Proof of concept: Emergency dosimetry in a realistic irradiation scenario using fortuitous dosimeters.

In 2002 a radiological incident occurred in Cochabamba, Bolivia, in which 55 passengers were exposed to ionizing radiation due to a malfunction of an industrial Ir-192 γ-radiography source, which was incidentally transported for repairs as cargo on a passenger bus. The International Atomic Energy Agency (IAEA) reconstructed this incident with a field experiment using TLDs to estimate the personal dose of the bus passengers and workers who handled the source [1]. In the past decade new physical methods for emergency dosimetry have emerged, such as optically stimulated luminescence (OSL) and thermally stimulated luminescence (TL) of so-called fortuitous dosimeters, which can be applied to determine the absorbed dose. If no personal dosimeter is available, mobile phones or other ubiquitous personal belongings, which are carried on or close to the body, can be used as accident dosimeters. This has been investigated by different research groups [2-7]. So far, these investigations were only carried out under laboratory conditions. Within the framework of a European FP7 security research project CATO (CBRN Architecture, Technologies and Operational Procedures) a repetition of the field experiment with a similar bus was carried out, which simulates the Bolivian radiological incident. In this field test, physical methods of retrospective dosimetry were tested and verified in a realistic irradiation scenario using mobile phones as emergency dosimeters, attached to water canisters and anthropomorphic phantoms. The results were compared to measured dose values from dosimeters placed in the mobile phone, TLDs, OSLDs and readouts of electronic personal dosimeters (EPD) fixed close to the mobile phones. The proof of concept affirmed the usability of the tested emergency dosimeter but also demonstrated the limitation of the proposed method. In addition, the experimental values were compared to results of radiation transport calculations using a Monte Carlo code, which simulated the exposure conditions of the emergency dosimeters in the bus on a sufficiently detailed level