The IUR Project on Soil-To-Plant Transfer Factors of Radionuclides Expected Values and Uncertainties

The large uncertainties which are associated with the values of the soil-to-plant transfer factors prompted the IUR (International Union of Radioecologists) some years ago to initiate a soil-to-plant transfer factor working group. This group is carrying out a joint project in which participate 20 research institutions. The aim of the project is to provide reliable estimates of the soil-to-plant transfer factors of different crops for different soils, environmental conditions, etc. Only data of experiments which met predefined criteria are included. Data of five years of experiments are now available.Expected values for transfer values have been derived statistically for a large number of combinations of different factors as radionuclides, crops and soils. The 95 percent confidence interval was derived for averaged estimates based on the observations present in the data set as well as the 95 percent confidence interval of single predicted values for specific combinations of factors. The latter confidence interval is much larger, due to the relatively limited number of data for many of the possible combinations of factors.