Beta radiation dose above a uranium-mine contaminated water disposal area

Between 1986 and 1992 some 90 and 2.4 GBq of U and 226Ra, respectively, were disposed of in 2.1 Mm3 of mine and mill runoff water by spray irrigation on the 34.8 ha of Ranger Uranium Mineʹs Land Application Area (LAA). The major proportion of these radionuclides have been fixed onto soil particles in a few centimeters of topsoil and in humic matter. Therefore, the most sensitive and express indicator of the LAAʹs surface contamination is β-radiation. The β-radiation monitoring methodology was proposed for use in monitoring trends in long-term behavior of spray irrigated radionuclides. Monitoring results of the in situ external β-radiation dose rate, the β-radiation attenuation, angular dependence and the assessed β-radiation dose equivalent rate above the LAAʹs surface are presented. The β-radiation dose equivalent rate in skin in contact with the surface of the LAA was measured in the range between 1 and 10 μSv h−1 and depends strongly on the distance from a sprinkler due to low surface homogeneity of water application and to variations in the surface cover by humic matter.