Browsing by Author "Brew, DRM"

Now showing 1 - 6 of 6
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    Appraisal of a cementitious material for waste disposal: neutron imaging studies of pore structure and sorptivity
    (Laboratoire SUBATECH, 2008-10-14) McGlinn, PJ; de Beer, FC; Aldridge, LP; Radebe, MJ; Nshimirimana, R; Brew, DRM; Payne, TE; Olufson, KP
    To characterise and to evaluate the durability, structural properties and sorptivity of a candidate wasteform for ILW and gain an understanding of the factors that control water movement through the matrix and the matrix and the resultant degradation process.
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    Appraisal of a cementitious material for waste disposal: neutron imaging studies of pore structure and sorptivity
    (Elsevier, 2010-08) McGlinn, PJ; de Beer, FC; Aldridge, LP; Radebe, MJ; Nshimirimana, R; Brew, DRM; Payne, TE; Olufson, KP
    Cementitious materials are conventionally used in conditioning intermediate and low level radioactive waste. In this study a candidate cement-based wasteform has been investigated using neutron imaging to characterise the wasteform for disposal in a repository for radioactive materials. Imaging showed both the pore size distribution and the extent of the cracking that had occurred in the samples. The rate of the water penetration measured both by conventional sorptivity measurements and neutron imaging was greater than in pastes made from Ordinary Portland Cement. The ability of the cracks to distribute the water through the sample in a very short time was also evident. The study highlights the significant potential of neutron imaging in the investigation of cementitious materials. The technique has the advantage of visualising and measuring, non-destructively, material distribution within macroscopic samples and is particularly useful in defining movement of water through the cementitious materials. © 2010 Crown Copyright published by Elsevier Ltd.
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    Development and evaluation of an early removal process for the beneficiation of arsenic-bearing copper ores.
    (Elsevier, 2010-12) Bruckard, WJ; Davey, KJ; Jorgensen, FRA; Wright, S; Brew, DRM; Hague, N; Vance, ER
    In conventional flotation flowsheets for treating copper sulphide ores containing small but significant amounts of arsenic, the arsenic is generally concentrated with the copper in final concentrate. Often, a penalty can be imposed by the smelter processing the concentrate, based on the arsenic content. In some cases the arsenic level is such that the smelter will not treat or accept the concentrate. A new approach to address this issue is reported in this paper, which is becoming more significant as the quality of the copper ore bodies currently being mined diminishes. A new flowsheet, based on the early removal of arsenic at the concentrator, has been developed and tested at bench-scale. The proposed flowsheet comprises three key steps: firstly, separation of arsenic and copper minerals using controlled-potential flotation to produce a low-arsenic high-copper concentrate and a high-arsenic low-copper concentrate. The low-arsenic concentrate can be sold without incurring any penalty for arsenic content. In the second stage, the high-arsenic concentrate is subjected to a low temperature roasting, where the arsenic is selectively fumed off into a low-volume stream product. The calcine from the roaster is high in copper and sulphur and can still be smelted directly. In the final stage of the flowsheet, the arsenic in the fume product is immobilised in a low temperature ceramic such that safe disposal back into the ground is possible. The new early removal flowsheet has been sequentially tested in the laboratory at small scale. The technical and economic merits of the flowsheet compared with that of the conventional copper flotation flowsheet show that there is a net benefit. © 2010, Elsevier Ltd.
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    Durability of a cementitious wasteform for intermediate level waste
    (Springer Nature, 2008-12-01) McGlinn, PJ; Brew, DRM; Aldridge, LP; Payne, TE; Olufson, KP; Prince, KE; Kelly, IJ
    Cementitious material is the most commonly used encapsulation medium for low and intermediate level radioactive waste. This paper focuses on the aqueous durability of a Materials Testing Reactor (MTR) cementitious wasteform – a possible candidate for the proposed intermediate level waste management facility in Australia. A series of medium term (up to 92 months) durability tests, without leachate replacement, were conducted on samples of this wasteform. The wasteform was made from cement, ground granulated blast furnace slag and a simulated waste liquor. The compressive strength (39 MPa) was typical of MTR cement wasteforms and well above that required for handling or storage. The wasteform was an inhomogeneous mixture containing calcite, a calcium silicate hydrate phase, hydrotalcite and unreacted slag particles. After leaching for 92 months the crystallinity of the calcium silicate hydrate phase increased. The majority of the releases of Ca, Si, Al, Sr, S, Na and K was reached within 4 days of leaching, with the maxima ie. the highest concentrations in the leachates, occurring at 3 months for Ca, Al, Sr, S, Na and K, and at 1 month for Si. For the longer leach periods (6 months and 3 months respectively) there was a slight reduction in concentration in the leachates, and these levels were similar to those for the longest period of 92 months, suggesting steady-state conditions prevailing after 3 to 6 months of leaching. The highest releases of matrix elements were for Na (37%), K (40%) and S (16%). Releases for elements such as Ca, Na, Al and Sr were similar in magnitude to those reported by the UKAEA in earlier MTR studies. After leaching for 92 months there was an alteration layer about 80 ∞m deep where calcium has been depleted. Na, K and Sr showed signs of diffusion towards the outer part of the cement samples. © 2008 Materials Research Society
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    The impact of alpha-emitting contamination on the handling and analysis of forensic evidence
    (Australian Nuclear Science and Technology Organisation, 2012-10-16) Evans, T; Toole, K; Brew, DRM; Colella, M
    A nuclear security event, where for example radioactive material is used in a malevolent act or where material is found outside of regulatory control will require an investigation. That investigation may require the collection, handling, and analysis of forensic evidence and hence it is highly likely that some of the physical evidence associated with such an event would have been exposed to radiation and possibly be contaminated with nuclear or other radioactive material. These scenarios present significant challenges to traditional approaches to crime scene investigation and it is well recognised by the international nuclear forensics community for the need to assess the application of existing forensic techniques to radiation-exposed samples and the implementation of procedures for safe and efficient examination of evidence contaminated with radioactive material. Previously, at the Australian Nuclear Science and Technology Organisation’s Nuclear Forensics Research Facility the effect of gamma radiation on forensic evidence as well as the impact of decontamination on evidence has been explored. This presentation will report on considerations for handling evidence contaminated with radioactive material and detail the latest developments in evaluating the application of forensic techniques to evidence exposed to, or contaminated with alpha-emitting radionuclides.
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    Water transport through cement-based barriers - a preliminary study using neutron radiography and tomography
    (Elsevier, 2009-06-21) Brew, DRM; de Beer, FC; Radebe, MJ; Nshimirimana, R; McGlinn, PJ; Aldridge, LP; Payne, TE
    In this preliminary study we use neutron radiography and tomography to examine differences in water transport through cement pastes and mortars. Bulk residual water contents and sorptivity curves determined using neutron radiography are compared with data obtained gravimetrically. In addition, macro-pore volume distributions of each sample were measured. Furthermore, it was possible to use neutron radiography to monitor the change in the mass of water when samples were dried or when water moved into the samples. The trends and absolute values of weight loss and gain obtained using both approaches are very consistent for mortars, especially when a neutron-scattering correction is applied. © 2009, Elsevier Ltd.