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

2.5.1 Introduction

Site remediation activities have to deal with risk assessment, risk management and risk communication [IAEA-2006c]. Risk assessment is used to determine the risk to human health and the environment, risk management efforts are directed towards control and mitigation of the potential long term risks of residual contamination, and risk communication actions are used to convey information to affected current and future stakeholders.

  • Environmental risk assessment. Environmental risk assessment is based on the source-pathway-receptor relationship and allows a prediction of the effects on the environment and human health over time to be made. Environmental risk assessment usually takes place prior to any remedial action in order to determine the levels and types of remediation required. The process needs to be rerun following the remediation phase so that the longer term risks of any remaining contamination can be assessed and appropriately managed during stewardship years.
  • Risk management. Three major traditions in sociological analysis of risk have been identified:
    1. A positivist/realist theory of knowledge, with a bureaucratic rationalistic policy orientation, whereby risk can be measured and mapped, and thus controlled (within limits), and where failures in risk management are understood as being due to inadequate knowledge or competence, or to a failure of political will;
    2. A social constructivist theory of knowledge, with a liberal pluralistic approach to integrating knowledge and action, whereby the understanding of risks is shaped by history, politics and culture, and risk management requires negotiation and dialogue to enable the inclusion of different perspectives;
    3. A constructivist theory of knowledge, focusing on the mediation of knowledge and power (among others), which makes risk analysis a particular discourse, and which empowers some groups and excludes others.

Current (radiological) risk management strategies as promoted by the International Commission on Radiological Protection (ICRP) and the International Atomic Energy Agency (IAEA) fall under model “1” listed above.

The acceptability of residual risks in general is a function of a wide variety of sociological, economic and political factors. It may vary over time for individuals or certain groups of individuals. This acceptability typically evolves as a balance between perceived risk and actual inconvenience imposed by institutional control measures. Inconvenience here is understood to encompass the restrictions on, for example, site use imposed. The higher the perceived risk, the more acceptable become institutional controls.

The definition of what constitutes a residual risk is subject to scientific developments and subsequent changes in the regulatory systems. A stewardship programme may have to include provisions for accommodating such changes in the regulatory system. While the legal framework usually ensures that the envisaged objectives do not change, the regulator may deem it necessary to reassess risks. Such reassessment may result in changes to the institutional control measures that in turn require changes in the stewardship arrangements. Therefore, a mechanism should be available for providing (additional) resources.

The need for remediation and the judgement about acceptable residual contamination levels are usually driven by society’s perception of the balance between the costs of measures and the benefits obtained. There is a certain ‘window’ for decision making, bound by minimum required benefits and maximum allowable expenditure. Expenditures for lowering residual risks typically increase in an exponential or similar way. This is captured in the requirement to optimise radiation protection measures.

As an example, the conceptual framework for long term stewardship can be represented on a scale (Figure 2.8). On the left hand side of the scale, a series of weights represent the hazard associated with residual contamination. On the right hand side of the scale, a series of weights represent technical, institutional and societal factors.

Figure 2.8 Conceptual framework for site remediation activities
Figure 2.8 Conceptual framework for site remediation activities

Technical factors may include, among others:

  1. Monitoring and surveillance;
  2. Verification and validation of predictive models for the fate and transport of contamination;
  3. Development of durable engineered protective measures.
    Institutional factors may include, among others:
  4. Safety assessments;
  5. Development of an action plan with contingencies;
  6. Development of durable institutional controls;
  7. Reliable funding mechanisms;
  8. Records and information management.|

Societal issues may include, among others:

  1. Risk perceptions;
  2. Public values;
  3. Stakeholder involvement.

When the scale is in balance then human health and the environment are considered to be protected to a level agreed by the stakeholders – for the present and in the future. The aim of long term stewardship for example is to ensure that the scale is kept in balance. Thus with time, if the level of hazard falls due to radioactive decay or natural attenuation, then less weight may need to be added to the right hand side of the scale in Figure 2.8. This may allow the site to reach an interim end state such that less restrictive land uses may be allowed while still maintaining protection of human health and the environment.

Conversely, if the hazard remains the same but there is a partial failure of, for example, a containment system, then further ‘weights’ need to be added to the right hand side in order to maintain protection of human health and the environment. These additional weights are likely to involve a technical or institutional solution – for the former this could be an engineering intervention to restore the required level of containment, whilst for the latter this might involve further restrictions on land use.

Each of the weights on the right hand side inevitably has an associated cost. Optimisation of a long term stewardship programme for example involves balancing these costs against the benefits of the actions required to contain the hazard and to retain an appropriate level of protection of human health and the environment.

  • Risk communication. Environmental risk assessment is sometimes viewed by the non-scientific community with suspicion, and terms such as ‘black box syndrome’ are quite often used. It is important, therefore, for scientists to be able to communicate the rationale and benefits behind undertaking environmental risk assessments as well as the results themselves.