1. J.P. Bolívar 1) and R. García-Tenorio 2)
OCCUPATIONAL EXPOSURES AND DISTRIBUTION OF NATURAL RADIONUCLIDES IN THE PHOSPHORIC ACID PRODUCTION BY THE WET PROCESS (SPAIN)
J.P. Bolívar 1) 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. LOCATION OF THE FACTORIES
Huelva
Town
Odiel river
Fertilizer plants
Tinto river
Odiel river
MINING AREA
50 km
Tinto river
NATURE RESERVE
Complex-2
Industrial

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

5. Concentrated Phosphoric acid
Phosphate Rock
CONCENTRATION
FILTRATION
MILLING
ACID ATTACK
Phosphogypsum: into piles
WATER
Sulphuric acid
P2O5 recycling (22%)
Production
acid
(27% P2O5 )
Concentrated Phosphoric acid
(54 % P2O5 ) PR
~ 2·106 Tm PA SA PG
~ 3·106 Tm
ANNUALLY CONSUMPTION - PRODUCTION
Sedimentary PR
238U ~ 1.5·103 Bq/kg; 232Th ~ 30 Bq/kg

7. PHOSPHATE ROCK (P R) Table 1 Table 2
Milling step. Activity concentrations (Bq/kg)
Sample type
238U
226Ra
228Ra
Raw PR
1840 ± 130
1560 ± 80
22 ± 2
Buk milled PR
1640 ± 90
1722 ± 90
20 ± 2
Optimum size PR
1630 ± 90
1780 ± 90
40K
16 ± 2
Table 1
Attack step. Activity concentrations in pulps (Bq/kg)
Sample type
238U
226Ra
228Ra
Liquid
1340 ± 90
5 ± 1
< 1.1
Solid
450 ± 30
760 ± 35
14 ± 2
40K
8 ± 2
14 ± 3
Table 2

8. Table 3 Table 4 Filtration step. Activity concentrations (Bq/kg)
Sample
238U
226Ra
228Ra
PG before washing
810 ± 50
880 ± 40
14 ± 2
PG after first washing
460 ± 30
1040 ± 50
15 ± 2
PG after second washing
450 ± 30
1000 ± 50
17 ± 2
PG to be stored
310 ± 20
900 ± 50
Table 3
Concentration step. Activity concentrations (Bq/kg)
Sample
238U
226Ra
228Ra
P2O5 (32%)
1300 ± 70
4 ± 1
< 1
P2O5 (54%)
1830 ± 180
8 ± 1
Table 4

9. Concentrations (Bq/kg) Concentrations (Bq/kg) Concentrations (Bq/kg)
HOT POINTS
Concentrations (Bq/kg)
Fraction
238U
230Th
226Ra
210Pb
Liquid
2100
1250
7.5 45
Solid
2000
4300
Sludges precipitated in the tanks
where phosphoric acid is stored
Table A
Concentrations (Bq/kg)
Fraction
238U
230Th
226Ra
210Pb
Liquid
1250
250
4.5 85
Solid
900
1300
1400
Sludges floating in the tanks
where phosphoric acid is stored
Table B
Concentrations (Bq/kg)
Fraction
238U
230Th
226Ra
210Pb
Prayon Filter
300
2300
3400
Milling Filter
1000
1200
2100
1100
PG from pipes
2000
830
1400
Scales and filters from the filtration
step collected during maintenance
Table C

10. 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

11. EXTERNAL GAMMA DOSE RATES
External gamma dose rates (mGy/y)
inside the factories above background
Morocco
Kola
Fertilizer stores
Inside a DAP store
0.25
Milling zone
Inside phosphorites silo
2.20
0.60
1 meter beside silo
0.35
1.50
1 meter away milled rock pile
0.40 --
Mill operator cabin
0.45
1 meter away rock dust pipes
0.80
Attack zone
Above compartments 3 and 4 of reactor
0.90
0.95
At 2 meters over reactors 4 and 5
0.10
Above compartments 4 and 5 of reactor

12. Table 6 External gamma dose rates (mGy/y)
inside the factories above background
Morocco
Kola
Filtration zone (ABOVE the filter, not accessible to the workers)
At 1 m between the pulp entrance and the 1st washing
6.75
4.20
At 1 meter of the 1st washing
9.20
8.95
At 1 meter between the 1st and 2nd washing
6.40
4.90
At 1 meter of the 2nd washing
8.65
9.90
Filtration zone ( AROUND the filter, accessible to workers)
Between the pulp entrance and 1st washing
1.50
1.05
Between the 1st and 2nd washing
1.20
Between the 2nd and 3rd washing
Concentration zone
At 2 meters of the concentration zone
0.10 --
Above the production acid decantation pool
1.85
Other places
Chemical laboratory
0.00
Control process room
Old control process room
Table 6

13. Distance factory - piles ~ 1 km
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

14. 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

15. Enhanced external dose rates in active PG piles
Point
Dose rate
(mGy/yr) 1
2.69 10
1.20 2
1.23 11
1.24 3
1.05 12
1.06 4
2.13 13
1.38 5
1.31 14
1.47 6 15 7
1.63 16
1.51 8
1.08 17
1.25 9
1.52 18
0.85

16. Δexternal doses (mGy/year)
ACTIVE PHOSPHOGYPSUM PILES
Entrance
Occupational factors < 0.2
Δexternal doses (mGy/year)
Entrance
2.70
Perimetral wall
1.40
Pumping station
~ 0
Surrounding soils

17. 222Rn exhalation rates in phosphogypsum piles
Point
Exh. rate
Uncert.
Mean
St. Desv.
Range of values:
Bq m-2 h-1
Average: ± Bq m-2 h-1

18. 222Rn in the piles PG Piles Huelva town 13,1 ± 1,6 12,6 ± 2,0 Hour5 10 15 20 25 30 35 1 3 7 9 11 13 17 19 21 23
Activity
222
Rn (Bq/m )
Exteriores Huelva
Exteriores Balsas
Hour
Huelva town outdoors PG Piles
PG Piles
Huelva town
13,1 ± 1,6
12,6 ± 2,0
Average values for Six months

19. Equipments used for samplings
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

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

27. ACKNOWLEDGEMENTS 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 is deeply acknowledged.
- We are indebted to FERTIBERIA staff (especially Mr. Garralda) for the collaboration in the performance of this work.

28. DANKE SCHON thank you MUCHAS GRACIAS
9th European ALARA Network Workshop. Augsburg, 18 – 21 October 2005

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

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

31. Activity concentrations in PG from active piles (Bq/kg)
Average concentrations (Bq/kg)
238U
230Th
226Ra
210Pb
200
550
650
500
Average concentrations (Bq/kg)
228Ra
40K
137Cs 20
< 20
< 0.7
Tables 7
Activity concentrations in WATERS from PG piles (Bq/L)
Sample
238U
230Th
226Ra
210Po
232Th
228Th
235U
40K E
200
2.5
0.8 5 1 9 8 P
180
2.3 3
0.4
{E} = Water from regulator pool (Bq/L)
{P} = Water from the leachated recovered in permitral channel (Bq/L)
Table 8

32. 222Rn in the piles Monthly average values
Activity concentration 222Rn (Bq m-3)
Monthly average values

33. “TOTAL SUSPENDED PARTICLES” IN PG PILES DOSIMETRIC IMPLICATIONS
Radionuclide
Average increment
(Bq m-3)
Dose Conversion Factor (Sv/Bq)
Dose increment (Sv/m3)
238U
1.34·10-5
8.0·10-6
234mPa
4.0·10-10
234Th
7.7·10-9
234U
9.4·10-5
230Th
7.42·10-6
1.4·10-5
226Ra
1.10·10-5
9.5·10-6
210Pb
Not detected
5.6·10-6
background
210Po
4.3·10-6
Dose increment
4.4·10-9 Sv m-3
Inhalated volume
8760 m3
Occupational factor
0.20
0.77 µSv·y-1