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- ItemPlutonium and neptunium incorporation in zirconolite(Materials Research Society, 1997) Begg, BD; Vance ER; Day, RA; Hambley, M; Conradson, SDThe incorporation of Pu and Np in zirconolite (CaZrTi2O7) has been investigated over a range of redox conditions. Zirconolite formulations designed to favour either trivalent or tetravalent Pu and Np were prepared by limiting the amount of charge compensating additives available to maintain electroneutrality. From near-edge X-ray absorption spectroscopy the Pu valence state was found to vary with the processing atmosphere, from completely tetravalent when fired in air, and located on either the Ca or Zr sites, to trivalent, when substituted on the Ca site after annealing in 3.5% H2/N2. Np was predominantly tetravalent over the range of redox conditions examined and was readily incorporated on either of zirconolite's Ca or Zr sites. The charge compensation mechanisms at work in different zirconolites are also discussed. © Materials Research Society 1997
- ItemMicrospectroscopy beamline at the Australian Synchrotron(American Institute of Physics, 2007-01-19) Paterson, DJ; Boldeman, JW; Cohen, DD; Ryan, CGThis dedicated beamline will provide sub‐micron spatial resolution with the highest flux possible and an energy tuning range of 4.7–25 keV using an in‐vacuum undulator source. It will combine 2D mapping with μ‐XRF, μ‐XANES and μ‐XAFS for elemental and chemical analysis to solve scientific problems that can only be understood using sub‐micron resolutions. The primary beamline design goal is to achieve sub‐micron spatial resolution, 100–200 nm, at energy resolutions approaching 1/10000. This spatial resolution will be achieved without a major compromise to the flux, as the beamline will simultaneously achieve detection sensitivities to sub‐ppm levels. The beamline will have the flexibility to trade‐off one parameter against gains in certain attributes, as dictated by the needs of the application. Fresnel zone plates are intended for the highest resolution applications, while the KB mirrors are shall be used for applications where achromatic focusing and high sensitivity are required. The beamline design will accommodate a diverse range of applications with greatly contrasting sample formats, sample composition and anticipated detector count rates. © 2007 American Institute of Physics.
- ItemPipesafe, engineering critical assessment software for pipe line girth welds(New Zealand Welding Committee, 1996-02-04) Moss, CJ; Irrgang, R; Stathers, PA; Barbaro, F; Bowie, GThe Australian Standard for Pipeline Construction, AS2885 (1995), considers pipeline girth weld defect acceptance using Tier 1 (workmanship standards), Tier 2 (fitness for purpose) and by Engineering Critical Assessment (ECA) as Tier 3. AS2885 makes provision for ECA in clause 22.4 by stating "if approved the acceptable criteria may be determined by using an approved ECA procedure or other approved method". The ‘fitness for purpose‘ approach adopted in AS2885 is related to that originating from the European Pipeline Research Group (EPRG). However, ECA is currently an unwieldy tool and unattractive to those who have only an occasional need to carry out assessment using fracture mechanics. This paper discusses the software PIPESAFE that has been developed to apply ECA defect acceptance methodology to girth welds in pipelines being built in Australia. PIPESAFE is a PC based software package which aims to enable pipeline engineers to assess the significance of flaws and is based on principles embodied in PD6493, 1991 ‘Guidance on Methods for Assessing the Acceptibility of Flaws in Fusion Welded Structures”. The software is currently being trialed in industry and will be commercially available in the near future.
- ItemHAZ cold cracking - a restrained view(Welding Technology Institute of Australia, 1994) Squires, IF; Feng, B; Mercer, D; Payten, WM; Dunne, D; Alam, NHeat affected zone (HAZ) hydrogen cracking occurs after the weld has cooled to ambient temperature when the HAZ has transformed and hydrogen has had time to diffuse into it from the weld metal. It is therefore referred to as “cold cracking”. For cracking to occur, a stress needs to be present This will arise inevitably from the local heating and cooling when making the weld, however, the magnitude of the stress will depend on the restraint applied to the weld, the welding conditions used and the geometry of the weld. Recommendations to assist with the avoidance of HAZ cold cracking are available in publications such as WTIA Technical Note 1 “Weldability of Steels” but these cover essentially only the control of the thermal cycle and hydrogen level. The more complex issue of restraint is not included. Consequently the recommendations tend to be either over conservative, hence not fully cost effective, or present unquantied risks. Research work by various authors in this area has been summarised by Suzuki(l) and a basic model produced. The work covered a variety of methodologies and these could not be considered consistent. The present study provides a consistent approach, based on the use of the rigid restraint cracking (RRC) test which allows direct measurement of weld stress. To enable the effect of local stresses to be understood and general models of restraint effects to be developed a finite element analysis (FEA) computer model is being developed in parallel with work on the RRC test Further inputs to the modelling process are being or will be generated from localised studies of mechanical properties in the weld and heat affected zone and from dilatometric studies of the weld. The former will allow more accurate assessment of the behaviour of local stress concentrators in the weld and HAZ. The latter will assist in quantifying the weld metal and HAZ contribution to stress generation.
- ItemDifferentiating between the d13C signature from environmental conditions and SOM cycling in eastern Australian peat sediments(Australasian Quaternary Association (AQUA), 2021-07-08) Forbes, MS; Cohen, TJ; Marx, SK; Sherborne-Higgins, B; Cadd, H; Francke, A; Cendón, DI; Peterson, MA; Mooney, SD; Constantine, M; Boesl, F; Kobayashi, Y; Mazumder, DThe analysis of stable carbon isotopes is commonly used in Quaternary science to reconstruct the environmental conditions and vegetation contributions to sedimentary sequences. However, the measured d13C signature of the total organic matter (OM) pool can also reflect other complexities within depositional environments. The peats of the Thirlmere Lakes system in the southern section of the Blue Mountains World Heritage Area provides an excellent opportunity to closely scrutinise such d13C dynamics. These deposits are rich in TOC (20-40%) meaning analytical techniques such as 13C-NMR, used to characterise the OM pool, can be applied effectively. Furthermore, the identification of several peat units deposited over the last ~130 ka allows for temporal comparisons. d13C values determined for a 7 m sediment sequence from Lake Couridjah representing both the MIS 1 and MIS 5e interglacial periods vary by up to 4 to 6‰. These trends were subsequently identified in two other sediment sequences (Lake Baraba and Lake Werri Berri) proximal to Lake Couridjah. Initially we interpreted our results as reflecting a C3 dominated vegetation environment with MIS 1 wetter than MIS 5e, following the established relationship between water stress and d13C enrichment. However, spectral analysis of the OM pool indicates that d13C is driven by changing OM dynamics rather than large changes in environmental conditions. In these environments, the greater presence of carbohydrates (i.e. cellulose) in MIS 1 result in more depleted d13C values. In contrast, the MIS 5e peat is dominated by relative inert OM C fractions including charcoal and lipids (such as leaf waxes), which influences environmental proxies such as C/N. Thus, it is likely that the older MIS 5e peat is a more decomposed version of the active MIS 1 peat, and thus differentiating environmental conditions between the two using d13C alone is not particularly illuminating. To overcome this, we describe the d13C values for a coarse charcoal and high temperature hydrogen pyrolysis fractions, modern vegetation, catchment POC and DOC, and n-alkanes composition and generate catchment carbon models for both MIS 1 and MIS5e. Finally comparing the size of the OM pools of both interglacial deposits can provide useful information in estimating the carbon storage capacity of peat deposits in eastern Australia over these time scales. © The Authors.