Assessment of doses from ingestion of contaminated agricultural products due to radioactive deposition

The releases of radioactive materials to the atmosphere can result in radiation exposure via several exposure pathways. The most important of those are external radiation from the radioactive cloud and from the contaminated ground, exposure to inhaled radionuclides and internal exposure to ingested contaminated food products. In the Nuclear Engineering Laboratory of the Technical Research Centre of Finland the code ARANO (Assessment of Risks of Accidents and Normal Operation) was developed to estimate radiation doses from radioactive releases and health effects to people and also economic losses due to radioactive contamination. The nutrition dose model AGRID, which is used to calculate internal dose from ingestion of contaminated food, is introduced in this report. The developed nutrition model is based on the English FOOD-MARC model, which is aimed for the same kind of assessment. However, the AGRID model includes some entirely new features. The dependence of the nutrition dose on the season, when the release has occurred, is the most important of these new features, especially applied to the Nordic countries. The five pathways, used to represent the transfer of radioactive material to man in the AGRID model, are: green vegetables, grain products, root vegetables, milk and meat from cattle. The weighted effective dose and also the thyroid dose from milk consumption can be obtained. The significance of radiation doses from the consumption of food stuffs in total dose due to the radioactive release has been studied with some examples. Generally, nutrition pathway proved out to be an important one. Especially concerning less severe releases, which will not result in any countermeasures, the dose via ingestion can be even 75 % of the total collective dose received during a few decades. As a result of severe accidents the collective nutrition dose would be reduced by ordering countermeasures for consumption of contaminated food products from cultivations. These countermeasures will, however, cause considerable economic losses.