Browsing by Author "Hart, KP"
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- ItemAlteration of cold crucible melter titanate-based ceramics: comparison with hot-pressed titanate-based ceramic(Materials Research Society, 1997) Advocat, T; Leturcq, G; Lacombe, J; Berger, G; Day, RA; Hart, KP; Vernaz, E; Bonnetier, ASynroc ceramics were synthesized in an induction-heated cold crucible at laboratory scale (1 kg) from an oxide mixture, and at industrial prototype scale (45 kg) from Synroc previously produced by sintering under load at high temperature. After melting, both materials contained the major phases of Synroc-C. The chemical durability of both melted materials, as determined by static leaching of powder samples in initially pure water at 90°C with an SA/V ratio of 20000m−1, was equivalent to that of conventional hot-pressed Synroc-C. Cerium, used in this investigation to simulate the presence of tri-and tetravalent actinides, was found in steady-state concentrations on the order of 1 ppb (i.e. NL(Ce) ≤ 10−6 g·m−2). The concentration in the leachates was independent of the initial CeO2 content of the Synroc (at least up to 10 wt%); moreover, it is similar to the results obtained with hot-pressed Synroc-C specifically formulated for conditioning long-lived actinides. © Materials Research Society 1997
- ItemCharacterization and leaching behavior of plutonium-bearing Synroc-C(Materials Research Society, 1997-04-22) Smith, KL; Lumpkin, GR; Blackford, MH; Hambley, M; Day, RA; Hart, KP; Jostsons, ASynroc-C containing 10wt% simulated PW-4b-D HLW including 0.62 wt% 239Pu was subjected to MCC-1 type leach tests at 70°C in deionised water, silicate and carbonate leachates for 53 d and deionised water for 2472 d. The normalised total (i.e. unfiltered leachate + vessel wall) Pu leach rates in deionised water, silicate and carbonate leachates for periods up to 53 d were found to be of the order of 10-5, 10-4 and 10-4 g m-2 d-1 respectively. After 2472 d, the differential, normalised, Pu leach rate in deionised water dropped to ∼5 × 10-6 (total) and ∼5 × 10-8 (solution - after filtration through a 1000NMW filter) g m-2 d-1. SEM and AEM were used to characterise our starting material and investigate the secondary phases on the surfaces of leached Synroc-C discs. Calculated and measured normalised Pu leach rates are compared and the partitioning of Pu between zirconolite and perovskite is discussed. © Materials Research Society 1997
- ItemCharacterization and leaching behavior of plutonium-bearing Synroc-C(Cambridge University Press/Springer Nature, 1996-02-05) Smith, KL; Lumpkin, GR; Blackford, MG; Hambley, M; Day, RA; Hart, KP; Jostsons, ASynroc-C containing 10wt% simulated PW-4b-D HLW including 0.62 wt% 239Pu was subjected to MCC-1 type leach tests at 70°C in deionised water, silicate and carbonate leachates for 53 d and deionised water for 2472 d. The normalised total (i.e. unfiltered leachate + vessel wall) Pu leach rates in deionised water, silicate and carbonate leachates for periods up to 53 d were found to be of the order of 10-5, 10-4 and 10-4 g m-2 d-1 respectively. After 2472 d, the differential, normalised, Pu leach rate in deionised water dropped to ∼5 × 10-6 (total) and ∼5 × 10-8 (solution - after filtration through a 1000NMW filter) g m-2 d-1. SEM and AEM were used to characterise our starting material and investigate the secondary phases on the surfaces of leached Synroc-C discs. Calculated and measured normalised Pu leach rates are compared and the partitioning of Pu between zirconolite and perovskite is discussed. © Materials Research Society 1997
- ItemDissolution of Synroc in deionised water at 150°C(Materials Research Society (MRS)/Cambridge University Press/Springer Nature, 1996-02-15) Smith, KL; Colella, M; Thorogood, GJ; Blackford, MG; Lumpkin, GR; Hart, KP; Prince, KE; Loi, E; Jostsons, ASynroc containing 20 wt% simulated high level waste (HLW) was subjected to two sets of leach tests at 150°C where the leachant was and was not replaced during the test (replacement and non-replacement testing). The leachant was a KH-phthalate buffered solution (pH 4.2). Samples were characterised before and after leach testing using SEM, AEM and SIMS. Elemental concentrations in leachates were measured using ICP-MS. In concert with the findings of i) a dissolution study of perovskite in a flowing leachant and ii) a previous Synroc dissolution study (wherein Synroc containing 10 wt% simulated HLW was subjected to periodic replacement, leach testing in deionised water at 150°C), the results of this study show that when the leachant replacement frequency is varied from 7 d to the duration of the test, there is no effect on leach rate or leaching mechanisms. © Materials Research Society 1997
- ItemInterface phenomena in synroc, a titanate-based nuclear waste ceramic(Elsevier, 1995) Vance, ER; Ball, CJ; Blackford, MG; Day, RA; Lumpkin, GR; Smith, KL; Hart, KP; McGlinn, PJ; Thorogood, GJSeveral aspects of Synroc which fall into the broad class of interface phenomena are discussed. These are radiation damage processes which give rise to interfaces between damage tracks and neighbouring unirradiated material, intergranular films which have deleterious effects on chemical durability, and aqueous leaching of Synroc which takes place primarily at the interface between the solid and groundwater. © 1995 Elsevier B.V.
- ItemJAERI/ANSTO co-operative research on radiation damage and actinide behaviour in Synroc(The Institution of Engineers Australia, 1994-05-01) Muraoka, S; Mitamura, H; Matsumoto, S; Vance, ER; Hart, KPANSTO and JAERI have collaborated formally since 1985 in the study of actinide behaviour in and self-irradiation studies of Synroc, a titanate ceramic designed for immobilising high-level waste from nuclear fuel reprocessing. JAERI has fabricated Synroc samples containing ∼1wt% of the short-lived actinide 244Cm(t1/2 18 yr), to produce in 2 years, alpha-damage which would take ∼ 105 yr to accrue in actual Synroc. The effects of the damage on the structure and aqueous leachabilities of various constituent elements will be discussed. Parallel experiments at Ansto have dealt with the aqueous dissolution of Synroc: containing sufficiently low levels of actinides to avoid significant radiation damage effects, the effects of fast-neutron irradiation and studies of radiation damage in natural analogues of Synroc phases, especially zirconolite. Difficulties associated with the presence of sodium in Japanese waste have been eliminated by a minor reformulation of Synroc. Recent work has focussed on developing a zirconolite-rich version of Synroc to immobilise actinide-rich wastes resulting from advanced reprocessing/partitioning schemes and progress will be reviewed.
- ItemJapan-Australian co-operative program on research and development of technology for the management of high level radioactive wastes, 1985 to 1998: final report(Australian Nuclear Science and Technology Organisation, 1998-12) Hart, KP; Mitamura, H; Vance, ER; Banba, T; Lumpkin, GRThe first five year phase (Phase I) of this Co-operative program commenced in 1985 as a consequence of technical and diplomatic discussions is the early 1980's. During Phase I, effective mechanisms of information transfer were established through personnel exchanges between JAERI and ANSTO, and a number of technical workshops. At the end of Phase I it was agreed that the Program should be extended into a second five-year period from 1990 to 1995, designated as Phase II. This latter phase was subsequently extended for a further three-year period from 1995 to 1998 to allow the collection of additional information on long-term accelerated damage tests and preparation of a final report. At the end of each phase of the Co-operative Program details results have been published in jointly-authored, formal documents. The key results, significance and recommendations of the entire Co-operative Program are summarised herein. The Co-operative Program has enhanced the excellent co-operative working relationship between the two institutions, and the arrangements developed under the original agreement should serve as a model for any other co-operative projects developed in the future. The main activities in the first phase of the Co-operative Program were the preparation, characterisation and subsequent testing of curium-doped Synroc containing simulated waste of the type produced by the PNC reprocessing facility at Tokyo in Japan namely JW-A containing elevated levels of Na. Here, the leach rates increased as a consequence of the radiation damage, due to (a) microcracking at a-doses corresponding to > 104 years of repository storage and (b) atomic displacements within the actinide-bearing phases, zirconolite and perovskite. At high doses, corresponding to > 3 x 104 years of storage, the former process led to leach rate enhancements of about a factor of 10 for Na and Ca, that were a further order of magnitude higher. Modifications to the Synroc composition were devised to prevent microcracking when the Na20 content of the Synroc exceeds ~ 1.5wt%. In the second phase of the Co-operative Program, comparative studies were carried out on Synroc containing Na-free PW-4b waste and in this case, after ~ 105 years of equivalent storage, Sr and Ca leach rates increased by a factor of 10, whereas the leach rate of Ba which is not contained in the actinide host phases did not increase with equivalent storage time. The density decrease due to radiation damage was less in samples stored at 200oC than at 30oC. Complementary studies on Cm-doped single-phase zirconolite and perovskite were carried out and studies on naturally-occurring zirconolites were initiated to provide insight into the long-term durability of zirconolite over geological time. In both phases of the Co-operative Program , the preparation of the Cm-doped samples was carried out in JAERI'S WASTEF facility at Tokai, with technical input and assistance provided by ANSTO where necessary. The results, described in greater detail in this report, have confirmed the potential of Synroc as a second-generation waste form.
- ItemManagement of wastes from the processing of rare earth minerals(Institution of Engineers Australia, 1988-08-28) Hart, KP; Levins, DMAustralia is the leading producer and exporter of the rare earth mineral, monazite, but currently does not process it beyond the physical beneficiation stage. Recent discoveries of new uses for rare earth has renewed interest in monazite processing in Australia. Two proposals of rare earth processing plants have been announced and a number of other companies are engaged in feasibility studies. Chemical processing of monazite involves digestion in caustic soda to 'crack' the phosphate matrix, dissolution of the rare earths in acid and their separation by multi-stage solvent extraction usually in mixer-settlers. The processing is complicated by the presence of 4-8 wt% thorium and 0.1-0.3 wt% uranium in the monazite. Experiments have shown that lead-210 and uranium are partially solubilized in the caustic digestion stage and radium is dissolved along with the rare earths. Over 99.5% of the radium can be precipitated as barium/radium sulphate by the addition of barium chloride and soluble sulphate. This radium-bearing solid waste can be combined with the uranium/thorium residue so that essentially all the radionuclides are contained in the one waste stream. The volume of this waste stream is not large and it is feasible to store it on-site in an engineered facility. The safe disposal of this waste would be facilitated by the establishment of a national facility for radioactive and other toxic wastes.
- ItemPartitioning and leaching behavior of actinides and rare earth elements in a zirconolite-bearing hydrothermal vein system(Cambridge University Press/Springer Nature, 2007) Payne, TE; Gieré, R; Hart, KP; Lumpkin, GR; McGlinn, PJChemical extraction techniques and scanning electron microscopy were used to study the distribution and behavior of actinides and rare earth elements (REE) in hydrothermal veins at Adamello, (Italy). The six samples discussed in this paper were from the phlogopite zone, which is one of the major vein zones. The samples were similar in their bulk chemical composition, mineralogy, and leaching behavior of major elements (determined by extraction with 9M HCl). However, there were major differences in the extractability of REE and actinides. The most significant influence on the leaching characteristics appears to be the amounts of U, Th and REE incorporated in resistant host phases. Uranium and Th are very highly enriched in zirconolite grains. Actinides were more readily leached from samples with a higher content of U and Th, relative to the amount of zirconolite. The results show that REE and actinides present in chemically resistant minerals can be retained under aggressive leaching conditions. © 2007 Materials Research Society
- ItemRadioactive waste management at ANSTO - managing current and historic wastes(International Atomic Energy Agency (IAEA), 2001-11-05) Harries, JR; Dimitrovski, L; Hart, KP; Levins, DMThe Australian Nuclear Science and Technology Organisation (ANSTO) site at Lucas Heights has operated as a nuclear site for over 40 years and most of the waste generated is still stored at the site. The 10 MW heavy water research reactor (HIFAR) has operated at Lucas Heights for over 40 years with associated radioisotope and radiopharmaceutical production facilities. HIFAR is scheduled to shut down in 2005 and a contract has been signed for a multipurpose 20 MW research reactor which, amongst other uses, will provide continued radiopharmaceutical production and neutron beam research. In addition to these activities, a wide range of nuclear science and technology R and D is carried out at the site. In 1995, ANSTO issued its radioactive waste management policy which made a commitment to: (a) complying with all regulatory requirements; (b) ensuring that radiation dose rates were kept as low as reasonably achievable (the ALARA principle); (c) disposing of waste when appropriate disposal routes are available; and (d) being in accord with international best practice. An extensive audit was earned out of ANSTO's waste management facilities and practices. The recommendations arising from this audit became the basis for an integrated five year Waste Management Action Plan, which began in 1996. The Plan dealt with legacy issues that had arisen from the accumulation of the radioactive waste at Lucas Heights. It involved construction and operation of improved storage facilities for low- level radioactive waste, better monitoring of existing storage facilities for spent research reactor fuel and intermediate level liquid wastes, and conversion of liquid and solid wastes into more stable forms suitable for prolonged storage. Solidification of the intermediate level liquid waste has been a major priority of the Waste Management Action Plan. This acidic waste is generated during the production of molybdenum-99 for radiopharmaceutical use. A hot cell process was developed involving concentration of the waste by evaporation, destruction of the ammonium ion by a novel process and solidification of the waste as a uranium-rich salt. Routine processing of the liquid waste commenced in 1999 and to date over 2 m3 of liquid waste has been converted to a solid. The solidified waste is stored in high- integrity stainless steel vessels with a design life of at least 50 years. Another project under way will convert this solid waste into a more durable waste form suitable for long term storage or disposal. Two waste forms were initially considered; a titanate-based variant of synroc and cement. Laboratory scale testing established the feasibility of producing the titanate based ceramic with a high waste loading (∼44 wt % U) and the superior performance of this matrix over cement. Engineering scale development of a hot cell process for production of the ceramic waste form is under way. Much of the historic waste was characterised when it was generated by external dose with little information recorded about the radionuclide content. In 1996, a radioactive waste scanning system was installed to determine the radionuclide content of drums of historic waste. A data base system is being developed to integrate the characterisation, treatment and location information on the radioactive waste at ANSTO including the results from the drum scanning measurements. An important objective of ANSTO's waste management policy is minimization of radioactive waste generated and stored. This is being achieved by a number of strategies: for example, in one radioisotope production area a threefold reduction in waste volume has been achieved by separating non-radioactive waste from radioactive waste at the source. A substantial reduction in radioactive gas emissions during the production of molybdenum-99 has also been achieved by changes in waste processing operations and procedures. As well as focussing on historical waste issues a number of initiatives within ANSTO aimed at improving current processes and waste systems are being carried out. Currently, waste water from active drains at ANSTO is treated by a flocculation/centrifugation process and discharged to the sewer. Over the next few years, ANSTO plans to upgrade its effluent treatment facilities using state-of-the-art technology. Pilot plant demonstration of a membrane-based process is in progress after which a specification will be prepared for a full scale plant. Planning is also under way for a new facility to treat and package ANSTO's radioactive waste in readiness for disposal in the national repository for low level and short lived intermediate level waste. © Author(s) 2001
- ItemA report to NERDDP on project no. 1319 entitled : description of synroc durability: kinetics and mechanisms of reaction(Australian Nuclear Science and Technology Organisation, 1990-08) Jostsons, A; Smith, KL; Blackford, MG; Hart, KP; Lumpkin, GR; McGlinn, PJ; Myhra, S; Netting, A; Pham, DK; Smart, RStC; Turner, PSThis is the technical report to NERDDP on Project 1313, "Description of Synroc Durability: Kinetics and Mechanisms of Reaction". Many physical and chemical processes occur, slightly and concurrently, when Synroc is exposed to leachants. A few of these include: * ion-exchange between Synroc and the leachant; * dissolution of some primary phases; * formation of colloids; * precipitation of secondary phases. All of these processes (and others) affect the durability of Synroc. Consequently, it has been necessary to apply an armoury of techniques, to unravel the various processes and their effects. Techniques used include: * solution analysis by inductivity coupled plasma mass spectrometry (ICP/MS) and inductivity coupled plasma optional emission spectroscopy (ICP/OES); * scanning and analytical transmissions electron microscopy (SEM and AEM respectively); * X-ray photoelectron spectroscopy (XPS) and Auger spectroscopy. We have matched or exceeded all the sub-objectives agreed to and funded by NERDDP in 1989/90. Furthermore we have begun to integrate the information generated under the auspices of the grant as well as information subsequently collected, into a comprehensive model. The information contained within the bulk of this report can be broken down into areas which relate to the sub-objectives of the project.
- ItemRetention of actinides in natural pyrochlores and zirconolites(De Gruyter, 1994-12-01) Lumpkin, GR; Hart, KP; McGlinn, PJ; Payne, TENatural pyrochlore and zirconolite undergo a crystalline-aperiodic transformation caused by alpha-decay of 232Th and 238U at dose levels between 2X1014 and 3X1017 α/mg. The principal effects of the transformation are volume expansion and micro-fracturing, providing potential pathways for fluids. Geochemical alteration of the minerals may occur under hydrothermal conditions or in low temperature, near surface environments, but Th and U usually remain immobile and can be retained for time scales up to 10 9 years. However, the Th-U isotope systematics of a zirconolite-bearing vein and dolomite host rock may provide evidence for disequilibrium between 230Th, 234U and 238U. © 1994 R. Oldenbourg Verlag, München
- ItemThe role of titanate ceramics in immobilisation of wastes arising from partitioning and weapons disposition(Japan Atomic Energy Research Institute (JAERI), 2002-03-01) Hart, KP; Zhang, YJ; Begg, BD; Aly, Z; Brownscombe, AJ; Day, RA; Stewart, MWA; Lumpkin, GR; Vance, ER; Jotsons, AThe development of ceramics for the immobilisation of radioactive wastes has been on-going at ANSTO since 1980 and has involved collaboration with JAERI, the USDOE, LLNL and other international laboratories. This work has examined various processing routes, radiation damage effects and long-term aqueous durability for a range of titanate ceramics. Within these studies, information on the long-term behaviour of ceramics chosen to immobilities excess Pu and actinide-rich wastes arising from partitioning strategies have been obtained. Overall, the long-term durability, limitations on criticality under processing and disposal conditions and existence of viable natural analogues endorse the use of titanate ceramics for immobilisation of actinide-rich wastes. © 2002 Japan Atomic Energy Research Institute
- ItemScientific Basis for Nuclear Waste Management XXIV(Cambridge University Press/Springer Nature, 2001-12) Hart, KP; Lumpkin, GRSafe and effective management of nuclear waste provides a broad range of challenges for materials science. Waste processing, waste form and engineered barrier properties, interactions between engineered and geological systems, radiation effects, chemistry and transport of waste species, and long-term predictions of repository performance are just some of the scientific problems facing modern society. This book, the 24th in a very successful series from MRS, offers an international and interdisciplinary perspective on the issues, and features developments in both fundamental and applied areas. Topics include: conditioning of wastes; immobilization of wastes in cement and bitumen; glass waste forms; ceramic waste forms; spent fuel; canisters; engineered barriers; microbiology and thermodynamics; repository studies; natural systems; and solubility, transport modeling and migration. © 2001 Materials Research Society
- ItemSynroc derivatives for the Hanford waste remediation task(Materials Research Society, 1997) Vance, ER; Hart, KP; Day, RA; Carter, ML; Hambley, M; Blackford, MG; Begg, BDThree wt% each of Cs and Tc were mixed with the standard Synroc precursor and the ceramic was formed by hot-pressing. Attempts were made to incorporate the Tc as either metal or Tc 4+, using different redox conditions in processing. Volatile losses of Tc during calcination were < 0.1% in all cases. Short-term Tc leach rates when the Tc was present as a metal alloy were in the order of 10−4 g/m /d at 90°C with frequently changed water, and decreased with increasing leaching time. The valence of the Tc was monitored by X-ray absorption spectroscopy at the drying and calcination stages of the production. The general viability of Synroc/glass composites for immobilising the Hanford HLW sludges is further demonstrated by using further refinements of additive schemes for the inactive “All-blend” formulation and initial studies using the U-containing “All-blend” waste formulation. © Materials Research Society 1997