The IAEA defines waste minimization as [4.12]:
The process of reducing the amount and activity of radioactive waste to a level as low as reasonably achievable, at all stages from the design of a facility or activity to decommissioning, by reducing waste generation and by means such as recycling and reuse, and treatment, with due consideration for secondary as well as primary waste.
The need for waste minimization arises from the fundamental principle of radioactive waste management that "The generation of radioactive waste shall be kept to the minimum practicable, in
terms of both its activity and volume, by appropriate design measures and operating and decommissioning practices” [6.2]. This principle is reflected in relevant IAEA documents as well as in regulatory and legislative documents in many IAEA Member States.
The first issue of this Status and Trends report stated that waste minimization activities should consider the following in the planning and implementation phases:
Minimization Strategy: A strategy should be established to serve as a conceptual basis for coordinated planning and implementation of desired measures. These measures should combine administrative considerations (e.g. a legislative basis, clearance policies and economic incentives) with technical and safety considerations (e.g. design principles of the nuclear facility and individual components; the expected operational lifetime of facilities;
the waste conditioning strategy (national and also facility-specific); and the waste disposal strategy, scale, type and location of storage and disposal facilities).
Minimization of Arisings: Radioactive waste avoidance should begin at the design and construction phases for new facilities by the proper choice of materials (e.g., with a low tendency to activate), by the application of reliable technologies (e.g. to minimize replacement and/or maintenance), by minimizing secondary waste (e.g. from cleaning operations), by the rigorous segregation of non-radioactive and radioactive materials and by the segregation of radioactive materials according to the type and activity of the radionuclides they contain. Considerations for optimal operating practices and of decommissioning procedures during a design phase for the new facilities or review and change of existing practices at operating facilities can also significantly reduce waste generation rates.
Minimization of Disposal: For radioactive waste that is generated (avoidance is not practicable), the following options can be pursued to minimize the amount of waste requiring disposal:
• Waste can be “decay stored” to reduce its radioactivity. This option can simplify and increase the effectiveness of waste treatment and/or conditioning or it can lead to clearance (see Subsection 3.1) of the waste from regulatory control.
• Clearance can be used to qualify some materials for restricted or unrestricted reuse or recycling (therefore, they are no longer considered waste) or waste can be cleared for disposal as non-radioactive waste. Both or these options can significantly reduce the amount of radioactive waste requiring disposal.
As mentioned on Page 55, the second issue of this Status and Trends report reported on waste minimization in the context of decommissioning and concluded that waste minimization should be an integral part of any decommissioning strategy. It elaborated on the variety of technical, regulatory, economic and social considerations that have to be taken into account for the selection of a decommissioning strategy. It also concluded that most of the factors that have to be considered when preparing the strategic, tactical and technical decisions required to choose an adequate decommissioning strategy are also the main elements used for choosing a waste minimization strategy, which include:
• source reduction,
• prevention of contamination spread,
• recycle and reuse, and
• waste management optimization.
As mentioned on Page 55, the third issue of this Status and Trends described innovative approaches to waste minimization. Notably it discussed material substitution and, in particular, the introduction of
polyvinyl alcohol (PVA) based clothing that could lead to dramatic reductions in waste requiring disposal.
This fourth issue considers the link between waste minimization and waste management. Optimization is applied to a waste management “system” while minimization refers to an activity that can positively impact on that system.
Nuclear technologies, including the technologies applied to waste arisings and their management, remain in a dynamic and evolving state. Given the pace of technological advances, it is likely that, within just a few decades, we will be able to reuse, recycle, treat, condition and/or reduce the volume all radioactive materials such that the wastes generated and disposed at various steps of waste management activities might represent only a small fraction of today’s waste arisings.
The optimization of a radioactive waste management system is a complex task, with many factors to be taken into consideration. Typically the system may be designed to maximize the value of available resources or facilities or to minimize total cost (or local costs). Other criteria, such as national regulations/policy and waste acceptance criteria for storage/disposal facilities, must also be considered and may tend to direct the waste management system towards or away from specific options.
Relative volumes of different types of waste, availability of disposal options, as well as availability and versatility of technical options for treatment, conditioning, etc., are also important considerations for designing an optimized, integrated waste management system. Minimization of wastes, by not generating them in the first place or minimizing their quantities if they are generated, is an important role of many integrated waste management systems.
Optimization may consider each step or waste stream in isolation and optimize a specific part of the system. This approach, however, may not necessarily optimize the total, or integrated, system. By understanding the interdependencies and interactions between various components of the system, one can often achieve an overall improvement.
By employing “waste minimization” techniques, each step of the waste management system can significantly reduce the total amount of waste destined for disposal. In all cases, this will reduce the down stream waste management resource requirements. In situations where the cost of disposal is high, waste minimization may have the added benefit of large financial savings in disposal costs.
A possible national level (or organization level) LILW minimization strategy applicable to all stages is depicted in Figure 6-1. In order to be effective, the strategy must have strong and visible support at all decision-making levels. If every nuclear worker is aware of the impacts of LILW generation, then reasonable efforts to reduce its generation at source can be accomplished with modest cost. The following discussion summarizes the key aspects and impacts of source reduction programmes, reuse/recycle programs, and volume reduction programmes.
Source reduction (waste avoidance) programmes
Often overlooked, a key method to reduce the overall impact of LILW management is “not to produce the waste in the first place.” Traditionally, the biggest gains in source reduction have come from:
• reduction in the number and size of contaminated areas,
• prevention of equipment leaks and subsequent contamination, and
• segregation of clean materials from contaminated materials.
Implementing reasonable efforts to avoid generation of radioactive wastes through source reduction and prevention will have high return on labour investment with low cost implementation.
Most
If waste generation cannot be avoided, many materials can be removed from the LILW stream through decontamination and subsequent reuse or recycling. For example:
• Waste can be minimized through substitution of disposable materials (such as paper and plastic products) with re-usable materials. The most effective substitution is the elimination of disposable paper/plastic protective clothing and sheeting materials and replacing them with washable, reusable materials.
• Tools and equipment can be decontaminated and reused in either nuclear or non-nuclear applications.
• Wooden scaffolding planks can be planed to remove the contamination, then recycled.
• Miscellaneous metallic objects can be decontaminated, then either reused or recycled as conventional scrap metal.
The initial investment in reusable/recyclable materials is typically offset by a reduction in the purchase, conditioning and disposal costs of disposable alternatives. This represents a high return on investment in terms of reduced waste generation and disposal volumes.
Volume reduction programmes
While source reduction avoids the generation of waste, volume reduction applies after waste has been generated. Once a material has been declared waste (i.e., of no further re-usable or recyclable benefit), a number of volume reduction techniques can be employed, depending on the local availability of technology, to reduce the “as disposed” volume of the waste. Typical methods include compaction, supercompaction, incineration, metal melting, sectioning of bulky objects, etc. New techniques are being developed to handle a wider range of wastes, with further reduction of volumes of waste that needs to be disposed.
Conditioning costs compete against direct disposal costs, therefore, a large reduction of disposed waste volumes can significantly lower unit disposal costs and can extend the operating life of a repository (within the constraints of safety considerations).
The IAEA is currently preparing a new publication that will examine radioactive waste arisings in various nuclear fuel cycles.