Assessment of glass dissolution kinetics, under disposal relevant temperature and pH environments, is required to credibly estimate radionuclide release rates from vitrified radioactive waste. Leaching of the International Simple Glass (ISG) under acidic to hyperalkaline conditions was examined. Forward rate measurements have been obtained using the dynamic leaching SPFT protocol and rate parameters for B, Na and Si in the basic regime; errors in rates predicted using these parameters at high pH and temperature are significant because the fitting uses logarithmic data. Longer term behaviour under hyperalkaline conditions, representative of some disposal environments, was investigated using the PCT and MCC-1 static leaching protocols with Ca(OH)2 solutions for up to 120 days (PCT) and 720 days (MCC-1). In hyperalkaline conditions dissolution was incongruent for all elements and the presence of alternating zirconia-rich and zirconia-poor alteration layers was observed on all leached monoliths, indicating the occurrence of a self-organisation phenomenon during leaching.

Standard methods to assess the durability of vitrified radioactive waste were first developed in the 1980’s and, over the last 40 years, have evolved to yield a range of responses depending on experimental conditions and glass composition. Mechanistic understanding of glass dissolution has progressed in parallel, enhancing our interpretation of the data acquired. With the implementation of subsurface disposal for vitrified radioactive waste drawing closer, it is timely to review the available standard methodologies and reflect upon their relative advantages, limitations, and how the data obtained can be interpreted to support the post-closure safety case for radioactive waste disposal.

Recent advancements in nanotechnology have led to the development of innovative, low-cost and highly efficient water disinfection technologies that may replace or enhance the conventional methods. In this study, we introduce a novel procedure for preparing a bifunctional activated carbon nanocomposite in which nanoscale-sized magnetic magnetite and antimicrobial silver nanoparticles are incorporated (MACAg). The antimicrobial efficacy of the nanocomposite was tested against Escherichia coli (E. coli). MACAg (0.5 g, 0.04% Ag) was found to remove and kill 10 6 -10 7 CFU (colony-forming units) in 30 min via a shaking test and the removing and killing rate of the nanocomposites increased with increasing silver content and decreased with increasing CFU. The inhibition zone tests revealed, among the relevant components, only Ag nanoparticles and Ag + ions showed antimicrobial activities. The MACAg was easily recoverable from treated water due to its magnetic properties and was able to remove and kill 10 6 CFU after multiple-repeated use. The MACAg nanocomposite also demonstrated its feasibility and applicability for treating a surface water containing 10 5 CFU. Combining low cost due to easy synthesis, recoverability, and reusability with high antimicrobial efficiency, MACAg may provide a promising water disinfection technology that will find wide applications.

We describe a 2 h introductory laboratory procedure that prepares a novel magnetic antimicrobial activated carbon nanocomposite in which nanoscale sized magnetite and silver particles are incorporated (MACAg). The MACAg nanocomposite has achieved the synergistic properties derived from its components and demonstrated its applicability as an effective and recoverable antimicrobial agent for water disinfection. The principle is successfully illustrated by a significant reduction in the number of microbes in an Escherichia coli (E. coli) solution of 2 × 106 colony forming units following its treatment with MACAg for 10 min. The exercise allows the college students to (1) be introduced to an exciting class of advanced materials, known as nanocomposites, at an early stage, (2) gain working experiences at nanochemistry–microbiology interface, and (3) see the use and experience the fun of chemistry. The experiment uses readily available materials, can be run in a general or introductory chemistry laboratory environment, and is well received and enjoyed by the students. The experiment is also suitable for advanced high school students.

Understanding the physical and chemical properties of materials arising from nuclear meltdowns, such as the Chernobyl and Fukushima accidents, is critical to supporting decommissioning operations and reducing the hazard to personnel and the environment surrounding the stricken reactors. Relatively few samples of meltdown materials are available for study, and their analysis is made challenging due to the radiation hazard associated with handling them. In this study, small-scale batches of low radioactivity (i.e., containing depleted uranium only) simulants for Chernobyl lava-like fuel-containing materials (LFCMs) have been prepared, and were found to closely approximate the microstructure and mineralogy of real LFCM. The addition of excess of ZrO 2 to the composition resulted in the first successful synthesis of high uranium-zircon (chernobylite) by crystallisation from a glass melt. Use of these simulant materials allowed further analysis of the thermal characteristics of LFCM and the corrosion kinetics, giving results that are in good agreement with the limited available literature on real samples. It should, therefore, be possible to use these new simulant materials to support decommissioning operations of nuclear reactors post-accident.

A preliminary investigation of the synthesis and characterization of simulant ‘lava-like’ fuel containing materials (LFCM), as low activity analogues of LFCM produced by the melt down of Chernobyl Unit 4. Simulant materials were synthesized by melting batched reagents in a tube furnace at 1500 °C, under reducing atmosphere with controlled cooling to room temperature, to simulate conditions of lava formation. Characterization using XRD and SEM-EDX identified several crystalline phases including ZrO2, UOx and solid solutions with spherical metal particles encapsulated by a glassy matrix. The UOX and ZrO2 phase morphology was very diverse comprising of fused crystals to dendritic crystallites from the crystallization of uranium initially dissolved in the glass phase. This project aims to develop simulant LFCM to assess the durability of Chernobyl lavas and to determine the rate of dissolution, behavior and evolution of these materials under shelter conditions.

We describe a 2 h general-chemistry experiment that introduces college students not only to the concepts, synthesis, and applications of nanomaterials at an early stage but also the use of a spectrophotometer for quantification and unknown determination based on Beer's Law. The procedure involves students (1) preparing a nanocomposite by chemically incorporating magnetite nanoparticles into activated carbon (AC), (2) using the as-prepared nanocomposite to treat an aspirin "metabolite" solution for 5 min, and (3) spectroscopically evaluating the nanocomposite's removal efficiency for this "pollutant". The spectroscopic measurement is based on a colored complex the pollutant forms with an acidified iron(III)-ion solution. The nanocomposite is magnetically recovered from treated water and is found to remove 90−130 mg of equivalent aspirin mass per gram of AC. The experiment, using commonly available chemicals and equipment, has been performed by 190 students in groups of two to three and is well-received and enjoyed by these students.

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