Investigation and calibration of various detection systems which can be used for emergency internal contamination checks

Abstract: In the case of a nuclear accident, the release of radioactive substances into the environment may pose a significant threat for the public health. One of the main concerns is radioactive iodine which tends to accumulate in the thyroid causing damage to the gland and increasing the cancer risk. As a result, a thyroid monitoring campaign on large groups of the population, should be an essential part of the emergency response should a nuclear accident ever occur. For this reason, various gamma spectrometers and monitors were calibrated so that they can be part of such a campaign. Neck/thyroid phantoms and vials containing radioactive solutions, simulating contaminated thyroid glands of different age groups, were used in specific geometries in order to study the response of the detection systems and derive their peak efficiency. In addition, the sensitivity of detection was estimated and quality assurance charts for the energy resolution and decay corrected area of certain energy peaks were established. A separate chapter was dedicated to the uncertainties due to anatomical and postural variabilities. Based on the overall results of this study, a technical manual was prepared, including guidelines for the use of these detectors in a rapid monitoring campaign in order to derive the activity of radioiodine in the thyroid gland. Finally, a simple method for triage was presented, including charts of warning and action levels for the present thyroid activity according to critical levels for the committed effective dose.