Dirk Mallants

Dirk Mallants
The Commonwealth Scientific and Industrial Research Organisation, · Land and Water

Doctor of Philosophy, Faculty of Agricultural and Applied Biological Sciences

About

409
Publications
140,353
Reads
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4,460
Citations
Introduction
I research fundamental processes at the geosphere-biosphere interface focusing on whole-of-system conceptualisation, characterization and model calibration. My research is applied to fate pathway analysis in coupled vegetation-soil-groundwater-resource systems. Examples include determining the degree of isolation of hydrocarbon resources from groundwater, deriving safe irrigation water quality conditions for sustainable agriculture and the long-term safety of radioactive waste disposal.
Additional affiliations
November 2014 - September 2016
The Commonwealth Scientific and Industrial Research Organisation
Position
  • Senior Principal Research Scientist
November 2011 - April 2016
The Commonwealth Scientific and Industrial Research Organisation
Position
  • Senior Principal Research Scientist
September 1997 - November 2011
Belgian Nuclear Research Centre
Position
  • Unit Head
Education
September 1990 - March 1996
KU Leuven
Field of study
  • Hydrology

Publications

Publications (409)
Article
Full-text available
Coal seam gas (CSG) or coal bed methane production has grown exponentially in Australia over the last two decades with currently nearly 7,000 productive wells and another 18,750 wells planned over the next five to ten years. To address concerns over environmental contamination by hydraulic fracture fluids (HFF) attributed to (i) incidents involving...
Article
Full-text available
Conceptual uncertainty is considered one of the major sources of uncertainty in groundwater flow modelling. In this regard, hypothesis testing is essential to increase system understanding by refuting alternative conceptual models. Often a stepwise approach, with respect to complexity, is promoted but hypothesis testing of simple groundwater models...
Article
Full-text available
Safety assessments for nuclear waste disposal require a comprehensive understanding of the complex disposal system based on simulation tools that are able to evaluate its performance and manage uncertainties. A recent work from Guo et al. 1 demonstrated that, under conditions similar to those found at the proposed Yucca Mountain repository in the U...
Article
Full-text available
This study introduces an efficient deep-learning model based on convolutional neural networks with joint autoencoder and adversarial structures for 3D subsurface mapping from 2D surface observations. The method was applied to delineate paleovalleys in an Australian desert landscape. The neural network was trained on a 6400 km2 domain by using a lan...
Article
Full-text available
Flowback water from shale gas operations contains formation-derived compounds, including trace metals, radionuclides, and organics. While accidental releases from storage tanks with flowback water are low-probability events if multiple containment barriers are put in place, they cannot be entirely excluded. Here the natural attenuation potential of...
Conference Paper
Full-text available
A potentially novel disposal pathway for small volumes of radioactive waste originating from reprocessing of spent nuclear fuels is in deep boreholes (DBs). The waste packages are stacked in a disposal zone at depths that would be considerably deeper than the typical depth of conventional mined repositories. DB disposal still requires considerable...
Conference Paper
Full-text available
For more than a century, the strong advice in geology has been to rely on multiple working hypotheses. However, in groundwater research, as supported by modelling, often a stepwise approach with respect to complexity is promoted and preferred by many. Defining a hypothesis, let alone multiple hypotheses, and testing these via groundwater models is...
Article
Full-text available
Disposal of radioactive waste originating from reprocessing of spent research reactor fuel typically includes stainless steel canisters with waste immobilised in a glass matrix. In a deep borehole disposal concept, waste packages could be stacked in a disposal zone at a depth of one to potentially several kilometres. This waste will generate heat f...
Conference Paper
Full-text available
Very low permeability and diffusion-dominated chemical transport are important features of a suitable host rock for deep borehole disposal of appropriately conditioned long-lived intermediate level waste. Such features support the safety case with evidence that the containment of radionuclides is guaranteed for a sufficiently long time. In this pro...
Article
Full-text available
The safety of high-level radioactive waste disposal has been studied across the world considering mined geologic repositories. Here, we introduce large-diameter, deep borehole disposal as one of the potential solutions for small volumes of long-lived intermediate-level waste (ILW). The short-and long-term stability of deep disposal boreholes is cri...
Conference Paper
Full-text available
The Australian Radioactive Waste Agency (ARWA) is considering establishing the National Radioactive Waste Management Facility to permanently dispose low-level waste and temporarily store intermediate-level waste at a remote site in South Australia, which is characterised by a semi-arid climate. Approximately 10,000 m3 of low-level waste will be dis...
Conference Paper
Full-text available
Nuclear waste canisters destined for deep geological disposal need sufficient mechanical strength and corrosion resistance to maintain their integrity for potentially at least 10,000 years, depending on the multi-barrier system that is chosen. One way of fabricating a cost-effective canister is to use a relatively inexpensive carbon-steel core to p...
Conference Paper
Full-text available
Borehole stability is critically important for deep borehole disposal of radioactive waste. Deep boreholes drilled 1000 m-2000 m into crystalline rocks in Australia for geothermal energy exploration are known to have experienced borehole breakouts. Large diameter boreholes are more likely to experience borehole breakouts than the smaller boreholes...
Conference Paper
Full-text available
The concept of the deep borehole disposal (DBD) is characterized by the use of low volume, non-shielded containers that are placed with the most reliable technology into a deep disposal zone. This way, DBD maximizes the tightness of a host rock as a key barrier in the safety concept while the large distance to the biosphere further contributes to t...
Conference Paper
Full-text available
Australia is evaluating deep borehole disposal as a potential solution for its long-lived intermediate level waste. The project will aim to demonstrate by means of a comprehensive RD&D program the technical feasibility and the long-term safety of vertical borehole disposal. The RD&D activities include demonstration of surface handling and full-scal...
Article
Full-text available
An attractive strategy for reducing the cost of nuclear waste canisters destined for deep geological disposal is to provide the necessary mechanical strength of the canister with a relatively cheap carbon steel core and to surround it with a corrosion resistant coating. Corrosion resistant materials that have previously been evaluated for nuclear w...
Article
Full-text available
Adsorption of aqueous uranyl species in pore spaces of clay minerals plays a key role in post-closure safety assessments for geological disposal of radioactive waste. Molecular Dynamics Simulations (MDS) were performed to study the adsorption of uranyl (UO 2 2+) to the clay mineral smectite from its aqueous solution in the presence of carbonate (CO...
Article
Full-text available
Understanding the factors controlling groundwater recharge in arid vadose zones is critical for sustainable groundwater management in the face of climate variability and change. Here we estimated groundwater recharge in data sparse regions under arid climate by implementing a multi-model approach using HYDRUS-1D for a century-long time series of me...
Article
Full-text available
Regulators require the gas industry to assess the risks of unintentional release of chemicals to the environment and implement measures to mitigate it. Industry standard models for contaminant transport in aquifers do not explicitly model processes in the unsaturated zone and groundwater models often require long run times to complete simulation of...
Article
Full-text available
Shale and tight gas developments in the Beetaloo (28,000 km²) and Cooper (139,000 km²) basins of Australia are subject to stringent State and Federal Government controls and assessments. Several scientific investigations are ongoing to improve the scientific basis of the risks from unconventional gas developments to water and the environment. In th...
Presentation
Full-text available
An international partnership between CSIRO, ANSTO and SANDIA aims to execute a full-scale borehole RD&D project in Australia. RD&D include basic research and a full-scale surface handling and waste/seal emplacement test in a large-diameter, deep borehole. We present the multi-barrier system and safety functions for deep borehole disposal, a frame...
Article
Full-text available
Around the world, deep borehole disposal is being evaluated for intermediate-level waste (ILW), high-level waste (HLW), spent nuclear fuel (SNF), separated plutonium waste and some very high specific activity fission product waste. In Australia, long-lived ILW from research reactors and radiopharmaceutical production represents the principal waste...
Technical Report
Full-text available
The Geological and Bioregional Assessment (GBA) Program is assessing the potential environmental impacts of unconventional gas resource development, to inform regulatory frameworks and appropriate management approaches. The geological and environmental knowledge, data and tools produced by the GBA Program will assist governments, industry, land use...
Technical Report
Full-text available
The Geological and Bioregional Assessment (GBA) Program developed a robust methodology using causal networks to assess the regional-scale risks of unconventional gas resource development on water and the environment. The methodology allows consistent analysis of risks at each step in a chain of events – called pathways – from gas resource developme...
Technical Report
Full-text available
An environmental tracer pilot study on two depth profiles using noble gases and conventional tracers to gain critical information on hydraulic connectivity
Conference Paper
Full-text available
Borehole disposal for the geologic isolation of spent nuclear fuel (SNF) and high-level radioactive waste (HLW) has been considered for many years, beginning with evaluations of nuclear waste disposal options in the U.S. in the late 1950s and continuing with recurrent evaluations in several countries. Borehole disposal may be particularly attractiv...
Article
Full-text available
Long-term use of recycled water (RW) for irrigation in arid and semiarid regions usually changes the soil solution composition and soil exchange characteristics, enhancing the risk for sa-linity and sodicity hazards in soils. This modelling study focuses on developing alternative management options that can reduce the potentially harmful impacts of...
Conference Paper
Full-text available
Australia is evaluating deep borehole disposal as a potential solution for its long-lived intermediate level waste (ILW). This waste originates mainly from research reactors and radiopharmaceutical production and requires deep geologic disposal. As there are relatively small volumes involved, deep borehole disposal would be a cost-effective, and mo...
Conference Paper
Full-text available
Deep boreholes (hundreds to thousands of metres) are considered to provide adequate isolation and containment for the safe and cost-effective disposal of long-lived intermediate-level waste (ILW). In this paper we numerically analysed heat transport in the near field and geosphere immediately surrounding deep vertical disposal boreholes for low-hea...
Conference Paper
Full-text available
Deep boreholes (hundreds to thousands of metres) are considered to provide adequate isolation and containment for the safe and cost-effective disposal of long-lived intermediate-level waste (ILW). In this paper we numerically analysed transport of typical radionuclides in the near field and geosphere immediately surrounding deep disposal boreholes...
Conference Paper
The Geological Bioregional Assessments (GBA) program assesses the potential impacts of shale and tight gas development on water and the environment. This will inform appropriate monitoring, mitigation and management approaches. A key part of the project is quantifying the potential for a decline in the condition of beneficial aquifers, wetlands and...
Article
Full-text available
The Geological and Bioregional Assessment Program examines the potential impacts of shale, tight and deep coal gas development on water and the environment. A key part of the project was quantifying the potential for a decline in the water quality of unconfined aquifers due to unintentional chemical release at the soil surface. To assess this hazar...
Presentation
Full-text available
IAEA Research Coordination Meeting and workshop on the feasibility of borehole disposal
Technical Report
Full-text available
This report presents the Groundwater Knowledge Information System (GKIS), which aims to provide an assessment of the probability of successfully siting a sustainable bore. Initially, based on information available from a desktop study, these probabilities will generally be low. By integrating additional information, these probabilities will be refi...
Technical Report
Full-text available
The G-FLOWS Stage-3 project has developed and applied an integrated approach to the measurement, analysis, and modelling of geophysical, geochemical and hydrogeological techniques, which aim to help more efficiently and effectively target groundwater resources in a remote part of arid Australia. The project has focused on groundwater in the Anangu...
Article
Full-text available
Conceptual uncertainty is considered one of the major sources of uncertainty in groundwater flow modeling. Hypothesis testing is essential to increase system understanding by analyzing and refuting alternative conceptual models. We present a systematic approach to conceptual model testing aimed at finding an ensemble of conceptual understandings co...
Article
Full-text available
Stable isotope compositions in groundwater are widely used to understand hydrological processes. To infer changes in isotope composition in the subsurface due to interacting processes such as dispersion, chemical reactions, and phase changes, numerical simulations were employed to relate the isotope composition in the groundwater to that in the rec...
Preprint
Full-text available
This study introduces an efficient deep learning approach based on convolutional neural networks with joint autoencoder and adversarial structures for 3D subsurface mapping from surface observations. The method was applied to delineate palaeovalleys in an Australian desert landscape. The neural network was trained on a 6,400 km2 domain by using a l...
Technical Report
Full-text available
A total of 116 chemicals have been identified as being associated with drilling and hydraulic fracturing at shale, tight and deep coal gas operations in the three regions (Cooper, Isa and Beetaloo) of the Geological and Bioregional Assessment (GBA) program between 2011 and 2016. Of the 116 chemicals, 9 were drilling chemicals, 99 were hydraulic fra...
Article
Full-text available
The variably-saturated flow and multi-component transport module UNSATCHEM of HYDRUS-1D was used to evaluate the impact of the long-term (2018-2050) application of recycled water (RCW) for irrigating perennial horticulture (almonds, pistachios), viticulture (grapevines), annual horticulture (carrot, onion, and potato), and pasture crops in represen...
Article
Full-text available
Source-pathway-receptor analyses involving solute migration pathways through soil and shallow groundwater are typically undertaken to assess how people and the environment could come into contact with chemicals associated with coal seam gas operations. For potential short-term and long-term release of coal seam gas fluids from storage ponds, solute...
Presentation
Full-text available
A recent Special Issue of the Energies Journal on Deep Borehole Disposal of Nuclear Waste has delivered a timely update on the science and technology of borehole disposal and the types of radioactive wastes it could potentially accommodate. The Special Issue papers discuss (i) circumstances under which a national waste management programme might wi...
Conference Paper
Full-text available
Radionuclide containing soil and rubble from the clean-up of a former uranium, thorium and rare earth minerals processing research facility carried out in the early 50's and 60's is currently stored at the Woomera Test Range in South Australia awaiting final disposal. Prior to developing a final disposal pathway commensurate with waste acceptance c...
Conference Paper
Full-text available
Radioactive waste containing predominantly soil and rubble from the clean-up of a former uranium and thorium minerals processing research facility is currently stored at the Woomera Test Range in South Australia awaiting final disposal. Prior to commencing any manipulation of the nearly 10,000 waste drums (205 L or 55 gallon each), radon concentrat...
Article
Background and Aims: Understanding the dynamics of the components of evapotranspiration and irrigation requirements in response to climate variation and change is essential to sustainably managing vineyards. Methods and Results: The FAO-56 dual crop coefficient was used to evaluate wine grape evapotranspiration (ETC_adj), seasonal transpiration (T...
Article
Full-text available
This Special Issue of the Energies Journal on Deep Borehole Disposal of Nuclear Waste has delivered a timely update on the science and technology of borehole disposal and the types of radioactive wastes it could potentially accommodate. The Special Issue papers discuss (i) circumstances under which a national waste management programme might wish t...
Article
Full-text available
The special issue is comprised of 26 articles, including a review paper on the history of the basin, and a profile of eminent researcher Justin Costelloe. Fourteen articles focus on the Surat Basin of Queensland, which saw a large expansion of the CSG industry over the past decade that led to the need to research the potential impacts of this indus...
Article
Large sedimentary basins with multiple aquifer systems like the Great Artesian Basin and the Beetaloo Sub-Basin are associated with large time and spatial scales for regional groundwater flow and mixing effects from inter-aquifer exchange. This makes them difficult to study using traditional hydrogeological investigation techniques. In continental...
Poster
Full-text available
Australia has several large sedimentary basins, including the Great Artesian Basin (GAB), one of the largest aquifer systems in the world, which has a long history of groundwater extraction for stock, agriculture and urban water supplies. With the recent onset of exploration and development for coal bed methane and shale gas and the extension of ex...
Poster
Full-text available
Radionuclide containing soil and rubble from the clean-up of a former uranium, thorium and rare earth minerals processing research facility is currently stored at the Woomera Test Range in South Australia awaiting final disposal. Prior to developing a final disposal pathway, a comprehensive baseline environmental monitoring has been carried out to...
Poster
Full-text available
Noble gas measurements in groundwater are an established tool to investigate groundwater systems including magnitude and timescales of fluid exchanges. In formations with very slow to no advective groundwater flow (e.g., aquitards and shales), noble gases, especially helium, are excellent tracers for confirming diffusion-dominated transport. In “dr...
Presentation
Full-text available
This presentation provides a high-level summary of the findings of the Goyder Institute for Water Research project on "Sustainable expansion of irrigated agriculture and horticulture in Northern Adelaide Corridor".
Technical Report
Full-text available
The Northern Adelaide Corridor (NAC) has significant potential for economic development through the expansion of irrigated agriculture. This would build on the success of established horticulture activities on the Northern Adelaide Plains (NAP) around Virginia. Recycled water is a significant irrigation source that could help expand irrigated agric...