Development of a large-area alpha imaging detector for hand and foot monitors

Abstract

— This paper describes the development of a large-area imaging detector capable of measuring the detailed distribution of alpha particles on hands and feet for use in entry/exit control monitors in decommissioning sites such as the Fukushima Daiichi Nuclear Power Plant. The detector was developed using a commercially available ZnS(Ag) scintillator and an electron multiplying CCD camera. The effectiveness of the detector was evaluated by measuring several types of radiation sources, and the results showed that it was possible to detect the position of alpha particles in a very short time, and contamination levels of up to 11 Bq/cm2 could be visualized. As a result of the minimal detectable surface activity concentration evaluations, 2.0 min or more is required to achieve 4 Bq/cm2, and 25.0 min or more is required to achieve 0.4 Bq/cm2. The field of view of the detector was also checked, and it was confirmed that the setup had a field of view that could cover most of the hand and the sole of the shoe. This detector is expected to be useful for preventing internal uptake and decontamination.