Assessing the dose received by the victims of a radiological dispersal device with Geiger-Mueller detectors
Manger, Ryan Paul
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This research investigates the use of G-M counters to triage the individuals who have been exposed to a Radiological Dispersal Device (RDD). Upon being exposed to an RDD, inhalation of the airborne radionuclide is a method which someone can receive a considerable amount of dose. Bioassay via analysis of excreta is a commonly used method of determining the dose received, yet it would be cumbersome if there are a large number of people needing to be screened. An in vivo method must be considered so that a non-intrusive and more efficient triaging method can be implemented. Whole body counters are commonly used in counting facilities as an in vivo bioassay method, yet they are limited in number and not easily portable. Therefore, a more portable and more common detection device should be considered. G-M survey meters are common devices that are highly portable, making them ideal candidates to fulfill this necessity. The ease of use contributes to the viability of the device as a portable, in vivo screening device. To analyze this detector, a Monte Carlo model of the detector was created to be used in simulations with the Medical Internal Radiation Dose phantoms. The detector was placed in a few locations on the phantoms. Four locations were strategically chosen for detector placement: the posterior upper right torso, the anterior upper right torso, the lateral upper thigh, and the anterior of the neck. Six phantoms were considered: Reference Male, Female, Adipose Male, Adipose Female, Post Menopausal Adipose Female, and a Child. Six radionuclides were investigated: Am-241, Co-60, Cs-137, I-131, Ir-192, and Sr-90. The nuclides were distributed throughout the phantoms according to Dose and Risk Calculation Software, a code that determines how a radionuclide is distributed over time upon inhalation, ingestion, or injection. A set of time dependent guidelines were developed, determining the count rate per unit dose inhaled for each detector location and phantom type.