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4.2.7 Technical and institutional considerations

Contents
4.2.7.1 Justification and optimization of remedial measures
4.2.7.1.1 Justification of remedial measures
4.2.7.1.2 Optimization of remedial measures
4.2.7.2 Remedial performance evaluations
4.2.7.3 Decisions regarding further action(s)
4.2.7.4 Post-remediation control and stewardship

4.2.7.1 Justification and optimisation of remedial measures

Interventions in the form of remedial measures should be intended to decrease existing and potential annual exposures, by removing existing sources, modifying pathways or reducing the number of exposed people. For contamination resulting from past activities and accidents, the required level of remediation should be established on a site specific basis and in accordance with the radiation protection principles that apply to intervention situations [IAEA-2007a].

These principles include the justification of remedial measures and the selection of the optimum measures among those justified. In applying these two principles to derive an optimized option for protection, all relevant advantages and disadvantages should be taken into account. These include avertable doses (individual and collective), radiological and non-radiological risks, environmental effects, risks to the workers implementing the remedial measures, economic costs, improvement of the economic situation, the generation of secondary waste, increased or reduced anxiety on the part of interested parties and social disruption arising during and after the implementation of the remedial measures.

4.2.7.1.1 Justification of remedial measures

The remedial measures should be justified by means of a decision aiding process requiring a positive balance of all relevant attributes relating to the contamination [IAEA-2007a]. The justification principle should be implemented by means of an assessment of the overall radiological impacts from the contaminated sites in question, identification of options for reducing these impacts, evaluation of the reductions achievable in doses and in other harmful impacts and assessment of the harm and costs associated with these remediation options. Decisions taken on this basis should involve balancing benefits from the reductions in impacts and costs and other factors of influence. An informed decision should be taken on the basis of a full integration of all the advantageous and disadvantageous attributes for society resulting from the proposed remediation options.
Situations giving rise to potential exposures as well as actual exposures should be considered during the assessment.

4.2.7.1.2 Optimization of remedial measures

The remedial measures should be optimized following the general approach to the optimization of protection in the context of practices. The optimum nature, scale and duration of the remedial measures should be selected from a set of justified options for remediation [IAEA-2007a]. The aim is to obtain not only a positive benefit but also optimized protection. The decision aiding techniques for deciding on the optimum remediation option are independent of the nature of the situation causing the exposure. Normally, there would be a range of justified remediation options for which the net benefit would be positive.

Some remediation options could involve restrictions on the use of the site, even when the remediation end criteria have been met. Such an option would, however, require institutional control as long as the restrictions are deemed necessary. Options that lead to unrestricted release of the site after the remediation criteria have been met have the additional benefit of not requiring institutional control or other regulatory burdens, and so should be favoured. It is recognized, however, that site specific features such as topography, size of the site and lack of waste management facilities might limit the feasibility of a remediation option that leads to unrestricted release.

In some circumstances, remediation may be required to protect the present population and may be justified on the basis of attributable health effects among people in future generations. While in most cases the cost of remediation, in terms of aspects such as disruption and inconvenience, will be borne by the present population, remedial measures taken to protect the present generation should be designed in such a way that predicted impacts on the health of future generations will not be greater than the levels of impact that are acceptable today.

When the performance and the costs of all remediation options have been assessed, a comparison should be performed to determine the optimum option. If this optimum is not obvious, the comparison should be performed using a quantitative decision aiding technique. The result of the application of quantitative techniques is termed the analytical solution. If, in addition, there are non-quantifiable, non-radiological factors to be taken into account, the analytical solution may not be the optimum solution. These qualitative factors should be combined with the analytical solution to determine a true optimum solution, after consultation with interested parties.

The optimization of remedial measures should result in reference levels expressed in terms of a residual activity concentration or dose criteria for the remediated site.

Remedial measures may remove all of the contamination, or remove only part of it, or may only alter the exposure pathways or the number of people exposed without removing the contamination itself. Depending on the expected residual dose, which can be derived from the expected effectiveness of the proposed remedial measures, associated restrictions should be defined as part of the remediation option, if necessary. The residual dose, as well as the advantages and disadvantages of the associated restrictions, should be integrated into the optimization process. If the option includes on-site disposal of radioactive waste, the resulting exposure from this disposal option should also be taken into account.

Owing to time or resource constraints, general sources of information or default parameters may have to be used for modelling calculations. Sensitivity analyses should be performed within the optimization procedure to assist in determining when and where generic input parameters should be replaced by site specific values.

4.2.7.2 Remedial performance evaluations

Performance evaluations of the full scale remedial action, based on monitoring data, should be conducted periodically to compare actual performance to expected performance. The performance monitoring should be designed to provide information as such, but not limited to the following [IAEA-1999a]:

  • Horizontal and vertical extent of the plume and contaminant concentration gradients, including a mass balance calculation;
  • Rate and direction of contaminant migration;
  • Changes in contaminant concentrations or distribution over time;
  • Rates of contaminant mass removal and transition from advective removal to diffusion rate limited removal;
  • Effects of hydrological events, such as above average rainfall, on contaminant mass;
  • Removal and changes to groundwater flow;
  • Calibration of model based on actual results and effects of changes of operational parameters to model predictions;
  • Effects on regional groundwater levels and the resulting impacts;
  • Effects of reducing or limiting surface recharge (if applicable);
  • Effects of re-injection (if applicable);
  • Effects of any modifications to the original remedial action;
  • Other environmental effects of remedial action, such as saltwater intrusion, land subsidence, and effects on wetlands or other sensitive habitats.

The frequency and duration of performance evaluations should be determined by site specific conditions. Conducting performance evaluations and modifying remedial actions is part of a flexible approach to attaining remedial action goals. Decisions should be verified or modified during remediation to improve a remedy’s performance and ensure protection of human health and the environment.

The performance assessment may provide information that can be used to determine whether the remediation goals are being met, have been achieved or, in some cases, are technically impracticable to achieve in a reasonable time.

4.2.7.3 Decisions regarding further action(s)

After all or most of the existing data and information on the contaminated site have been collected and analysed, a determination for further action should be made. The alternatives to be considered may include:

  1. No further action needed. A decision of no further action can be made if it is determined that there is no radiological contamination present or that the extent of the radiological contamination is below an acceptable risk level and below the regulatory requirements of concentration or radiological dose.
  2. Further monitoring of contaminant plume is required. Although no further action (e.g., remedial action) may be required, it might still be necessary or advisable to continue to monitor the site to ensure that the initial assessment of the situation is correct. For example, this could be the outcome when it appears that natural processes such as dispersion and radioactive decay would result in the contamination having no significant impact on the receptors (i.e., affected population). Continued monitoring would allow the assumptions regarding movement of the groundwater contaminant to be routinely checked. In addition, continued monitoring could provide comforting reassurance to affected parties such as the local population.
  3. Insufficient data exist to make a decision. Following the assessment of existing data and information, it could develop that there are insufficient data to make an informed decision regarding the possibility or advisability of remedial action. Under such a circumstance, it is common that a site characterization programme be implemented to fill the identified gaps in information and data. If there is a decision to collect additional data, the data collection objectives should be clearly identified and used in designing the site characterization programme.
  4. Direct environmental remedial action(s) is required. In some cases, there will be wholly sufficient data and information regarding a site and the groundwater contamination problem to conclude that remedial action is required. In such a case, the strategy will advance to the technologies evaluation and remedial design phases.

4.2.7.4 Post-remediation control and stewardship

For some sites, it may not be practicable to reduce the contamination, whether radioactive or hazardous, to such low levels that they are suitable for unrestricted use. This will result in the imposition of restrictions referred to as institutional controls. These could involve surveillance of the site and control access systems. Regulatory authorities are typically responsible for approving the design of the programme, its implementation, and the evaluation of the results with respect to the residual impact on the public and the environment. Maintenance of institutional control over extended periods of time is a concern. The collection of processes and provisions for this are generally referred to as stewardship [IAEA-2006b]. Stewardship is further discussed in Section 5 of this document.