EVALUATION OF RADIOACTIVITY IN THE PHOSPHOGYPSUM STOCKPILE OF “HIV” VELES, THE REPUBLIC OF NORTH MACEDONIA

Abstract

The production of phosphoric acid from natural phosphate ore generates an industrial waste product named phosphogypsum. Phosphogypsum contains considerable amounts of natural radionuclides from the 238U chain, originating from the ore but enriched during the technological process. In order to perform radiological characterization of the “HIV” (Chemical Industry Veles) phosphogypsum stockpile, five phosphogypsum samples were collected and analyzed. The mean values of gross alpha and beta specific activities ± standard deviation values were: (950±104) Bq/kg and (1694±220) Bq/kg, respectively. Further analysis showed increased gross activities of radionuclides of the 238U chain, while the radionuclides of the 232Th chain and 40K were below the detection limit. The mean values of the specific activities of 238U and 226Ra were (360±55) Bq/kg and (280±84) Bq/kg, respectively. The estimated annual outdoor effective dose, at 1m received by adults was 0.25 mSv/y, which is below a dose limit of 1 mSv/y for members of general public. The results obtained in this study show that radionuclides, although present in relatively high concentrations in the phosphogypsum pile, do not imply an increased external radiation risk for members of the population. The possible use of phosphogypsum in civil construction and agriculture may not be excluded if conditions of prior good planning taking into account the radionuclides activities exist.
Keywords: Phosphogypsum, Radioactivity, 238U chain.