A considerable amount of radioactive waste is generated by the production and usage of nuclear energy. The disposal of this waste is strictly regulated due to its toxicity to all living beings and the environment.
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In response to the rapid increase in human demand for nuclear energy, new materials and technologies are projected to play a vital role in developing sophisticated nuclear energy systems.
Technology innovation is critical to waste and environmental management. This technological achievement involves the development of materials that can be used for safe disposal, classification, storage, and tracking or radioactive nuclear waste.
The wide range of potential uses for nanomaterials and nanotechnologies, which have received a great deal of attention recently, might help the development of safe nuclear energy systems and their safe disposal. The relevance of nanotechnology in the safe disposal of nuclear waste is explored in this article.
What Techniques Are Currently in Practice to Clear Nuclear Waste?
Radionuclides, due to their extremely long half-life, are a major problem in clearing up or decontamination of nuclear waste. Researchers have proposed several techniques for cleaning soluble radionuclides, including membrane separation, ion exchange, and chemical precipitation.
Current wastewater treatment and solid waste disposal procedures are unsuitable for dealing with radioactive wastewater. Furthermore, the amounts of certain radionuclides in wastewater may be substantially lower than those of other components. As a result, high-efficiency selective removal is required.
With the advent of nanomaterials and nanotechnology, industries can now design and manufacture new specialized functional materials on a nanoscale. The unique physical and chemical features of nanomaterials, including the effects of nanoscale, high chemical reactivity, and greater specific surface area, have made them an excellent choice for the safe disposal of radioactive nuclear waste.
Techniques Used to Decontaminate Nuclear Waste?
Different types of nanomaterials are currently being used to clear nuclear waste or remove the radioactive components. Adsorption is known for its excellent performance in removing soluble maters from wastewater.
Because of their higher specific surface area and stable nanostructure, nanomaterials have a great proclivity for diverse interfacial interactions. This is required for high-efficiency selective adsorption of soluble radionuclides in wastewater than standard materials.
An article published in the journal Environmental Science Nano discusses various techniques from nanotechnology for the decontamination of nuclear waste. One of the most efficient ways to clean nuclear waste is the use of carbon nanotubes (CNT).
Role of Carbon-based Nanomaterials in Decontaminating Nuclear Waste
CNTs, because of their exceptional physicochemical properties, have the potential to be stabilized with other atoms. CNTs, when used as an adsorbent, were discovered to be capable of isolating radionuclides from nuclear waste streams.
To boost the adsorption capacity of CNTs, the chemical modification of their surfaces has been widely investigated to create a high number of functional groups on the surfaces of CNTs, resulting in better radionuclide removal.
Apart from CNTs being used as a chemical adsorbent, they have also been used as an electrically switched ion exchanger to remove radioactive cesium ions from nuclear wastewater.
Graphene oxide (GO) has a vast surface area and a high concentration of oxygen-containing functional groups on the surface. Because of the anchoring sites provided by the oxygen groups that protrude from the outer layers, radionuclides can easily be added to GO.
It is possible to significantly boost the adsorption by functionalizing GO or by combining it with other functional materials that have logically defined characteristics. This reduces GO aggregation and increases its dispersion in nuclear wastewater.
However, there are issues associated with the use of graphene oxide in this application. Its low adsorption of radio-anions and the presence of several functional groups on its surface mean that GO must be surface-modified with anions affinity if it is to be used with radioactive cations.
Due to its strong interplanar contacts, GO tends to form aggregates. Significant amounts of GO surface area are lost, limiting the technology's use in wastewater treatment. With the goal of improving the graphene oxide’s adsorption capability, nanopolymers have been grafted across GO's surface to avoid self-aggregation.
Use of Nanoparticle Modified Microrobots to clean up Nuclear Waste
Researchers, in their article published in ACS Nano, have discussed the possibility of removing radioactive components from the nuclear wastewater using tiny, self-propelled microrobots.
As a result of their ability to combine extremely adsorptive qualities with rapid autonomous mobility in liquid medium, these microrobots hold great promise for the cleanup of nuclear waste.
The researchers used ZIF-8 rods with a diameter of around 1/15 of a human hair to build these microrobots. They used iron atoms and iron oxide nanoparticles to stabilize and magnetize the formations. Hydrogen peroxide "fuel" in the water was transformed into oxygen bubbles, which pushed the microrobots at 60 times their own length per second.
In one hour, microrobots recovered 96% of uranium from simulated radioactive wastewater. The scientists used a magnet to capture the uranium-loaded rods, allowing them to be recycled. Researchers suggest that these microrobots might help manage and remediate radioactive waste.
Future of Nanotechnology in Nuclear Energy
Multiple nanomaterials based on metals, cellulose, biogenic, hydroxyapatite and natural nanosized materials are currently being investigated for their potential use in cleaning up the nuclear waste.
The current challenges associated with nanotechnologies in cleaning nuclear waste include the cost and large-scale emergency applications, environmental impact, regeneration and reusability, functionalization and separation efficacy.
Despite the multiple techniques already being used in clearing up nuclear waste, extensive research is still needed to overcome the problems associated with the rapid expansion of nuclear programs worldwide.
References and Further Reading
Belloni, F. et al. (2009) 'Can carbon nanotubes play a role in the field of nuclear waste management?', Environmental Science and Technology, 43(5), pp. 1250–1255. doi.org/10.1021/es802764g.
Nath, D. (2020) 'Handbook of Ecomaterials', Handbook of Ecomaterials [Preprint], (March). doi.org/10.1007/978-3-319-48281-1.
Shi, W.Q. et al. (2012) 'Nanomaterials and nanotechnologies in nuclear energy chemistry', Radiochimica Acta, 100(8–9), pp. 727–736. doi.org/10.1524/ract.2012.1961.
Ying, Y. et al. (2019) 'Radioactive Uranium Preconcentration via Self-Propelled Autonomous Microrobots Based on Metal-Organic Frameworks', ACS Nano, 13(10), pp. 11477–11487. doi.org/10.1021/acsnano.9b04960.
Zhang, X. and Liu, Y. (2020) 'Nanomaterials for radioactive wastewater decontamination', Environmental Science: Nano, 7(4), pp. 1008–1040. doi.org/10.1039/c9en01341e