Development of an Assessment Method for Radiation Exposure from NORM in Construction Materials - 19032

Once radiological impact is usually considered to be related to nuclear energy accidents and atomic bombs, most of the research on radiation protection has been focused on artificial radionuclides and radioactive waste. Less attention had been given to radiation exposure due to the presence of naturally occurring radioactive materials in raw materials usually considered as not radioactive and used in manufacturing of many building materials. At national level, radiological data from building materials is not available as the control of building materials regarding the content of naturally occurring radionuclides is addressed for the first time in the EU Directive 2013/59/EURATOM. At international level the research developed is largely incomplete: data on the activity concentration measurements of Ra-226, Th-232 and K-40 in building materials used in the construction industry in the EU is non-statistically representative. The data collected are not enough to have an idea of the European situation, but they confirm high concentration of Ra-226, Th-232 and K-40, in some cases. Moreover, most of the research studies carried out in the EU are based on the assessment of the activity concentration index, which was derived for practical monitoring purposes to identify whether a dose criterion is met; to be used only as a screening tool for identifying materials which might be of concern. The dose criterion considers only effective dose due to γ-radiation, but population at home is also exposed to Rn-222 (and Rn-220) from soil, water and building material itself, sometimes to β radiation from superficial materials, and even to Cs-137 from some types of wood. The indoors exposure can be actually much higher than the value assessed with the dose criterion method. Also, in most cases toxic and radioactive components are inseparably. Therefore, all technical questions related to the toxic part of these materials should be addressed: an integrated approach is needed to assess the impacts of using these materials (new materials, recyclates and by-products). Until recently, radiation from natural sources seemed both unremarkable and unalterable - a background phenomenon. It is now known that doses from natural sources and in particular, decay products of radon can be remarkably high within houses in some areas. Therefore, concerning exposure to natural radiation sources, special provisions have been laid down in the EU Directive 1996/28 EURATOM. Still, the radiological evaluation of building materials was not mandatory in this Directive. The most recent EU Directive 2013/59/EURATOM brings some changes concerning the exposure to natural occurring radioactive materials but the previous screening method was kept. An effective dose of 1 mSv/year was set, as a basis for the exposure to radionuclides of natural origin (except for radon). This work seeks to develop an integrated radiological and chemical-mineralogical assessment methodology for realistic exposure scenarios concerning different types of raw materials, by-products and recyclates and used as building materials. The methodology includes the characterization of selected materials accounting for radiological exposure - calculation of effective dose; toxicity assessment - determination of chemical composition and leaching tests, study of changes in the microstructure and consequently in the radon emanation coefficient. (authors)