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Nuclear power plants and research purposed reactors produce spent nuclear fuel, which leads to a need for safe spent fuel management and radiation protection. Traditionally, concrete with the addition of different aggregates has been the primary material for shielding against radiation and is used also for transport and storage of radioactive waste. Despite these applications, there is still a need to develop new composite materials that will preserve the radiation shielding properties of concrete, while offering superior mechanical and also cost effective benefits. This article investigates the radiation shielding properties of HI-STORM containers, made of a new composite material, and reinforced with basalt-boron fibre for human and environment protection. In the concrete recipe, part of the cement is replaced by oil shale ash with cementitious characteristics. The formulation of concrete reinforced with basalt-boron fibre (with the addition of 6% boron oxide) is presented. Oil shale ash (OSA) is a class-C fly ash, a by-product in the energy production process. OSA can be used as a partial replacement to cement in concretes, thanks to its cement-like qualities and low carbon content, which contributes to a reduction in the overall CO2 footprint of concrete. In our investigated concrete mixes 5 to 35% of cement was replaced by OSA (Electrostatic Precipitator Ash) coming from Auvere (Estonia) thermal power plant. Using the Monte Carlo method, the Serpent code was used to simulate the passage of neutron radiation through a composite material to assess its biological shielding properties. It is shown that the addition of basalt-boron fibre to concrete improves the protective properties of biological shielding against neutron radiation. [ABSTRACT FROM AUTHOR]

A basalt micro-fiber bundle (yarn), slightly twisted and impregnated by polymeric matrix with uniformly distributed within the matrix volume microscopical particles of oil shale ash (OSA) is used in textile reinforcement of a composite structure. Oil shale ash (OSA) is a powder, obtained in the combustion process, during generation of electricity at electrical power plants in Estonia. Polymeric matrix is epoxy resin. Mechanical properties of the hybrid composite - epoxy matrix (with OSA) reinforced by continuous basalt fibers depend significantly on the stress transfer and failure mechanisms occurring at the micro-fiber-matrix interface. The present work experimentally investigates the strength of such basalt fiber/epoxy (with OSA) composite rod, emphasizing its dependence on length. Composite samples were experimentally fabricated with 10 wt.% of OSA in polymeric matrix impregnated basalt micro-fiber bundles forming rods with a diameter of 0.13cm. Experimentally fabricated rods are with the length 1, 10 and 82 cm. The rods were tested by tension till rupture and the stochastic Weibull approach was used for rod strength statistical evaluation. The results revealed a scale effect, where shorter rods exhibited higher tensile strengths compared to longer rods, attributed to the lower probability of critical flaws in smaller volumes. The experimental strength data were analyzed using the twoparameter Weibull distribution. The shape parameter α ranged from 3.87 (82 cm) to 8.98 (10 cm), while the scale parameter β increased from 891 MPa (82 cm) to 1169 MPa (1 cm). These Weibull parameters quantify the lengthdependent strength variability of the basalt fiber/epoxy composite rods, enabling stochastic modeling of the reinforcement fragmentation process when such rods are used in composite structures. [ABSTRACT FROM AUTHOR]

The elastic properties of composites with reinforcing particles are under investigation in this research. Oil shale ash (OSA), produced in Estonia, is a powder and a by-product of the combustion process in generation of electricity at power plants. During previous years many thousands of tons of OSA have been collected. Starting from 2018 in the European Union, oil shale ash is no longer considered as toxic and hazardous waste, this is opening new possibilities for commercial application of OSA in new products and giving it a second life. Recycling and reusing oil shale ash is therefore an important problem for environmental sustainability. The use of this product as a reinforcement for epoxy resin matrix as well as for the concrete matrix in Epoxy/OSA and Concrete/OSA composites was experimentally investigated in this work. Several sets of Epoxy/OSA specimens were experimentally fabricated: Epoxy resin without OSA, Epoxy resin with 10% of oil shale ash by weight and sets of specimens with increasing ratios (10% increase between) of oil shale ash by weight, until a 50% ratio of OSA was reached. The tensile test experiments were conducted with the goal to obtain elastic modulus of the oil shale ash composite material. Tensile tests were realized according to ISO 527-1:2012 and specimens were fabricated according to ISO 527-2:2012 1B standards. Tensile tests were performed, and the experimental results were compared with predictions from analytical approaches. According to the obtained tensile test results and analytical predictions (using the rule of mixture and other approaches), the modulus of elasticity increases in direct proportion with increasing weight fraction of the oil shale ash in the composite material. Finally, samples of concrete with OSA were fabricated and tested until failure. Different amounts (by weight) of cement (0%, 5%, 10%, 15%, and 35%) in the samples were replaced by OSA. The elastic properties of these samples were also experimentally evaluated and compared with theoretical prediction results. [ABSTRACT FROM AUTHOR]