Environmental Decrease of 137Cs-Activity Concentration in Milk in Central Europe After a Nuclear Fallout - A Comparison

Full text: 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 or a prohibition to consume local foodstuff. In that respect, the time 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 is relevant. Therefore, the decrease in activity concentration in milk and other foodstuffs is investigated in several central-European countries and compared to each other. The decrease of activity concentration in the most important foodstuff is very similar in all these countries indicating that this decrease by natural effects is a universal effect typical for agricultural soils. Typically, in the first three years an effective half-life for 137Cs of 1 y, in the following years one of 5 y is observed. Including the first-to-second year decrease this results in a rapid decrease by about three orders of magnitude within a decade after fallout. Implications to long-term counter measures are discussed. (author)