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Instruments / Technical Area	Publication Details	Published
B18-Core EXAFS	A universal uptake mechanism for cobalt(II) on soil constituents: ferrihydrite, kaolinite, humic acid, and organo-mineral composites Gemma Woodward , Caroline L. Peacock , Alba Otero-Farina , Olivia R. Thompson , Andrew P. Brown , Ian T. Burke Geochimica Et Cosmochimica Acta DOI: 10.1016/j.gca.2018.06.035 Diamond Proposal Number(s): [13037, 13580] Open Access Show Abstract ▼ Abstract: Cobalt is a waste product in many industrial processes and its most common radioactive isotope – 60Co – is a by-product of nuclear reactors. To better understand the mobility and fate of Co in natural and contaminated environments we investigated Co sorption behaviour to the common soil and sediment constituents ferrihydrite, kaolinite, humic acid (HA), and ferrihydrite-HA and kaolinite-HA organo-mineral composites using sorption batch experiments, synchrotron X-ray absorption spectroscopy (EXAFS), and scanning transmission electron microscopy (STEM). We measured the sorption of Co to the end-member mineral and organic phases and the composites as a function of pH, ionic strength and Co concentration, and also for the composites as a function of organic carbon concentration, with composites made containing a wide range of organic carbon contents. We then determined the molecular mechanisms of Co sorption to the end-member phases and the composites, and used this information to develop molecularly constrained thermodynamic surface complexation models to quantify Co sorption. Sorption to the ferrihydrite-HA and kaolinite-HA organo-mineral composites was found to be intermediate to both of the end-member phases, displaying enhanced sorption respective to the mineral end-member phase at mid-low pH. EXAFS analysis shows that there is a universal sorption mechanism accounting for Co sorption to the end-member mineral and organic phases and the organo-mineral composites at mid-high pH, in which Co sorbs to these phases via inner-sphere bidentate binuclear surface complexes. At mid-low pH, sorption to all the phases except ferrihydrite is the result of outer-sphere complexation. Our new molecularly constrained thermodynamic surface complexation models for Co sorption to ferrihydrite, kaolinite, HA, and ferrihydrite-HA and kaolinite-HA organo-mineral composites, show that Co sorption to the composites cannot be modelled assuming linear additivity of Co sorption to the end-member phases.	Jul 2018
I18-Microfocus Spectroscopy	Uranium contamination of stainless steel in nuclear processing plants Timothy Kerry , Anthony W. Banford , William Bower , Olivia R. Thompson , Thomas Carey , J. Frederick W. Mosselmans , Konstantin Ignatyev , Clint Sharrad Industrial & Engineering Chemistry Research DOI: 10.1021/acs.iecr.7b05139 Diamond Proposal Number(s): [12505] Show Abstract ▼ Abstract: Stainless steel coupons have been exposed to uranium-containing nitric acid solutions, in conditions similar to those found in various uranium handling nuclear facilities across the nuclear fuel cycle. Solid state analysis of the stainless steel samples and solution composition analysis were undertaken to gain a better understanding of the contamination process mechanisms. Stainless steel coupons were immersed in 12 M HNO3 containing uranium (1 g/L), in the form of uranyl, for periods of up to 255 days. Uranium contamination was observed across all time lengths of exposure. Solution analysis indicated that the levels of contamination reached an equilibrium state after ~14 days. Investigations using Raman microscopy, synchrotron microfocus X-ray fluorescence and X-ray absorption spectroscopy showed inhomogeneous localization of uranyl species within the passive layer of the stainless steel surface. Over longer time lengths of exposure these contaminant species were predominantly found to locate within intergranular regions of the stainless steel. This finding should be taken into consideration when developing decontamination protocols for corroded stainless steel that has been exposed to uranium, to facilitate metal reuse/recycle and minimize hazardous waste volumes.	Feb 2018
I18-Microfocus Spectroscopy	Characterising legacy spent nuclear fuel pond materials using microfocus X-ray absorption spectroscopy W. R. Bower , K. Morris , J. F. W. Mosselmans , O. R. Thompson , A. W. Banford , K. Law , R. A. D. Pattrick Journal Of Hazardous Materials DOI: 10.1016/j.jhazmat.2016.05.037 Diamond Proposal Number(s): [9045] Open Access Show Abstract ▼ Abstract: 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 137Cs and 90Sr) 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 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 aggregate. This study provides a crucial insight into poorly understood infrastructural contamination in complex systems and is directly applicable to the UK’s decommissioning efforts.	May 2016

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