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Occupational Exposures & Distribution of Natural Radionuclides in Phosphoric Acid Production in Spain

This study examines the fluxes and distribution of radionuclides in the phosphoric acid production process in Spain, evaluating the radiological impact on workers. It includes analyses of mining areas, factories, water, and hot spots.

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Occupational Exposures & Distribution of Natural Radionuclides in Phosphoric Acid Production in Spain

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  1. OCCUPATIONAL EXPOSURES AND DISTRIBUTION OF NATURAL RADIONUCLIDES IN THE PHOSPHORIC ACID PRODUCTION BY THE WET PROCESS (SPAIN) J.P. Bolívar1) and R. García-Tenorio 2) • Department of Applied Physics, University of Huelva (Spain) • Department of Applied Physics II, University of Seville (Spain) 9th European ALARA Network Workshop. Augsburg, 18 – 21 October 2005

  2. MAIN OBJETIVES • To study the fluxes and distribution of natural radionuclides in the industrial process of phosphoric acid production, in Huelva (Spain). • To evaluate the radiological impact of this industrial activity on the workers.

  3. MINING AREA Odiel river Tinto river 0 50 km LOCATION OF THE FACTORIES Huelva Town Odiel river Fertilizer plants Tinto river NATURE RESERVE Industrial Complex-2

  4. Phosphogypsum active piles Phosphate rock (PR) +Sulphuricacid (SA) Phosphoric acid (PA) + Phosphogypsum (PG) Huelva town Tinto river Restored piles Fertilizer plants Common river mouths DischargePR point Odiel river Salt marshes

  5. WATER Phosphogypsum: into piles Sulphuric acid Phosphate Rock Concentrated Phosphoric acid (54 % P2O5 ) Production acid P2O5 recycling (22%) (27% P2O5 ) ACID ATTACK FILTRATION CONCENTRATION MILLING ANNUALLY CONSUMPTION - PRODUCTION Sedimentary PR 238U~ 1.5·103 Bq/kg; 232Th ~ 30 Bq/kg

  6. PHOSPHATE ROCK (P R) Table 1 Table 2

  7. Table 3 Table 4

  8. HOT POINTS Sludges precipitated in the tanks where phosphoric acid is stored Table A Sludges floating in the tanks where phosphoric acid is stored Table B Scales and filters from the filtration step collected during maintenance Table C

  9. Dosimetric study inside the Factories External irradiation: gamma - beta Internal irradiation 222Rn + daugthers In progress Ready Indirect route ingestion Internal irradiation dust inhalation In progress

  10. EXTERNAL GAMMA DOSE RATES

  11. Table 6

  12. PG PILES IN OPERATION Huelva town Restored piles Regulating water reservoir Pipes pumping waters Piles Factories Pumping station Pipes pumping waters Factories  Piles Perimetral wall Perimeter Channel Tinto river Distance factory - piles ~ 1 km

  13. Dosimetric study in PG piles External irradiation: gamma - beta Internal irradiation 222Rn+daugthers Preliminary results Ready Indirect route ingestion Internal irradiation dust inhalation Preliminary results

  14. Enhanced external dose rates in active PG piles

  15. Entrance Occupational factors < 0.2 ACTIVE PHOSPHOGYPSUM PILES

  16. 222Rn exhalation rates in phosphogypsum piles Range of values: 55 - 2300 Bq m-2 h-1 Average: 613 ± 286 Bq m-2 h-1

  17. 35 ) 30 3 Rn (Bq/m 25 20 222 15 Activity 10 5 0 1 3 5 7 9 11 13 15 17 19 21 23 Exteriores Huelva Exteriores Balsas 222Rn in the piles Hour Huelva town outdoors PG Piles Average values for Six months

  18. SAMPLING OF “TOTAL SUSPENDED PARTICLES” (TSP) Equipments used for samplings in both PG piles and the background Area Thershold = 150 µg m-3 Average = 50 µg m-3 TSP concentrations in the PG piles

  19. RADIOACTIVITY IN “TOTAL SUSPENDED PARTICLES” IN PG PILES Doses estimated through this route: < 10 µSv/y Sample

  20. MAIN CONCLUSIONS • The distribution and fluxes of several natural radionuclides from the U-series have been analysed along the industrial process. It has served as a basis for the design of dosimetric campaigns. • An external gamma dose rate map has been performed inside one of the factories. Taking in consideration the occupational factors, doses lower than 1mSv/year are received by the workers trough this route. • The effective doses received by the workers involved in the construction and maintenance of the piles is also lower than 1 mSv/year, taking into consideration external radiation, inhalation of 222Rn and inhalation of suspended particles. ACKNOWLEDGEMENTS • Financial support from Spanish National Security Council (CSN) through its I+D programme 2004-2007 is deeply acknowledged. • - We are indebted to FERTIBERIA staff (especially Mr. Garralda) for the collaboration in the performance of this work.

  21. DANKE SCHONthank youMUCHAS GRACIAS 9th European ALARA Network Workshop. Augsburg, 18 – 21 October 2005

  22. PR discharge point Odiel Channel P2O5 factory (AF1) PR stores PG pumping to the piles

  23. EXTERNAL GAMMA DOSE RATES Milling 0.35 - 3.2 Attack ~ 0 Filtration 4 - 12 Worker rooms ~ 0 Concentration step 1.6 - 2.8 Estores PR ~ 0.30 Acid Tanks 0.7 - 4.4 Δexternal doses (mGy/yr) Entrance factory 0 (Background) Background = 0.60 mGy/yr

  24. Activity concentrations in PG from active piles (Bq/kg) Tables 7 Activity concentrations in WATERS from PG piles (Bq/L) {E} = Water from regulator pool (Bq/L) {P} = Water from the leachated recovered in permitral channel (Bq/L) Table 8

  25. 222Rn in the piles Activity concentration 222Rn (Bq m-3) Monthly average values

  26. “TOTAL SUSPENDED PARTICLES” IN PG PILES DOSIMETRIC IMPLICATIONS

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