Waste management steps

Waste management is typically divided into pre-disposal and disposal steps. Pre-disposal comprises all the steps in the management of radioactive waste (RAW) from its generation up to disposal, including processing (e. g., pre­treatment, treatment and conditioning), temporary (interim) storage and transport. Disposal envisages permanent emplacement of waste in an appropriate facility without the intention of retrieval. Radioactive waste is prepared for disposal by processing technologies primarily intended to produce a waste form that is compatible with the selected or anticipated disposal option. For evaluation of a particular process or technology, it is necessary to review the availability of selected options to meet waste processing, storage and disposal requirements.

The life cycle of radioactive waste consists of a number of steps:

• Pre-treatment includes any operations prior to waste treatment, to allow selection of technologies that will be further used in processing of waste (treatment and conditioning), such as: collection, segregation, decon­tamination, chemical adjustment and fragmentation [10].

• Treatment of RAW includes those operations intended to improve safety or economy by changing its characteristics. The basic objectives of treat­ment are: volume reduction; radionuclide removal from waste; and change of physical and chemical composition. Treatment includes operations intended to benefit safety and/or economy by changing the characteristics of the waste [11]. Some treatment may result in an appropriate waste form. However, in most cases the treated waste requires further conditioning either by solidification, immobilization or encapsulation.

• Conditioning covers those operations that produce a waste package suitable for handling, transportation, storage and/or disposal. It may include: immobilization of the waste; enclosure of the waste in contain­ers; and, if necessary, provision of an overpack. Immobilization refers to

the conversion of waste into a waste form by solidification, embedding or encapsulation. Common immobilization matrices include cement, bitumen and glass.

• Storage of RAW involves maintaining it such that retrievability is ensured and confinement, isolation, environmental protection and mon­itoring are provided during the storage period.

• Transportation refers to the deliberate physical movement of RAW in specially designed packages from one place to another. For example, raw waste may be transported from its collection point to centralized storage or a processing facility. Conditioned waste packages may be transported from processing or storage facilities to disposal facilities.

• Disposal envisages emplacement of waste in an appropriate facility without the intention of retrieval. Note that in some countries controlled discharge of effluents to the environment is often considered as a regu­lated disposal option.

• Characterization of RAW is an important aspect at every stage of waste management. It involves determination of the physical, chemical and radiological properties of the waste to establish the need for further adjustment, treatment, conditioning, or its suitability for further handling, processing, storage and disposal. Up-front characterization as part of the pre-treatment stage is essential for technical decision making involving the selection of the most efficient treatment process. Methods of RAW characterization and the methodology of characteri­zation, including sampling procedures, are described in detail in Refs [8] and [9].

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