Evaluation of long-term countermeasures in mitigating consequences of environmental contamination following a nuclear accident

An airborne radioactive release from a reactor accident can result in contamination of vast areas. As a consequence of external radiation (groundshine) exposure, the health risk of the population living in the fallout area is increased. Furthermore consumption of agricultural food products produced in the contaminated area may bring about an extra health risk. The employment of long term mitigating measures - decontamination, relocation and food control - reduces chronic exposure but results also in economic losses. The mitigating actions depend on radiological dose criteria and economic consequences. In addition, social and political considerations may play an influential role when intervention levels are defined. National dose criteria should be based on international recommendations on intervention levels, taking into account, however, local conditions. In the event of a real accident, the decision to apply or withdraw a certain countermeasure is determined on a case by case basis at different decision making levels. Predictive analysis of the effectiveness of alternative countermeasures can be performed with the probabilistic consequence model employing hypothetical source terms. In the paper the intervention levels of international recommendations as well as other assumed dose criteria have been utilized for calculations of dose savings, economic losses from different mitigating measures, and cost effectiveness of food control. The reference nuclear power plant site is located in southern Finland. Site weather data and the pertinent population, agricultural production and working place statistics have been employed in the study.