Assessment of Radiologically
Contaminated Land
Drew Watson
[email protected]
Radiation & Nuclear Sciences Unit,
Public & Environmental Health,
Forensic & Scientific Services,
Health Support Queensland,
Queensland Department of Health, Australia
Contents
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Health Physics
Radiological Contamination Assessment Criteria
Computer Modelling
Radiation Sources: NORM
Radiation Sources: Anthropogenic
Survey Meters
Field Sampling & Laboratory Analysis
Examples of Mineral Sand Contaminated Sites
Conclusion
Health Physics
"Health physics" is the profession devoted to protecting people and
their environment from potential radiation hazards, while making it
possible to enjoy the benefits of the peaceful use of the atom.
http://www.hps.org/
HEATLH PHYSICS PROFESSIONS
• Regulatory
• Medical
• Reactor / Nuclear
• Environmental
–
–
–
–
–
Dose assessments
Contaminated land
Environmental monitoring/surveillance
Environmental modelling – transport & impact
Decontamination & Decommissioning
Radiological Contamination Assessment Criteria
Dose Based
NEPM: National Environment Protection (Assessment of Site Contamination)
Amendment Measure 2013 (No. 1).
The purpose of the Measure is to establish a nationally consistent approach to
the assessment of site contamination to ensure sound environmental
management practices by the community which includes regulators, site
assessors, environmental auditors, land owners, developers and industry. The
desired environmental outcome for this Measure is to provide adequate
protection of human health and the environment, where site contamination has
occurred, through the development of an efficient and effective national
approach to the assessment of site contamination.
Queensland 0.3 mSv/y
MARSSIM: Multi-Agency Radiation Surveys and Site Investigation Manual
Provides detailed guidance for planning, implementing, and evaluating
environmental and facility radiological surveys conducted to demonstrate
compliance with a dose- or risk-based regulation. MARSSIM focuses on the
demonstration of compliance during the final status survey following scoping,
characterization, and any necessary remedial actions. http://www.marssim.com/
Radiological Contamination Assessment Criteria
Dose Based
DESIRED OUTCOME
characterise only = nil change
remediate = managed
remediate = cleared
MEASUREMENTS
gamma survey
surface cont. survey
soil
water
air
0.3 mSv/y
LAND USE
residential
commercial
industrial
parkland
EXPOSURE SCENARIO
time on-site
site activities
EXPOSURE PATHWAYS
external
inhalation
ingestion
absorption
CALCULATIONS
corr. for background exposure
unit conversions (mGy/hr, Bq/kg to Sv)
exposure factors (occupancy, intakes)
Computer Modelling
RESRAD is a computer model designed to estimate radiation doses and risks
from RESidual RADioactive materials. https://web.evs.anl.gov/resrad/
ERICA-tool is a software system that has a tiered approach to assessing the
radiological risk to terrestrial, freshwater and marine biota. http://erica-tool.com/
Radiation Sources
Naturally Occurring Radioactive Material (NORM)
NORM is present within the earths
crust and can be extracted and
concentrated such as during mining
activities, the processing or use of
minerals. And may appear in byproducts and waste streams.
INDUSTRIES
• Uranium
• Mineral sands
• Coal seam / natural gas
• Phosphate fertilizers
• Rare earths
PRODUCTS
• Metal alloys
• Ceramics
• Tile glazes
• Gas lantern mantles
• Welding rods
Radiation Sources
Naturally Occurring Radioactive Material (NORM)
Uranium 238
4.47x109 y
Uranium 234
2.46x105 y
alpha
PRIMORDIAL DECAY SERIES’
Uranium-238
Thorium-232
Uranium-235
alpha
beta
Protactinium 234m
1.17 m
Thorium 234
24.10 d
beta
#
Thorium 230
7.54x104 y
alpha
Radium 226
1600 y
alpha
#
Radon 222
3.82 d
alpha
Polonium 218
3.05 m
Polonium 214
0.16 ms
Polonium 210
138 d
alpha
alpha
Bismuth 214
19.9 m
alpha
beta
(99.98%)
#
beta
Bismuth 210
5.01 d
alpha
(0.02%)
Lead 214
26.8 m
# denotes significant gamma emitter
beta
#
Lead 210
22.3 y
Thallium 210
1.30 m
beta
#
beta
#
Lead 206
stable
Radiation Sources
Anthropogenic
INDUSTRIAL
• Level / density gauges (Cs137, Co60)
• Radiography (Ir192, Co60)
MEDICAL
• diagnostic & treatment radiopharmaceuticals
(Tc99m, F18, Ga67, I131, I123, In111)
RESEARCH
• Radiolabelling (Cr51, H3, C14)
• Gas Chromatograph Mass Spectrometry (Ni63, H3)
SELF POWERED LIGHT SOURCES
• Exit signs, watches, compasses
(Ra226, Pm147, H3)
OTHER
• Smoke detectors (Am241)
• Electricity meters
Gamma Survey Meters
PROTECTION LEVEL
• Small detector volume
• Rapid response time
• Wide measurement range
• Low cost
ENVIRONMENTAL LEVEL
• Large detector volume
• High accuracy at low doses
• Radionuclide identification
• High cost
• Audible / visual adjustable alarms
• Data storage / downloadable
• Ruggedised
Field Sampling
Sampling for radiological assessment
is comparable to sampling for other
contaminants.
Target areas & materials of interest
based on observation, history, field
surveys, etc.
In-situ monitoring equipment for realtime or grab sample results.
Laboratory Analysis
Lab assessment of samples provides low detection limits and high accuracy, but take longer.
ALPHA SPECTROMETRY
• Water / Soil / Dust
• Alpha emitting radionuclides
• Intensive sample prep = high cost
LIQUID SCINTILLATION COUNTING
• Water / TCLP solutions
• Alpha/Beta emitting radionuclides
• Gross alpha/beta activity
• Activity concentration (Ra226, Pb210)
GAMMA SPECTROMETRY
• Soil / Water / Dust
• Identify gamma emitting radionuclides
• Measure activity concentration
Mineral Sands
COMMON SITE ACTIVITIES
• Abrasive blasting
• Processing & storage
• Foundry
• Fill
abrasive blasting site
ilmenite under microscope
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surface gamma radiation survey map of mineral sands processing site
LEGEND
2.001 – 5.000
1.001 – 2.000
0.501 – 1.000
mGyh-1
0.301 – 0.500
0.201 – 0.300
0.101 – 0.200
≤ 0.1
surface gamma radiation survey map of industrial site – abrasive blasting / fill
Conclusion
The type of radioactive material/s and how they present at a site can be
simple or complex.
How to measure the contaminant depends upon characteristics of the
radionuclides and exposure scenarios.
Assessments usually involve a combination of measurements
(eg. gamma survey, gamma spectrometry).
Comparison of site radiological properties with dose based compliance
criteria can be complex and subjective.
A team effort between the Environmental Consultant and Health
Physicist provides the best outcome for radiologically contaminated
land assessments.
THANK YOU
Drew Watson
[email protected]
Radiation & Nuclear Sciences Unit,
Public & Environmental Health,
Forensic & Scientific Services,
Health Support Queensland,
Queensland Department of Health, Australia