Comments on the TG93 Draft Report for Public Consultation from ICRP

Introduction

The Swedish Radiation Safety Authority (SSM) supports the work by the Commission to improve the recommendations on how to apply the system of radiological protection during large nuclear accidents. SSM therefore welcomes the opportunity to comment on the draft report “Radiological Protection of the People and the Environment in the Event of a Large Nuclear Accident”.

General comments

Phases and exposure situations during a nuclear accident

The Commission distinguishes between emergency response (early and intermediate phase) and the recovery process (long-term phase). The Commission considers emergency response as an emergency exposure situation and the recovery process as an existing exposure situation for implementation of the system of radiological protection. An emergency is a situation requiring urgent actions to mitigate a hazard or adverse consequences for human health and safety, quality of life, property or the environment. An emergency exposure situation is an emergency where the hazard is a radioactive source.

When urgent actions are no longer needed to mitigate a hazard or adverse consequences due to the radioactive source, emergency response, and hence the emergency exposure situation, can be terminated given that conditions applicable to terminating any emergency are fulfilled, e.g. restricting access to hazardous areas. In the opinion of SSM, the time available to plan and implement protective actions is the key parameter for an exposure situation to be considered as an emergency exposure situation. When there is sufficient time to plan and implement protective actions, it is no longer justified to define an exposure situation as an emergency exposure situation. In this respect, emergency response in connection with large nuclear accidents are not different from emergency response in connection with other large scale emergencies. Consider for example an extensive forest fire affecting large areas and many people. When the fire is under control, people have been evacuated and access to dangerous areas is restricted and controlled, the emergency response can be terminated. Administrative decisions on the future of both more and less affected areas are part of the recovery process, not emergency response. The Commission includes administrative decisions on the future of affected areas as part of emergency response for large nuclear accident. In the opinion of SSM, decisions not needed to terminate emergency response should be part of the recovery process.

Furthermore, an emergency exposure situation must be defined with geographical boundaries to be meaningful. The area where there is an ongoing emergency exposure situation is only a part of the total area that can be or is affected by a large nuclear accident. Thus, the transition from an emergency exposure situation to an existing exposure situation can be executed in a step-wise process until the emergency response has been terminated in all areas off-site. In the opinion of SSM, this is not consistently applied by the Commission in the present draft.

The Commissions recommends that evacuees should start to return during the intermediate phase of a large nuclear accident. In the opinion of SSM, however, the return of evacuees will reasonably only take place after emergency response has been terminated and the transition to an existing exposure situation has been completed. It would not be justified for evacuees to return from a safe area to an area with an ongoing emergency exposure situation. This does not exclude that planning for return of evacuees could start during the intermediate phase.

The Commission recommends to start both planning and implementation of decontamination during the intermediate phase of a large nuclear accident. SSM agrees that it is indeed important to plan for decontamination during the intermediate phase. This may include the initiation of projects to evaluate the efficiency of different decontamination methods. However, in the opinion of SSM, it would generally not be justified to start actual decontamination of buildings, roads, open spaces, recreational areas and agricultural land in areas with an ongoing emergency exposure situation. Instead, implementation of decontamination reasonably starts in an area after emergency response has been terminated and the transition to an existing exposure situation has been completed.

The use of reference levels in emergency exposure situations

The key to successfully optimize radiation protection for the public during emergency exposure situations lies in emergency response planning. However, the focus in the draft report instead lies on optimization during emergency response using the reference level as a benchmark against which protection actions can be judged retrospectively. In the opinion of SSM, this approach is difficult to implement in practice. It is unlikely that residual doses incurred by different parts of the public during the early phase can be known or even estimated with a sufficient level of precision to be compared with a reference level during the intermediate phase of the emergency response.

In the opinion of SSM, different approaches in emergency response planning to aid decision makers in optimizing radiation protection for the public during emergency response should be described by the Commission. One such approach would be to use two reference levels with corresponding dose criteria for urgent and early protective actions associated with different release magnitudes. In areas where the projected dose exceeds the higher dose criterion for a protective action, it is prioritized. In areas where the projected dose only exceeds the lower dose criterion for a protective action, it may be justified depending on prevailing circumstances. In areas where the projected dose does not exceed the lower dose criterion for the protective action, it is unlikely to be justified under any circumstances.

The use of reference levels in existing exposure situations

In ICRP Publication 103, the Commission recommends that reference levels for existing exposure situations should be selected within or below the band 1-20 mSv/year effective dose. In ICRP Publication 111, the Commission recommends that a reference level from the lower part of the 1-20 mSv/year effective dose band should be selected to meet the long-term objective “to reduce exposures to levels that are close or similar to situations considered as normal”. In the present draft, the Commission instead recommends that the reference level in existing exposure situations would generally not need to exceed 10 mSv per year, with the objective to reduce exposure progressively to levels on the order of 1 mSv. With this, the Commission in practice introduces a new dose band for existing exposure situations as 1-10 mSv/year effective dose. This may make it more difficult to handle future large nuclear accidents as outlined below. SSM is therefore of the opinion that the present recommendations by the Commission as outlined in ICRP Publication 103 and ICRP Publication 111 should be retained.

A prerequisite for making a transition from an emergency exposure situation to an existing exposure situation is the possibility to set a reference level within the dose band recommended by the Commission valid for the first year of the existing exposure situation. With the recommendations in ICRP Publication 103, this would be possible when a reference level of 20 mSv/year effective dose could be set. However, with the recommendations from the Commission in the present draft, a transition can reasonably not take place until it is possible to set a reference level of 10 mSv/year effective dose.

To support the new recommendation, the Commission argues that consecutive annual exposures of the order of 10 mSv during the first years of the recovery process, added to exposure received during the emergency response, could lead to total exposures greater than 100 mSv in a relatively short period of time for some affected people. However, to avoid such an outcome, focus should be on developing a protection strategy for emergency response that facilitates optimization and that is proactive rather than reactive. Furthermore, the situation described by the Commission is unlikely to occur. Instead, decay and natural weathering processes will most probably lead to a relatively fast reduction in exposure levels during the first years following the end of the release.

The Commission does not recommend any specific value for a radiation protection criterion above which it is mandatory to relocate the population permanently, and below which inhabitants are allowed to stay subject to the implementation of protective actions. However, it is likely that such a dose criterion will be set at the same level as the reference level taking only exposure from ground contamination into account. The dominating pathways in existing exposure situations is intake via contaminated food and exposure to ground contamination. The intake from contaminated food is likely to be restricted to be below 1 mSv/year effective dose by regulation and control measures. This leaves, in practice, only exposure from ground contamination. It is, however, unlikely that a dose criterion allowing people to stay permanently in an area would include restrictive protective actions to reduce the exposure from ground contamination.

Emergency responders

The Commission recommends to treat all workers involved in both emergency response and the recovery process as emergency responders. SSM recognizes that it may be difficult to differentiate between workers and the public during emergency response and the recovery process. Despite this, SSM is of the opinion that a clear distinction between workers and the public should be retained when applying the system of radiological protection in large nuclear accidents.

In emergency exposure situations, the Commissions recommends using a reference level for emergency workers at or below 100 mSv effective dose during the early phase of the emergency response. The Commission should, in the opinion of SSM, clarify that the reference level for emergency workers in emergency exposure situations should, when feasible, be set at or below a value equal to the dose limit. Emergency workers should, to the extent possible, be protected at the same level during emergency exposure situations as during planned occupational exposure. Furthermore, the Commission mentions informed consent in the draft report, but does not discuss at what level of residual dose an emergency worker should have the right to refuse to perform a task during an emergency exposure situation. In ICRP Publication 96 (85), the Commission states that “Under conditions that may lead to doses above normal occupational exposure limits, workers should be volunteers…”. The present standpoint by the Commission is not clear from the draft. SSM is of the opinion that the responsibility of the organisation with the authority to handle the emergency response not to set higher reference levels than necessary, as well as the right of an emergency worker to refuse to perform a task during emergency exposure situations at some level of residual dose, are important ethical questions that should be more extensively discussed by the Commission as they may have implications for both planning and executing emergency response.

In the opinion of SSM, members of the public may participate in emergency response, but either they fall under the responsibility of an organisation with the authority to handle the emergency response and therefore should be treated as emergency workers or they take their own initiatives and should then be treated as members of the public.

In the present draft, the Commission recommends to treat workers who are involved in the recovery process and who have assignments where they may be exposed as emergency responders and use reference levels as a tool for optimisation. In ICRP Publication 103, the Commission states that “Exposures resulting from long-term remediation operations or from protracted employment in affected areas should be treated as part of planned occupational exposure, even though the source of radiation is ‘existing’”. SSM questions the ethical foundation to change this recommendation. Workers involved in decontamination following a large nuclear accident would generally be employed by companies procured by the state. These workers should reasonably be treated as part of planned occupational exposure, as previously recommended by the Commission. The situation is well under control, projected doses can be estimated with reasonable precision and, even though there is a strong interest in finalizing decontamination, it is not urgent enough to motivate a lower level of protection than applied during planned occupational exposure situations.

In the opinion of SSM, workers not taking part in the recover process who, as a result of their occupation, are exposed in existing exposure situation should in general be treated as members of the public. However, some of those workers may be exposed to such levels that they instead should be treated in the same manner as workers in dwellings with high concentrations of Radon.

Estimating health risks for exposed persons

The right of individuals exposed in a large nuclear accident to be informed about the incurred health risks associated with the exposure is not mentioned by the Commission in the present draft. In large nuclear accidents, this is likely a complex task. It is usually not possible to estimate radiation doses and health risks on an individual level and the uncertainties may be considerable. Despite these difficulties, it is the opinion of SSM that estimating health risks for the exposed population, as detailed as circumstances allow, is a fundamental task in the recovery process which should be described by the Commission.        

Detailed comments