View
736
Download
2
Category
Tags:
Preview:
DESCRIPTION
Background on Caetite deposit, Lago Real, Brazil
Citation preview
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)
Recommended