Nuclear Waste Management Approach, Types and Aspects Explained
Nuclear waste management is the sum total of steps taken in order to effectively isolate nuclear waste from the environment; such as collection, pretreatment, treatment, conditioning and disposal.
This article discusses nuclear waste management approach, types and aspects, as outlined below;
-Types of Nuclear Waste Management
How Nuclear Waste is Managed
Nuclear waste is managed and stored by the implementation of steps that aim to effectively isolate such nuclear waste materials from both abiotic and biotic components of the ecosystem, especially on the Earth's surface and in the shallow subsurface.
These steps of management of radioactive waste are; pretreatment, treatment, conditioning, containment or storage, and disposal [3].
Each of these is discussed briefly below;
1). Pretreatment (as one of the Steps of Nuclear Waste Management)
Pretreatment or pre-treatment of radioactive waste is the sum total of all steps or measures taken to prepare waste for actual treatment; or all forms of alterative nuclear waste handling that occur before treatment.
As a step in the overall process of nuclear waste management, pretreatment is essential for optimizing the efficiency and effectiveness of the process.
It is versatile, and comprises of techniques that apply to nuclear waste materials in various physical states that include liquid and solid.
As earlier stated, the aim of pretreatment is to prepare nuclear waste for actual treatment, which would occur subsequently in the management process.
One of the key mechanisms by which this is achieved is segregation.
Pretreatment of radioactive waste always involves separating or segregating the waste into various categories based on composition, level of radioactivity and potential effect.
This implies that the waste is usually segregated into high, intermediate and low-level categories [4].
For nuclear waste segregation to be effective, some other measures often need to be taken, such as preliminary decontamination, and physicochemical adjustment. These measures therefore are part of the pre-treatment step.
The outcome of pretreatment of nuclear waste is usually an array of sorted radioactive materials, which have been decontaminated and packaged as much as necessary, to allow for effective treatment.
2). Treatment
Treatment and conditioning of nuclear waste are steps which are taken to alter the physicochemical characteristics of radioactive waste materials in such a manner that makes them suitable for effective transportation, storage and disposal.
As stated above, the aim of nuclear waste treatment is to ensure that the remaining steps in the process of nuclear waste management are safe, less-difficult, and effective.
Nuclear waste treatment (or nuclear waste processing) is a continuation from the pretreatment stage, and involves further decontamination. Water-based leaching can be applied to decontaminate nuclear waste, among other methods.
The methods of treating nuclear waste include evaporation, ion exchange, ultrafiltration (reverse osmosis), and chemical precipitation [7].
Thermal treatment by incineration, can be applied where safe and suitable, to reduce waste volume.
Nuclear wastewater is treated mainly by evaporation and ultrafiltration.
The expected outcome of nuclear waste treatment is a residue of lower volume and reactivity.
3). Conditioning (as one of the Steps of Nuclear Waste Management)
Conditioning of radioactive waste refers to post-treatment measures that are taken to convert radioactive waste into a form that is easier and safer to handle during transport, storage and disposal.
This means that nuclear waste conditioning is very similar to (and usually conducted alongside with) waste treatment. It generally falls between the stages of waste collection/pretreatment and final disposal [6], and represents the effort to ensure an effective and less-challenging transition from the early to late phases of nuclear waste management.
The objectives of nuclear waste conditioning include; detoxification, volume reduction, and stabilization.
To achieve these objectives, conditioning of nuclear waste often employs methods like vitrification, cementation, and bitumization, among others [1].
Compaction can also be implemented to reduce waste volume for easy containment and transport [3].
4). Storage
Nuclear waste is stored in inert environments where they are impounded within radiation-resistant systems.
The particular method used to store nuclear waste depends on the size and composition of the waste, as well as the objective(s) of storage in any given scenario. It must also be noted that nuclear waste storage can be long-term or short-term.
Materials used in storing nuclear waste are generally those capable of absorbing and containing significant amounts of radiation for a period of time; such as water, concrete and steel.
In all cases, radioactive waste storage is carried our for the ultimate purpose of achieving effective nuclear waste containment. This step is very crucial to ensure that nuclear waste handling is optimal especially during final disposal..
The safest way to store nuclear waste in the short-term is through containment in steel vessels known as 'dry casks', while long-term storage is safest where concrete containment is available.
It is hard to store nuclear waste, especially on-site, because it requires intensive care to ensure that storage systems are always in good condition, and safety is not compromised. The environmental and materialistic requirements for nuclear waste storage can be difficult to meet, especially when long-term containment is involved.
5). Disposal (as one of the Steps of Nuclear Waste Management)
Nuclear waste dumping or disposal is the final (and one of the most important) steps in the management of radioactive waste.
Steps that should be taken before the disposal of nuclear waste are those required to detoxify, condition and transport the waste, so that it becomes stable, easy to handle, and safe for disposal.
Nuclear waste is disposed by isolating it in an inert environment for long periods of time, to prevent it from releasing harmful radiation into the environment till it breaks down and becomes non-hazardous.
Disposal of nuclear waste is a problem due to the challenge of finding a suitable method or site of disposal, and the need for disposed materials to remain isolated for very long periods of time.
It rakes nuclear waste between minutes and thousands of years to breakdown or decay completely; and for the commonly-used fuels like uranium; their waste generally requires several thousands of years to become completely harmless.
The most common method of nuclear waste disposal is arguably land-based dumping, by deep-burial in remote locations. Other methods include synthetic rock encapsulation, space dumping, and glacial burial [8].
Types of Nuclear Waste Management
The types of nuclear waste management are; passive and active.
1). Passive Management (as one of the Types of Nuclear Waste Management)
Passive management of nuclear waste involves using methods and equipment that do not require regular or active human intervention.
Examples of this type of nuclear waste management include the use of storage pools, landfilling and incineration to store, dispose and condition waste respectively.
This type of management is suitable for only low-level waste. Intermediate and high-level waste management require a more intensive approach in order to protect the ecosystem, due to their relatively-high nuclear energy content.
2). Active Management (as one of the Types of Nuclear Waste Management)
Active nuclear waste management involves energy-intensive measures and careful, regular maintenance in all phases of the process.
It aims to reduce the hazardous impact of waste while minimizing volume [2].
Measures like compaction and vitrification fall under this type of nuclear waste management, which is especially suitable for intermediate and high-level wastes.
Conclusion
Steps of nuclear waste management are;
1. Pretreatment
2. Treatment
3. Conditioning
4. Storage
5. Disposal
The types of nuclear waste management are;
1. Passive Management
2. Active Management
References
1). Jantzen, C.; Lee, W. E.; Ojovan, M. I. (2013). "Radioactive waste (RAW) conditioning, immobilization, and encapsulation processes and technologies: Overview and advances." Radioactive Waste Management and Contaminated Site Clean-Up. Processes, Technologies and International Experience. Woodhead Publishing Series in Energy 2013, Pages 171-272. Available at: https://doi.org/10.1533/9780857097446.1.171. (Accessed 4 February 2023).
2). Nash, K. L.; Lumetta, G. J. (2011). "Advanced separation techniques for nuclear fuel reprocessing and radioactive waste treatment." Oxford, UK: Woodhead Publishing. Available at: https://lib.ugent.be/catalog/ebk01:2670000000076583. (Accessed 4 February 2023).
3). Ojovan, M. I.; Lee, W. E. (2005). "An Introduction to Nuclear Waste Immobilisation." Available at: https://www.sciencedirect.com/book/9780080444628/an-introduction-to-nuclear-waste-immobilisation. (Accessed 4 February 2023).
4). Wilmarth, W. R.; Lumetta, G. J.; Johnson, M. E.; Poirier, M.; Thompson, M. C.; Suggs, P. C.; Machara, N. P. (2011). "Review: Waste-Pretreatment Technologies for Remediation of Legacy Defense Nuclear Wastes." Solvent Extraction and Ion Exchange 29(1):1-48. Available at: https://doi.org/10.1080/07366299.2011.539134. (Accessed 4 February 2023).
5). Ojovan, M. I. (2011). "Handbook of Advanced Radioactive Waste Conditioning Technologies." Woodhead Publishing Series. Available at: https://www.sciencedirect.com/book/9781845696269/handbook-of-advanced-radioactive-waste-conditioning-technologies. (Accessed 4 February 2023).
6). Trauwaert, E. (1998). "Waste Conditioning Methods: Economical and Ecological Impact." In: Stenhouse, M.J., Kirko, V.I. (eds) Defence Nuclear Waste Disposal in Russia: International Perspective. NATO ASI Series, vol 18. Springer, Dordrecht. Available at: https://doi.org/10.1007/978-94-011-5112-2_4. (Accessed 4 February 2023).
7). Valdovinos, V.; Monroy-Guzman, F.; Bustos, E. (2014). "Treatment Methods for Radioactive Wastes and Its Electrochemical Applications." Environmental Risk Assessment of Soil Contamination. Available at: https://doi.org/10.5772/57445. (Accessed 4 February 2023).
8). Vidal, J. (2019). "What should we do with radioactive nuclear waste?" Available at: https://www.theguardian.com/environment/2019/aug/01/what-should-we-do-with-radioactive-nuclear-waste. (Accessed 5 February 2023).
