Corrosion of Aluminium and Zinc in Concrete at Simulated Conditions of the Repository of Low Active Waste in Sweden

The corrosion performance of Aluminium (Al) and zinc (Zn) is of interest in repositories for radioactive waste as the production of hydrogen gas during their anoxic corrosion may create open pathways for the transport of radioactive ions. Al and Zn rods were embedded in concrete cylinders and immersed in artificial groundwater at anaerobic conditions for 2 weeks and up to 2 years in laboratory conditions. Corrosion rates were determined to enable predictions and estimations of risks for gas evolution and the assessment of the potential impact of corrosion on the structural integrity of concrete in the final repository of low and intermediate level metal-containing waste from dismantled nuclear power plants. Samples were collected after 2, 4, 12, 26, 52 and 104 weeks. The observed corrosion rates were higher for Al compared with Zn, as expected, but both materials revealed comparatively high initial corrosion rates that decreased with time, reaching steady state after 26–52 weeks. Some of the Al containing concrete cylinders were cracked as a result of the corrosion processes after 2 years of exposure, thereby providing free passage between the embedded metal and the surrounding environment. No such effects were observed for Zn. Comparative studies were performed on non-concrete-embedded Al and Zn immersed in artificial groundwater. Observed long-term corrosion rates (1–2 years) were similar to corresponding corrosion rates in concrete. The results indicate that immersion studies in artificial groundwater can be used to estimate the long-term corrosion performance of Zn and Al in concrete.

Role of protein degradation in growth laws

Growing cells adopt common basic strategies to achieve optimal resource allocation under limited resource availability. Our current understanding of such “growth laws” neglects degradation, assuming that it occurs slowly compared to the cell cycle duration. Here we argue that this assumption cannot hold at slow growth, leading to strong qualitative consequences. We propose a simple framework showing that at slow growth protein degradation is balanced by a fraction of “maintenance” ribosomes. Through a detailed analysis of compiled data, we show how this model is predictive with E. coli data and agrees with S. cerevisiae measurements. Intriguingly, model and data show an increased protein degradation at slow growth, which we interpret as a consequence of active waste management and/or recycling. Our results highlight protein turnover as an underrated factor for our understanding of growth laws across kingdoms.

Understanding dilatancy in rocksalt: a microphysical model of rocksalt at the grain-scale

<p>The use of underground repositories excavated in low-permeability formations, such as rock salt, to store high-level, radioactive waste requires the analysis of its isolation properties. Underground excavation disturbs the original stress state of the rocksalt, resulting in a deviatoric stress distribution around the walls of excavated galleries and boreholes. At high deviatoric stresses and low confinement, dense rocksalt produces an increase in porosity and permeability. The extent of dilatancy in this disturbed zone, as well as the impact of dilatancy on the transport properties, are important for assessing the safety of radio-active waste disposal as well as the integrity of salt caverns and boreholes in the context of energy storage, brine cavern abandonment and gas well abandonment.  </p><p>The stress conditions at which dilatancy occurs have been measured experimentally, and are typically determined on the basis of macroscopic (sample-scale) measurements of volumetric strain and permeability, and/or acoustic velocity changes or emissions. However, the detailed mechanisms causing dilatancy at the grain-scale are poorly understood. We have developed a microphysical model for dilatancy in rocksalt, both under dry and wet conditions, including mechanisms such as slip and opening of grain boundaries. This model enables us to describe and predict the dilatancy behaviour of rocksalt based on physical, mechanical and chemical processes. The model is presently being independently verified through comparison with existing literature data, and new experiments.</p>

PUBLIC AWARENESS OF CIRCULAR ECONOMY: CASE OF THE SLOVAK REPUBLIC

The paper aimed to identify the awareness and behavior of the population of Slovakia concerning the circular economy. Awareness of the circular economy is a vital factor in effective public participation. The quality of the environment also depends on the level of environmental awareness in society. The circular economy is a very complex issue which requires involvement of all actors in society. The circular economy is currently an actively discussed topic, and therefore we focused on examining the level of awareness of this issue. In general, it is perceived mainly as an economic model that takes the environment into account and prioritizes active waste management. The conducted survey focused on the level of awareness in Slovak respondents. The questionnaire was designed to include all principles of circular economy. We focused on determining the rate of recycling, reusing, reducing, and also the new concept of refusing. Consequently, several hypotheses were analyzed to identify the degree of involvement of the population. At the same time, the survey was intended to introduce the respondents to the idea that they too can participate more actively in the principles of circular economy. In the introduction, we defined the theoretical basis and principles of the circular economy. Subsequently, in the Methodology section, we identified the techniques used to process the questionnaire survey. The Research section describes the outputs and analyzes the established hypotheses. In the discussion, we summarized the results from the Research section and mentioned some of the authors who had handled the same issue in the past. The Conclusion section summarizes the research paper.

EXPERIMENTAL STUDY ON RADIOACTIVE WASTE IMMOBILIZATION IN LOW-TEMPERATURE MAGNESIUMPOTASSIUM PHOSPHATE CERAMIC MATRIX

Results of the studies carried out in NSC KIPT on application of magnesium-potassium phosphate ceramic matrices for immobilization of cesium, clinoptilolite with a cesium and solidified simulators of highly-active waste with high salt content are presented. The high radiation stability and corrosion resistance of the magnesiumpotassium phosphate ceramic matrices to leaching of radionuclide simulators, as well as basic components of solidified ceramic compounds were determined. It was shown that magnesium-potassium phosphate matrices for the solidification of liquid radioactive wastes of low and middle activity level, including waste with increased salt content, can be used in Ukrainian NPPs.

Long-Term Radiotoxicity Evaluation of PWR Spent Uranium and MOX Fuel and Highly Active Waste

One of the main concerns related to nuclear power production is the generation and accumulation of spent nuclear fuel. Currently most of the spent fuel is stored in interim storage facilities awaiting final disposal or reprocessing. The spent fuel is stored in isolation from the environment in protected facilities or specially designed containers. Nevertheless, spent fuel and highly active waste might get in the environment in case the protective barriers are compromised. In such a case, spent fuel may pose risk to the environment and human health. Those risks depend on the concentration of the given radionuclide and are measured by the value of potential danger. The potential danger is called also ’radiotoxicity’. The paper examines spent uranium and MOX fuels from a reference PWR, as well as the highly radioactive wastes of their reprocessing. The radiotoxicity of the four materials is examined and evaluated for a cooling time of 1000 years. The contribution of different radionuclides is assessed and the cases of reprocessing and no reprocessing of spent fuel have been compared.

Identification of Waste Flow in Semarang City Through Community-Based Waste Management

Community-based waste management is a form of waste management recommended by the government because it is very effective in creating a zero-waste society. In Indonesia, community-based waste management can be realized through the development of waste banks at the neighbourhoodlevels. In 2019, the City of Semarang has 48 units of active waste banks. Waste that is managed by the wastebank is plastic, paper and metal. However, there is organic waste which is also managed by several wastebanks. The purpose of this study is to identify and analyze the flow of waste through community-basedwaste management, in this case of the waste bank, in the city of Semarang. The method used is in-depth surveys and interviews related to the waste bank management system in the city of Semarang. The results showed that the activity of the existing garbagebank was able to reduce waste in the city of Semarang by 0.07% of the total garbage generation in the city of Semarang. This research can be used as a reference for developing better community-based waste management strategies, especially in Semarang City