Le Centre d’étude sur l’Evaluation de la Protection dans le domaine Nucléaire (CEPN) est une association à but non lucratif, fondée en 1976, pour évaluer la protection de l’homme contre les dangers des rayonnements ionisants, sous ses aspects techniques, sanitaires, économiques et sociaux.
SCHNEIDER T., LOCHARD J.
Veröffentlichung der Strahlenschutzkommission, Band 65, Bundesminsterium für Umwelt, Naturschutz und Reaktorsicherheit, 2010, pp. 31-43.
The long term management of the Chernobyl accident has lead to the emergence of key radiation protection issues. Among them, the selection of dose criteria for implementing different types of countermeasures, notably relocation, was largely debated during the years following the accident. For the population and the experts, the questions to be solved were: is it safe or not to live in contaminated territories? which types of countermeasures can be set up to reduce the individual exposures? how to optimise their implementation in the long term? Beyond the selection of the criteria, the questions were focussed on the issue of "return to normality".
From the management of the Chernobyl accident and based on feedback experiences from other accidental situations, it clearly appears that long term contamination of the environment creates a complex situation where all the dimensions of the daily life of the inhabitants are affected. Furthermore, the presence of contamination has a direct impact on the social and economic activities. In this context, the rehabilitation has to be considered in the perspective of improving the living conditions of the inhabitants and needs to address all the relevant dimensions such as health, environmental, economic, social, psychological, cultural, ethical, political, etc… This creates a new situation and although the reference to normality (or normal exposure situation) remains, it progressively appeared that the future of the contaminated territories would be different from the past situation and had to be envisaged in a long term perspective.
In order to cope with this new perspective and with the new ICRP 103 publication which introduced the concept of "existing exposure situations" (i.e. situations that already exist when a decision on control has to be taken), a report has been prepared and recently endorsed by the Commission on the application of the Commission's recommendations to the protection of individuals living in long term contaminated territories after a nuclear accident or a radiation emergency.
This report analyses in the first part the characteristics of post-accident situations, notably the types of exposed populations, the main exposure pathways, and the strategies developed in the past to cope with the long term contamination. It underlines the large variation of contamination levels generally observed after a nuclear event. Such levels lead to a large range of individual exposures. Furthermore, it is clearly mentioned that the day-to-day life or work in contaminated territories inevitably leads to some exposures. All these characteristics call for favouring the development of a good knowledge of the radiological situation among the affected population in order to facilitate the empowerment of inhabitants and local professionals in the management of the situation, which has proved to be an effective way to improve the rehabilitation process.
In a second part, the report addresses the Commission's principles. The justification of protection strategies corresponds to decision taken toward the end of the emergency exposure situation to allow people to live permanently in the contaminated territories, taking into account psychological, social, economic and political dimensions. In this context, mandatory relocation may be necessary depending on the severity of the accident, and voluntary relocation is always an option, creating a good basis for dealing with long term living conditions in the territories. Concerning optimisation of protection strategies, it is now considered by ICRP as central to the system of protection and has to be applied for existing exposure situations. Therefore, there is no endpoint fixed a priori for this process. Its implementation is a step by step process and needs a constant re-evaluation, notably due to the long term dimension of the post-accidental situation. In addition, a reference level to restrict individual exposures has to be fixed and is considered as the level of dose or risk above which it is judged to be inappropriate to plan to allow exposures to occur and below which optimisation of protection should be implemented. The reference level has to be fixed taking into account the prevailing circumstances of the considered exposure. ICRP recommends to select values for constraining the optimisation process in long term post-accident situations "close or similar” to those used to manage exposure situations considered as normal i.e in the order of 1 mSv per year. Past experience has demonstrated that the value generally used for constraining the optimisation process in long term post-accident situations is 1 mSv per year
In this perspective, the practical aspects of this implementation, both by authorities and the affected population are described in the report, which introduces the distinction between protection actions implemented by authorities and those implemented by the affected persons themselves called self-help protection actions. For the long-term management of the situation, this is the responsibility of the authorities to provide infrastructure and practical guidance for the implementation of these self-help protection actions. As mentioned above, the development of mechanisms for engaging with stakeholders is crucial for the sustainability of the rehabilitation programme.
The following part of the report deals with the radiation monitoring and health surveillance. It is essential that individuals concerned receive general information on the exposure situation and the means of reducing their doses. Due to the large sensitivity of individual exposure according to life-styles, individual monitoring is generally an important requirement. Furthermore, given the uncertainties concerning future potential health effects, the implementation of a radiation and health surveillance programme is needed.
The last part of the report refers to the management of contaminated foodstuffs and other commodities. In fact, long-term restrictions on the consumption of foodstuffs are difficult to maintain and are conflicting with the sustainable development of contaminated territories. The Commission recommends to authorities to set contamination levels (in Bq/kg or Bq/l) below or above the guidelines level of the Codex Alimentarius according the relative importance of local foodstuffs in the diet of the population residing on the territories. In the long-term perspective, there is a need to reconcile the interests of local farmers and the local population with those of consumers and the food distribution sector outside the affected territories.
This new report to be published by ICRP sets up the key principles for rehabilitation of living conditions in contaminated territories. It has to be kept in mind that such a situation is characterised by a variety of dimensions to be considered for defining the rehabilitation strategies. In practice, there is a need to adopt criteria and to develop methods to implement the optimisation of protection strategies and assess the vulnerability of territories to post-accident situations.