Reusing Phosphate Fertilizer By-products in Construction: Balancing Circular Economy Benefits with Radiological Safety

Naturally Occurring Radioactive Material (NORM) are of increasing interest for radiation protection due to the recent economic guidelines, aimed at a complete reuse of each component of a production cycle for a sustainable use of the natural resources. Of particular interest is the industrial sector of phosphate fertilizers, which produces phosphogypsum and metasilica phosphate as primary and secondary byproducts. Due to the favorable mechanical properties, these materials have been studied as additive for mortar and cements. This study focuses on the city of Crotone (Italy), where in the past 50 years many reconstruction works have been incorporating residues of the local fertilizer industries, bringing to an enhanced activity concentration of radionuclides such as238U,226Ra and40K. International reference tools like the Radium Equivalent Activity and the Activity Concentration Index were calculated for samples collected from different hot spots around the city and a dose assessment for construction workers was performed using the IAEA's NORMALYSA software. Results indicated that despite the indexes being above the indicated safety values, doses to workers were below the reference levels. Overall, this study supports the idea of a complete radiological assessment when introducing NORM residues into new exposure situation for a fully sustainable strategy of industrial waste reuse. This complies with the principles of Green Economy while at the same time ensures the complete radiation protection of all individuals involved.