Caetité Uranium Production Facility

Chaitanyamoy GangulyIAEA

UPSAT MISSION, 26 April 2009

Brazil – U Resources

Occurrence Measured and Indicated Inferred TOTAL

Deposit/Mine < 40US$/kg U < 80US$/kg U Sub-Total

< 80US$/kg U  

Caldas (MG)   500t 500t 4, 000t 4, 500t

Lagoa Real/Caetité (BA)

24,200t 69, 800t 94, 000t 6, 770t 100, 770t

Itataia (CE) 42, 000t 41, 000t 83, 000t 59, 500t 142, 500t

Others       61, 600t 61, 600t

TOTAL 66, 200t 111, 300t 177, 500t 131, 870t 309, 370t

Source: INB Website, 2009

~ 5% of world total

Caetité Uranium Mine and Mill

Heap Leaching Pads

2 X 35,000 t

U Liquor tanks

U in Lagoa Real

• In Proterozoic granites and gneissic rocks - Lagoa Real Igneous Metamorphic Complex and São Timóteo granite

• Occur as discontinuous tabular and lenses like bodies

• Most bodies trend N40E to N30W and dip 30° to 90°to the SW or NW

• Northernmost deposits dip to the east

• In the central part of the region dips are almost vertical

• Each albitite body may vary up to 3 km in length,

• Av 10 m in width (max. 30 m). • Mineralization extends up to

850 m depth from surface• Each albitite body contains

one or more mineralized levels, which may be interrupted in places.

• The contacts between mineralized levels with host rocks is transitional or abrupt

• Age: Albitite 700 – 500 Ma

Location mine and mill

Leached ore encapsulated in Waste rock

Open Pit Mine Mill

Caetité deposit details

• Caetité, Bahia state• Av Annual Precipitation –

927 mm• Semi – arid• Evapo-transpiration 1500

– 2000 mm• Rainfall often high and

erratic

• Metasomatite type• Host rock – Albitite (70%

Albite - NaAlSi3O8 ; 10-20% pyroxene; 2-5% garnet and 1-3% magnetite)

• Av U3O8–0.3% (0.25% U)

• 35 anomalies in an area of 1200 km2

• Structurally controlled

Deposit details

• Top weathered zone: (Surface to 40m depth)- uraninite, uranophane and autunite: easier to leach

• Fresh rock: (below 40m)uraninite

• Uraninite occurs as tiny round and irregular crystals (20 a 30 μm)

• included or associated to mafic minerals

• Deposit Width:Av 6m. Up to 40 m

• Deposit Length:50 to 1200 m

• Deposit Depth:750 m form surface

Waste-rock material generated

Observed

Predicted

Average 2.7 times more that predicted; Av Waste rock/ore ratio – 8.1:1

Lack of accurate delineation of ore bodies and absence of precise mining plan

Average rock composition

Oxide Concentration (%) Oxide Concentration (%)

SiO2 43.1±1.3 BaO 0.16±0.05

CaO 6.8±1.1 ZrO2 0.04±0.01

Al2O3 13.8±0.8 ZnO 0.011±0.002

Fe2O3 5.4±0.8 SnO2 0.0056±0.06

TiO2 2.4±0.4 Cr2O3 0.0056±0.0005

U3O8 0.35±0.009 MnO 0.094±0.001

MgO 2.4±0.4 Nb2O5 0.1±0.02

V2O5 0.1±0.02    

Source: INB (1999)

Heap Leach

• Operations– Crushing + H2SO4 in

heaps 25 000 to 35 000 tonnes

– 3 washing step cycle– Solutions collected in

ponds 2gL-1 U3O8

– Extraction by organic solvent

– Stripped by NaCl – Precipitated by

ammonium hydroxide solution

– Av Recovery – 75%

7% tertiary amine 3% tridecanol 90% kerosene

Process Improvements already implemented

• crushing circuit to give ore size -13 mm

• ore agglomeration and acid cure

• synthetic flocculent

• mixer-settler

• centrifuge

Future plans

• increasing production capacity

• underground mining

• conventional leaching

• direct uranium precipitation with H2O2

Water demand - supply

• Water demand for human and industrial consumption met by a series of driven wells and a dike to store surface water collected in rainy periods

• Total consumption: 280,000 m3/year

• Recycled volume: 180,000 m3/year

• Fresh water demand: 100,000 m3/year

• More than 100 tube wells• Dike to store surface rain

water: 226,000 m3

Potential Impacts on environment

• Groundwater contamination

• Atmospheric impacts low

• Leached ore encapsulated in waste rock

• Waste ponds – potential long term contaminant

• 238U from mine waters in to the aquifer

• tailings may induce acidification and salinization in the surrounding environment

Radiological characterization

Material 238U 226Ra 228Ra

Ore (Bq kg−1) 53080 ± 11975 33280 ± 9549 83.0 ± 21.0

Leached ore (Bq kg−1)seco 7582 ± 3290 34520 ± 9512 75.00 ± 12

Leaching solution (Bq l−1) 157400 ± 30770 23.0 ± 4.0 6.0 ± 0.5

1st washing water (Bq l−1) 54840 ± 13162 16 ± 4.5 2.3 ± 0.6

2nd washing water (Bq l−1) 526 ± 176 10.0 ± 3.0 <0.5

Radionuclide concentrations in vegetables

Product 238U 226Ra 210Pb 232Th 228Ra

Corn 0.023 ± 0.017 0.13 ± 0.11 0.12 ± 0.049 0.051 ± 0.031 0.22 ± 0.16

Manioc 0.11 ± 0.07 5.7 ± 4.17 2.7 ± 1.9 0.028 ± 0.047 31.0 ± 22.0

Black beans 0.19 ± 0.19 0.45 ± 0.36 0.17 ± 0.062 0.73 ± 1.23 0.60 ± 0.46

Pasture 0.53 ± 0.18 0.38 ± 0.26 4.98 ± 0.76 0.45 ± 0.32 0.83 ± 0.62

Bq kg−1(dry)

Calculated soil–plant transfer factors

Product 238U 226Ra 210Pb 232Th 228Ra

Corn 3.36 × 10−4 2.03 × 10−3 7.06 × 10−4 8.97 × 10−4 2.75 × 10−3

Manioc 1.54 × 10−3 9.07 × 10−2 1.57 × 10−2 4.90 × 10−3 3.84 × 10−1

Black bean 2.75 × 10−3 7.19 × 10−3 9.80 × 10−4 1.27 × 10−2 7.36 × 10−3

Pasture 2.68 × 10−3 6.03 × 10−3 2.88 × 10−2 7.84 × 10−3 1.02 × 10−2

Average 1.82 × 10−3 2.65 × 10−2 1.16 × 10−2 6.59 × 10−3 1.01 × 10−1

Radionuclide concentrations in aerosols samples

Sampling point 238U 226Ra 210Pb 232Th 228Ra Weight (g)

INST 001 (×10−5Bq m−3) 68 ± 42 19 ± 9.8 44 ± 13 4.92 ± 2.0 7.40 ± 4.7 1.10 ± 0.23

(Bq kg−1) × 103 15 ± 7.4 4.4 ± 1.8 9.7 ± 3.0 1.08 ± 0.56 1.57 ± 0.97  

INST 008 (×10−5Bq m−3) 94 ± 49 90 ± 52 94 ± 35 4.92 ± 4.0 43 ± 50 1.06 ± 0.16

(Bq kg−1) × 104 1.90 ± 0.9 2.1 ± 1.7 2.1 ± 1.2 0.1 ± 0.06 1.0 ± 0.12  

(Inside the uranium mining and milling area)

Radionuclide concentrations in aerosols samples

Sampling points 238U 232Th 226Ra 228Ra 210Pb Particulate (g)

AERO 001 (WSW) 10–15 km 3.53 0.68 0.45 0.94 22 1.03

AERO 008 (WSW) 0–5 km 3.04 1.23 1.11 1.47 27 1.86

AERO 010 (WNW) 0–5 km 11.7 0.75 5.49 2.61 27 1.08

AERO 013 (W) 0–5 km 8.1 3.65 3.28 6.56 27 3

AERO 042 (ESE) 5–10 km 3.67 0.48 0.28 0.63 22 0.62

(Outside the mining plant)

(x105 Bq m-3)

Radon concentration

Sampling station Description Bq m−3

Rn 001 (n = 8) Milling plant 90 ± 71

Rn 003 (n = 8) Waste-rock piles 102 ± 50

Rn 004 (n = 20) Leached ore piles 627 ± 238

Rn 008 (n = 8)Ponds with sub-aerial drains 118 ± 61

Rn 009 (n = 8)250 m away from the leaching platform 104 ± 82

Rn 010 (n = 8) Open pit, ore body 1 116 ± 60

Rn 011 (n = 8) Open pit, ore body 3 135 ± 71

(Inside the uranium mining and milling area)

IAEA – BSS Guidelines

Dwellings – 200 – 600 Bq m-3

Workplaces – 1000 Bq m-3

Typical average concentrations in mining and processing of uranium ore: 500 – 700 Bq m-3

Radon concentration

Sampling station Sector Bq m−3

AERO 001 (n = 4) W 109

AERO 008 (n = 4) WSW 57

AERO 010 (n = 4) WNW 77

AERO 013 (n = 4) WNW 73

AERO 042 (n = 4) SE 44

(Outside the uranium mining and milling area)

Activity concentrations in groundwater

Well 238U 226Ra 210Pb

ASUB001 (n = 12) 7.3 0.42 0.2

ASUB279 (n = 12) 12.3 0.064 0.13

ASUB276 (n = 12) 0.09 0.039 0.086

ASUB211 (n = 3) 0.15 0.75 0.1

Results from Brazilian groundwater 0.015 0.014 0.04

 <1.2 × 10−4

−0.0930.001–3.79

0.009–0.98

  n = 210 n = 358 n = 210

(Bq l−1)

Average radionuclide activity concentrations in mine pit waters

Sampling station 238U 226Ra 210Pb 232Th 228Ra pH

Area body 01 (n = 16)

4.95 ± 5.5 or 0.41 ppm 0.15 ± 0.16 0.05 ± 0.03 0.04 ± 0.08 0.05 ± 0.10 8.27 ± 0.66

Area body 03 (n = 22)

57 ± 6.4 or 4.70 ppm 2.03 ± 1.29 0.22 ± 0.16 0.21 ± 0.25 0.23 ± 0.25 7.84 ± 0.40

(Bq l−1)

Suggested measures

• Modeling of long-term release of Ra isotopes

• Detailed hydrogeological studies

• Improved mining operation

• Improvement in measures to avoid groundwater contamination from waste ponds

• Drainage water treatment plant

Suggested Queries

• Exploration data – including maps, sections, data quality (…in view of ore body delineation issues)

• Ore reserves – cut-offs, methods • Baseline data• EIA documents• EMP documents• Monitoring details, schedules etc• Drainage management – Details of

hydrogeological studies carried out / to be carried out

Suggested Queries

• Open pit mining– Mine plans– Details of flooding incidences– Steps that can be taken to minimize flooding– Details of reclamation plans

• Underground– Mode of entry– System hoisting– Underground layout - longitudinal sections and level plans – Method and sequence of stoping – Mine ventilation– Extent of mechanization

Suggested Queries

• Underground (continued)– Depth of water table– quantity and quality of water likely to be

encountered and pumping arrangements – places where the mine water is finally

proposed to be discharged

• Waste rock / tailing management– Siting and details of the tailing pond/s

Suggested Queries

• Processing plant– Details– Advantages of direct precipitation– Solid/liquid wastes, treatment and disposal

Suggested Queries

• Regulatory issues– Independent mining / radiation regulator

exists?– Adequate regulations are in place?– Incidence reporting practice?

Suggested Queries

• Public perception– Channels of outreach– Elevated U in groundwater in the mineral

district – to be communicated to public

Thank you

Geological Setting - Lagoa Real

U mineralisation - Metasomatic type

Site topography

Waste rock

Mine Mill

Drainage management • Liquid effluent

– Acid solution with high Al, Fe, Ca, Mg and Si

– Treated with CaO - pH 8.0

– Pumped into HDPE lined ponds with drains – settling of solids

– Supernatant re-circulated to the process

– Closed circuit – no release in normal operation

Unforeseen discharges - Need for alternate drainage management

Total- 110 000 m3

Radioecological characterization

Radionuclide activity concentrations in soil

Sampling station

238U 226Ra 210Pb 232Th 228Ra

A1

TC 180 143 156 – 99.4

RAC 28 18 3 10 23

A2

TC 46.5 43.4 158 – 87.6

RAC 9 5 7 9 22

B1

TC 41.9 41.1 154 84.8 62.5

RAC 4 5 4 4 11

B10

TC 70.5 53.2 203 92.9 98

RAC 7 8 3 5 13

(TC - total concentration; RAC -readily available concentration; in Bq kg−1)

Sampling station

238U 226Ra 210Pb 232Th 228Ra

TC 68.4 87 140 74 75.6

RAC 10 9 4 48 22

D

TC 53 50 204 99 89.7

RAC 5 6 3 2 20

E1

TC 41.6 48.3 149 – 82

RAC 4 6 3 3 14

E2

TC 48.3 47 175 – 59.6

RAC 5 5 3 3 12

AVG

TC 68.7 ± 45.0 62.6 ± 32.6 173 ± 42.4 87.7 ± 10.8 80.8 ± 19.6

RAC 9.0 ± 8.0 8.0 ± 4.0 4.0 ± 1.0 8.0 ± 15 17 ± 5.0

Pocos de Caldas

184 ± 107 148 ± 103 135 ± 101 359 ± 85.6 284 ± 97.6

Chemical characterization of underground waters

Chemical species (mg l−1)

ASUB001

ASUB27

9ASU

B211

Na 100 107 176

K 7.67 7.67 6.33

Mg 10.8 7.33 12.9

Ca 81 52 27

Ba 0.32 0.09 6.19

Mn 0.77 0.19 0.67

Fe 1.13 1.79 0.53

SiO2 57 62 98

PO4 0.04 0.03 0.05

SO4 2.4 11 20

F− 2.13 1.77 0.37

Cl− 107 173 425

HCO3− 288 194 9.9

Al3+ – – 0.36

pH 6.6 6.75 4.8

Permissible limits of U

• Industrial waste water discharge (Carvalho et al 2009)– Brazil - 0.4 Bq L-1 (30.8 μg L-1 U)– United States - 1.1 Bq L-1 (84.7 μg L-1 U) – France - 23.4 Bq L-1 (1800 μg L-1 U).

• WHO guideline value for drinking water – 0.2 μg L-1 U (Provisional)