ENVIRONMENTAL DOSIMETRY AND RADIOGENIC LUMINESCENCE RESEARCH AT THE UNIVERSITY OF ADELAIDE Adjunct Prof. Nigel A. Spooner Institute for Photonics and Advanced Sensing School of Physical Sciences, University of Adelaide, & Defence Science and Technology Group 1
Prescott Environmental Luminescence Laboratory University of Adelaide / DST Group Facility 19 personnel, $10M laboratory facility in The Braggs Bldg. Environmental Dosimetry Optical Dating: Archaeology/Palaeoanthropology/Palaeontology mass extinctions/earth Sciences Radiation Event Dosimetry Retrospective Population Dosimetry dose mapping using TL and OSL Radionuclide measurements Ge-gamma & NaI-gamma ray spectrometry; alpha counting Radiation-sensitive optical fibres Portal sensors Mining & Mineral Processing: Process monitoring Medical Devices: Targeted Alpha Therapy / 3D gamma beam measurement Materials characterisation Fluorescence & luminescence techniques Food Irradiation Testing Test for spoilage masking Check compliance with dosing requests Certify for export
Pulsed - OSL (a.u.) Environmental Luminescence Facilities & Capabilities Radiogenic Luminescence, Single-Grain Dating, Spatially-Resolved TL/OSL Key Research Capabilities 1. Radiogenic Luminescence Dosimetry 2. Spatially-Resolved Luminescence 3. TL Spectral Measurement 4. Time-Resolved OSL 5 4 3 1 0.1 5. Fluorescence Measurement 2 1 0.01 0 500 1000 1500 0 0 500 1000 1500 2000 Time (ms) 6. Radiation Dose-Rate and Radioisotope Identification 7. Radiation-Sensitive Optical Fibres - distributed sensing
Atom Trap Trace Analysis (ATTA) The most sensitive radionuclide measurement technique isotopic abundance 1 part in 10 11 10 16. Establishing world s most sensitive ATTA facility in UoA IPAS, in collaboration with CSIRO & ANSTO 3 Key Noble Gas RN s 85 Kr 10.8 yr. Fission product from 235 U and 239 Pu. Ideal nuclear waste containment monitor 81 Kr - 229,000 yr. Cosmogenic. Ideal for groundwater dating and ice core dating 39 Ar 269 yr. Cosmogenic. Ideal for oceanography
Radiation Dose Reconstruction using Luminescence The luminescence utilised is a radiation damage effect in solids quantity of luminescence produced is proportional to the radiation dose Enables dosimetry using materials opportunistically available in the environment - Modern: - Radiation accidents and events Retrospective Population dosimetry and forensic dosimetry Ancient: - Luminescence Dating ( Geochronology ) applied to Palaeontology, Archaeology and Earth Sciences
Modern Day - Dose Reconstruction Luminescence is a unique means for quantifying the spread of radiation dose following a nuclear event Chernobyl porcelain by Thermoluminescence Semipalatinsk brick
ANSTO Moata Concrete Shielding Analyses Goal: Investigate Luminescence as a means of determining if an unknown concrete sample had prior exposure to radiation sources. i.e., shielding in a nuclear facility 2. 2000mm 1. 1550mm Subfloor core 7 portions 3. 1760mm Estimated boundary of activated region Horizontal Core Holes (Plan View - Not to Scale). The labels show the length of each core 7. 2250mm; below Moata @ 30 o 4. 1495mm
TL Depth Profile a measure of deposited radiation with proximity to the core TL at 220 C is the marker of recent (decadal-century timescale) irradiation 100 mm dia. core section Core section A Core section H Reactor biological shield (concrete) Reactor core 1000 900 800 700 600 500 400 300 200 100 0-100 Natural TL Glow Curves Paired discs for core sections A,H,U frag A Natural #1 frag A Natural #2 frag H Natural #1 frag H Natural #2 frag U Natural #1 frag U Natural #2 0 100 200 300 400 500 600 Core section U Side elevation
Moata core #2 TL Emission Spectra from sedimentary quartz grains extracted from Moata concrete as-received Peak counts 4 k 8 k 12 k 18 K 0 mm 1300 mm 2000mm Sub floor (closest to core) Sample distance from external surface TL emission peak centred at 600 nm wavelength, with increasing intensity of metastable dosimetry signal around 220-250C as sample distance from the core decreases
Radiation damage marker TL peak ratios Irradiated (beta) sedimentary quartz grains TL peak occurrence and ratios show dose-dependent 32 Gy 64 Gy 128 Gy 256 Gy 500 Gy 1 kgy 2 kgy 4 kgy 8 kgy 16 kgy Emission spectra measured after 100 Gy test dose following prior doses as shown
Ancient World: - Geochronology - Luminescence dating U Adelaide key directions include: 1. Single-grain Optical Dating 2. Extended-range dating techniques (TT-OSL, post-ir IRSL) Applications Arnold et al., Quaternary International, in press 1. Landscape evolution 2. Megafaunal extinction chronologies 3. Reconstructing archaeological histories in Europe, Australia and Africa 4. Dating Quaternary palaeoenvironmental records
Normalised luminescence Optical dating Introduced by Huntley et al. (1985) Nature. Advantages: - Provides numerical age estimates - Applicable to ubiquitous material - Direct dating of depositional events - Wide environmental & archaeological applications - Complex age calibration not required - Applicable over relatively broad age range Several key methodological advancements - Multiple aliquot single aliquot D e measurement - Single-aliquot regenerative-dose (SAR) protocol D e Additive dose curve Dose (Gy) SAR curve D e Dose (Gy)
Age (ka) = D e (Gy) Dose rate (Gy ka -1 ) Dendrochronology Radiocarbon Potassium-argon & argon-argon (1 Gy = 1J kg -1 ) Pb-210 U-series U-Pb Fission track Age range: Luminescence Youngest: 0-100 yrs Electron spin resonance Optimum: 1-100 ka Cosmogenic nuclides Oldest: ~ several hundred ka Amino acid racemisation Obsidian hydration Precision: typically ~5-10% Archaeomagnetism Magnetic polarity 0.1 1 10 100 1000 Age (thousands of years) After Lee Arnold, Modified from Walker (2005)
OSL signal (counts / 0.02 s) Normalised OSL Single-grain OSL dating Multi-grain aliquot = 10 1 10 3 grains 1000 800 Atapuerca quartz grain 8 6 600 4 2 400 0 0 200 400 600 200 Natural 15 Gy test dose Dose (Gy) Single-grain aliquot 0 0 0.5 1 1.5 2 Risø single-grain attachment unit
Relative probability Frequency Frequency Relative probability Frequency Relative probability Single-grain OSL: Advantage Improved reliability in complex sedimentary contexts (a) Adequate bleaching (b) Partial bleaching (c) Post-depositional mixing OSL signal signal zeroed by light exposure level of natural signal signal reduced by light exposure larger natural signal t 0 Residual signal resetting event burial time resetting event burial time t i 30 30 30 25 25 25 20 20 20 15 15 15 10 5 SG 10 5 10 5 0 0 0 0 10 20 30 40 50 0 10 20 30 40 50 60 0 10 20 30 40 50 Equivalent dose dose (Gy) (Gy) Equivalent dose dose (Gy) (Gy) Equivalent dose dose (Gy) (Gy)
Naracoorte Caves World Heritage Site Key scientific questions: When did the iconic Australian megafauna become extinct in this region? - What factors contributed to their demise? Global consequences - How does the local extinction history compare with other regions & countries? Excavations Victoria Fossil Cave Marsupial lion den Henschke s Quarry
Megafaunal Extinction & Palaeoanthropology We use the radiation dose accrued in the sand grains in which the bones are buried to measure the time since burial the age. Age = total radiation dose during burial environmental dose rate Environmental radiation dose rate Luminescence from single sand grains Collinsville Diprotodon excavated by Rod Wells and SAM/FU team, dated by IPAS - Age 45-60,000 years
Environmental Dose-Rate Luminescence signal builds up during burial due to energy absorption from exposure to ionising radiation: naturally occurring radioisotopes + cosmic rays,, from the decay of 238&235 U, 232 Th, 40 K
Dosimetry techniques in use by U Adelaide Environmental Luminescence 1. Applied portable NaI gamma-ray spectrometry for quantitative field dosimetry since 1980 s U & Th chains (Bi-214 & Tl-208 only) and K-40 2. Pioneered Thick Source Alpha Counting (TSAC) in the late 1970 s total alpha counts for U+Th chains 3. High-Res. Ge-gamma ray spectrometers 3 Coaxial detectors (for samples > 20 g 300 g) 3 Well detectors (16 & 28 mm wells on order; for small samples)
FWHM (kev) New Acquisition - SAGe Well Detectors for Gamma Spectrometry Small Anode Germanium (SAGe) - New technology; best available for Pb-210 best resolution & sensitivity Counting time: typically 3-5 times faster than current wells Samples: solids or fluids in vials or cans (~0-300 g) or Marinelli Beakers Acquired with BHPB sponsorship for research in the ARC Australian Cu-U Hub 16 mm - on order 28 mm - acquire Energy (kev) Energy resolution (FWHM) as a function of energy for different detector types ARC Research Hub for Australian Copper- Uranium
Graduate Certificate in Radiation Management First tertiary-level Radiation Management course in Australia 6 months full time equivalent, delivered half-time over 1 year to enable participation by members of the workforce GCRM offers practical and theoretical learning for supervision and management of radiation safety in a broad spectrum of industries Program Structure: 4 Courses, including 12 practicals jointly hosted by UoA and SA Gov EPA Course Topics: 1. Radioactivity, Radiation Detection and Dosimetry 2. Ionising Radiation - Biological effects and incident response 3. Radiation in the Environment Management and Regulatory Control 4. Radiation Safety in the Workplace
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