International Atomic Energy Agency IX.4.9. Mining Waste Disposal options for different waste types,...

International Atomic Energy Agency

IX.4.9.IX.4.9.Mining WasteMining Waste

Disposal options for different waste types, safety principles and technologies for assuring long-term

safety, safety assessment methods

International Atomic Energy Agency04/19/23NSRW/WSS 2

Waste streams generated during the different phases of Waste streams generated during the different phases of mining projectsmining projects

• Exploration wastes

• Mining wastes

• Milling wastes

• In situ leach (ISL) wastes

• Miscellaneous wastes

• Decommissioning wastes


Tailings properties: Tailings properties: Radiological componentsRadiological components

• The major portion of the radionuclides present in the ore remains in the tailings after uranium has been extracted

• Significant radionuclides are the decay series for uranium and thorium

• 226 Radium is often considered as the most important radiotoxic decay product in the decay series

• 226 Radium produces 222 radon-a radioactive inert gas, whose decay products can cause lung cancer


Radioactive decay series for uranium and thoriumRadioactive decay series for uranium and thorium


Waste streams- Waste streams- Exploration WastesExploration Wastes

• Material excavated from trenches etc

• Drilling sludge, cuttings and dust

• Core samples

• Disturbed ground, overburden materials

• Drilling fluids, mechanical scrap, grout and cement residues, general refuse

Drill rig P.Waggitt


Waste Streams: Waste Streams: Mining WastesMining Wastes• Solid wastes

• Waste rock and low grade ore from open pits and underground mines (including sub-economic material)

• Industrial waste

• Liquid wastes• Contaminated mine dewatering

water

• Contaminated surface water (process residues, oily wastes etc)

• Airborne emissions• Radon emissions from waste rock

and ore piles, open-pits and underground mines

• Dust emissions from mining and hauling activities

Tailings dam and waste stockpilesP.Waggitt


Waste Streams: Waste Streams: Milling wastesMilling wastes• Solid wastes

• Tailings

• Sludge, filter cakes and scales

• Process residues e.g. sulphur, scats

• Liquid wastes• Barren and Decant solutions

• Seepage from tailings management areas

• Leachate and runoff from waste rock, low grade ore and ore piles

• Plant washings

• Airborne emissions• Dust from screening and crushing

operations

• Toxic fumes from the mill, acid plant, calciner etc

• Yellow cake particles No.1 pit & tailings repository, Ranger Uranium Mine, Australia P.Waggitt


Waste Streams: In situ leaching (ISL) wastes

• Extraction plant liquid waste solutions (bleed solution, wasted barren solution, filter backwash)

• Small amount of solids in the form of sludge and salts

• Ion exchange residues

• Used filter media

• Chemical residues

• Industrial waste

Beverley ISL wellfield,

Heathgate Resources Pty Ltd


Waste streams: Waste streams: Miscellaneous wastesMiscellaneous wastes

• Domestic solid and liquid wastes

• Contaminated scrap material and equipment

• Hazardous substances (oils, chemicals and others)

• Laboratory wastes (solid, gaseous and liquid)


Waste streams: Waste streams: Decommissioning wastesDecommissioning wastes

• Decommissioning procedures generate wastes

• Scale from pipes and process vessels

• Residual liquids from mill components

• Decontamination residues, both solid and liquid

• Building materials, possibly contaminated

• Contaminated scrap metal from plant and machinery

• Process residues

• Unprocessed ore and low grade rock materials

Nabarlek Mill, Australia

P.Waggitt


Radiological and non-radiological properties of wastesRadiological and non-radiological properties of wastes

• Properties of tailings• The major component of wastes in terms of volume and probably

radioactivity

• Need to be managed for a long time

• Other liquid and solid wastes• May be no less important than tailings as contaminant source

• May have potential to move into wider environment relatively easily


Properties of TailingsProperties of Tailings

• Main properties to be considered when considering tailings management options include:

• Uranium ore grade

• Radiological components

• Acid generation potential

• Non-radiological contaminants

• Waste concentrates

Sub aerial tailings deposition in mined out pit

P.Waggitt


Properties of Tailings: Uranium Ore GradeProperties of Tailings: Uranium Ore Grade

• Uranium content of ore ranges from less than 0.1% to over 40%

• High grade ore is usually diluted with low grade or waste rock prior to milling to produce a constant U content for efficient process input and control

• Feed grades to the mill usually range from 0.1% to several per cent

• Tailings produced from high grade ore contain proportionally higher concentration of radionuclides per unit of product

• Low grade ore produces proportionally more tailings per unit of product


Tailings properties: Ore Grade versus tailings volumeTailings properties: Ore Grade versus tailings volume

Mine

Ore Grade

(%)

Uranium Production

(t)

Volume of Tailings

(t)

Uranium / Tailings

Ratio

Beaverlodge 0.21 21,236 10,100,000 475

Key Lake 1.95 71,611 4,400,000 61

McArthur River

12.75 160,200 4,400,000 27


Tailings properties: Tailings properties: Acid Mine DrainageAcid Mine Drainage• Caused by the oxidation and

hydrolysis of sulfide materialssuch as pyrite and pyrrhotite in the presence of moisture and oxygen

• Common problem around the world in many mines in both tailings and waste rock

• Oxidation process forms sulfuric acid, which results in:

• Elevated concentrations of toxic heavy metals and radionuclides in discharges and seepage from the tailings

• Reduction in pH of adjacent water systems

• Unacceptable environmental impacts

Acid drainage seeping from waste rock stockpile

Rum Jungle Uranium Mine, Australia. P.Waggitt


Tailings properties: Tailings properties: Non-radiological ContaminantsNon-radiological Contaminants

• Large number of non-radiological contaminants, mostly metals

• Contaminants in tailings depend on the ore and milling process used

• Non-radiological contaminants most commonly found in the tailings

• are listed in the next slide

• May be potential sources of contamination

• Useful as tracers in monitoring


Tailings properties: Tailings properties: Non-radiological Contaminants Non-radiological Contaminants (continued)(continued)

• Metallic componentsArsenic Barium Boron Cadmium Calcium Chromium

Copper Iron Lead Magnesium Manganese Mercury

Nickel Selenium Silver Vanadium Zinc

Molybdenum

• Non-MetalsAmmonium Carbonates Chlorides Cyanide

Isodecanol

Kersosene Nitrates Phosphoric acid Pyrite Pyrrhotite

Sulphates Tertiary amines Tributyl phosphate


Tailings properties: Tailings properties: Waste Precipitates and ConcentratesWaste Precipitates and Concentrates

• Solid wastes formed as the result of mill effluents and other contaminated waters treatment

• Examples:

• Sludge from the neutralization of acidic solutions

• Sludge from the treatment process of mill effluent with barium chloride

• Brine streams from water treatment e.g. reverse osmosis or ion exchange

• Usually stored within the tailings management areas

• May cause problems due to their poor consolidation properties and contaminant content


Contaminant Release from Uranium Mill tailingsContaminant Release from Uranium Mill tailings

• Most important release mechanisms

• Air emissions: radon and dust

• Seepage from tailings management areas

• Structural failure of containment structures

• Spills during the transport of tailings

• Erosion of covers

• Unauthorized disturbance or removal of tailings

Unauthorized digging in tailingsD.Reisenweaver


General Exposure Pathways to HumansGeneral Exposure Pathways to Humans• Atmospheric pathways

• Inhalation of radon and its daughters

• Inhalation of radioactive particulates

• External irradiation (gamma)

• Atmospheric and terrestrial pathways

• Ingestion of contaminated foodstuffs

• External irradiation

• Aquatic pathways• Ingestion of contaminated water

• Ingestion of foods produced using irrigation, fish and other aquatic biota

• External irradiation

Sheep grazing on tailings areaD.Reisenweaver


Environmental transfer and Dose Model (chart) Environmental transfer and Dose Model (chart)


Non-Radiological ContaminantsNon-Radiological Contaminants

• Often the impacts of non-radiological contaminants is as important or even more important than radiological impacts (however radiological impacts may be more important to the public)

• Non- radiological parameters may also be necessary to understand the environmental processes driving the dispersion of radioactive contaminations (e.g. ph, ground water head, etc.)

• Non-radioactive parameters may also be used as:

• analogues for radioactive contaminants (e.g. natural lead for lead-210 where there is a direct relationship)

• tracers for contamination studies and models


Long Term ImpactLong Term Impact

• The radiation in uranium waste rock and tailings is extremely long lived

• Impacts cannot only be considered in the short term but must include the potential effects on future generations

• Often larger impacts occur after the closure of a facility

Wall made using tailings in the mortarD.Reisenweaver


Institutional ControlInstitutional Control

• Radiation Protection and Safety can only be assured if there is a system in place and it is working and it is consistent

• The system has to be organized and implemented by an independent “power” to ensure it is effective

• Because the potential problems are so long lived, safety has to be organised by a body that will also be long lived

• Governments are probably the only organisations likely to be around long enough

• We call the process behind these systems Institutional Control

• Includes:

• Laws to provide a legal basis for control and penalties for breaches

• Funding to implement the process, provision of inspectors and safety guides, manuals etc

• Setting approved levels of training for operators and regulators alike

• Providing for continuous improvement in the system and interaction with other authorities, both national and local, as well as international


SummarySummary

• Mining and milling generates a range of different wastes which have the potential to impact the public and the environment in a number of ways

• There is a range of pathways by which the operation may cause exposure and these may change over the life of the facility

• Tailings and sometimes waste rock generally have the most potential for providing significant impacts

• Non-radiological contaminants are important in their own right, but also may give information about the dispersal of the radioactive components

• Economic and social factors are an important consideration for both the operator and the regulator

• Long term impacts often are potentially more important than impacts arising during operations

• The creation of Institutional Control provides a mechanism for assurance of protection and safety in the long term

International Atomic Energy Agency IX.4.9. Mining Waste Disposal options for different waste types,...

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