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4.6.2 Operational aspects of remediation

Contents
4.6.2.1 General
4.6.2.2 Radiation protection during remediation
4.6.2.3 On-site and off-site monitoring during remediation
4.6.2.4 Waste management
4.6.2.5 Emergency planning
4.6.2.6 Site security
4.6.2.7 Quality assurance
4.6.2.8 Ensuring compliance with requirements

4.6.2.1 General

Once the preferred option has been selected and the planning for remediation has been completed and approved, implementation of the remediation should begin within an appropriate time frame, normally within one to two years.

During the implementation of remedial measures, consideration should be given to radiation safety, transport safety and waste safety, so as to minimize hazardous impacts, and to the potential for prolonged exposure after termination of remediation operations. Consideration should also be given to general health and safety issues and environmental issues.

Activities for predisposal waste management should be undertaken, where appropriate, to treat and condition the contaminated material arising from remediation operations, including secondary waste generated by the remediation activities. The associated safety programme should include considerations of occupational protection and safety, such as training, the use of protective clothing and respiratory equipment, and cleaning facilities.

For the management of radioactive waste arising from the implementation of remedial measures, the objective of the protection of human health and the environment now and in the future without imposing undue burdens on future generations, as set out in the IAEA Principles of Radioactive Waste Management [IAEA-1995], should all apply, with due consideration of the amounts, characteristics, properties and types of radioactive waste [IAEA-2003].

The following sections identify issues that should be addressed during the implementation phase.

4.6.2.2 Radiation protection during remediation

Remediation workers will receive doses only if remedial measures are introduced. In the implementation of remedial measures, the exposure of workers should be controlled under the system of radiation protection for practices. The actual radiological conditions and the effectiveness of specific protective actions taken during the remediation should be compared with initial estimates of exposures and releases and the goals established for their control.

If the remediation operations would give rise to exposure of the general public living in or near the contaminated areas, the resulting doses should be controlled under the system of radiation protection of the public that is applied for practices. Normally, these doses would be justified in the light of future doses that would be averted by the remediation. If the doses would be significant, evacuation or relocation of the public should be considered based on the intervention levels for these measures and the system of protection for interventions should be applied. Unacceptable effects on the environment should also be avoided during the remediation, and environmental protection programmes should be considered, to minimize any harmful consequences that might result in the near term or that might occur in the future [IAEA-2007a].

4.6.2.3 On-site and off-site monitoring during remediation

The area should be monitored and surveyed regularly during remediation so as to verify the levels of contamination and to ensure compliance with the requirements for waste management. Regular surveillance should also enable the organization responsible for the remediation to detect any unexpected levels of radiation and to modify the remediation plan accordingly. Revisions to the remediation plan should be subject to the approval of the regulatory body. There may need to be several iterations of review and revision of the remediation plan [IAEA-2003].

The extent of on-site and off-site monitoring programmes should be determined on the basis of the activities that will be performed during the remediation and the degree of uncertainty concerning the performance of these activities, and should be consistent with longer term monitoring programmes set up to verify the long term stability of exposure conditions (e.g., by monitoring the covering of mining residues, protection against the infiltration of water and protection against erosion or atmospheric dispersion).

Monitoring should be performed to evaluate the expected and actual level of safety of workers and the public and protection of the environment during the remediation. On-site monitoring should be conducted to provide information for use in identifying and mitigating hazards. It should be ensured that all potential exposure pathways are monitored. Off-site monitoring should be designed to monitor whether and to what extent discharges to the environment occur and to verify that regulatory requirements for the protection of the public and the environment are being met [IAEA-2007a].

4.6.2.4 Waste management

The waste arising from remediation operations should be accommodated within an existing waste management system established for practices, particularly if the amounts of wastes expected are small. Waste may include: solid waste, such as vegetation or metallic waste from initial activities for site preparation; soil and rock; material from buildings or other structures; used personal protective equipment; disposable items used during the collection, preparation or packaging of samples; liquid and solid residues from samples sent for analysis; liquid and solid waste from hygiene and changing facilities; and water used for cleaning and decontamination or water abstracted from groundwater on the site. If the existing waste management system is not capable of dealing with the types and quantities of waste that will be generated during the remediation activities, the system should be adapted or supplemented accordingly. During the planning activities, the inventory of contaminated areas should include an evaluation of the amounts and characteristics of the waste that could be generated by the remediation operations. The management of radioactive waste arising from the implementation of remedial measures should be considered one component of the entire decision making process. The costs of transport and disposal of the waste, the radiation exposure of and other risks to the workers handling it, and, subsequently, the exposure of the public associated with its disposal should all be taken into account in the process of determining the optimum option for remediation.

The management of radioactive waste should include predisposal management, transport and disposal. The management of radioactive waste should comply with the international and national requirements for waste management facilities. An additional dose criterion of the order of 10 μSv/a should be used for the clearance of material from a site that contains radionuclides of artificial origin. For material that is contaminated with radionuclides of natural origin (except for 40K), a clearance criterion of an activity concentration of 1 Bq/g could be used.

The following factors should be considered for the operations relating to the management of the waste arising during the implementation of the remediation programme:

  • The types of waste may be very different, ranging from spent fuel and fission products following a nuclear accident, to naturally occurring radionuclides resulting from past industrial processes such as fertilizer production and the mining and processing of uranium and thorium ores;
  • The amount of waste arising from the remediation operations may be very high (e.g., in the event of the removal of contaminated soil);
  • Transport options to disposal sites may be limited;
  • There may be no appropriate waste management facilities available for dealing with waste of these types, or such facilities may be limited in capacity.

The above factors should already have been dealt with in the optimization process when the remediation option was selected; however, during remediation activities, situations may arise that necessitate modification of the remediation programme in response to changing conditions. The regulatory body and the organization responsible for the remediation should then evaluate whether there is a need to return to the justification and optimization process that is required for interventions [IAEA-2007a].

4.6.2.5 Emergency planning

A programme for emergency planning that is applicable for remediation activities should be established and described in the remediation plan. Operating organizations should ensure that procedures for dealing with unforeseen events that may occur during remediation are prepared and put into place. Personnel should be trained in emergency procedures. Provision should be made for the periodic testing and updating of these procedures by conducting periodic exercises. In the event of an unforeseen incident happening during remediation, the responsible parties should without delay notify the regulatory body [IAEA-2007a].

4.6.2.6 Site security

Appropriate means, commensurate with the associated hazards, for restricting access to the area should be maintained throughout the remediation activities. These measures should be described in the remediation plan.

4.6.2.7 Quality assurance

The organization conducting remediation activities should implement an appropriate quality assurance programme under its management system. Activities for remediation and waste management should be performed by properly trained individuals in accordance with approved work procedures. Work procedures should be prepared for each activity. In the development of the quality assurance programme, the need for the acquisition and retention of records and information relevant to the area being remediated should be emphasized.

A record should be maintained of each task carried out in the remediation operations. Accurate and complete information concerning the locations, configurations, types and amounts of radionuclides remaining in the area after remediation is essential and should be acquired and maintained. For the unrestricted release of the area, these records should be used to demonstrate that all the radioactive material that was present at the beginning of the activities has been properly accounted for and that its ultimate destinations and uses have been specified and confirmed [IAEA-2007a].

4.6.2.8 Ensuring compliance with requirements

The regulatory body should confirm that the remediation criteria were correctly chosen and applied by the responsible party. The regulatory body is required to ensure compliance with the legal and regulatory requirements, and should verify that the remediation end criteria have been met.

The responsible party should be required to submit to the regulatory body a final remediation report, including any necessary final confirmation survey that shows that the remediation criteria have been met. The regulatory body should use the information in the remediation report to develop a confirmation plan and should implement this plan as an independent confirmation of the responsible party’s survey data.

The regulatory body should compare the data presented in the results of the final confirmation survey with the information presented in the responsible party’s final survey report, and should verify compliance with the requirements. If there is an assurance that the remediation end criteria have been met, the regulatory body should agree that remediation has been concluded. If it is determined that compliance with the requirements has not been achieved, the responsible party should evaluate how to proceed. The options to be considered should include further remedial work or the imposition of institutional controls. Again, preference should be given to meeting the original objectives. If revision of the remediation plan is envisaged, the process for a new consideration of possible options as discussed in Section 2.3.2 and illustrated in Figure 2.4 should be followed.

Any quantitative recommendations will be difficult to implement unless there are agreed approaches to the estimation of exposures for the purpose of demonstrating compliance with the recommendations. Long term scenarios should be specified to characterize the individuals potentially exposed and the ways in which they may be exposed.

The quantification of uncertainties should be an integral part of the estimation of annual radiation doses. Methods for estimating uncertainties may vary significantly, ranging from qualitative judgements about variability to more rigorous approaches that include a statistical analysis of distributions for a range of input values that have a bearing on the dose estimate. Uncertainty analysis is evolving rapidly, and techniques for estimating dosimetric uncertainties are still being developed. Whenever possible and appropriate, annual doses should be assessed as a distribution of possible values rather than as single point values.

Radioactive residues are usually unevenly distributed in space, creating heterogeneous situations of prolonged exposure. These should be addressed on a case-by-case basis by making realistic assumptions about the patterns of individual exposures. The selection of methods for evaluating heterogeneous exposure will depend on the situation and on the objectives of the evaluation.

Annual doses in exposure situations involving long lived radionuclides should be estimated on the basis of the assumption of unrestricted use of the site under remediation. This assumption implies that all exposure pathways that could realistically apply at any time in the future should be taken into account. However, the outcome of the optimization process may be restrictions on area use. Restrictions on use may preclude certain pathways and thus may reduce exposures, thereby achieving some advantages while introducing the disadvantage of having the restriction imposed. Scenarios describing restricted use following remediation of a site will be case specific. Furthermore, decisions about possible restricted uses may vary significantly within and between different countries. Restricted use will usually involve some form of ongoing institutional control such as by means of a land use registry. The possibility of the failure of this institutional control should be taken into account in the estimation of exposures. For areas that are contaminated with long lived radionuclides, consideration should be given to the fact that most restrictions and institutional controls have a limited time period of implementation, and sometimes this period is not commensurate with the half-life of the radionuclide.

For areas where there is more than one site giving exposure at high levels, the necessary degree of remediation should be determined by taking account of the annual doses arising from all the high exposure sites as well as those arising from the area as a whole. When there are sites giving high exposure levels within a larger area where exposure has been prolonged, remediation of these sites giving high exposure levels may be governed by local regulations for decontamination [IAEA-2007a].