Combined X‐ray microanalytical study of the Nd uptake capability of argillaceous rocks

Abstract

Argillaceous rocks are considered as suitable host rock formation to isolate the high‐level radioactive waste from the biosphere for thousands of years. Boda Claystone Formation, the possible host rock formation for the Hungarian high‐level radioactive waste repository, has geologically and mineralogically been studied in detail, but its physico‐chemical parameters describing the retention capability of the rock needed further examinations. Studies were performed on thin sections subjected to 72 h sorption experiments using inactive Nd(III). Nd(III) has been used as a chemical analogue for transuranium elements of the radioactive waste to examine the ion uptake capability of the micrometre size mineral phases occurring in the rock. The elemental mapping of synchrotron radiation‐based microscopic X‐ray fluorescence (micro‐XRF) combined with scanning electron microscopy energy dispersive X‐ray analysis (SEM/EDX) has sufficient sensitivity to study the uptake capability of the different mineral phases on the microscale without the necessity of applying radioactive substances. Elemental maps were recorded on several thousand pixels using micrometre magnitude spatial resolution. By interleaving micro‐XRF and SEM/EDX data sets from the same sample area and applying multivariate methods, calcite and clay minerals could be identified as the main mineral phases responsible for Nd(III) uptake without using additional microscopic X‐ray diffraction mapping. It should be highlighted that the ion uptake capability of dolomite containing calcium and magnesium could be distinguished from the characteristics of calcite only by the interleaving of micro‐XRF and SEM/EDX data sets. The presence of minerals was verified by applying microscopic X‐ray diffraction point measurements. Copyright © 2015 John Wiley & Sons, Ltd.

Automated mineralogy based on micro-energy-dispersive X-ray fluorescence microscopy (µ-EDXRF) applied to plutonic rock thin sections in comparison to a mineral liberation analyzer

“…Micro-energy-dispersive X-ray fluorescence microscopy (µ-EDXRF) is a new and versatile technique commonly used in various fields such as art (Keune et al, 2016), archeol-ogy (Kozak et al, 2016), biology (Figueroa et al, 2014), medicine (Wandzilak et al, 2015) and also with increasing extent in geosciences, mostly for visualization and quantification of element distributions (Belissont et al, 2016;Croudace and Rothwell, 2015;Flude and Storey, 2016;Gergely et al, 2016;Kéri et al, 2016;Lombi et al, 2011;Melcher et al, 2006;Poonoosamy et al, 2016;Rammlmair et al, 2001Rammlmair et al, , 2006Redwan et al, 2016). The combination of spatial and spectral information for large samples of up to 20 cm length with almost no sample preparation opens many fields of applications.…”

Non-negative matrix factorization for the near real-time interpretation of absorption effects in elemental distribution images acquired by X-ray fluorescence imaging

“…Matrix factorization with non-negative constrains has long been used in spectroscopic imaging (Kotula et al, 2003), but has found only limited use in the interpretation of XRF imaging data until now. Osan et al used positive matrix factorization of the EPA PMF 3.0 software package in a study on the sorption capacity of claystone for several radionuclides, to identify the most strongly absorbing mineral phases (Osá n et al, 2014;Ké ri et al, 2016). Lahlil et al used the NMF routines implemented in the PyMCA software package to identify components present in micro-XRF maps of lead antimonate-based opacifiers in glass samples from several epochs (Lahlil et al, 2011).…”