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2.9.4 Management of problematic waste and material generated during remediation of radioactively contaminated sites

Environmental remediation activities related to any nuclear licensed facility (e.g., NORM industry, nuclear power plants, defense sites, etc.) present several problems in the management of the generated waste and obsolete redundant material. The waste arising from environmental remediation is often different from the waste generated during normal operations or routine maintenance of the facility.

These differences may include its chemical, physical and radiological characteristics, the physical form and the general amounts or volumes. Owing to these specific characteristics, some of the waste could be considered as being problematic, for example waste for which application of routine methods of handling, treatment and conditioning is not appropriate and therefore requires special considerations for the selection of specific management options. For such environmental remediation waste and material proper planning and selection of appropriate waste management and material management options are of particular importance from the organizational, health physics, safety and economic points of view.

Some examples of the problematic nature of specific environmental remediation waste are as follows:

  • High volume-low activity material may give rise to economic concerns over the disposal of the waste (e.g., contaminated soil). The volume of waste in this category is dependent on the national clearance levels.
  • Some waste may be considered problematic because of the inventory of radionuclides that it contains (e.g., waste containing radionuclides of high radiotoxicity and mobile radionuclides such as 14C and tritium).
  • Some waste may be considered problematic because it is difficult to encapsulate in cementitious matrices (e.g., soil containing aluminium, beryllium and uranium –depleted metal). Corrosion of the material can lead to the generation of high levels of hydrogen, which can disrupt the encapsulation matrix and can introduce a risk of explosion. Also, expansion of the waste form can occur, due to the formation of corrosion products.
  • Additional problems can occur in the encapsulation of waste material in a cementitious grout, in which the waste material can affect the product properties of the grout (e.g., high nitrate, fluoride and borate bearing liquid waste). The immobilization of phosphate, such as tributyl phosphate, or high levels of sodium hydroxide in some waste streams, can cause accelerated cement setting, leading to ‘flash’ setting of the waste form.
  • Some types of waste can be problematic because of their physical nature (e.g., non-aqueous phase liquids such as oils, organic complexants and the degradation products of organic polymers). These components of waste may enhance the mobility of radionuclides in the disposal environment. They are difficult to immobilize because they are often just absorbed and not chemically bound within the immobilization matrix.
  • Waste may also be considered problematic because it is hazardous due to either its physico-chemical properties or its inherent toxicity. These types of material represent a potential hazard to human health or the environment when improperly treated, stored or disposed of, or otherwise mismanaged. Among these types of waste the main concerns are on material that is hazardous and/or toxic by its chemical or physical nature. An analysis of the specific characteristics of such waste, and of its possible management options, is important for ensuring the safety of environmental remediation activities.

In this section problematic waste and material are identified as those that require special handling and treatment because of their unique combination of radioactivity, toxicity or chemical and physical hazards. This section reviews the origins of these types of waste and their characteristics, potential hazards and management options [IAEA-2006].

An integrated approach to the consideration of organizational principles, the regulatory background and the technical options for dealing with these types of waste and material is important in order to ensure the efficiency of the selected options, the safety of workers and public, stakeholders, and the protection of the environment.

Information already exists on the management of some problematic types of waste and material and on particular technologies and their application for handling, storage and processing. A review of the available information on this subject, analysis of related data and experience, and discussion of related problems would be of particular benefit for all parties planning environmental remediation activities.

The information summarized in this section will assist in the selection of adequate processes and technologies to solve particular waste management problems with different types of problematic waste and material during environmental remediation activities.

The overall approach (see Section 2.2.2.1) is not influenced by the requirements for the management of toxic and hazardous waste. However, the presence of these material types needs to be fully considered. In contrast with radioactive waste, which decays with time, delayed environmental remediation would not lead to a decrease in the associated hazards and toxicity of such waste; in fact the opposite is the case, in that delay may lead to decreasing integrity of the material and components, which may cause additional problems with the environmental remediation and management of the associated waste. This important factor should be taken into consideration when defining the environmental remediation strategy and making the selection of appropriate remediation options and associated techniques.

The choice of an environmental remediation option will mainly be based on technical, safety, economic and regulatory considerations. These considerations will enable the operator to select the most appropriate environmental remediation option. Although radiological hazards predominate in environmental remediation activities, toxic and other conventional hazards must be taken into account during the decision making process.

The definition of an environmental remediation and waste management strategy needs to fully consider the technical problems associated with the management and processing of all radioactive and hazardous waste. Experience of environmental remediation has shown that while the use of and requirements for personal protective equipment for radiological purposes during clean-up of sites may decline with time because of radioactive decay, the use of personal protective equipment for toxic and hazardous waste may remain constant or increase with time as material degrades.

For each option it is necessary to consider the volume and physico-chemical form of the toxic and hazardous material generated. ‘Cradle to grave’ processes should be available for the handling and treatment of all material (including waste) arising from any environmental remediation activity before these activities are undertaken. It should be kept in mind that in most countries no waste repository is available and that therefore safe interim storage facilities should be provided for the material until a suitable disposal option becomes available. Therefore, involved regulatory agencies should be consulted in an early stage and have to be taken in during the total planning process to get approval for selected options.

To determine a suitable environmental remediation strategy, information about the site and operational history is required (see Section 2.4, Historical site assessment). It has to be stressed, therefore, that record keeping during the operational life of a site and careful radiological and physicochemical characterization of waste and material are crucial.

For the purposes of this section the following definitions of hazardous and toxic waste and material are used:

  • Hazardous. Waste and material that because of their quantity, concentration and/or physical, chemical or infectious characteristics may pose a substantial potential threat to human health or the environment when improperly handled, treated, stored or disposed of, or otherwise mismanaged.
  • Toxic. Waste and material that contain certain substances determined to be harmful to human health in very small concentrations.

To distinguish between the two definitions, it is helpful to consider that all toxic waste is hazardous but not all hazardous waste is toxic.

There are some general considerations that are common to toxic and hazardous waste. The disposal of toxic waste in either shallow land burial or in deep geological facilities needs to consider the long term behaviour of the waste and has to respect the national regulations for its disposal. Special requirements may also be defined by regulatory authorities for the long term storage of hazardous waste if a disposal option is at present not defined or not available. As was indicated above, it should be considered that unlike the hazards related to radioactivity, the hazard from toxic waste will not reduce with time. However, some unstable toxic waste, mainly of an organic nature, could degrade while in storage or disposal, resulting in the generation of non-toxic products.

There are various national regulations concerning the limits for emission of toxic compounds, their concentration in drinking water, etc. These particular limits should be respected when preparing the safety analysis for toxic waste treatment, conditioning and disposal.

One of the possible options for the management of environmental remediation waste, including some hazardous components, is to consider recycling and reuse of components of the waste. Another option is the processing of this waste for storage and final disposal. These options are discussed in general in the following sections of this report in relation to particular types of hazardous material.

Hazardous material Probability of commonly
occurring radiological hazard
Comments
Activation Contamination

Beryllium High Medium The degree of contamination of the beryllium depends on whether it is cladded

Sodium and sodium-potassium alloys High Medium Contamination in secondary circuit sodium is low and consists mainly of tritium

Cadmium High Low When cadmium is used in fuel storage flasks it may be only slightly activated

Mercury Low High Activated mercury may be used as shielding in research reactors or as target material in accelerators

Lead Low High Where lead is activated it can be difficult to demonstrate compliance with clearance levels because of selfshielding effects

Cyanide None High Cyanide is used for caesium removal purposes and hence is not activated

Decontamination chemicals None High Some spent decontamination solutions may contain activation products

Asbestos Low Medium Asbestos may be used as insulation material on reactor pressure vessels, but commonly the radiological hazard occurs from contamination on the surface

Polychlorinated biphenyls None Medium Polychlorinated biphenyls are commonly found in oils, paints and other organic based material

Table 2.10 Commonly occurring radiological hazards associated with problematic waste and material in a nuclear power facility

All types of material arising during environmental remediation activities, including chemically toxic and other hazardous material, could be activated or radioactively contaminated depending on the nature of the nuclear facility in which the material originated and/or the purpose for which the material was employed. Therefore their treatment, conditioning and disposal consider both the radiological and non-radiological hazards associated with these types of material and waste 55. Table 2.10 summarizes the commonly occurring radiological hazards associated with the problematic waste and material generated during decommissioning and of which the possibility exists that it has to be taken into account during environmental remediation.

In [IAEA-2006] information can be found about:

  • Form of the problematic waste;
  • Typical hazards;
  • Possibilities for recovery and reuse;
  • Waste treatment and management.