Evaluation of post-accidental rehabilitation strategies

Post-accidental management aims at restoring acceptable life conditions for population on sanitary, social and economic aspects. It is then a matter for an optimisation process in a multicriteria context, which has to combine quantitative parameters as well as qualitative parameters. In order to fit with this problematic a methodological work has been realised at IPSN. The methodology consists in making a systematic evaluation of indicators in order to provide intercomparing data for many rehabilitation strategies. It relies on four steps: characterisation and formalization of the geographic and demographic environment, radiological diagnosis, selection of countermeasures from a well characterised set of techniques, and last, evaluation of the intercomparing factors. The methodology has been applied to the Becquerel national exercise. Rejects were limited and the contaminated area was less than 2000ha. Conclusions proposed depend on this context. For the selected countermeasures, radiological benefit and some incidences have been calculated: duration of realisation of the counter-measure, materials and human means, worker doses, and amount of generated wastes. In this context, calculations highlighted the importance of external exposition in built areas from the first year after the accident, for most of the reference groups. Ingestion is important only the first year for the highly autarkical level reference groups. Consequently, countermeasures applied to built areas, such as washing of sidewalks, of streets and roofs, or such as trees pruning ,are the most effective for the dosimetric criteria. In agricultural zone, taking off vegetation and ploughing enable to strongly reduce specific activity on food products. Reduction by soil removal is more effective. But here, management problems due to the large amount of generated waste could discard this kind techniques. Countermeasures on milk applied the first year reduce by 3 the dose for highly autarkical level groups. Nevertheless, except for this particular case, dosimetric gains by agricultural countermeasures are not significant because of the low part of ingestion in the total dose. This work is a first and useful contribution to the clarification of the post-accidental rehabilitation problem. It has also underscored two important needs: adaptation of calculation tools to make their use easier, and improvement of the knowledge about the operational of the interventions. (author)