Natural radioactivity studies of phosphate fertilizers applied on greek farm soils used for wheat cultivation

Naturally Occurring Radionuclide Materials (NORM) such as fertilizers, agricultural soils fertilized and wheat grain cultivated at those soils were studied regarding the radiation hazard to the public and workers. Activity of ²³⁸U, ²²⁶Ra, ²³²Th and ⁴⁰K was measured hermetical sealing the marinelli beaker using the Stopaq FN 2100L material that prevent ²²²Rn escape from the baker. The phosphate fertilization of soil did not affect natural radioactivity in comparison with non-fertilized soils and also did not affect natural radioactivity of wheat grain cultivated since only ⁴⁰K was measured. The high mean value of D_air ²¹¹ nGy h^-1 for fertilizers compared to soils fertilized 53 nGy h^-1 highlights the raising concern about radioprotection of workers occupied with tasks involving fertilizers. The maximum external dose rate 1.15 mSv y^-1 calculated for truck drivers involved to transportation section is similar to annual external effective dose limit 1 mSv. Real concerns rise for workers in the fertilizers storage and supply department since the maximum dose rate estimated is 1.98 mSv y^-1, while the mean value is 0.89 mSv y^-1. (authors)