Mineralogical transformations controlling acid mine drainage chemistry

The role of Fe(III) minerals in controlling acid mine drainage (AMD) chemistry was studied using samples from two AMD sites [Gum Boot (GB) and Fridays-2 (FR)] located in northern Pennsylvania. Chemical extractions, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) were used to identify and characterize Fe(III) phases. The mineralogical analysis revealed schwertmannite and goethite as the principal Fe(III) phases in the sediments. Schwertmannite particles occurred as sub-micron sized spheroids. Their transformation into goethite occurred at the GB site where poorly-crystallized goethite rich in surface-bound sulfate was initially formed. In contrast, no schwertmannite transformation occurred at the FR site. The resulting goethite in GB sediments was also of spherical morphology and resulted from an in situ phase transformation involving the conversion of bulkbound schwertmannite sulfate ions into goethite surface complexes. Chemical extractions moreover showed that the poorly-crystallized goethite particles were subject to further crystallization accompanied by sulfate desorption. Changes in sulfate speciation preceded its desorption, with a conversion of bidentate- to monodentate-bound sulfate surface complexes. Laboratory sediment incubation experiments were conducted to evaluate the effect of mineral transformation on water chemistry. Incubation experiments were carried out with schwertmannite-containing sediments and aerobic AMD waters with different pH and chemical composition. The pH decreased to 1.9–2.2 in all suspensions and the concentrations of dissolved Fe and S increased significantly. Regardless of differences in the initial water composition, pH, Fe and S were similar in suspensions of the same sediment. XRD measurements revealed that schwertmannite transformed into goethite in GB and FR sediments during laboratory incubation. The incubation experiments demonstrated that schwertmannite transformation controlled AMD water chemistry under no-flow, batch conditions

Irradiation effects on the electrochemistry and corrosion resistance of stainless steel

Nickel-ion irradiation at 500{degrees}C is shown to have a strong effect on the surface electrochemistry and intergranular corrosion of stainless steel. Measured current densities in a 1N H{sub 2}SO{sub 4} solution at room temperature are increased at active-passive, passive, and transpassive potentials. Irradiation effects on the current decay behavior and susceptibility to intergranular corrosion were similar for a microcrystalline, fine-grained stainless alloy and for a very large-grained stainless steel. Radiation-induced segregation at the surface is believed to promote higher currents, whereas segregation at grain boundaries prompts intergranular attack. Analytical electron microscopy measurements reveal silicon enrichment and chromium depletion at internal interfaces in irradiated specimens. Silicon enhances dissolution at transpassive potentials, whereas chromium depletion does the same at active-passive and passive potentials

ESARDA Bulletin n. 59

ESARDA is an association initially formed to advance and harmonize research and development for nuclear safeguards whose scope has in recent year expanded as the number and type of its working groups’ activities below indicates. Esarda is currently composed of about 30 laboratories, private and governmental institutions worldwide. Within Esarda (http://esarda.jrc.ec.europa.eu/), a number working groups have been over the years established and active namely: Techniques and Standards for Destructive Analysis, Techniques and Standards for Non-Destructive Analysis, Containment and Surveillance, Novel Approaches / Novel Technologies, Implementation of Safeguards, Verification Technologies and Methodologies, Training and Knowledge Management, Editorial Committee. ESARDA publishes a Bulletin containing peer reviewed scientific related to nuclear Safeguards, verification and non-proliferation. This publication appears generally twice a year. In addition, thematic special issues are published as proposed by the ESARDA community. The Bulletin Editorial Board is composed of about 10 experts in the various technical and scientific fields related to safeguards. They are all actively engaged in safeguards R&D or in safeguards implementation and other fields. The Editorial Board decides the contents of the Bulletin, selects the papers to be published and reviews them before publication. All ESARDA editorial activities are carried out at JRC in Ispra. Scientific papers submitted for publication are reviewed by independent authors and by members of the Editorial Committee. The Bulletin is currently submitted to Scopus for evaluation in view of citation. ESARDA Bulletin is published jointly by ESARDA and the Joint Research Centre of the European Commission and distributed free of charge to over 1000 registered members, libraries and institutions worldwide.JRC.G.II.7-Nuclear securit