Radiological impacts of natural radioactivity from phosphogypsum piles in Huelva (Spain)

The activity concentrations of Ra-226, Th-232 and K-40 have been measured by gamma spectroscopy in samples of soil collected from the different zones of around Huelva (Spain). The average activity concentrations of Ra-226 (Bq kg(-1)) in the active phosphogypsum (PG) stacks, unrestored and restored zones were 647, 573 and 83 respectively. The corresponding values for Th-232 and K-40 (Bq kg(-1)) were 8,10 and 25 and 33, 47 and 225 respectively. As a measure of radiation hazard to the occupational workers and public, the Ra equivalent activities, representative level index and dose rates due to natural radionuclides at 1 m above the ground surface were estimated. The average of absorbed dose rates due to Ra-226, Th-232 and K-40 (nGy/h) from active PG stacks, unrestored and restored zones are 284, 255 and 55. The calculated external gamma-radiation average dose (mSv/y) received by the workers of the phosphogypsum piles are estimated to be 0.293, 0.262 and 0.057 which is far below the international agreed dose limit of 20 mSv/y (ICRP-60, 1990) for workers. Also, the radiation dose to a member of the public resulting from the use of PG is negligible compared to the average annual effective dose from natural sources (2.4 mSv/y). (C) 2010 Elsevier Ltd. All rights reserved.