5.1. As stated in para. 5.1(a) of GSR Part 3 [2]:
“The requirements for existing exposure situations…apply to:
(a) Exposure due to contamination of areas by residual radioactive material deriving from:
(i) Past activities that were never subject to regulatory control or that were subject to regulatory control but not in accordance with the requirements of these Standards;
(ii) A nuclear or radiological emergency, after an emergency has been declared to be ended….”
5.2. The exposure referred to in para. 5.1 may be incurred directly from the residual radioactive material itself, or may be incurred indirectly from commodities that incorporate radionuclides arising from the residual radioactive material. Such commodities include food, feed, drinking water and construction materials. The radionuclides in the residual radioactive material may be radionuclides of artificial origin or radionuclides of natural origin.
5.3. Contamination of areas can also arise from facilities and activities that are subject to regulatory control in terms of the requirements for planned exposure situations, as a result of authorized activities such as discharges, the management of radioactive waste and decommissioning. An exposure situation resulting from such contamination is controlled as part of the overall practice and is, therefore, a planned exposure situation and not an existing exposure situation.
5.4. In terms of para. 5.1(c) of GSR Part 3 [2], the requirements for existing exposure situations also apply, in general, to exposure due to natural sources, where such exposure is not excluded from the scope of GSR Part 3 [2] (see para. 2.4 of this Safety Guide). Natural sources include:
(a) Materials (in a natural or processed state) in which the radionuclides are essentially all of natural origin;
(b) 222Rn and 220Rn, together with their progeny, as specified in para. 3.161;
(c) Cosmic radiation.
5.5. Measures for preventing or reducing doses that might otherwise occur in an existing exposure situation may take the form of remedial actions or protective actions:
(a) Remedial actions in an existing exposure situation involve removal of the source or reduction of its activity or amount. An example of a remedial action is the removal of residual radioactive material from a contaminated site.
(b) Protective actions in an existing exposure situation involve measures that act on the exposure pathways rather than on the source itself. Examples of protective actions are the control of access to a contaminated site and restrictions on the use of contaminated water for drinking purposes.
5.6. Categories of exposure in existing exposure situations are occupational exposure and public exposure. In considering occupational exposure, two groups of exposed workers can be identified:
(a) Workers who are exposed while carrying out remedial actions. The exposures of these workers may be increased as a direct result of their work (i.e. when such action involves the handling, transport or disposal of residual radioactive material).
(b) Workers who are exposed in the existing exposure situation but who do not carry out any remedial action. The exposures of these workers might eventually be reduced as a result of remedial or protective actions.
5.7. The doses received in existing exposure situations are expected to be well below the threshold for deterministic health effects. Therefore, stochastic health effects are the only health effects of concern.
PROTECTION STRATEGIES
5.8. According to paras 5.2 and 5.3 of GSR Part 3 [2], the government has certain responsibilities with regard to existing exposure situations. It is required to ensure that existing exposure situations are identified and evaluated to determine which exposures (including occupational exposures) are of concern from the point of
view of radiation protection. It is also required to make provision in the legal and regulatory framework for the management of exposures of concern, including the assignment of responsibilities for protection and safety, the establishment of appropriate criteria for protection and safety in the form of reference levels (see paras 5.19–5.23) and the making of decisions on the reduction of exposures by means of remedial and/or protective actions.
5.9. Where it is decided that exposures need to be reduced, appropriate protection strategies need to be established. Formal provision for the development and implementation of protection strategies is required to be made by the government in the legal and regulatory framework, including the following:
(a) Specification of the general principles underlying the protection strategies;
(b) Assignment of responsibilities for the development and implementation of the protection strategies to the regulatory body or other relevant authority (e.g. a health authority or an environmental protection agency)11 and to the parties involved in the implementation process;
(c) Provision for the involvement of interested parties in the decision making process, as appropriate.
5.10. In terms of the graded approach (see para. 2.20), the government, in conjunction with the regulatory body or other relevant authority identified in para. 5.9(b), should ensure that protection strategies for existing exposure situations are commensurate with the associated radiation risks.
5.11. In terms of para. 5.4 of GSR Part 3 [2], the regulatory body or other relevant authority is required to ensure that the protection strategy for a particular existing exposure situation defines the objectives to be achieved and includes appropriate reference levels (see paras 5.19–5.23).
5.12. Various remedial and protective actions will generally be available for achieving the objectives of the protection strategy for a particular existing exposure situation. In terms of para. 5.5 of GSR Part 3 [2], the regulatory body or other relevant authority, in implementing the protection strategy, is required to make arrangements for these remedial actions and protective actions to be evaluated. This evaluation will include an evaluation of the effectiveness of those actions eventually planned and implemented.
11 More than one authority may be involved, in which case the term ‘authority’ refers to the system of authorities.
5.13. The regulatory body or other relevant authority, in implementing the protection strategy, is required to ensure that information is available to exposed individuals on the potential health risks associated with the exposure and on the means available for reducing their exposures and associated risks.
JUSTIFICATION
5.14. The regulatory body or other relevant authority should establish the protection strategy for a particular existing exposure situation in accordance with the principle of justification. This means that only those remedial actions and/or protective actions that are expected to yield sufficient benefits to outweigh the detriments associated with taking them, including detriments in the form of radiation risks, the costs of such actions and any harm or damage caused by the actions, should be considered for inclusion in the protection strategy.
5.15. The detriments in the form of radiation risks to be considered in the justification process should include exposures of workers engaged in taking any remedial actions.
OPTIMIZATION General approach
5.16. The regulatory body or other relevant authority and other parties responsible for the establishment of a protection strategy should ensure that the form, scale and duration of remedial and protective actions are optimized (i.e. they will provide the maximum net benefit, in that all exposures are controlled to levels that are as low as reasonably achievable, economic, societal and environmental factors being taken into account). The implementation of the optimized protection strategy will not necessarily result in the greatest reduction in dose, since dose reduction is only one of several attributes considered in the optimization process.
5.17. As in the case of the justification process (see paras 5.14 and 5.15), the detriments in the form of radiation risks to be considered in the optimization process should include the exposures of workers engaged in any remedial actions.
5.18. Optimization of protection in an existing exposure situation is achieved by:
(a) An evaluation of the exposure situation, including any potential exposure;
(b) Identification of the possible protection options expressed in terms of justified remedial actions and/or protective actions;
(c) Selection of the best option under the prevailing circumstances;
(d) Implementation of the selected option.
Reference levels
5.19. A reference level should be used in the optimization process. It represents a level of dose above which it is judged to be inappropriate to plan to allow exposures to occur. In considering the various possible remedial actions and protective actions, a reference level serves as an upper bound on the range of options considered; this will ensure that the optimized protection strategy will be aimed at reducing doses to some value below the reference level.
5.20. A reference level also serves as a tool for prioritizing the implementation of remedial actions and protective actions. When an existing exposure situation has been found, actual exposures could be above or below the reference level.
While the process of optimization is intended to provide optimized protection for all exposed individuals, priority should be given to those groups receiving doses above the reference level by taking all reasonable steps to reduce those doses to below the reference level.
5.21. Reference levels are generally expressed in terms of annual effective dose to the representative person in the range of 1–20 mSv. However, reference levels for exposure due to radon are expressed in terms of annual average radon concentration in air.
5.22. A reference level for a particular existing exposure situation should be established by the government or by a regulatory body or other relevant authority acting on behalf of the government. The value should be chosen by taking into account all relevant factors, including:
(a) The nature of the exposure and the practicability of reducing the exposure;
(b) Societal implications;
(c) National or regional factors;
(d) Past experience in the management of similar situations;
(e) International guidance and good practice elsewhere.
5.23. The regulatory body or other relevant authority should review reference levels periodically to ensure that they remain appropriate in the light of the prevailing circumstances.
EXPOSURE ARISING FROM REMEDIAL ACTIONS IN AREAS WITH CONTAMINATION BY RESIDUAL RADIOACTIVE MATERIAL Application of the requirements for protection and safety
5.24. As stated in para. 5.6(a), workers carrying out remedial actions in connection with areas with contamination by residual radioactive material may be subjected to increased exposure as a result of activities such as the handling, transport or disposal of residual radioactive material. According to para. 5.26 of GSR Part 3 [2], the employers of such workers are required to ensure that exposures of the workers are controlled in accordance with the relevant requirements for planned exposure situations as established in section 3 of GSR Part 3 [2]. The guidance given in Section 3 of this Safety Guide is therefore applicable to such workers. The guidance given in paras 5.38, 5.39 and 5.42–5.44 is also relevant.
5.25. As stated in para. 5.6(b), workers who are not carrying out remedial actions may nevertheless be exposed in an existing exposure situation as a result of exposure levels in their workplaces being affected by the residual radioactive material. Exposures of such workers are also subject to control, in the sense that such exposures may be reduced as a result of remedial actions. The requirements for protection and safety under which this control is exercised are the same as those for controlling exposures of members of the public in existing exposure situations. In essence, therefore, the exposures of such workers are controlled as though they were members of the public. Guidance on the reduction of exposures by remedial actions, together with any necessary post-remediation activities, is given in paras 5.28–5.44. More detailed guidance is given in IAEA Safety Standards Series No. WS-G-3.1, Remediation Process for Areas Affected by Past Activities and Accidents [34].
Protection strategies
5.26. In formulating protection strategies for areas with contamination by residual radioactive material, all areas with, or potentially with, contamination should be monitored or surveyed by the regulatory body or other relevant authority so that those areas requiring remedial actions and/or protective actions can be identified and appropriate reference levels can be specified. It will be necessary to involve a number of governmental and private organizations, and provision should be made for liaison between them and for their input to the process. Account should be taken of any possible effects on neighbouring States.
5.27. The regulatory body or other relevant authority should establish safety criteria for the development and implementation of protection strategies, including criteria and methods for assessing the effectiveness of any remedial measures and criteria specifying conditions on the end points of the remediation.
Organizational arrangements for remedial actions
5.28. The organizational arrangements for remedial actions, funding mechanisms and roles and responsibilities, including the legal and regulatory framework, should be in accordance with the guidance provided in WS-G-3.1 [34].
Roles and responsibilities
5.29. Since the remediation of an area with contamination can involve several entities that include individuals who may be unfamiliar with the requirements for radiation protection and safety, the roles and responsibilities of the different parties involved in the remediation process should be clearly defined in the legal and regulatory framework. In particular, responsibilities should be specified for the protection of workers in the planning and implementation of the remediation programme.
5.30. Those persons or organizations responsible for providing adequate human resources, equipment and supporting infrastructure for occupational radiation protection in accomplishing the remediation should be clearly specified.
Regulatory considerations
5.31. The legal and regulatory framework, supported where necessary by guidance material, should provide for adequate protection of individuals (including workers) and the environment when remediation is undertaken.
5.32. Protective actions in the form of restrictions on the use of, or access to, the area should be considered before, during and, if necessary, after remediation.
The basis for establishing such restrictions should be provided in the legal and regulatory framework.
5.33. The regulatory process for situations of remediation involves more than just radiation protection. Other laws and regulations covering such matters as occupational health and safety, environmental protection, land management, and food and drinking water standards are likely to be administered by different
governmental bodies. These other laws and regulations should be applied, as appropriate, to create a coherent regulatory approach.
Remediation programme
5.34. Remediation of an area with contamination involves the prior radiological evaluation of the situation, the preparation and approval of a remediation plan, the remediation work itself, and the management of radioactive waste arising from the remediation activities. In the prior radiological evaluation, the nature of the problem and the associated concerns in relation to radiation protection of workers should be appropriately characterized.
5.35. As part of developing a remediation plan, the following aspects, among others, relevant to protection of workers should be considered:
(a) Determining the nature and extent of the contamination;
(b) Identifying exposure pathways for workers;
(c) Assessing individual doses via all routes of exposure;
(d) Evaluating health and safety issues during remediation work, including the use of appropriate personal protective equipment.
5.36. The design of the site characterization survey is determined by the conditions in the area, the type and extent of on-site contamination and the available resources. It should be ensured that the most suitable instruments and sampling and measurement techniques are selected, and that proper attention is given to the calibration of instruments and the recording of data (see Section 7).
Collection of data will most probably necessitate measurements of ambient gamma radiation as well as collection and measurement of samples of surface and subsurface soil, airborne radioactive material, water and biota.
5.37. The remedial actions and protective actions that are to be implemented should be justified and optimized (see paras 5.14–5.23). Priority should be given to situations in which the applicable reference level is exceeded (see para. 5.20).
Decisions on remedial actions and protective actions should be made with the involvement of the relevant parties concerned with the situation of contamination.
Protection and safety considerations should take account of future generations as well as of the present generation, including workers.
5.38. In the justification process, the positive attributes of remediation that should be taken into account include not only the eventual reductions in individual doses and collective doses, but also the expected reductions in anxiety among
individuals, including workers. The negative attributes that should be taken into account include not only the direct financial costs of the remediation, but also the societal and economic costs, the health and environmental impacts of the remediation work (including the radiation risks to workers undertaking such work), and the disruptive effects of the remediation work on society. While the overall objective is to reduce the doses received by individuals, the remediation work itself might temporarily give rise to additional doses. Such additional doses should be justified on the basis of the resulting net benefit, including consideration of the consequent reduction of the annual dose.
5.39. In the optimization process, remedial actions and protective actions should be optimized in accordance with the same general approach as that used for the optimization of protection in planned exposure situations (see paras 3.8–3.33), with the role of the reference level being, in some respects, equivalent to the role of the dose constraint in planned exposure situations. The optimum nature, scale and duration of remedial actions and protective actions should be selected from a set of justified options for remediation. In choosing the optimized remediation option, radiological impacts on individuals and on the environment should be considered together with non-radiological impacts, as well as technical, societal and economic factors. Factors relating to radioactive waste management should also be taken into account. These include the costs (including transport costs) of waste management, the radiation exposure of, and the health risks to, the workers managing the waste, and any subsequent exposure associated with disposal of the waste. In some cases, the outcome of the optimization process for remediation may be one in which the use of human habitats is subject to certain restrictions, in which case institutional controls to enforce those restrictions should be continued.
5.40. The remediation plan should include a monitoring programme to ensure that all necessary information on radiological conditions is gathered before, during and after the remediation process. To ensure that the remediation programme is adequately documented, a system of record keeping should also form part of the remediation plan, and should include the following:
(a) Descriptions of activities performed;
(b) Data from monitoring and surveillance programmes;
(c) Records of occupational health and safety for remediation workers;
(d) Records of the types and quantities of radioactive waste generated and of its management;
(e) Data from environmental monitoring;
(f) Records of financial expenditures;
(g) Records of the involvement of interested parties;
(h) Records of any continuing responsibilities for the site;
(i) Identification of locations that were remediated and those with residual contamination;
(j) Specifications of any areas to which access remains restricted and the restrictions that apply;
(k) Statements of any zoning or covenant restrictions or conditions;
(l) Statements of lessons identified.
5.41. Procedures should be established to ensure that any abnormal conditions relevant to protection and safety are reported to the regulatory body or other relevant authority. Individuals, including workers, should be kept informed and parties affected by the situation should be involved in the planning, implementation and verification of the remedial actions and of any post-remediation monitoring and surveillance. The remediation plan, supported by the prior radiological evaluation, should be submitted to the regulatory body or other relevant authority for approval. Its approval, depending on the circumstances, might involve the issue of an authorization in the form of a registration or licence, as might be
5.41. Procedures should be established to ensure that any abnormal conditions relevant to protection and safety are reported to the regulatory body or other relevant authority. Individuals, including workers, should be kept informed and parties affected by the situation should be involved in the planning, implementation and verification of the remedial actions and of any post-remediation monitoring and surveillance. The remediation plan, supported by the prior radiological evaluation, should be submitted to the regulatory body or other relevant authority for approval. Its approval, depending on the circumstances, might involve the issue of an authorization in the form of a registration or licence, as might be