Environmental Restoration by Natural Effects - Advantages and Limits

After a major contamination of a territory due to fallout from a reactor accident, a reprocessing plant accident or a weapon's detonation one of the important questions to be addressed is the period required for the countermeasures to be applied. This-is particularly important for countermeasures with high costs and consequences to the involved population such as relocation. Therefore, the period required for a contamination with long-lived fission products to decrease below established intervention levels by natural processes of decay and removal from the soil layer relevant to the exposure is investigated. Natural processes which result in a decrease in activity concentrations in foodstuffs and external exposure, are the least detrimental to a territory as compared to other long-term countermeasures and therefore, the most favorable in that respect. The influence of the contribution of different foodstuffs on the time-span required until a resettlement of a dislocated population is feasible, is assessed and the advantages and limits of natural restoration effects on the required intervention periods are discussed. It is shown that natural restoration effects may contribute substantially to an environmentally safe and sustainable resettlement of an area substantially contaminated with fission products.