Ex vivo ESR measurements associated with Monte Carlo calculations for accident dosimetry: application to the 2001 Georgian accident.
Isabelle Clairand, François Trompier, Jean-François Bottollier-Depois and Patrick Gourmelon, 14th International conference on solid state dosimetry, 27/06-02/07/2004, Yale, USA.
In case of radiological accident, the dose distribution within the body of the victim can be assessed by physical means based on ESR measurements performed on biological samples associated with Monte Carlo simulations. One of the difficulties of the dose reconstruction using only numerical tools lies in the lack of reliable knowledge of the scenario of the accident usually based on incomplete testimonies. Typically, the uncertainty on the exposure time is often very high. Hence, Monte Carlo calculations can only provide a dose distribution per unit of time. When it is possible, the information given by ex vivo ESR measurements performed on victim biological materials such as teeth or bone samples are very useful since they are objective data obtained without having to know the exact circumstances of the accident. Nevertheless, such a technique is able to give dose information only for the locations corresponding to the studied samples. Consequently, ESR data are complementary to Monte Carlo simulations as a normalization tool. These two techniques were applied successfully in the case of the accident which occurred on December 2nd 2001 in Georgia: three persons were exposed to two very-high-activity (2.6 1015 Bq) Strontium-90 sources. Following this exposure, the two most affected victims exhibited severe radiological injuries localised in the back as well as a haematopoietic syndrome. The information concerning the circumstances of the accident were not clearly established. The physical dose reconstruction of the accident was performed on one victim treated in France using, on the one hand, ESR measurements on samples of vertebrae and ribs removed for medical reasons and, on the other hand, Monte Carlo calculations. The complementarity of the two tools allowed to estimate the dose distribution in the tissue with a satisfying accuracy and helped the treatment strategy development.