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3.12.2 Soil shielding

The most common mistake made during the interpretation of radiological survey data is to assume that if the survey does not highlight any areas of elevated radioactivity, the site is ‘clean’. However, the shielding afforded by the soil can significantly attenuate all types of radioactivity, including gamma activity. The ability to detect buried radioactivity will depend on the type of detector used, the type and specific activity of the buried material, the depth of burial and the quantity of the buried material. In many circumstances, gamma-emitting radionuclides buried at greater than a few tens of centimetres below ground surface cannot be detected at surface.