As part of the Baltic Research Programmeš project, Riga Technical University scientists are collaborating with scientists from Estonia, Lithuania and Norway to develop materials for a new generation of nuclear power plants and hazardous waste repositories.
Problems addressed by the project
Nuclear energy is the most powerful source of energy on Earth. Nuclear power facilities (plants, storage facilities) must be safe and predictable. Concrete is the main building material used in the construction of nuclear power plants and hazardous waste storage facilities. Concrete is an artificial stone, it resists tensile stress weakly and its main component is cement. The cement industry is one of the largest producers of greenhouse gases (6-7% of global CO2 emissions). Worldwide, cement production released 2.9 billion tonnes of CO2 into the atmosphere in 2021, despite the adoption of intergovernmental documents and the European Climate Act of the European Parliament, which show that the industry must achieve a net zero target by 2050.[1]
How to deal with a situation where demand for concrete is growing exponentially but emissions need to be reduced to zero? The answer lies in “green” low carbon footprint fibre concrete. Fibre concrete – concrete with short fibres scattered throughout its body, which make it much more resistant to tension and shear. “Green concrete – concrete in which some of the cement has been replaced by a cheaper powder such as shale ash. Adding shale ash (waste from the Estonian energy sector) to standard cement reduces natural resource and energy consumption, pollution and raw material costs, as well as CO2 emissions.
Figure 1 shows the ash hill at Kivieli. Does ash reduce the strength and other mechanical properties of concrete? How can the tensile mechanical properties of concrete be improved while at the same time increasing its ability to shield radioactivity? These questions are answered by research carried out within the ICONDE project. The ICONDE (Innovation in CONcrete DEesign for hazardous waste management applications) project (No EEA-RESEARCH-165) is one of the Baltic Research Programme projects supported by European Economic Area (EEA) grants from Iceland, Liechtenstein and Norway. The project brings together materials specialists (expertise in basalt fibre and various concrete applications) from the Arctic University of Norway (UiT), chemists, geologists and radiation specialists (expertise in shale ash properties and radiation studies) from the University of Tartu (TU), nuclear power plant specialists (experience in hazardous radioactive waste management at Ignalina NPP) from the Lithuanian Energy Institute (LEI) and materials mechanics (with more than 15 years of experience in fibre concrete research) from Riga Technical University.
Project achievements
The aim of the project is to create new types of fibre concrete by replacing part of the cement with oil shale ash.The second problem the project has to solve is that ‘green’ concretes require the addition of basalt fibres with boron, resulting in an increase in the tensile and shear strength of the material.Why with boron?One of boron’s isotopes is excellent at shielding ‘thermal’ neutrons, making the material highly desirable in structures in contact with radioactive substances (nuclear power plants, radioactive waste storage facilities, etc.).All these questions were answered in the project.
The new type of fibre was even invented and a Latvian patent application was written, which was not foreseen in the plan. 1450 different fibre concrete samples were experimentally produced and mechanically tested. Some of them were exposed to different types of radioactive radiation.The shielding capacities of the fibre-reinforced concrete were compared and modelled using numerical Monte-Carlo based approaches and computer programs.Concretes and fibres were studied chemically.Three groups of fibre concrete (low-medium and high-strength) have been identified, their optimum shale ash concentrations have been determined, as well as their preferred fibre contents.Work has started on polymer composites to which shale ash has been added.
Figure 2: Fabrication of fibre-reinforced concrete specimens (with shale ash and Basalt-Bora fibre) in the RTU laboratory.
Regular rallies to discuss the results of the projects were held remotely and in person in Narvik, Tallinn, Kaunas and Riga.
Figure 3: ICONDE participants in Riga, RTU lab, Tallinn and Narvik.
The synergy of approaches has borne fruit. 15 scientific publications indexed in SCOPUS have been submitted and published, project results have been discussed in 16 conference presentations and the process is ongoing. An international scientific school on radioactive materials was organised. Four Bachelors and Masters theses related to the ICONDE project were defended. Six PhD students, one in Narvik, three in Riga, two in Tartu and one in Kaunas, carried out research related to the ICONDE project objectives.
Visits to oil shale mines in northern Estonia and the Ignalina nuclear power plant in Lithuania (Figure 4)
Figure 4: ICONDE participants at the Kohtla-Nõmme oil shale mine and Ignalina nuclear power plant
Were there any challenges to the project?
These include the need to change the project principal investigator in the project field. Another serious challenge was the plan, at the beginning of the project, to carry out radiation experiments at the Chernobyl site in Ukraine. And then the war in Ukraine starts. The experiments took place in the Czech Republic, but this required a lot of effort from the project team.
Figure 5 “Green” fibre-reinforced concrete with shale ash and Basalt-Borreaux short fibres
Project benefits and follow-up
Benefits are cooperation, scientific results – joint publications, one RTU employee now working at UiT, Narvik. Several PhD theses will be defended next year. The European project EURIZON FELLOWSHIP PROGRAMME: “Remote Research Grants for Ukrainian Researchers” Project Title: EnhanCed fibrOus compoSite Concrete with improved Radiation shiElding properties for Energy applications and waste maNagement (ECOSCREEN) has been applied for and received a positive evaluation. All ICONDE members will participate in the project (funding is restricted to Ukrainian researchers). New project proposals will be written in collaboration with the partners.
The Baltic Research Programme is implemented with the support of EEA grants within the framework of programme “Research and Education”, which is implemented by the Ministry of Education and Science and the Latvian Council of Science. The total funding of the programme is 8,676,084 euros, of which the state budget co-financing is 15% or 1,301,413 euros and the EEA co-financing is 85% or 7,374,671 euros. In the Baltic research programme, 9 research projects and 5 small cooperation projects are implemented in Latvia.
The Baltic Research Programme’s project “Innovation in CONcrete DEesign for hazardous waste management applications” is implemented by Riga Technical University (Latvia), Arctic University of Norway (Norway), Lithuanian Energy Institute (Lithuania), University of Tartu (Estonia).
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