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4.2.3 General environmental remediation design aspects

The application of environmental remediation operations consists of a phased strategy to allow flexible decision making for the most cost-effective and environmentally sound remedial approach. Its application allows all of the decisions and choices made during the management and selection process to be clearly seen and examined. This is an essential part of the process, and it can be particularly important, for example, when communicating with affected parties such as members of the public and regulators.

In the developed environmental remediation plan, due consideration should be given to:

  • Sound principles and ALARA. Implementation of environmental remediation activities should be based on sound principles of project management and the ALARA (As Low As Reasonably Achievable) radiation protection principles formulated in the IAEA Basic Safety Standards [IAEA-1999]. Only following the completion of all necessary measures, a remediation programme can be considered.
  • Applicable environmental remediation options. For all the environmental remediation options identified as applicable, a study should be performed to determine the option that is best for the site. The study should factor in both justification and optimization. This study should include estimates of the costs and other resources associated with the treatment, removal, transport and disposal of contaminated material for each option; the estimated doses to workers and the public due to exposure before, during and after the remediation; the overall safety issues during remediation; the available technologies; the considerations for monitoring and sampling; the amount of waste that will be generated; and the institutional controls required after implementation of the option, if applicable.
  • Optimization of protection. For the set of options under consideration, optimization of protection should be performed for the justified options, to determine the option that has the highest net benefit. On the basis of this optimization, a preferred option should be selected that also takes into account non-quantitative considerations such as social and political aspects.
  • Selected environmental remediation option. For the selected option, a detailed “environmental remediation plan showing that remediation can be accomplished safely should be prepared for each contaminated site, unless otherwise required by the regulatory body” and the “environmental remediation plan should be subject to the approval of the regulatory body prior to its implementation”.
  • Post-remediation. Plans should be provided for both the environmental remediation work and the possible necessary measures for post-remediation, such as maintenance, monitoring and institutional controls to enforce restrictions on land use and buildings, if applicable. Although institutional controls (long-term stewardship as indicated in Section 5) may last for a long period of time, they are part of the post-remediation as defined in this context and should thus be covered in the environmental remediation plan.
  • Approved plans. Once the environmental remediation plan including post-remediation has been approved, it should be implemented as soon as possible. If it is decided not to remediate the site, decisions should be made on imposing restrictions on its use or access prior to release. If remedial actions are required, they should be implemented as soon as possible.
  • Regulatory control. After the approved environmental remedial actions have been completed, the regulatory body should evaluate the effectiveness of the implementation.

Further, three basic planning approaches in environmental remedial actions are possible:

  • Monitored non-intervention. This planning approach relies on natural processes to prevent significant exposure, meaning that the site will be undisturbed, while establishing a monitoring scheme for determining the evolution of the exposure of the site in time. The entire process needs to be carefully monitored so that alternative action can be initiated if required, and may be based on:
    • Natural attenuation. Natural attenuation is the least invasive of the four technical remediation principles. The concept is based on geochemical processes to retard radionuclide migration to the biosphere.
    • Physical processes. Physical processes are based on physical phenomena, e.g., volatilisation, dispersion, retention mechanisms, etc.
    • Chemical processes. Chemical processes are based on a chemical treatment of the radioactively contaminated materials.
    • Biological processes. Biological processes are based on bio-degradation. Bio-degradation is a process or a collection of processes (e.g., bio-mineralization, ‘bio-sorption’ and microbially mediated phase transfer) in which naturally occurring micro-organisms such as yeast, fungi and bacteria, effect the fixation or mobilization of metals, including radionuclides, in various types of soil ecosystems.
    • Alternative land uses. When extensive areas have been contaminated, many of the discussed remediation methods may be too expensive to carry out or too intrusive. In particular, when the land was used for agricultural purposes, alternative uses may need to be considered. Such alternative uses may range from switching to different crops to turning to completely different uses, such as parkland [IAEA-2004b].
  • Containment of blocking pathway(s). This planning approach restricts the mobility of the radioactive contaminants: this involves immobilizing the contaminants inside the area in which they already exist, reducing the potential for further migration or entry into active pathways of exposure.
  • Source removal. This planning approach relies on the removal of the radioactive contaminants from the site, using an appropriate treatment scheme: this involves extracting, concentrating and then safely disposing of the contaminants at another location.

The above mentioned planning approaches and principals are discussed in detail in Section 4.3.

If the established environmental remediation criteria have been met after source removal actions, the site should be possibly released without further restrictions. If the criteria have been met after pathway change actions, the site should be possibly released with appropriate restrictions (e.g., the radioactive source is still present). These restrictions could be in the form of institutional control on the use of the site and/or groundwater, for example, to ensure that restrictions on grazing are followed.

If, after the environmental remedial actions have been carried out, the criteria have not been met, the responsible party should determine whether further environmental remediation is feasible or whether the site should be released with restrictions, and should submit a proposal accordingly to the regulatory body for approval.

In the following paragraphs, the main issues regarding the remediation process are described in more detail.