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1
Greece, phosphate processing
About 1 MBq of U-238 and Ra-226 each are discharged to the environment each year from a phosphate rocks processing plant in Thessaloniki area in Northern Greece. The collective dose to lung tissue resulting from atmospheric release estimated 3.3x10(-4) man Gy/yr for U-238 and 0.26x10(-4) man Gy/yr for Ra-226 (10 times lower than reported in UNSCEAR 1982)
P-01
2
Brazil, phosphate processing
Brazilian phosphate rock activity for U-238 is in range 0.164 - 1.128 Bq/g, in approximate equilibrium. Th-232 series activity 0.2 - 0.3 Bq/g. During the production of phosphoric acid about 80-100% of Ra-226, Pb-210, Po-210 and thorium isotopes are 'fractionated' to the phosphogypsum. Concentrations in it range Ra-226: 0.022-0.695 Bq/g, Pb-210: 0.047-0.894 Bq/g, Po-210: 0.053-0.677 Bq/g, Th-232: 0.007-0.175 Bq/g
M-03
3
Sweden, phosphate processing
Phosphate ore from Syria is used as raw material to produce di-calcium phosphate, source of calcium and phosphorus for domestic animals. U-238 in the raw phosphate ~ 0.83 Bq/g in equilibrium. Most Ra-226 found in produced calcium chloride, the highest concentrations of U-238 found in di-calcium phosphate, about 0.95 Bq/g.
G-01
4
Belgium, phosphate processing
For over half a century, phosphate ores of marine origin, have been processed in Belgium, to produce calcium phosphate for use in cattle food. The ore contains about 1.5 Bq/g of Ra-226. As a results there is a radium contamination of the river banks of the Laak and of some areas that are regularly flooded by this river. The contamination is mostly confined to a narrow zone of about 10 m along the Laak banks, due to periodic dredging with mud deposition on the banks. The average Ra-226 content of the soil samples was about 3 Bq/g.
P-02
5
European Union, phosphate processing
Estimated annual doses in phosphate production and use: transport worker 0.1-0.3 mSv, storage worker 0.1-0.5 mSv, phosphoric acid production worker 4.0-10.0 mSv, phosphogypsum worker 0.1 mSv, public 2.0 mSv, fertiliser use - public 2.0 mSv.
Worker gamma dose from storage or disposal of phosphate fertilisers - 0.1 mSv/yr, phosphogypsum waste, phosphate slag - 1 mSv/yr
S-06
6
Brazil, phosphate processing
Phosphate fertiliser is produced by chemically processing phosphatic rock with sulfuric acid. For every ton of P205 produced about 4-6 tons of phosphogypsum is generated. Besides being mainly composed of CaSO4.2H2O, it contains heavy metals, trace elements, rare earth elements and naturally occurring radionuclides originating from the phosphate rock. These constituents have been identified as a potential environmental hazard related to the stockpiling of phosphogypsum, its utilisation in soil amendment and as building materials. The geochemical processes that control leaching must be understood to evaluate the environmental impact of phosphogypsum.
C-02
7
Brazil, phosphogypsum production
The phosphate rock milling through the wet process, reacting phosphate rock with sulfuric acid produces substantial quantities of calcium sulfate as a by-product known as phosphogypsum, that are stored in stockpiles. The phosphate rock contains radionuclides of the U and Th decay series.
During the chemical attack these radionuclides are distributed in different proportions between the phosphoric acid and the phosphogypsum, depending on the process.
Several countries use to adopt a methodology based on the Ra-226, Th-232 and K-40 content in order to allow the use of materials with natural radionuclides. Dose assessment for the use of phosphogypsum as building material have shown that methodology is not adequate when disequilibrium exists.
Regulations for phosphogypsum based on Ra-226 and Th-232 are not acceptable, as the effective dose decreases with time and becomes stable in ~40 years.
R-01
8

Australia, phosphate processing
The amount of uranium in phosphate ores ranges between 20 and 300 ppm (0.26 - 3.7 Bq/g). The main waste from the process of producing phosphoric acid (wet process) is phosphogypsum, and for elemental phosphorus, phosphate slag is the principal waste by-product. The majority (over 80%) of the radium is retained by the phosphogypsum waste stream with only small amounts entering the fertiliser. However the wet process involves a selective separation with most of the uranium and thorium found in the phosphoric acid. Phosphate waste is stored in large stacks, usually under ponds or in ditches. Phosphate slag has been found to contain uranium and thorium. The slag is produced at high temperatures and some radionuclides (up to 95% of Pb210 and Po210) are vaporised. Phosphate slag has been used as aggregate in making streets, pavements, concrete, railroad, ballast, and buildings.
C-03
9
European Union
Phosphate industry (fertiliser production) - feed material ~ 1.5 Bq/g U; Phosphoric acid (detergents & food) - by-product gypsum ~ 1 Bq/g Ra-226
J-02
10
European Union
Mining and milling of phosphate ore
Ore - calcium phosphates Ca3(PO4)2 - phosphorites (typical U ~1.5 Bq/g, Th ~ 0.1 Bq/g), apatite (3Ca3(PO4)2›CaF2) (0.2-0.4 Bq/g U, 0.1 Bq/g Th)
Phosphate ore wet process
Produces phosphoric acid (H3PO4) by reaction with sulphuric acid, by-product - phosphogypsum (CaSO4). Alternatively, this process produces superphosphate (a combination of phosphoric acid & phosphogypsum). Phosphogypsum contains Ra-226 and its progeny (Florida: 0.9 - 1.3 Bq/g).
Phosphate ore thermal process
Ore is crushed, mixed with silica (SiO2 gravel) and coke, heated to 1500 degrees in an electric furnace, to produce phosphorus. Fused calcium silicate slag (CaSiO2) and ferro-phosphorus are waste and by-products. Most of the U (and decay products) from the phosphate ore are retained in the slag (U-238, Th-230 ~ 1.0 - 2.7 Bq/g). Because of high temperature ~95% of volatile radionuclides are released to the air, - typically 50 - 500 Bq/g of Pb-210 & Po-210 in some electrostatically precipitated dusts.
Fertilisers
Vary widely, U-238: 0.3 - 3.0 Bq/g, U-234, Th-230 about the same, Ra-226 & Pb-210 0.2 - 1.0 Bq/g, Th-228 & Ra-228 0.01 - 0.04 Bq/g.
General ranges of activity in phosphate industry (Bq/g)
Th-232 0.01 - 2.0, U-238 0.01 - 5.0, R-a226 0.02 - 5.0, Pb-210 0.01 - 500
Doses in phosphate industry
Normal conditions, min act conc 0.0014 mSv/y; Normal conditions, max act conc 31.0 mSv/yr
Unlikely conditions, min act conc 0.01 mSv/y; Unlikely conditions, max act conc 69.0 mSv/yr
General ranges of activity for fertilisers (Bq/g)
Th-232 0.008 - 0.06, U-238 0.03 - 2.6, Ra-226 0.003 - 0.79, Pb-210 0.02 - 0.92, K-40 0.04 - 9.6
Doses (fertilisers)
Normal conditions, min act conc 0.1 mSv/y; Normal conditions, max act conc 2.0 mSv/yr
Unlikely conditions, min act conc 0.48 mSv/y; Unlikely conditions, max act conc 5.7 mSv/yr
D-02
11

UK, phosphoric acid production
Phosphoric acid scale typical concentrations (Bq/g): Ra-228 20.0, Ra-226 100.0, Pb-210 100.0, Po-210 100.0.
H-01
12

European Union
Radionuclide concentrations in phosphate ore: K-40 <0.05-0.05 Bq/g, Ra-226 0.032-1.095 Bq/g, Th-232<0.005-0.204 Bq/g
Radionuclide concentrations in waste products: K-40 <0.05-0.076 Bq/g, Ra-226: 0.053-7.320 Bq/g, Th-232 0.038-0.183 Bq/g
V-02
13

Brazil, phosphate processing
The apatite from Araxá and Tapira, in Minas Gerais, and from Catalão, in Goiás, are ground and separated magnetically, before being chemically attacked to form P2O5 to be used as phosphate fertiliser. Process wastes contain at least 3.0 Bq/g of Ra226 & Ra228.
P-04
14

European Union, phosphorus production
Phosphate ore milled into fine powder, then granulated. Reaction at ~1500 degrees: 2Ca3(PO4)+6SiO2+10C=6CaSiO3+10CO+P4
(phosphate ore+gravel+coke=slag+carbon monoxide+phosphorus). CO & P leave furnace as a gas. Dust separated in electrostatic precipitator. Gas cooled - liquid phosphorus.
Mix of sedimentary & magmatic phosphate ore contains ~ 1 Bq/g U-238. Po210 in precipitator dust is ~ 1000 Bq/g (1000 times enrichment)
Individual dose in a village 4 km away ~ 30 microSv/year (96% inhalation).
Slag - secondary product that looks like stone and is used for hydraulic engineering and road building (substitute for gravel), contains about 1 Bq/g U-238 in equilibrium. (tope layer of road shields the phosphorous slag). Dose is about 40 microSv/year for someone who spends 1 hour/day on bicycle path or 8 hours/day on the road.
Workplace doses:
Operators ~ 1 mSv/year (possible range 0-5)
Dose rates up to 1 milliSv/hour were observed if parts of equipment covered with high concentrations of radionuclides are polished or subjected to other operations to clean up the contaminated surface.
E-03
15

Spain, phosphoric acid production
U concentrations in phosphate rock range from 50 to 300 ppm.
Phosphate rock activities (Bq/g), Senegal: U-238 0.705, Po-210 0.984, Ra-226 1.025; Morocco: U-238 1.005, Po-210 1.303, Ra-226 1.310; Togo: U-238 1.040, Po-210 0.931, Ra-226 1.207
Wet process - ore is treated with sulphuric acid and phosphoric acid is produced together with phosphogypsum, a waste by-product, formed mainly by impure Ca sulphates.
~90% of Ra226 and Po210 from rock goes into phosphogypsum, remainder - in the acid
~90% of U238 from rock goes to acid, remainder - to phosphogypsum
Due to the operation of phosphoric acid factories a non-negligible radioactive impact in produced - river sediments, mainly.
G-03
16

Netherlands, fertiliser production
Some sedimentary phosphate rock contains up to 2.0 Bq/g of U-238.
Phosphoric acid extracted from rock (using sulphuric acid) and is used in production of fertilisers. Waste product - phosphogypsum.
70-90% of U-238 goes into fertiliser, all Ra-226, Po-210, Pb-210 follow the gypsum.
Average Ra-226 in effluent (phosphogypsum) - 0.55 Bq/g, late 80s' - >1.0 Bq/g.
Reduction due to declining production and selection of source material (less contaminated sedimentary ores or ores of magmatic origin (like apatite with U-238<0.1 Bq/g)
Ra-226 in river sediments may be up to 0.28 Bq/g (background level in range 0.008 - 0.035 Bq/g).
L-04
17

European Union, fertiliser production
Thin layer of scale in the tubing with a rubber lining: Ra-226 + Ac-227 + Ra-228 + daughters (almost no Th-232 series) = 7,000 - 17,000 Bq/g, dose rate 0.2 - 1.5 microSv/hr. Tubing, valves with thick scales, fertiliser industry: relatively high Po-210, almost no activity due to Th-232 series: 1-60 Bq/g, dose rate 0.1-0.5 microSv/hr
A-04
18

Belgium, phosphate processing
Two different processes are used, one using HCl and another - using H2SO4. Phosphate ore of sedimentary origin in combination with the specific production processes, causes enhanced values in the Rn-222 concentration (>400 Bq/m3)
Rn measurements over the year in specific areas (Bq/m3): storage of phosphate ore: 78-253, storage of the end product: 35, dehydration of the waste product: 269-782, storage of the waste product: 69-144, background value: 19
Also - enhanced value of gamma-radiation. By dehydrating the silt waste, radium is prevented to stay in the production water. The quantity of waste is greatly decreased by this new process but the radium activity is concentrated in the remaining solid fraction - up to more than 7 Bq/g.
Gamma-measurements:
Dehydration building: 0.09-0.53, peak value above waste pipe ~1.75, storage waste before dehydration: ~0.88, road to waste storage: 0.18-0.35
storage of solid waste fraction: 2.6-4.4, background: 0.09
V-03
19

Spain, phosphoric acid production
Phosphogypsum was released directly into the river or stored in a 1000 Ha open air piles area near the factories.
Radionuclides in suspended matter from the plants (Bq/l): U-238: 0.7-140, U-234 0.7-145, Po-210 0.8-1015
Radionuclides in sediment & soil samples (ppm) - values in Bq/g, value <> is ppm (parts per million): U 20-90 <5>, Th 9-30 <14>, Ra-226 80-1400 <60>, Pb-210 250-900 <100>, Po-210 90-1200 <100>
V-03
20

USA, phosphate processing
Phosphate (Bq/g): total U 0-3.0, total Th 0-1.8, total Ra 0.4-3700
Phosphogypsum (Bq/g): total U 0-0.5, total Th 0-0.5, total Ra 0.9-1.7
Slag (Bq/g): total U 0.8-30, total Th 0.7-1.8, total Ra 0.4-2.1
Scale (Bq/g): total Ra 1.1-3700
S-10
21

Italy, phosphoric acid production
During the production of phosphoric acid about 90% of Ra-226 precipitates with the solid phase and insoluble radium sulphate and forms phosphogypsum slurry. Ground samples ~0.35 Bq/g Ra226, max less than 6 Bq/g.

G-07
22

Greece, phosphate processing
Sedimentary phosphate 1.5 Bq/g U-238, apatite 0.07 Bq/g.
Phosphoric acid produced by two processes:
Wet process
Usually used for the production of fertilisers. H2SO4 mixed with ground phosphate rock. Reaction results in phosph.acid and gypsum:
Ca10F2(PO4)6+10H2SO4+20H20 = 10CaSO4.2H2O+6H3PO4+2HF
Ra-226 is co-precipitated with the gypsum, U-238 & Th-232 follow the phosphorus into the phosphoric acid that is used for fertiliser production.
Thermal process
For high-grade acid and phosphates. Coke and silica are added to phosphate rock in an electirc furnace. Chem.reaction at high temp. produces elemental phosphorus, which is relatively free of radioactivity and several by-products among them which calcium siliscate slag, which carries the bulk of the activity.
Concentrations (Bq/g)
Phosphate rock: U-238 0.18-1.80, av.0.98; Ra-226 0.11-1.80, av.1.05;
Phosphate fertiliser: U-238 0.31-0.94, av.0.64; Ra-226 0.02-1.13, av.0.42;
Phosphoric acid: U-238 0.66-2.26, av.1.31; Ra-226 0.16-1.29, av.0.68;
Phosphogypsum (CaSO4.2H2O): U-238 0.15-0.21, av.0.18; Ra-226 0.26-0.47, av. 0.38.
Th-232 was not found in significant specific activities in all samples.
P-07
23

Radionuclides in raw materials: Ra-226 in Senegal rock 2.27 Bq/g, in Florida pebble 1.58 Bq/g.
Unspecified plant: During the process radium sulphate deposited in various parts of the plant. In one plant concentrations of Ra-226 up to 8500 Bq/g were measured, and the total Ra-226 activity deposited in the plant was estimated to be 10 GBq. Maximum external dose was 260 microSv/hour.

A-07
24

Concentrations of U-238 in phosphate rock: sedimentary phosphate rock (global average) - 1.50 Bq/g, phosphate rock from Chatham Rise in New Zealand - 1.79 Bq/g, Nauru Island - 0.72 Bq/g, North Carolina - 0.74 Bq/g, Christmas Island - 0.27 Bq/g.

T-07
25
 Saudi Arabia, fertilizers
In Saudi Arabia more than 50% of phosphate fertilizer samples have very high Ra-226 concentrations, mean = 0.62 Bq/g, U-238 mean = 2.6 Bq/g (these two radionuclides are far from equilibrium). Values for K-40 are low, about 0.09 Bq/g.
K-08
26
 Australia, phosphogypsum
Phosphogypsum plaster board is a substitute for natural gypsum. It contains on average 0.4 Bq/g of Ra-226 and an annual dose should not exceed 0.13 mSv.
O-01
27
 Tanzania, phosphate mining
Minjingu phosphate mine is located in the north of the country. Average northern Tanzania background levels are 0.10 microGy/hr, but levels at the mine are on average 1.41 microGy/hr.
Phosphate contains 5.76 Bq/g of Ra-226, 0.50 Bq/g of Ra-228, 0.35 Bq/g of Th-232, and 0.28 Bq/g of K-40. These values are higher than the highest ones reported by UNSCEAR.
B-09
28
 Egypt, fertilizer production
Radioactivity content in phosphoric acid used in fertilizer production has been measured as follows: alpha spectroscopy U-235 - 601 Bq/l, U-238 - 507 Bq/l, total uranium 45.4 ppm (545 Bq/l), gamma spectroscopy results: K-40 - 17 Bq/l, U-238 - 644 Bq/l, U-235 - 19.5 Bq/l, Pb-214 - 1.2 Bq/l, Bi-214 - 1.3 Bq/l, Tl-208 - 9.4 Bq/l, Po-210 - 3.4 Bq/l.
I-07
29
 The Netherlands, phosphorus production
The mix of sedimentary and magmatic phosphate ore contains approximately 1 Bq/g of U-238. During the electro-thermal phosphorus production, the radionuclides are unintentionally enriched. The operators of the plant receive a dose of approximately 1 mSv/year. The daily measurements, however, show a large variation and it is theoretically possible to receive a dose of 1 mSv in only one hour of work, if this work is carried out on surfaces with contamination of up to several hundred Bq/cm2.
E-09
30
 EU
The concentrations of natural radioactivity in phosphate ore vary from roughly 0.1 to 5.0 Bq/g and are dominated by the contribution from the U-238 series. However, as a result of the chemical process, the fertiliser product contains uranium concentrations approximately 50% higher than in the ore, and most of the radium is left in the phosphogypsum waste.
E-08

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