Assessment study for multi-barrier system used in radioactive borate waste isolation based on Monte Carlo simulations

Incorporation of spent ion exchange resin simulate into cement composites

Solidification/Stabilization (S/S) of spent radioactive ion exchange resins (IER) is one of many critical problems facing developing nuclear industries all over the world. Immobilization technology using Ordinary Portland Cement (OPC) as an inert matrix, has been widely applied for the solidification/stabilization of spent ion exchange resin. In this study incorporation of simulated IER into cement matrix and characterization of the final solid waste form (FWF) had been searched practically in laboratory scale experiments. Factors that can affect the properties of the FWF including the water/cement (w/c) ratios and the resin concentration were studied systematically. Mechanical integrities, thermal analysis, and mass loss during hardening and curing for 28 days were evaluated for FWF hard blocks. Scanning Electron Microscope (SEM) and X-Ray Diffraction (X-RD) examinations were performed to investigate the internal architecture of the FWF. Moreover, the heat of cement hydration reactions was recorded during the IER solidification process. Based on the experimental results obtained, it is worth to state that according to its acceptable characteristics and advantages of cement as an inert matrix, it can be suggested safely for the immobilization of untreated spent radioactive ion exchange resins.

Asphaltene or Polyvinylchloride Waste Blended with Cement to Produce a Sustainable Material Used in Nuclear Safety

The current research uses sustainable methods to preserve the environment, such as exploiting municipal or industrial waste that may harm the environment. The wreckage of polyvinyl chloride (PVC) pipes and asphaltene are used as additives to cement to improve its mechanical properties, while stabilizing the radioactive waste resulting from the peaceful uses of nuclear materials, or enhancing its radiation shielding efficiency. New composites of Portland cement with ground PVC or asphaltene up to 50% are investigated. Fast neutron removal cross-section (ƩR) and gamma shielding parameters, such as mass attenuation coefficient (MAC), half-value layer (HVL), effective atomic number (Zeff), and exposure build-up factor (EBF) at wide energy range and thickness, are determined. The compressive strength and apparent porosity of the examined composites are examined to test the durability of the prepared composites as stabilizers for radioactive waste. The obtained results show that the bulk density of hardened cementitious composites was slightly increased by increasing the additive amount of PVC or asphaltene. The compressive strength of cement composites reached more than 4.5 MP at 50 wt.% PVC and 8.8 MPa at 50 wt.% asphaltene. These values are significantly higher than those recommended by the US Nuclear Regulatory Commission (3.4 MPa). Additionally, the obtained results demonstrate that although the gamma MAC is slightly decreased by adding asphaltene or PVC, the neutron removal cross-section was highly increased, reaching 171% in the case of 50 wt.% asphaltene and 304% in the case of 50 wt.% PVC. We can conclude that cement composites with PVC or asphaltene have optimized radiation shielding properties and can stabilize radioactive waste.

A critical review on radioactive waste management through biological techniques

Our world is subject to various kinds of pollution and contamination due to rapid growth and development of industrialization. Though, industries are helping to improve the human life style in many ways in day to day life such as power generation to treatment of diseases. At the same time, industries emit the waste which causes major environmental pollution and leads to harmful for all living organism. As the renewable energy sources are depleting, energy/power generation become a major research around the world. Nuclear energy is one of the promising energy to sort out the energy demand, but the problem associated with the nuclear energy is the management and treatment of radioactive waste/emission/effluent since which is more dangerous to all living organism. There is a large scale contamination of radioactive waste associated for the past 60 years of global nuclear activity. It is necessary to pay special attention to the management of radioactive wastes in order to approach pollution-free environment and avoid diseases to living organism through various clean-up strategies. In this review, we discussed the wide ranges of strategies available for radioactive waste management such as physical, chemical, and biological methods. Bioremediation may be the powerful tool for treatment of radioactive wastes. Additionally, discussed on recent advancement have been made in treatment of radioactive waste through microbial transformation as well as phytoremediation which play a major role in disposal of radioactive waste.