ORCID Profile
0000-0002-1938-8119
Current Organisation
Australian National University
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Synchrotrons; Accelerators; Instruments and Techniques | Atomic, Molecular, Nuclear, Particle and Plasma Physics | High Energy Astrophysics; Cosmic Rays | Nuclear Physics
Expanding Knowledge in the Earth Sciences | Expanding Knowledge in the Physical Sciences |
Publisher: Elsevier BV
Date: 08-2019
DOI: 10.1016/J.SCITOTENV.2019.04.251
Abstract: The
Publisher: Elsevier BV
Date: 12-2016
DOI: 10.1016/J.JENVRAD.2016.09.015
Abstract: A comprehensive series of nuclear tests were carried out by the United States at Enewetak Atoll in the Marshall Islands, especially between 1952 and 1958. A Porites Lutea coral that was growing in the Enewetak lagoon within a few km of all of the high-yield tests contains a continuous record of isotopes, which are of interest (e.g.
Publisher: Elsevier BV
Date: 2019
Publisher: Elsevier BV
Date: 2016
DOI: 10.1016/J.JENVRAD.2015.06.021
Abstract: The isotopes (236)U and (239)Pu, both produced during nuclear weapons tests carried out in the 1950s and 1960s, are present in the environment and may be used as tracers for soil erosion studies. Although these radionuclides occur only at ultra-trace levels in nature, they can be readily measured by accelerator mass spectrometry with the 14UD heavy ion accelerator at the Australian National University. We have analysed a series of vegetation s les for their (236)U and (239)Pu concentration and compared the results with those found in the surrounding soil. (236)U could be measured in all collected s les whereas (239)Pu could not be detected in several vegetation s les due to its very low concentration, although it was readily detectable in the soil. We find that, relative to plutonium, (236)U is preferentially taken up by plants with enrichment factors ((236)U/(239)Pu)veg/((236)U/(239)Pu)soil that range between 7 and 52 in the present study.
Publisher: arXiv
Date: 2022
Publisher: Elsevier BV
Date: 2016
DOI: 10.1016/J.JENVRAD.2015.06.020
Abstract: The isotopes (236)U, (239)Pu and (240)Pu are present in surface soils as a result of global fallout from nuclear weapons tests carried out in the 1950's and 1960's. These isotopes potentially constitute artificial tracers of recent soil erosion and sediment movement. Only Accelerator Mass Spectrometry has the requisite sensitivity to measure all three isotopes at these environmental levels. Coupled with its relatively high throughput capabilities, this makes it feasible to conduct studies of erosion across the geographical extent of the Australian continent. In the Australian context, however, global fallout is not the only source of these isotopes. As part of its weapons development program the United Kingdom carried out a series of atmospheric and surface nuclear weapons tests at Maralinga, South Australia in 1956 and 1957. The tests have made a significant contribution to the Pu isotopic abundances present in the region around Maralinga and out to distances ∼1000 km, and impact on the assessment techniques used in the soil and sediment tracer studies. Quantification of the relative fallout contribution derived from detonations at Maralinga is complicated owing to significant contamination around the test site from numerous nuclear weapons safety trials that were also carried out around the site. We show that (236)U can provide new information on the component of the fallout that is derived from the local nuclear weapons tests, and highlight the potential of (236)U as a new fallout tracer.
Publisher: Elsevier BV
Date: 10-2015
Publisher: Elsevier BV
Date: 10-2009
DOI: 10.1016/J.APRADISO.2009.05.007
Abstract: We present a first effort to investigate (236)U in the environment near a shutdown nuclear power plant far away from highly contaminated sites, by using accelerator mass spectrometry. The detection limit of about 1pg (236)U allowed us to identify a minimal increase of the (236)U/(238)U isotopic ratio correlated to a peak of (137)Cs in river sediments downstream of the nuclear power plant, and to detect anthropogenic (236)U also upstream, where it is probably not related to the power plant but to global fallout. The (236)U content shoved variations of the (236)U/(238)U isotopic ratio in relation to the chemical-physical characteristics of the sediments. This demonstrates the potential of (236)U as an environmental tracer, and as an indicator for releases from nuclear facilities.
Publisher: Elsevier BV
Date: 11-2022
Publisher: arXiv
Date: 2022
Publisher: Springer Science and Business Media LLC
Date: 07-2022
DOI: 10.1038/S41598-022-14179-W
Abstract: Plutonium (Pu) has been used as a mid-twentieth century time-marker in various geological archives as a result of atmospheric nuclear tests mainly conducted in 1950s. Advancement of analytical techniques allows us to measure 239 Pu and 240 Pu more accurately and can thereby reconstruct the Pacific Pu signal that originated from the former Pacific Proving Grounds (PPG) in the Marshall Islands. Here, we propose a novel method that couples annual banded reef building corals and nearshore anoxic marine sediments to provide a marker to precisely determine the start of the nuclear era which is known as a part of the Anthropocene. We demonstrate the efficacy of the methods using sediment obtained from Beppu Bay, Japan, and a coral from Ishigaki Island, Japan. The sedimentary records show a clear Pu increase from 1950, peaking during the 1960s, and then showing a sharp decline during the 1970s. However, a constantly higher isotope ratio between 239 Pu and 240 Pu suggest an additional contribution other than global fallout via ocean currents. Furthermore, single elevations in 240 Pu/ 239 Pu provide supportive evidence of close-in-fallout similar to previous studies. Coral skeletal radiocarbon displays a clear timing with the signatures supporting the reliability of the Beppu Bay sediments as archives and demonstrates the strength of this method to capture potential Anthropocene signatures.
Publisher: Elsevier BV
Date: 10-2022
Publisher: Elsevier BV
Date: 06-2014
DOI: 10.1016/J.JENVRAD.2014.02.022
Abstract: The variation of the (236)U and (239)Pu concentrations as a function of depth has been studied in a soil profile at a site in the Southern Hemisphere well removed from nuclear weapon test sites. Total inventories of (236)U and (239)Pu as well as the (236)U/(239)Pu isotopic ratio were derived. For this investigation a soil core from an undisturbed forest area in the Herbert River catchment (17°30' - 19°S) which is located in north-eastern Queensland (Australia) was chosen. The chemical separation of U and Pu was carried out with a double column which has the advantage of the extraction of both elements from a relatively large soil s le (∼20 g) within a day. The s les were measured by Accelerator Mass Spectrometry using the 14UD pelletron accelerator at the Australian National University. The highest atom concentrations of both (236)U and (239)Pu were found at a depth of 2-3 cm. The (236)U/(239)Pu isotopic ratio in fallout at this site, as deduced from the ratio of the (236)U and (239)Pu inventories, is 0.085 ± 0.003 which is clearly lower than the Northern Hemisphere value of ∼0.2. The (236)U inventory of (8.4 ± 0.3) × 10(11) at/m(2) was more than an order of magnitude lower than values reported for the Northern Hemisphere. The (239)Pu activity concentrations are in excellent agreement with a previous study and the (239+240)Pu inventory was (13.85 ± 0.29) Bq/m(2). The weighted mean (240)Pu/(239)Pu isotopic ratio of 0.142 ± 0.005 is slightly lower than the value for global fallout, but our results are consistent with the average ratio of 0.173 ± 0.027 for the southern equatorial region (0-30°S).
Publisher: Elsevier BV
Date: 2019
Publisher: Elsevier BV
Date: 04-2011
DOI: 10.1016/J.JENVRAD.2011.01.004
Abstract: S les from a marine sediment core from the Irish Sea (54.416 N, 3.563 W) were analyzed for the isotopic composition of uranium, plutonium and americium by a combination of radiometric methods and AMS. The radiochemical procedure consisted of a Pu separation step by anion exchange, subsequent U separation by extraction chromatography using UTEVA® and finally Am separation with TRU® Resin. Additionally to radiometric determination of these isotopes by alpha spectrometry, the separated s les were also used for the determination of (236)U/(238)U and plutonium isotope ratios by Accelerator Mass Spectrometry (AMS) at the VERA facility.
Publisher: Elsevier BV
Date: 09-2022
Publisher: American Association for the Advancement of Science (AAAS)
Date: 14-05-2021
Abstract: The rapid neutron capture process (r-process) produces many of the heavy chemical elements, but the astrophysical settings where it occurs remain unclear. Leading candidates are neutron star mergers and some types of supernovae. Wallner et al. analyzed the plutonium content of a deep-sea crust s le, identifying a few dozen atoms of the r-process isotope plutonium- 244 that were delivered to Earth within the past few million years. There was a simultaneous signal of iron-60, which is known to be produced in supernovae. Comparing the ratios of these isotopes constrains the relative contributions of supernovae and neutron star mergers to r-process nucleosynthesis. Science , this issue p. 742
Publisher: Elsevier BV
Date: 05-2023
Publisher: Elsevier BV
Date: 11-2017
DOI: 10.1016/J.JENVRAD.2017.05.009
Abstract: A slice from a Porites Lutea coral core collected inside the Enewetak Atoll lagoon, within 15 km of all major nuclear tests conducted at the atoll, was analysed for
Publisher: Elsevier BV
Date: 2019
Publisher: Elsevier BV
Date: 09-2019
DOI: 10.1016/J.JENVRAD.2019.05.003
Abstract: Anthropogenic radionuclides, like
Publisher: Elsevier BV
Date: 06-2011
Publisher: Wiley
Date: 31-03-2020
DOI: 10.1111/MAPS.13466
Publisher: Springer Science and Business Media LLC
Date: 28-09-2023
Publisher: Elsevier BV
Date: 10-2015
Publisher: Walter de Gruyter GmbH
Date: 11-2008
Abstract: The occurrence of 238 Pu, 239(40) Pu, 241 Am, 90 Sr and 137 Cs in the region of Nassfeld (Salzburg, Austria) is discussed at four different locations by evaluating a depth profile for each radionuclide. Furthermore, the plutonium separated from the soil s les was measured by Accelerator Mass Spectrometry (AMS) to get information on the isotope ratio 240 Pu/ 239 Pu. The radiochemical procedure consisted of a Pu separation step from Am and Sr by anion exchange in 8 M HNO 3 after oxidation state adjustment to Pu(IV). Am and Sr were coprecipitated with calcium oxalate. Am was separated from Sr by extraction chromatography using TRU-resin. The Sr separation was performed also by extraction chromatography using Sr-resin after coprecipitation as oxalate, 90 Sr was measured in a gas proportional counter. For the determination of 239(40) Pu and 241 Am by α-spectrometry thin sources were prepared by microprecipitation with NdF 3 . With the respective Pu isotope ratios, it was possible to identify the global fallout as source of the contamination. This was confirmed by the ratio 241 Am/ 239(40) Pu. From the activity ratio 90 Sr/ 137 Cs, it could be shown that most of these radionuclides stem from the reactor accident in Chernobyl.
Publisher: Elsevier BV
Date: 04-2010
Publisher: Elsevier BV
Date: 2019
Publisher: Elsevier BV
Date: 2019
Publisher: Wiley
Date: 02-11-2015
Publisher: EDP Sciences
Date: 2013
Publisher: Elsevier BV
Date: 12-2009
DOI: 10.1016/J.APRADISO.2009.04.011
Abstract: For determining natural levels of (236)U with its environmental abundance of 10(-16)% rather large s le volumes (approximately 30L) are necessary, therefore the conventional radiochemical uranium analysis (pre-concentration and column chromatography) is very time consuming. To speed up the procedure hydrophobic ionic liquids (ILs) were evaluated as a potential extraction agent for uranium from aqueous solutions. High selectivity and efficiency for uranium compared to calcium and magnesium in natural water was achieved with tricaprylmethylammonium thiosalicylate, [A336][TS]. Uranium was stripped successfully from the investigated ILs with 2M HNO(3).
Publisher: Walter de Gruyter GmbH
Date: 19-04-2023
Abstract: Uranium ores and yellow cake s les of known geographic origin were investigated for their n ( 236 U)/ n ( 238 U) isotope abundance ratio. S les from four different uranium mines in Australia, Brazil and Canada were selected. Uranium was separated by UTEVA ® Resin and was measured by Accelerator Mass Spectrometry (AMS) at the Vienna Environmental Research Accelerator (VERA). The measurement of the isotope abundance ratio n ( 236 U)/ n ( 238 U) will be used to investigate possible correlations between the original mineral (uranium ore) and the intermediate product (yellow cake). Such correlations are useful indicators for nuclear forensic or for non-proliferation purposes.
Publisher: Proceedings of the National Academy of Sciences
Date: 24-08-2020
Abstract: Nearby supernova explosions shape the interstellar medium. Ejecta, containing fresh nucleosynthetic products, may traverse the solar system as a transient passage, or alternatively the solar system may traverse local clouds that may represent isolated remnants of supernova explosions. Such scenarios may modulate the galactic cosmic-ray flux intensity to which Earth is exposed. Varying conditions of the traversed interstellar medium could have impacts on climate and can be imprinted in the terrestrial geological record. Some radionuclides, such as 60 Fe, are not produced on Earth or within the solar system in significant quantities. Their existence in deep-sea sediments demonstrates recent production in close-by supernova explosions with a continued influx of 60 Fe until today.
Publisher: Springer Science and Business Media LLC
Date: 09-03-2020
DOI: 10.1038/S41467-020-15008-2
Abstract: Isotopic ratios of radioactive releases into the environment are useful signatures for contamination source assessment. Uranium is known to behave conservatively in sea water so that a ratio of uranium trace isotopes may serve as a superior oceanographic tracer. Here we present data on the atomic $$^{233}$$ 233 U/ $$^{236}$$ 236 U ratio analyzed in representative environmental s les finding ratios of (0.1–3.7) $$\\cdot$$ ⋅ 10 $$^{-2}$$ − 2 . The ratios detected in compartments of the environment affected by releases of nuclear power production or by weapons fallout differ by one order of magnitude. Significant amounts of $$^{233}$$ 233 U were only released in nuclear weapons fallout, either produced by fast neutron reactions or directly by $$^{233}$$ 233 U-fueled devices. This makes the $$^{233}$$ 233 U/ $$^{236}$$ 236 U ratio a promising new fingerprint for radioactive emissions. Our findings indicate a higher release of $$^{233}$$ 233 U by nuclear weapons tests before the maximum of global fallout in 1963, setting constraints on the design of the nuclear weapons employed.
Publisher: Elsevier BV
Date: 2016
DOI: 10.1016/J.JENVRAD.2015.06.008
Abstract: Anthropogenic (236)U and (239)Pu were measured in European roe deer antlers hunted between 1955 and 1977 which covers and extends beyond the period of intensive nuclear weapons testing (1954-1962). The antlers were hunting trophies, and hence the hunting area, the year of shooting and the approximate age of each animal is given. Uranium and plutonium are known to deposit in skeletal tissue. Since antler histology is similar to bone, both elements were expected in antlers. Furthermore, roe deer shed their antlers annually, and hence antlers may provide a time-resolved environmental archive for fallout radionuclides. The radiochemical procedure is based on a Pu separation step by anion exchange (Dowex 1 × 8) and a subsequent U purification by extraction chromatography using UTEVA(®). The s les were measured by Accelerator Mass Spectrometry at the VERA facility (University of Vienna). In addition to the (236)U and (239)Pu concentrations, the (240)Pu/(239)Pu isotopic ratios were determined with a mean value of 0.172 ± 0.023 which is in agreement with the ratio of global fallout (∼0.18). Rather high (236)U/(238)U ratios of the order of 10(-6) were observed. These measured ratios, where the (236)U arises only from global fallout, have implications for the use of the (236)U/(238)U ratio as a fingerprint for nuclear accidents or releases from nuclear facilities. Our investigations have shown the potential to use antlers as a temporally resolved archive for the uptake of actinides from the environment.
Publisher: Elsevier BV
Date: 11-2022
Publisher: Elsevier BV
Date: 07-2022
DOI: 10.1016/J.JENVRAD.2022.106871
Abstract: Concentrations of
Publisher: EDP Sciences
Date: 2020
DOI: 10.1051/EPJCONF/202023201002
Abstract: The direct detection of dark matter is a key problem in astroparticle physics that generally requires the use of deep-underground laboratories for a low-background environment where the rare signals from dark matter interactions can be observed. This work reports on the Stawell Underground Physics Laboratory – currently under construction and the first such laboratory in the Southern Hemisphere – and the associated research program. A particular focus will be given to ANU’s contribution to SABRE, a NaI:Tl dark matter, direct detection experiment that aims to confirm or refute the long-standing DAMA result. Preliminary measurements of the NaI:Tl quenching factor and characterisation of the SABRE liquid scintillator veto are reported.
Publisher: Elsevier BV
Date: 02-2013
DOI: 10.1016/J.JENVRAD.2012.09.013
Abstract: Accelerator Mass Spectrometry (AMS) and alpha spectrometry were used to determine uranium ((236)U, (238)U, (234)U) and plutonium isotopes ((239)Pu, (240)Pu) in sea and river water s les. Plutonium was separated by Dowex(®) 1 × 8 resin and UTEVA(®) resin was used for uranium purification. The measured (236)U/(238)U isotopic ratios for surface water from the Atlantic Ocean, the Pacific Ocean and the Black Sea were in the order of 10(-9), while values for river water were in the order of 10(-8). These contaminations may be attributed to global fallout. A s le of the reference material IAEA-443, collected from the Irish Sea, showed, in accordance to the reference value, a ratio that was 10(3) times higher due to effluents from the reprocessing plant at Sellafield. These results underline the good suitability of (236)U/(238)U as a tracer for hydrology and oceanography, and show that relatively small water s les are sufficient for the determination of (236)U by AMS, which is not the case for plutonium with present techniques. The plutonium concentrations in our water s les could only be measured with large uncertainties and were in the order of 10(-3) mBq/L (with the exception of the Irish Sea s le).
Publisher: Informa UK Limited
Date: 31-05-2016
Publisher: Elsevier BV
Date: 2023
Publisher: SAGE Publications
Date: 19-12-2022
DOI: 10.1177/20530196221135077
Abstract: For assessment of the potential of the Beppu Bay sediments as a Global boundary Stratotype Section and Point (GSSP) candidate for the Anthropocene, we have integrated datasets of 99 proxies. The datasets for the sequences date back 100 years for most proxy records and 1300 years for several records. The cumulative number of occurrences of the anthropogenic fingerprint reveal unprecedented increases above the base of the 1953 flood layer at 64.6 cm (1953 CE), which coincides with an initial increase in global fallout of 239 Pu+ 240 Pu. The onset of the proliferation of anthropogenic fingerprints was followed by erse human-associated events, including a rapid increase in percent modern 14 C in anchovy scales, changes in nitrogen and carbon cycling as recorded by anchovy δ 15 N and δ 13 C, elevated pollution of heavy metals, increased deposition of novel materials (spheroidal carbonaceous particles, microplastics, polychlorinated biphenyls), the occurrence of hypoxia (Re/Mo ratio) and eutrophication (biogenic opal, TOC, TN, diatoms, chlorophyll a), unprecedented microplankton community changes (compositions of carotenoids, diatoms, dinoflagellates), abnormally high spring air temperatures as inferred from diatom fossils, and lithological changes. These lines of evidence indicate that the base of the 1953 layer is the best GSSP level candidate in the stratigraphy at this site.
Publisher: Elsevier BV
Date: 09-2015
Publisher: Springer Science and Business Media LLC
Date: 17-03-2017
DOI: 10.1038/SREP44679
Abstract: Unusually high concentrations of americium and plutonium have been observed in a sediment core collected from the eastern Lombok Basin between Sumba and Sumbawa Islands in the Indonesian Archipelago. Gamma spectrometry and accelerator mass spectrometry data together with radiometric dating of the core provide a high-resolution record of ongoing deposition of anthropogenic radionuclides. A plutonium signature characteristic of the Pacific Proving Grounds (PPG) dominates in the first two decades after the start of the high yield atmospheric tests in 1950’s. Approximately 40–70% of plutonium at this site in the post 1970 period originates from the PPG. This sediment record of transuranic isotopes deposition over the last 55 years provides evidence for the continuous long-distance transport of particle-reactive radionuclides from the Pacific Ocean towards the Indian Ocean.
Start Date: 2018
End Date: 2020
Funder: Australian Research Council
View Funded ActivityStart Date: 02-2018
End Date: 12-2021
Amount: $520,865.00
Funder: Australian Research Council
View Funded Activity