6.6. Special attention should be paid to the establishment of a baseline for disposal facilities for waste from mining and mineral processing. Such facilities are developed for the disposal of radionuclides naturally occurring in the surroundings, such as radionuclides from the uranium and thorium decay chains. Measurements made later in the lifetime of the facility should therefore be compared with the baseline, in order to determine changes in concentrations of such radionuclides in environmental media. By contrast, the surroundings of facilities for the disposal of either LLW and ILW or HLW and spent nuclear fuel contain characteristic radionuclides that are more easily distinguished from background levels of radiation. For example, it is noted in Ref. [9] that 3H, 137Cs and 14C are likely to be present at detectable levels in the surroundings of near surface disposal facilities. Given their low background levels, incremental increases in amounts of these radionuclides may be more easily detected than is the case for the radionuclides characteristic of disposal facilities for waste from mining and mineral processing. In the case of mining waste, such as covered tailings, low grade ore or waste rock, the radionuclide most likely to be detectable on the surface is naturally occurring radon, 222Rn.