The characterization and removal of Chernobyl debris in garden soils

Severe nuclear accidents such as the one in Chernobyl in 1986 may give unacceptably high external radiation levels, which even in the late phase may make a resettlement of an evacuated population impossible unless action is taken to decrease the exposure. As the urban land areas to be reclaimed may be very large the cost of the dose reducing countermeasure to be used may be an important factor. In the Chernobyl debris the most important radionuclides concerning the long term external radiation were found to be Cs137, Cs-134, and Ru-106. Therefore, the aim of this work is to investigate the behaviour of these radionuclides in garden soils, and on this background to examine cost-effective methods by which a reduction of the dose from such areas to people living in urban or sub-urban environments can be achieved. The fixation of the radioactive cations in soil was investigated by means of soil profile sampling, soil texture analysis, and speciation experiments. It was found that most of the Chernobyl fallout caesium was extremely firmly fixed. Much of the ruthenium was more loosely bound, to organic material. The cost-effectiveness of some dose reducing countermeasures was examined on the background of small scale tests. Here it was found that about 95 % of the activity could be removed with peel able fixatives based on PVA or lignin.