Browsing by Author "Rowling, B"
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- ItemContaminant release, mixing and microbial fluctuations initiated by infiltrating water within a replica field-scale legacy radioactive waste trench(Elsevier B. V., 2022-12-10) Kinsela, AS; Payne, TE; Bligh, MW; Vázquez-Campos, X; Wilkins, MR; Comarmond, MJ; Rowling, B; Waite, TDNumerous legacy near-surface radioactive waste sites dating from the mid 20th century have yet to be remediated and present a global contamination concern. Typically, there is insufficient understanding of contaminant release and redistribution, with invasive investigations often impractical due to the risk of disturbing the often significantly radiotoxic contaminants. Consequently, a replica waste trench (~5.4 m3), constructed adjacent to a legacy radioactive waste site (Little Forest Legacy Site, LFLS), was used to assist our understanding of the release and mixing processes of neodymium (Nd) — a chemical analogue for plutonium(III) and americium(III), two significant radionuclides in many contaminated environments. In order to clarify the behaviour of contaminants released from buried objects such as waste containers, a steel drum, representative of the hundreds of buried drums within the LFLS, was placed within the trench. Dissolved neodymium nitrate was introduced as a point-source contaminant to the base of the trench, outside the steel drum. Hydrologic conditions were manipulated to simulate natural rainfall intensities with dissolved lithium bromide added as a tracer. Neodymium was primarily retained both at its point of release at the bottom of the trench (>97 %) as well as at a steel container corrosion point, simulated through the emplacement of steel wool. However, over the 8-month field experiment, advective mixing initiated by surface water intrusions rapidly redistributed a small proportion of Nd to shallower waters (~1.5–1.7 %), as well as throughout the buried steel drum. Suspended particulate forms of Nd (>0.2 μm) were measured at all depths in the suboxic trench and were persistent across the entire study. Analyses of the microbial communities showed that their relative abundances and metabolic functions were strongly influenced by the prevailing geochemical conditions as a result of fluctuating water depths associated with rainfall events. The site representing steel corrosion exhibited divergent biogeochemical results with anomalous changes (sharp decrease) observed in both dissolved contaminant concentration as well as microbial diversity and functionality. This research demonstrates that experimental trenches provide a safe and unique method for simulating the behaviour of subsurface radioactive contaminants with results demonstrating the initial retention, partial shallow water redistribution, and stability of particulate form(s) of this radioactive analogue. These results have relevance for appropriate management and remediation strategies for the adjacent legacy site as well as for similar sites across the globe. © 2022 Elsevier B.V.
- ItemEstablishing a radioanalytical capability to support reactor decommissioning(South Pacific Environmental Radioactivity Association, 2018-11-06) Harrison, JJ; Martiniello, J; Mokhber-Shahin, L; Rowling, B; Silitonga, AS; Thiruvoth, S; Vardenega, C; Van De Voorde, R; Wilsher, KL; Wong, HKYAustralia’s first reactor, the 1O megawatt High Flux Australian Reactor (HIFAR) vi/as operated between 1958 and 2007. HIFAR was one of six DIDO reactors which were installed in the UK, Denmark, Germany and Australia. HIFAR was a multi-purpose reactor, initially used for nuclear material research followed by production of medical radioisotope; an: neutron diffraction experiments. Atter HIFAR was closed, a process of decommissioning commenced. Initially, internal components such as the fuel and heavy water (which acted as primary coolant and neutron moderator) were removed. Currently, HIFAR is in a “care and maintenance" phase whereby short-lived radionuclides can decay and non-radioactive equipment and instrumentation removed. Approximately 1OO research and power reactors have been decommissioned around the world including two of the DIDO class reactors at Harwell, UK and Risø, Denmark. ANSTO can draw on international experience as we as well as experience gained during decommissioning of its own 100 kilowatt Moata reactor in 2010. Accurate identification and quantification of radioactivity is a critical safety, environmental and economic aspect of any nuclear reactor decommissioning project as it supports decision making around long-term storage of disposal options of reactor materials as well as environmental assessment of the reactor site. A capability to quantify typical radionuclides found in reactor materials and environmental samples is being developed at ANSTO. Reactor materials that may require assessment include concrete, graphite and steel and environmental samples include soils and waters. Radionuclides of interest are predominantly beta- and gamma-emitting fission and activation products. Non—destructive, high resolution gamma spectrometry will be applied to quantify gamma emitting radionuclides such as 60Co, 66Zn, 133 Ba, 137Cs, 152 Eu, and 154Eu. The complex matrix of some reactor materials will cause attenuation of gamma photons and empirical and/or theoretical corrections will be applied. Beta-emitting radionuclides with weak or no gamma emission lines cannot be easily identified or quantified in solid materials using non-destructive techniques. This is due to attenuation of the beta particles, the nature of the beta emission spectrum and interferences from other beta- and gamma-emitting radionuclides. A suite of destructive radioanalytical techniques, designed to isolate and quantify beta-emitting radionuclides such as 3H, 14C, 36CI, 55Fe, 63Ni, 98Sr and 99Tc is being developed. This paper will present the timeline for development and the progress to date of this radioanalytical capability which will support the current and future decommissioning needs of Australia and our region.
- ItemEstimates of site-scale groundwater recharge variability across a legacy low-level radioactive waste disposal facility in the Sydney Basin(National Centre for Groundwater Research And Training, 2017-07-12) Anderson, D; Hughes, CE; Rowling, BThe Little Forest Legacy Site (LFLS) is a legacy, low-level radioactive waste disposal facility located at Lucas Heights in eastern NSW, Australia. The site was operated by the Australian Atomic Energy Commission between 1960 and 1968. Landfilling of wastes was to a maximum depth of three (3) metres into clay and shale material of the Hawkesbury Sandstone Formation. Monitoring of radionuclide containment at LFLS has been ongoing since the emplacement of waste. In recent decades the level of characterisation at LFLS has intensified to develop a more comprehensive understanding of the site geology, hydrogeology and hydro-geochemistry. This additional work is being undertaken to support detailed plans for site management. Recent site characterisation activity has included coring and geological logging, a range of geophysical surveys, monthly monitoring of groundwater and surface water quality and various laboratory analyses. Groundwater levels have also been recorded every 15 to 30 minutes since mid-2007 at twenty-three (23) locations about the site. This paper reports the results of our preliminary analysis of the comprehensive groundwater level monitoring data at the LFLS. This includes an analysis of the data with the episodic master recession (EMR) tool recently published by USGS. The EMR program provides a largely automated workflow to estimate groundwater recharge as a function of individual groundwater recharge events. When coupled with historical and/or synthetic rainfall time-series data the output of the tool can also be used to support simple but rapid simulation of past and/or future site groundwater levels. The data analysis techniques trialled in this study will be of interest to most hydrogeologists routinely involved in site characterisation studies. Our estimates of groundwater recharge rates into the clays and shales of the Hawkesbury Sandstone Formation at the LFLS may also be of interest to many practitioners working in the Sydney Basin.
- ItemEstimating diffusion in heterogeneous groundwater systems using short-llived radio-isotopes and stable isotopes or bromine(Geological Society of Australia, 2014-07-07) Peterson, MA; Cendón, DI; Andersen, MS; Mokhber-Shahin, L; Wong, HKY; Rowling, BDiffusion is an important and ubiquitous phenomenon in nature, but too often neglected or unmeasured in water resource hydrogeology or solute transport. Diffusion may, in fact, be the dominant process that dictates hydrogeochemistry and affects tracers. Conservative and age tracers are commonly used for water resource or contaminant plume transport estimations, but will give misleading results, if diffusion is ignored. Diffusion of tracers into aquitards, matrix pores of fractured rocks, blind fractures or other low conductivity zones lead to retardation and possible adsorption, exchange, precipitation or decay. This becomes increasingly important as heterogeneity of flow domains increase, for example, in fractured rock aquifers, interlayered sediments or aquifers associated with aquitards. Traditional methods of measuring diffusion coefficients in small slices of heterogeneous rock are unreliable for upscaling, so this study presents an alternative method based on lab-scale drill-core tests and suggests field-scale borehole tracer tests. Fick’s first law shows that diffusion rates are driven by concentration gradients. Short-lived radiotracers soon reach a steady-state concentration gradient with enhanced flux where diffusion rate equals decay, while stable tracers trend towards saturation and ever-decreasing fluxes. We compare diffusion of short-lived radiotracers 131I half-life 8 days) or 82Br (half-life 1.5 days) to their stable equivalent (I or Br) into 45–50 cm lengths of ~60 mm diameter drill core. Five cores were selected from three fractured rock environments: sandstone, limestone and metavolcanics. By regularly sampling and refilling the annulus with tracers around the enclosed core, we are able to discern differential in-diffusion between stable- and radio-tracers. For example, the annulus was sampled and refilled weekly with an (equivalent decayed) 131I activity of 22 Bq/g and within three weeks (2.6 half-lives) each core had reached a characteristic steady state flux. The net fluxes were 7 around 1.0 Bq/cm2/week in the sandstone cores, 0.2 Bq/cm2/week in the metavolcanics, and 0.05 Bq/cm2/week in the limestone. This was compared to stable iodine weekly refills at 2.6 mg/L, which gave ever-diminishing diffusion results. The net fluxes of stable iodine diminished steadily, e.g. over three weeks from 98 to 26 ng/cm2/week for the most porous (medium sandstone ~15%), and from 11 to 7 ng/cm2/week for the least porous (limestone ~2%). Experiments were also performed using 82Br and stable bromine, with sampling and refills performed on a daily (0.68 half-lives) basis. Similar trends were apparent, though the data was noisier due to more frequent refills and less time for diffusion to generate significant changes in the annulus reservoir solutions. This method enables analysis of drill cores for comparative effective diffusion coefficients of different systems. Quantitative interpretation is currently being refined. In principle, the method should be transferrable to single boreholes or tracer tests between multiple boreholes to gain larger scale representation of effective diffusion within a groundwater system. The normally confounding factors, such as dilution, advection, exchange, adsorption and precipitation, are negated by comparing the stable with radio-tracer results, as all isotopes of these elements are identically affected by such processes and losses. © Geological Society of Australia Inc
- ItemFertilizers rule REYs: agricultural catchments of Eastern Australia(Goldschmidt, 2019-08-18) Cendón, DI; Harris, SJ; Kelly, BFJ; Peterson, MA; Hankin, SI; Rowling, B; Watson, J; Xiao, SLanthanides, generally named Rare Earth Elements (REE), are part of the internal transition metals forming a group of 15 elements with very similar chemical characteristics and physical properties. REEs and Yttrium (named REY) are widely used to understand geochemical processes. The increasing use of REYs in technology as well as their presence as a by-product in some fertilizers has opened new pathways for these metals to enter the water cycle, thus making REYs tracers of anthropogenic activity. In this study we investigate the concentration and distribution of REYs in two predominantly agricultural catchments of Eastern Australia: the Namoi River with a 43,000 km2 catchment, which forms part of the headwaters of the Murray- Darling Basin; and the Nogoa River with a 27,600 km2 catchment, which forms part of the Fitzroy River catchment, the largest in eastern Australia flowing into the Great Barrier Reef. Bi-monthly sampling during 18 months was conducted at seven selected sites along both rivers. The [REY] in water samples were analyzed by automated chelation pre-concentration (SeaFast, ESI), followed by ICP-MS. Samples were automatically loaded onto a loop and injected to an iminodiacetate column that chelates REY allowing matrix Na+, Cl-, Ca2+, Mg2+ and, more importantly, Ba2+ ions to be rinsed out. The pre-concentration process allowed a ~20-fold increase in concentration. Results are compared to those obtained from commonly used fertilizers in the region. REY trends suggest a link to the fertilizers used in both catchments. No regional variations were apparent, possibly due to the prevailing dry conditions during the sampling period. Stream flow was controlled by dam releases in the upper ridges for both catchments.
- ItemIdentification of sources and processes in a low-level radioactive waste site adjacent to landfills: groundwater hydrogeochemistry and isotopes(Taylor & Francis Group, 2014-11-25) Cendón, DI; Hughes, CE; Harrison, JJ; Hankin, SI; Johansen, MP; Payne, TE; Wong, HKY; Rowling, B; Vine, M; Wilsher, KL; Guinea, A; Thiruvoth, SMultiple tracer-element and isotope approaches were applied at a 1960s-era low-level radioactive waste burial site located in the Lucas Heights area on the southwest urban fringe of Sydney, Australia. The site is situated among other municipal and industrial (solid and liquid) waste disposal sites causing potential mixing of leachates. Local rainfall contains marine-derived major ion ratios that are modified during infiltration depending on waste interactions. The local geology favours the retention of contaminants by ion-exchange processes within the clay-rich soils and the shale layer underlying the burial site. Local soils experience periodic infiltration and wetting fronts that can fully saturate the waste trenches (bathtub effect) while surrounding soils are mostly unsaturated with discontinuous perched lenses. Within the trenches, the degradation of organic matter results in localised methanogenesis, as suggested by enriched δ2H and δ13CDIC values in adjacent subsurface water. Movement of contaminants from the trenches is indicated by Na+, Br? and I? concentrations, variations in 87Sr/86Sr, enriched δ13CDIC values and evolution of δ34S of dissolved sulfate in perched water bodies above the shale. Although transport is limited by the low transmissivity of the clay-rich soils, migration and mixing processes are indicated by the variation of concentrations with distance from the trenches, disappearance of δ2H enrichments, mixing with other sources of Sr and sulfate isotope fractionations. The depth distribution of waste-derived contaminants (specifically 3H and Be) between the perched water surrounding the trenches, and the underlying shale and sandstone layers, indicates limited downward transport of contaminants. Past removal of the shale layer in an adjacent site, Harrington's Quarry, has facilitated the mixing of some municipal waste leachates (characterised by circum-neutral pH, high alkalinity, low sulfate, high 3H, high Be, enriched δ2H and δ13CDIC) into the underlying groundwater system as suggested by high TDS, Cl?/Br? ratios, Be and 3H found in deeper wells. This study demonstrates the applicability of using trace elements, stable- and radio-isotopes to document the existing geochemistry and the contaminant transport from the waste trenches. The multiple tracer approach addresses the complexities of transport at the site and differentiates various municipal, industrial and radioactive waste sources. © 2014 Informa UK Limited
- ItemInstallation of a pilot experimental trench at the Little Forest legacy site(Australian Nuclear Science and Technology Organisation, 2018-07-30) Payne, TE; Kinsela, AS; Rowling, B; Hankin, SI; Cendón, DI; Comarmond, MJ; Bligh, MW; Hughes, CE; Anderson, D; Wilsher, KLDuring 2017, a pilot experimental trench was constructed at the Little Forest Legacy Site (LFLS). The objective of installing this trench was to facilitate experimental field-work aimed at further characterising the site, in particular the hydrology of the excavated trenches and of the near-surface layers in which the trenches are located. The test trench is of similar depth to the waste disposal trenches at the legacy site (3 metres) and extends 6 m in length. However, unlike the disposal trenches, the experimental trench contains no waste materials of any kind. Instead, the trench contains a number of sampling points and other instrumentation, and is back filled with river gravel to provide a uniform composition and maintain structural stability. It is intended that the pilot trench will be followed by other trenches with specific experimental objectives. The purposes of this report are to discuss the background, rationale for, and implementation of the facility; to provide a detailed description of the pilot trench; and to compile information and photographs documenting the excavation process. Although some preliminary hydrological data and comparisons with the legacy trenches are presented, the scientific data will be fully discussed and interpreted in future scientific reports.
- ItemInstallation of an experimental trench at the Little Forest Legacy Site(South Pacific Environmental Radioactivity Association, 2018-11-06) Payne, TE; Kinsela, AS; Bligh, M; Anderson, D; Rowling, B; Hughes, CE; Hankin, SI; Cendón, DI; Wilsher, KL; Comarmond, MJDuring 2017, a pilot experimental trench was constructed at the Little Forest Legacy Site (LFLS), a 1960s era disposal site for low-level radioactive waste. The objective of installing this trench was to facilitate experimental field-work aimed at further characterising the site, in particular the hydrology of the excavated trenches and of the near-surface layers in which the trenches are located. The test trench is of similar depth to the waste disposal trenches at the legacy site (8 metres) and extends 6 m in length. However, unlike the disposal trenches, the experimental trench does not contain waste materials. instead, the trench contains a number of sampling points and other instrumentation, and is back filled with river gravel to provide a uniform composition and maintain structural stability. in this paper, the excavation of the trench is described, together with observations made during the excavation. in addition, some preliminary hydrological data and comparisons with the legacy trenches are presented.
- ItemMeasurement of tributyl phosphate (TBP) in groundwater at a legacy radioactive waste site and its possible role in contaminant mobilisation(Elsevier B. V., 2017-11) Rowling, B; Kinsela, AS; Comarmond, MJ; Hughes, CE; Harrison, JJ; Johansen, MP; Payne, TEAt many legacy radioactive waste sites, organic compounds have been co-disposed, which may be a factor in mobilisation of radionuclides at these sites. Tri-butyl phosphate (TBP) is a component of waste streams from the nuclear fuel cycle, where it has been used in separating actinides during processing of nuclear fuels. Analyses of ground waters from the Little Forest Legacy Site (LFLS) in eastern Australia were undertaken using solid-phase extraction (SPE) followed by gas chromatographic mass spectrometry (GCMS). The results indicate the presence of TBP several decades after waste disposal, with TBP only being detected in the immediate vicinity of the main disposal area. TBP is generally considered to degrade in the environment relatively rapidly. Therefore, it is likely that its presence is due to relatively recent releases of TBP, possibly stemming from leakage due to container degradation. The ongoing presence and solubility of TBP has the potential to provide a mechanism for nuclide mobilisation, with implications for long term management of LFLS and similar legacy waste sites. © 2021 Elsevier B.V.
- ItemMethods for the determination of U-238, Pu-239, Pu-240 and Am-241 from Little Forest Legacy Site (LFLS) groundwater using on-line SeaFast pre-concentration coupled to ICPMS(South Pacific Environmental Radioactivity Association, 2018-11-06) Rowling, B; Wong, HKY; Harrison, JJ; Wilsher, KL; Payne, TEAnalyses of groundwaters within Little Forest Legacy Site in eastern Australia have been performed using a number of techniques. Uranium concentration has been analysed using a combination of ICPMS and alpha spectrometry whilst plutonium and americium activity measurements have been performed using alpha spectrometry and accelerated mass spectrometry (AMS). The SeaFAST is an automated on-line lCPMS sample introduction system without sample preparation required for the determination of ultra-trace metals in undiluted water samples. The use of sample pre-concentration and procedural blanks eliminates matrix effects whilst improving reliability. This system is often applied to swiftly analyse for rare earth elements as well as uranium and thorium in surface and groundwater systems. The development of a method which could be used to analyse for plutonium and americium could extend the application of the SeaFAST-ICPMS system whilst also providing a complementary or quick screening technique. This paper presents the significant steps in developing and validating the SeaFAST-lCPMS method as well as reporting isotope ratio results.
- ItemRare earth elements and yttrium as tracers of waste/rock-groundwater interactions(Elsevier, 2022-07-15) Cendón, DI; Rowling, B; Hughes, CE; Payne, TE; Hankin, SI; Harrison, JJ; Peterson, MA; Stopic, A; Wong, HKY; Gadd, PSFine particle air pollution is a significant problem in large urbanised areas across the Asian region. With funding from the International Atomic Energy Agency (IAEA) fifteen countries in Asia have been collecting weekly samples on filters of fine and coarse particles in major cities for the past 15 years. These filters have been analysed for over 20 different chemical species from hydrogen to lead using a range of analytical techniques including accelerator based ion beam techniques such as PIXE, PIGE, PESA, RBS, as well as XRF and NAA. These data have been included into a major database, which is generally available, containing over 17,000 combined sampling days from these fifteen countries spanning an area of the globe from ± 50° latitude and from 70° to 180° longitude. That is, the sampling covers an area north-south from Mongolia to New Zealand and west-east from Islamabad, Pakistan to Wellington, NZ. Crown Copyright © 2019 Published by Elsevier B.V.
- ItemTrench 'bathtubbing’ and surface plutonium contamination at a legacy radioactive waste site(American Chemical Society, 2013-11-20) Payne, TE; Harrison, JJ; Hughes, CE; Johansen, MP; Thiruvoth, S; Wilsher, KL; Cendón, DI; Hankin, SI; Rowling, B; Zawadzki, ARadioactive waste containing a few grams of plutonium (Pu) was disposed between 1960 and 1968 in trenches at the Little Forest Burial Ground (LFBG), near Sydney, Australia. A water sampling point installed in a former trench has enabled the radionuclide content of trench water and the response of the water level to rainfall to be studied. The trench water contains readily measurable Pu activity (∼12 Bq/L of 239+240Pu in 0.45 μm-filtered water), and there is an associated contamination of Pu in surface soils. The highest 239+240Pu soil activity was 829 Bq/kg in a shallow sample (0–1 cm depth) near the trench sampling point. Away from the trenches, the elevated concentrations of Pu in surface soils extend for tens of meters down-slope. The broader contamination may be partly attributable to dispersion events in the first decade after disposal, after which a layer of soil was added above the trenched area. Since this time, further Pu contamination has occurred near the trench-sampler within this added layer. The water level in the trench-sampler responds quickly to rainfall and intermittently reaches the surface, hence the Pu dispersion is attributed to saturation and overflow of the trenches during extreme rainfall events, referred to as the ‘bathtub’ effect. © 2013 American Chemical Society
- ItemUsing hydro-geochemistry and isotopes to trace groundwater flow from Little Forest Burial Ground and surrounding landfills(Australian Nuclear Science and Technology Organisation, 2012-10-16) Cendón, DI; Hughes, CE; Harrison, JJ; Hanklin, SI; Johansen, MP; Payne, TE; Wong, HKY; Rowling, B; Vine, M; Wilsher, KL; Guinea, A; Thiruvoth, SMultiple tracer-element and isotope approaches were used to study groundwater near a legacy low-level radioactive waste burial site surrounded by municipal and industrial waste sites. The interaction of rainfall, with its marine-derived major ion ratios, and waste from the sites is apparent, however, clay-rich soils and shale at the site tend to retain many contaminants via ion exchange and other processes. High permeability of the disposal trenches provides a pathway for groundwater recharge, with discontinuous perched groundwater lenses found in their vicinity. Within the trenches, the degradation of organic matter results in localised methanogenesis, as suggested by enriched δ2H and δ13CDIC in adjacent subsurface water. Movement of contaminants from the waste sites is indicated by Na+, Brˉ and Iˉ concentrations, variations in 87Sr/86Sr, enriched δ13CDIC and evolution of δ34S of dissolved sulfate in perched water bodies above the shale. There is clear evidence of a tritium plume from the LFBG trenches, although the adjacent landfills provide an additional tritium source. Waste burial records show that over 1000 kg of Be (mostly BeO) were disposed in the LFBG trenches. However, beryllium concentrations in groundwaters near the trenches are quite low, and appear more likely to be controlled by the host lithologies and the other sources of contamination in the vicinity, rather than by leaching of Be from the LFBG waste. Past removal of the shale layer in an adjacent site, Harrington’s Quarry, has led to the mixing of municipal waste leachates into the underlying groundwater system as suggested by high TDS, Cl−/Br− ratios, Be, and 3H found in deeper wells. The multiple tracer approach addresses the complexities of transport at the site and differentiates various municipal, industrial, and radioactive waste sources