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Radiation damage from long-term alpha particle bombardment of silicates – a microfocus XRD and Fe K-edge XANES study

DOI: 10.1180/minmag.2015.079.6.20 DOI Help

Authors: W. R. Bower (University of Manchester) , C. I. Pearce (University of Manchester) , G. T. R. Droop (University of Manchester) , J. F. W. Mosselmans (Diamond Light Source) , K. Geraki (Diamond Light Source) , R. A. D Pattrick (University of Manchester)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Mineralogical Magazine , VOL 79 (6) , PAGES 1455 - 1466

State: Published (Approved)
Published: December 2015
Diamond Proposal Number(s): 6208 , 9044

Open Access Open Access

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 structure's 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 Keywords: radiation damage; alpha particle; silicates; Fe K-edge; XRD; XANES

Subject Areas: Environment, Materials, Earth Science

Instruments: I18-Microfocus Spectroscopy