Kharkov National Automobile and Road University (Kharkov, Ukraine):

Khobotova E. V., Dr. Chem., Prof., Head of the Chemistry chair, e-mail: chemistry@khadi.kharkov.ua
Kalmykova Yu. S., Cand. Eng., Assistant
Ignatenko M. I., Cand. Eng., Ass. Prof.

V. N. Karazin Kharkov National University (Kharkov, Ukraine)
Larin V. I., Dr. Eng., Prof., Director of Scientific and Research Institute on Chemistry

The regularities of the distribution of natural radionuclides (NRN) and the types of their excessive concentration in the dump blast furnace slag used as raw materials in the production of building materials have been studied. The earlier results of determining of chemical composition of dump blast furnace slag of 5 Ukrainian metallurgical combines have been used in the work. The NRN: ²²⁶Ra, ²³²Th and 40К have been detected in the composition of dump blast furnace slag fractions. The main contribution to the effective specific activity (Сef.) value in almost all cases is made by a radionuclide ²²⁶Ra, then — ²³²Th. Dump blast furnace slag fractions have been selected and recommended as the safest, taking into account two factors: γ-radiation and the probability of radon emanation from the material pores, due to ²²⁶Ra activity in material. Comparative evaluation of the chemical element, mineral and radionuclide composition of blast furnace slag fractions has shown that the most probable mechanism of NRN accumulation is heterovalent isomorphic substitution in the structures of the minerals of studied raw materials in the crystalline and amorphous state. It has been shown that the isomorphous substitution of impurity elements (Na, K, Mn, Ti, Fe) by natural radionuclides was realized. The impurities substitute the mineral elements isomorphically in its turn. This leads to effective specific activity increase. The certain impurity elements by type of raw materials have been concretized. The discovered regularities of NRN distribution point the way for environmentally safe recycling of dump blast furnace slag. It can be concluded that in the formation of the minerals there are no mechanisms that can ensure the exceeding of eff ective specific activity for I class materials (370 Bq/kg) used in building within settlements.

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