IAEA International Atomic Energy Agency
An Overview of IAEA Industry Specific Safety
Reports on NORM
P.P. Haridasan
Radiation Safety and Monitoring Section
Division of Radiation Transport and Waste Safety
International Working Forum on Regulatory Supervision of Legacy Sites (RSLS)
Technical Meeting - 22 - 24 October 2013
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What is NORM?
“Naturally occurring radioactive material”
• It is the radionuclides that are naturally occurring, not necessarily the material (e.g. process residues)
• All materials contain certain amount of natural radionuclides
• Does that mean - Everything in the environment is NORM ?
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Definitions: IAEA Safety Glossary (version 2.0):
Material designated in national law or by a regulatory body as being subject to regulatory control because of its radioactivity
Radioactive material (as defined above)
containing no significant amounts of radionuclides other than naturally occurring radionuclides
Radioactive material
NORM
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Natural radionuclides
• U-238 and Th-232 series - prominent
• Mixture of radionuclides
• K-40
• Long-lived to short-lived radionuclides
• Gaseous forms – Rn-222 (radon)
Rn-220 (thoron)
• Alpha emitters, beta-gamma emitters
• Very high energies – Po-212 8.78 MeV alpha
• Gamma – 2.6 MeV Tl-208 IAEA TM RSLS, 24 October 2013 4
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Hazards
• External – mainly gamma exposures
• Internal – inhalation of airborne dust
– inhalation of radon/thoron and
short-lived progeny nuclides
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NORM Safety Issues
• Exposure of the workers.
• Exposure of the public.
• Protection of the environment.
• Physical security of the product.
• Transport of radioactive material.
• Ensuring the long term stability of the waste
disposal options.
• Limiting effluent discharges.
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Radionuclide behaviour during mining and mineral
processing
Mining and processing of minerals: Radionuclides can become mobilized
Disruption of equilibrium conditions that existed in the ore
Possibility of much higher activity concentrations in certain process
materials, sometimes by orders of magnitude
Main processes : Mining of ore
Physical mineral separation processes
Wet chemical extraction processes
Thermal processes for extraction, processing and
combustion of minerals
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1. Mining and comminution of ore Open pit mining
Vertical shaft
Inclined shaft
Underground drilling
Underground rockhandling
Dredge mining
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1. Mining and comminution of ore
Ore - usually in equilibrium (approximately)
Radionuclide mobilization & disruption of equilibrium - limited
Gamma exposure depends on geometry
Radon exhalation and airborne dust generation depend on:
Geology/mineralogy, e.g. igneous - sedimentary,
rock - mineral sand
Mining method, e.g. underground , surface, wet , dry
Ore comminution method, e.g. dry vs wet, crushing vs
grinding
Dust activity concentration may be different from that of ore
Wet mining and comminution may cause dissolution and
subsequent precipitation of radionuclides on equipment
surfaces
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2. Physical mineral separation processes
Phosphate rock beneficiation
plant
Gravity separation of mineral sand
Flotation
Heavy mineral concentrate
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2. Physical mineral separation processes
Includes gravity concentration, magnetic separation, electrostatic
separation, flotation in a chemically inactive environment
Limited opportunity for radionuclide mobilization & disruption of equilibrium
Gamma exposure depends principally on geometry and can be calculated
Airborne dust exposure likely to be dominant in dry separation
Activity concentration of dust may be significantly different from that of ore,
due to differing mechanical properties of ore components
e.g. preferential concentration of Th-rich monazite in dust
Wet physical processes can cause precipitation of radionuclides on
equipment surfaces, sometimes at high concentrations
e.g. precipitation from produced water in oil & gas extraction
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2. Physical mineral separation
processes
Radium-rich pipe scale in the oil and gas industry
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3. Wet chemical extraction processes
Chemical leaching is applied in situ or to crushed/milled ore
Strong acid or alkali leaching results in significant extraction of
radionuclides
Dissolved radionuclides can precipitate out in scales, sludges,
filters, rubber linings and resins, often at high
concentrations
Most prevalent during solvent extraction, ion exchange,
metal recovery by electrochemical processing
(electrowinning), etc.
Implications for exposure to gamma radiation and dust
Chemistry of the radio-elements involved differs widely
Radionuclide-specific analyses usually needed
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4. Thermal processes for extraction, processing
and combustion of minerals
Includes:
Metal production/refining by melting or reduction
Recycling of scrap
High temperature separation of minerals
Calcining (roasting to decompose hydrates, carbonates etc. and to expel volatile material)
Combustion of fossil fuels Main radiological concern is exposure to furnace fume and dust
Low boiling point radionuclides are volatilized (e.g. 210Pb, 210Po and sometimes Ra isotopes)
Volatilized radionuclides condense in scrubbers, filters and stacks — risk of inhalation of airborne dust during maintenance
Non-volatilized radionuclides tend to migrate to slag, ash, scale — possible risk due to gamma radiation or airborne dust during disposal or use as by-product
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4. Thermal processes for extraction, processing
and combustion of minerals
Melting of scrap steel in an arc furnace
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NORM Residues
• Large volumes - 104-106 tonnes/ or more per year per facility
• Residues may be chemically toxic and/or radioactive
• Residues can range from dry solids (varying from rocks to fine powders),
through slurries to liquids containing
dissolved material
• Other chemical constituents within the material may include heavy metals,
inorganic elements (e.g. arsenic) and
various organic compounds. The
potential for such non-radiological
substances to cause detriment needs
to be considered when planning the
management of NORM residues.
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Often occurs in large quantities
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Residues: properties
• Scale: few Bq/g.. or even up to 1000 Bq/g Ra-226
• Possibility for inhomogeneous activity distribution
• If scale are of Ra-type, hot spots can be identified by gamma measurements
• For Pb-210 scale, beta-sensitive equipment must be used
• Required radionuclide chracterisation
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Protection and safety considerations
• Occupational Health and Safety in place
• Ventilation – in confined areas and underground mines
• Spillage and contamination
• Potential for personal contamination in chemical process plants
• Follow the RP rules
• Use personal protective equipments where appropriate
• Radiation protection to be tailored to the particular type of industry or process
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Industry sectors of interest
1. Uranium mining and processing 2. Rare earths extraction SR68 3. Thorium extraction & use 4. Niobium extraction 5. Non-U mining – incl. radon 6. Oil and gas SR34 7. TiO2 SR76 8. Phosphates SR78 9. Zircon & zirconia SR51 10. Metals production (Sn, Cu, Al, Fe, Zn, Pb) 11. Burning of coal etc. 12. Water treatment – incl. radon
The following industry sectors have been identified, roughly in descending order, as being the most likely to require some form of
regulatory consideration
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For Industrial NORM issues –
IAEA Safety Reports Series
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The NORM Symposia
Amsterdam, Netherlands 1997
Krefeld, Germany 1998 (NORM II)
Brussels, Belgium 2001(NORM III)
Szczyrk, Poland 2004 (NORM IV)
Seville, Spain 2007 (NORM V)
Marrakesh, Morocco 2010 (NORM VI)
Beijing, China 2013 (NORM VII)
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Other documents
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THANKS.
contact : [email protected]
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mailto:[email protected]