A study of radioactivity level of the cements containing fly ash of Soma power plant

Cement is a product that is formed by grinding gypsum with clinkers resulted by burning the mixture that is obtained after mixing and grinding mainly silicium, calcium, alumina and iron oxides containing raw materials in certain proportions, to sintered degrees. When combined with water it posses binding properties. For portland cements, % 3-6 proportion gypsum (CaSO4.2H2O) in weight are added to clinkers at the grinding step in order to adjust the hydration degrees. By this way it prevents tricalcium aluminate (3CaO.Al2O3) from rapid hardening. If ground without gypsum addition, clinkers when combined with water, harden rapidly. Additives such as fly ash, blast furnace slag, natural slag and trash possessing puzzolanic properties are also added to portland cement clinkers. At power plants, during the burning process of coals, light elements such as hydrogen and carbon are converted to their gaseous forms, and remaining ashes than become rich with uranium content. Thus fly ashes contain radioactive elements such as U-238 (Uranium), Th-232 (Thorium) and K-40 (Potassium). U-238 found in fly ash is not an intensively radioactive element at the beginning. It disintegrates naturally by losing its and particles and is transformed to some radio nuclides. Ra-226 (Radium) is the most active element among these radio nuclides and it is transformed to radon gas (Rn-222) by losing new particle. The rare gas radon and radioactive radium extremely jeopardize human health. Fly ashes when used in cements, it can lead to increase in the radioactivity level which is of prime public concern. It is therefore important to determine the radioactivity level formed in the cements and compare with the standard values. In this study, photon emissions and mechanical strength tests of C type fly ash of Soma power plant and portland cements containing this fly ash under laboratory conditions were measured. In that manner it has been examined whether fly ashes may cause some significant increase in nuclear radiation.According to results of the measurements, the radioactivity levels of portland cements and fly ashes were determined to be under the limit values of the report of the United Nations Scientific Committee that states the harmful radioactivity values to human health.