Leaching assessment as a component of environmental safety and durability analyses for NORM containing building materials

NORMs (naturally occurring radioactive materials) may be considered for use as construction material if, in the form that they are used, they meet appropriate standards for protection of human health and the environment. When evaluating construction materials, it is important to consider the full life cycle of the material, including the use scenario as well as the potential for reuse and disposal. If demonstrated to be safe, then use of NORM offers potential sustainability benefits through reduction in energy use and reduction in mining or use of virgin natural resources for production of construction materials (e.g., aggregate, cement, concrete, paving block, tiles, filler for road works, etc.). Important pathways to be evaluated for potential human health and environmental impacts include (i) direct exposure to radiation, (ii) emission of radon, (iii) potential exposures through ingestion and inhalation, and (iv) waterborne pathways through leaching of radionuclides or other contaminants of potential concern (COPCs). Additionally, the potential benefits derived from the use of NORM require demonstration of durable products with acceptable environmental safety.An important reason to focus on natural radioactivity is that alternative materials (by-products) used in construction as part of the new circular economy targets set by the European Commission may contain natural radioactivity in elevated levels compared with traditional materials used in construction. However, many traditional materials (e.g., granites) also may contain elevated levels of radionuclides depending on their origin and therefore, both traditional and alternative materials require consideration of radiation exposure as part of the determination of their suitability for use (as was already discussed in Chapters 3–7).This chapter focuses on the waterborne pathway of potential impacts through leaching of radionuclides and other COPCs and methods to assess and predict leaching behaviour. Recently there is a shift toward measurement of intrinsic leaching characteristics (i.e., characterization of leaching as a function of key release controlling parameters such as pH, liquid-to-solid ratio (L/S), or time) of a material over a range of conditions as a basis for comparison between materials, and using mass transport relationships to estimate anticipated leaching under the range of likely field conditions. The LEAF (Leaching Environmental Assessment Framework) approach will be used as the basis for discussion of leaching from naturally occurring radionuclides (NOR) here, based on similarities in leaching behaviorbetween radionuclides and the corresponding stable isotopes.