RELEASED IN CASE OF NUCLEAR EXPLOSION USING THE NORWEGIAN SNAP MODEL

Severe Nuclear Accident Program (SNAP) has been developed at the Norwegian Meteorological Institute (met.no) for modelling dispersion of radioactive debris in case of nuclear accidents. The model has been tested based on the data available from the Chernobyl accident as well as from the ETEX experiments. The main user of model results is the Norwegian Radiation Protection Authority (NRPA) which is responsible for calculating doses in case of a real accident. The model is fully operational for NRPA as well as for met.no. Following a request from NRPA, the SNAP model was modified in such a way that not only dispersion from nuclear accidents can be simulated, but dispersion from nuclear explosions as well. The source term for the model run in case of nuclear explosion has been developed based on cooperation among Scandinavian countries. The source term includes mainly particles of different size and density, which are subject to dry and wet deposition during atmospheric transport. Description of the model and examples of the simulations related to hypothetical nuclear explosions are presented and discussed

Using a chain of models to predict health and environmental impacts in Norway from a hypothetical nuclear accident at the Sellafield site

Embargo until 23 January 2022When a nuclear accident occurs, decision makers in the affected country/countries would need to act promptly to protect people, the environment and societal interests from harmful impacts of radioactive fallout. The decisions are usually based on a combination of model prognoses, measurements, and expert judgements within in an emergency decision support system (DSS). Large scale nuclear accidents would need predictive models for the atmospheric, terrestrial, freshwater, and marine ecosystems, for the connections between these in terms of radionuclide fluxes, and for the various exposure pathways to both humans and biota. Our study showed that eight different models and DSS modules could be linked to assess the total human and environmental consequences in Norway from a hypothetical nuclear accident, here chosen to be the Sellafield nuclear reprocessing plant. Activity concentrations and dose rates from 137Cs for both humans and the environment via various exposure routes were successfully modelled. The study showed that a release of 1% of the total inventory of 137Cs in the Highly Active Liquor Tanks at Sellafield Ltd is predicted to severely impact humans and the environment in Norway if strong winds are blowing towards the country at the time of an accidental atmospheric release. Furthermore, since the models did not have built-in uncertainty ranges when this Sellafield study was performed, investigations were conducted to identify the key factors contributing to uncertainty in various models and prioritise the ones to focus on in future research.acceptedVersio

Modellering av vulkanaske i norsk luftrom. Pkt. 2.3.1 Sammenligning av modeller for askeberegninger for bedre å forstå usikkerheter.

De tre transportmodellene EEMEP, SNAP og FLEXPART har simulert askespredning og avsetning fra Eyjafjalljökull utbruddet i 2010. Alle modellene har blitt kjørt med identisk kildeledd, og modellresultatene har blitt sammenlignet i detalj opp mot hverandre og opp mot observasjoner. Dette gir en økt forståelse av modellenes evne til å simulere askespredning, og av ulikhetene mellom modellresultater som ofte oppstår, spesielt under en askesituasjon i nær sanntid