Search Results (6)

In most countries, low- and intermediate-level wastes (LILWs) are cemented in carbon steel drums for later disposal. The durability of waste packages is determined by the chemical environment generated by both cement-based engineered barrier systems and the aggressive species present in the waste. Decontamination sludges are challenging wastes that are currently not accepted for final disposal due to their acidic nature and high concentrations of organic species and complexants. Thus, it was proposed to use electrochemical measurements to study the corrosion of steel sheets, simulating drums embedded in new alkali-activated slag (AAS) formulations with surrogate decontamination liquids, and determine their viability for use as confining matrices in order to increase the service life of the drums. The carbon steel coupon embedded in the Portland cement reference (R-L) paste showed the best corrosion resistance, followed by that of steel embedded in sodium silicate-activated slag (BFS-S-L) paste. This behaviour may be related to an improvement in the protective nature of the surface film. However, in sodium carbonate-activated slag (BFS-C-L) paste, the effect of the sludge in the matrix seemed to be more intense, leading to a pH decrease in the paste porewater, an effect that could hinder the formation of a passive layer on the surface of the carbon steel. Under such conditions, the initiation of the corrosion process seems to be favoured, resulting in the formation of a non-protective scale consisting mainly of hematite. Full article

In the framework of the PREDIS EU project, a wireless battery-operated gamma-ray detection system was developed in order to provide a medium-to-long-term monitoring system for radioactive waste drums. It was initially proposed to monitor the gamma radioactivity outcoming from steel drums containing cemented radwaste, even though it could be usefully employed in a wider range of applications. Gamma rays are penetrating and convey information from the drum's internal structure, as the count rate measured on the surface depends on the thickness and density of the crossed materials. A number of sensors arranged around a drum, typically four units, provide indications of the emission anisotropy, and any sensitive change in the measured count rate would hint at some anomaly, thus triggering a suitable inspection by operators. Full article

This paper presents a numerical study to investigate delayed ettringite formation (DEF) that may pose a long-term durability risk by altering the microstructure with consequent swelling leading to cracking. A chemo–thermal model is used to predict the evolution and distribution of temperature and hydration phases in a wide range of blended cements. In particular, the influence of nuclear waste loading, waste package size, and the addition of supplementary cementitious materials (SCMs) on DEF is systematically and numerically investigated. The analyses show that higher amounts of ordinary Portland cement (OPC) and waste loadings result in higher hydration temperatures and consequently increased DEF potential by enhancing sulfoaluminate dissolution and hydrogarnet precipitation. Partial replacement of OPC with SCMs reduced hydration heat and mitigated DEF risks. The analysis indicated that the DEF evolution may be different for waste packages of different sizes due to a shift from sulfate-controlling to aluminate-controlling reactions at high temperatures. Interestingly, higher temperatures did not necessarily induce higher DEF potential due to the excessive precipitation of aluminates in the form of hydrogarnet. This research enriches our understanding of DEF’s complex behavior, providing valuable insights for engineering applications beyond civil engineering, such as nuclear waste conditioning. Full article

The present study aimed to evaluate the utility of the cement solidification process for stably disposing of waste ion exchange resin generated during the treatment of radioactive wastewater. The cement solidification process using the in-drum mixing system was selected to be used for the solidification process of waste ion exchange resins. The disposal safety of waste forms was evaluated according to the waste acceptance criteria (WAC) applicable to domestic waste disposal sites, and the tests were conducted for six test items provided in the WAC. A total of 15 representative samples were collected from the waste-form drums produced using the optimum operating conditions, and their structural stability for disposal considerations was evaluated. In addition, the leaching index of the samples was 11.05, 10.12, 8.39 for Co, Sr, and Cs, respectively, and it was found to exceed 6, the leaching index standard of WAC. The results confirmed that cement waste forms including waste ion exchange resins produced through this process were considered to be conforming to the requirements for disposal safety. Full article

50 m³ of legacy liquid radioactive waste at the Saakadze site in Georgia was treated using a modular type facility with apparatuses encased in three metallic 200 L drums using as purification method the sorption/ion exchange technology. The main contaminant of water in the underground tank was the long-lived radionuclide ²²⁶Ra. The casing of processing equipment enabled an effective conditioning of all secondary waste at the end of treatment campaign which resulted in the fully purified water stored on site for further reuse or discharge, and three 200 L metallic drums with cemented radioactive waste which are currently safely stored. Full article

The paper presents an analysis of the possibilities of using glass waste from recycled lighting materials as aggregates for cement concrete. The research material was obtained from a company that utilizes electrical waste. Glass from pre-sorted elements was transported to the laboratory and crushed in a drum crusher. In this way, the aggregate obtained was subjected to the basic tests that are carried out for aggregates traditionally used in construction. The specific density of aggregate, bulk density, absorbability, crushing index, grain shape, texture type and aggregate flatness index were examined. In the next stage of research work, concrete mixtures were made in which crushed aggregate from crushed fluorescent lamps was used as a substitute for gravel aggregate. Mixtures containing 10%, 30%, 50% and 100% aggregate were made. A mixture containing only sand and gravel aggregate was made as a comparative mixture. Basic tests of both fresh concrete mix and hardened concrete were carried out for all concrete made. The consistency of the fresh concrete mix, the air content in the concrete mix, the density of hardened concrete, absorbability, water permeability under pressure and the basic compressive and tensile (flexular) strength tests were performed. The test results showed that the greater the addition of recycled glass aggregate, the less advantageous are the features of the concrete obtained with its participation. Microscopic analyses carried out in order to explain this phenomenon indicated an unfavorable influence of the grain shape of the aggregate thus obtained. Despite this fact, recycling of lighting waste in concrete composites is recommended as a pro-ecology measure; however, attention was paid to the benefits of using only 30% by mass of said waste in relation to the weight of the traditional aggregate used. Composite with such a quantity of waste retained the characteristics of cement concrete, which qualified its use for construction concrete. Full article