NORM waste treatment

Conventional industries generally produce large volumes of residues con­taining naturally occurring radioactive materials (NORM), of the order of 104-106 t/a. This necessitates a different, pragmatic approach from typical RAW management, for which the principle of concentration and contain­ment is used [28] . For most NORM residues containment is not possible, and in many cases it is not waste but a useful recyclable residue. Therefore, for NORM residues the principle of dilution and dispersion should be pre­ferred wherever possible. It saves resources of other materials and it reduces waste volumes. Furthermore, one should keep in mind that concentration/ containment and dilution/dispersion are complementary, not contradictory, concepts. Processing of NORM waste consists of pile stabilization by various processes in order to increase the safety of storage and disposal sites. Large solid pieces of NORM waste, such as pipes from the oil industry, are frag­mented for handling and transport purposes. Liquid effluents are generated at all stages of the uranium production cycle that use process water and chemicals, including crushing, grinding, leaching, precipitation and tailings disposal and management. In addition, leaching of ore and mineralized waste rock by groundwater and surface water, respectively, can result in generation of acid mine water, which must also be contained and treated. The effluents contain radioactive and non-radioactive elements and com­pounds that, if not properly contained, can contaminate drinking water resources or enter the food chain, potentially harming the environment and endangering the health and well-being of human populations. Scales and sludges, which are generated in small volumes but which may have activity concentrations reaching very high levels, such as those originating from the oil and gas industry, are usually held in storage pending the establishment of suitable disposal facilities [28].

Criteria for exemption, without further consideration, of substances con­taining radionuclides of artificial origin are based on the premise that exemption will be the optimum option when the dose incurred by an indi­vidual is of the order of 10 pSv or less in a year [11]. For NORM, the situ­ation is quite different. Owing to the existence of significant and highly variable levels of background exposure to radionuclides of natural origin, exemption is likely to be the optimum option over a much wider range of doses, typically doses of the order of 1 mSv or less in a year.

The use, reuse and recycling of NORM residues and NORM contami­nated items — including, where appropriate, the dilution of NORM residues to reduce the activity concentration — is now starting to be recognized as a legitimate and desirable option for minimizing the quantities of NORM that need to be disposed of as waste. In particular, the beneficial (and safe) uses of phosphogypsum as a co-product of fertilizer production are now very much in the spotlight and, in some countries at least, there is already evidence of a shift in regulatory attitude towards this approach. However, when considering the use of NORM residues in the construction of dwell­ings, as a component of either landfill material or construction material, the possibility of increased radon exposure needs to be carefully taken into account.

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