Index > 2 Development of a strategy, implementation and execution program to remediate radioactively contaminated sites >

2.10.5 Start of a long term stewardship

Contents Overview of long term stewardship drivers Challenges of long term stewardship Components of long term stewardship

Figure 2.13 shows the generic life cycle management of a (nuclear) facility [IAEA-2006c], [USNRC-2003]. The early stages of the life cycle consist of identifying the need for an activity site and selecting the site as well as designing, constructing and operating the facility (e.g., a facility processing minerals causing a contamination of NORM or TENORM material (Technically Enhanced Natural Occuring Radioactive Material) or a nuclear facility.
At the end of the operational phase, the site undergoes decommissioning and active remediation. Decommissioning involves actions such as decontamination, demolition and dismantling of buildings and equipment, and sometimes waste conditioning depending on national regulations and licenses.

Figure 2.13 Life cycle management
Figure 2.13 Life cycle management

During active remediation, engineered, physical and chemical measures (e.g., caps, liners, reactive barriers and micro-organisms) may be put into place to protect human health and the environment. In some countries, decommissioning and active remediation are considered as an integrated process. In these countries, the boundary between decommissioning and the onset of site remediation is blurred, and there might be different cycles of decommissioning and site remediation. In some countries, these cycles may last for decades to allow the decay of short-lived radioactivity and this process is called ‘safestore’.

In these cases, there may be interim ‘fit for purpose’ land uses at the end of each cycle. In contrast, in other countries, decommissioning is completed before site remediation begins, so that the boundaries are clearly defined.

A site may also be split into sub-sites that are fit for free release and others that require institutional control. A suitable split may greatly facilitate a subsequent stewardship programme.

The determination of estimation of the time when remediation is complete and long term stewardship begins may differ between countries and may well vary for different types of sites within a country [IAEA-2006c]. Many times the determination of when remediation is complete is based on when the regulator certifies or by some means designates that the remedial actions taken have met the originally established remedial objectives. Groundwater remediation in some cases tends to have very long remedial durations, which creates a unique timing issue over when remediation is complete and long term stewardship begins. The duration depends on the time needed for active water treatment. This is a critical issue to consider early in the remediation phase, especially if the parties responsible for remediation and long term stewardship are not the same entity or may change over time.

Long term stewardship begins after the end of decommissioning and active remediation [IAEA-2006c]. The intermediate guarantee phase of several years that is sometimes imposed for engineered structures, etc., might be viewed as part of the active phase or already be part of the stewardship phase. Long term stewardship fundamentally does not encompass any active remediation. Hazards on the site will have been removed or been contained by engineered systems put into place during the active remediation phase, or natural processes, such as attenuation, dispersion or radioactive decay, will have been used to keep exposures below levels of concern. Long term stewardship primarily involves the care and maintenance of the site and any structures built as part of the remediation solution. Monitoring activities ensure that the remediation solution behaves as predicted and that any land use restrictions are complied with. In some cases, a permanent solution may have been deferred until a (more) suitable remediation technology has been developed, and the site has been put into a stewardship-like state in the interim period.

A long term stewardship programme is being developed during the active remediation and decommissioning phase, and addresses monitoring and maintenance as well as including provisions for corrective actions in case of deviation from the predicted behaviour of the site. The final end state is ideally the unrestricted release of the site. However, if any control measures remain necessary, long term stewardship needs to be put into place. If unrestricted release is not possible, the site can still be used for specific purposes (e.g., industrial use) but the steward needs to ensure that the restrictions are complied with. Overview of long term stewardship drivers

Principal drivers for needing long term stewardship at a site may be a combination of:

  • Priorities – Owner, local, federal priorities may not support funding for clean-up to free-release levels;
  • Long-lived contaminants – Radionuclides, chemicals, and metals may not be easily or quickly broken down to safe constituents;
  • Lack of technology – No further environmental benefit from remediation may be attainable with existing technology or asymptotic levels have been reached, e.g., groundwater and vadose zone;
  • Risk – Short term human health or environmental risks of conducting remedial activities may outweigh the benefits of remediation. Challenges of long term stewardship

The challenges of long term stewardship are associated with the time frames under consideration. Many regulations assign authority and responsibility for environmental contamination into the foreseeable future, i.e., decades, but residual contamination at facilities or sites may remain hazardous for a very long time. The objectives of long term stewardship should be to ensure adequately long-lived monitoring, institutional controls, engineering controls, maintenance activities and information management for the related radioactively contaminated sites and/or groundwater.

The societal aspects of long term stewardship may present several important challenges, such as building trust, communicating the nature of the risks and of the remediation and stewardship options, reconciling economic, management and technical issues with considerations of public values and beliefs, resolving ethical questions and engaging stakeholders in the decision making process, and thereafter retaining stakeholder commitment [IAEA-2006c]. Components of long term stewardship

Many aspects of long term stewardship are intended to maintain the long term protectiveness of the remedy. Components of long term stewardship therefore should include:

  • Management – Stewardship for radiological liabilities must be framed for very long time horizons. Given the long half-lives of many relevant radionuclides, and compared to the average human life, “long term” in essence means eternity. However, it is also clear that, during the life cycle of site management, the stewardship will encompass an extremely broad range of issues and activities 16.
  • Institutional/Administrative Controls – Control exposure to hazardous substances by establishing (governmental) controls and providing legal enforcement tools. It is recommended that institutional control activities defined for a remediated site where restrictions are maintained after remediation has been completed should be included in a monitoring and surveillance plan that should be subject to periodical review and to approval by the competent authority.
  • Physical/Engineered Controls – Implemented to treat or stabilize contamination, to physically contain or isolate waste, or to prevent access.
  • Monitoring and Maintenance – Ongoing environmental monitoring to determine the effectiveness of the remedy, improve understanding of the contaminant interactions with the site, and support maintenance of engineered controls to guide decisions on when and how to modify long term stewardship activities.
  • Information Management Systems and Repositories – Maintenance of environmental data and other information relevant to the remedy including public communication. When sites make the transition from clean-up to long term stewardship, site stewards and stakeholders should be given detailed information about the location and the nature of residual hazards, the processes that generated them, and the engineered and institutional controls that are part of the remedy [Principle 5].
  • Periodic review of the remedy and, if needed, alteration of the remedy – At regular intervals, for example, every five years, a review should be conducted to evaluate the implementation and performance of a remedy in order to determine if the remedy is or will be protective of human health and the environment.
  • Site access – Restriction of access to contaminated sites and/or institutional control may be required to be maintained in cases of serious residual contamination 12.
  • Removal of restrictions – If the monitoring and surveillance programme has verified the long term effectiveness of the remedial measures in eliminating unacceptable risks to human health and the environment, consideration should be given to removing any restrictions applied to the site and ending or reducing the extent of the monitoring and surveillance.