William R. Bower
University of Manchester
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Featured researches published by William R. Bower.
Mineralogical Magazine | 2015
William R. Bower; Carolyn I. Pearce; G. T. R. Droop; J.F.W. Mosselmans; K. Geraki; R. A. D. Pattrick
Abstract A detailed understanding of the response of mineral phases to the radiation fields experienced in a geological disposal facility (GDF) is currently poorly constrained. Prolongued ion irradiation has the potential to affect both the physical integrity and oxidation state of materials and therefore may alter a structures ability to react with radionuclides. Radiohalos (spheres of radiation damage in minerals surrounding radioactive (α-emitting) inclusions) provide useful analogues for studying long term α-particle damage accumulation. In this study, silicate minerals adjacent to Th- and U-rich monazite and zircon were probed for redox changes and long/short range disorder using microfocus X-ray absorption spectroscopy (XAS) and high resolution X-ray diffraction (XRD) at Beamline I18, Diamond Light Source. Fe3+ → Fe2+ reduction has been demonstrated in an amphibole sample containing structural OH- groups - a trend not observed in anhydrous phases such as garnet. Coincident with the findings of Pattrick et al. (2013), the radiolytic breakdown of OH - groups is postulated to liberate Fe3+ reducing electrons. Across all samples, high point defect densities and minor lattice aberrations are apparent adjacent to the radioactive inclusion, demonstrated by micro-XRD.
Journal of Hazardous Materials | 2018
Adam Lang; Dirk Engelberg; Nicholas T. Smith; Divyesh Trivedi; Owen Horsfall; Anthony Banford; Philip A. Martin; Paul Coffey; William R. Bower; Clemens Walther; Martin Weiß; Hauke Bosco; Alex Jenkins; Gareth T. W. Law
Laser Induced Breakdown Spectroscopy (LIBS) has the potential to allow direct, standoff measurement of contaminants on nuclear plant. Here, LIBS is evaluated as an analytical tool for measurement of Sr and Cs contamination on type 304 stainless steel surfaces. Samples were reacted in model acidic (PUREX reprocessing) and alkaline (spent fuel ponds) Sr and Cs bearing liquors, with LIBS multi-pulse ablation also explored to measure contaminant penetration. The Sr II (407.77nm) and Cs I (894.35nm) emission lines could be separated from the bulk emission spectra, though only Sr could be reliably detected at surface loadings >0.5mgcm-2. Depth profiling showed decay of the Sr signal with time, but importantly, elemental analysis indicated that material expelled from LIBS craters is redistributed and may interfere in later laser shot analyses.
Journal of Hazardous Materials | 2016
William R. Bower; Katherine Morris; J.F.W. Mosselmans; Olivia R. Thompson; Anthony W. Banford; Kathleen Law; R. A. D. Pattrick
Analysis of a radioactive, coated concrete core from the decommissioned, spent nuclear fuel cooling pond at the Hunterston-A nuclear site (UK) has provided a unique opportunity to study radionuclides within a real-world system. The core, obtained from a dividing wall and sampled at the fill level of the pond, exhibited radioactivity (dominantly (137)Cs and (90)Sr) heterogeneously distributed across both painted faces. Chemical analysis of the core was undertaken using microfocus spectroscopy at Diamond Light Source, UK. Mapping of Sr across the surface coatings using microfocus X-ray fluorescence (μXRF) combined with X-ray absorption spectroscopy showed that Sr was bound to TiO2 particles in the paint layers, suggesting an association between TiO2 and radiostrontium. Stable Sr and Cs sorption experiments using concrete coupons were also undertaken to assess their interactions with the bulk concrete in case of a breach in the coating layers. μXRF and scanning electron microscopy showed that Sr was immobilized by the cement phases, whilst at the elevated experimental concentrations, Cs was associated with clay minerals in the aggregates. This study provides a crucial insight into poorly understood infrastructural contamination in complex systems and is directly applicable to the UKs nuclear decommissioning efforts.
American Mineralogist | 2016
William R. Bower; R. A. D. Pattrick; Carolyn I. Pearce; G. T. R. Droop; Sarah J. Haigh
Abstract The complex, nanometer-scale structural changes resulting from long-term α-particle bombardment of the mineral biotite are revealed for the first time using high-resolution transmission electron microscope (HRTEM) imaging. Radiohaloes are the product of high-energy α-particles emitted from radioactive inclusions penetrating into the surrounding mineral over long (∼1.8 Ga) timescales, resulting in intense discoloration attributed to ionization events and structural damage. HRTEM analysis of these radiohaloes reveals the long-term breakdown of the biotite structure into three distinct domains. Nanometer-scale, neo-phase regions of dilated and contracted mica structure, with periodicities comparable to 1:1 phyllosilicates, are bound by semi-amorphous, high-defect density domains. These are periodically interspersed with areas of near-original biotite structure. Across the halo region, damaged crystallites have become misoriented, revealing changes in the mica layer-to-layer spacing. This nanoscale response of the mica structure has profound implications for understanding the performance of phyllosilicates in barrier systems employed in the safe isolation of nuclear waste, as materials such as these will be relied upon to retard radionuclide migration over the lifetime of a geological disposal facility.
American Mineralogist | 2016
William R. Bower; Carolyn I. Pearce; Andrew D. Smith; Simon M. Pimblott; J. Frederick W. Mosselmans; Sarah J. Haigh; James P. McKinley; R. A. D. Pattrick
Abstract A critical radiation damage assessment of the materials that will be present in a Geological Disposal Facility (GDF) for radioactive waste is a priority for building a safety case. Detailed analysis of the effects of high-energy α-particle damage in phyllosilicates such as mica is a necessity, as these are model structures for both the clay-based backfill material and the highly sorbent components of a crystalline host rock. The α-radiation stability of biotite mica [general formula: K(Mg, Fe)3(Al, Si3O10)(F, OH)2] has been investigated using the 5 MV tandem pelletron at the University of Manchester’s Dalton Cumbrian Facility (DCF) and both the microfocus spectroscopy (I18) and core X-ray absorption spectroscopy (B18) beamlines at Diamond Light Source (U.K.). Microfocus X-ray diffraction mapping has demonstrated extensive structural aberrations in the mica resulting from controlled exposure to the focused 4He2+ ion (α-particle) beam. Delivered doses were comparable to α-particle fluences expected in the highly active, near-field of a GDF. At doses up to 6.77 displacements per atom (dpa) in the region of highest particle fluence, biotite mica displays a heterogeneous structural response to irradiation on a micrometer scale, with sequential dilation and contraction of regions of the structure perpendicular to the sheets, as well as a general overall contraction of the phyllosilicate layer spacing. At the peak of ion fluence, the structure collapses under a high point defect density and amorphous areas are pervasive among altered domains of the original lattice. Such structural alterations are likely to affect the material’s capacity to sorb and retain escaped radionuclides over long timescales; increased edge site availability may favor increased sorption while interlayer uptake will likely be reduced due to collapse. Radiation-induced reduction of structural iron at the region of highest structural damage across an α-particle’s track has been demonstrated by Fe K-edge X-ray absorption near edge spectroscopy (XANES) and local structural disorder has been confirmed by analysis of both potassium K-edge XANES and Fe K-edge extended X-ray absorption fine structure analysis. An infrared absorption study of deformations in the OH– stretching region, along with electron probe microanalysis complements the synchrotron data presented here.
Review of Scientific Instruments | 2015
William R. Bower; A.D. Smith; Richard A D Pattrick; Simon M. Pimblott
Evaluating the radiation stability of mineral phases is a vital research challenge when assessing the performance of the materials employed in a Geological Disposal Facility for radioactive waste. This report outlines the setup and methodology for efficiently allowing the determination of the dose dependence of damage to a mineral from a single ion irradiated sample. The technique has been deployed using the Dalton Cumbrian Facilitys 5 MV tandem pelletron to irradiate a suite of minerals with a controlled α-particle ((4)He(2+)) beam. Such minerals are proxies for near-field clay based buffer material surrounding radioactive canisters, as well as the sorbent components of the host rock.
Mineralogical Magazine | 2015
William R. Bower; W. Head; G. T. R. Droop; Recep Zan; R. A. D. Pattrick; P.L. Wincott; Sarah J. Haigh
Abstract We have applied mechanical exfoliation for the preparation of ultra-thin samples of the phyllosilicate mineral biotite. We demonstrate that the ‘scotch tape’ approach, which was made famous as an early method for production of single-atom-thick graphene, can be used for production of sheet-silicate specimens that are sufficiently thin to allow high-resolution transmission electron microscope (HRTEM) imaging to be achieved successfully while also being free from the specimen preparation artefacts that are often caused by ion-beam milling techniques. Exfoliation of the biotite parallel to the (001) planes has produced layers as thin as two structural TOT units thick (~2 nm). The minimal specimen thickness enabled not only HRTEM imaging but also the application of subsequent exit wave function restoration to reveal the pristine biotite lattice. Exit wave function restoration recovers the full complex electron wave from a focal series of HRTEM images, removing the effects of coherent lens aberrations. This combination of methods therefore produces images in which the observed features are readily interpreted to obtain atomic resolution structural information.
Environmental Science & Technology | 2018
Ryohei Ikehara; Mizuki Suetake; Tatsuki Komiya; Genki Furuki; Asumi Ochiai; Shinya Yamasaki; William R. Bower; Gareth T. W. Law; Toshihiko Ohnuki; Bernd Grambow; Rodney C. Ewing; Satoshi Utsunomiya
Industrial & Engineering Chemistry Research | 2018
Timothy Kerry; Anthony W. Banford; William R. Bower; Olivia R. Thompson; Thomas Carey; J. Frederick W. Mosselmans; Konstantin Ignatyev; Clint A. Sharrad
The American Mineralogist (Print). 2015;. | 2015
William R. Bower; R. A. D. Pattrick