A new thyroid monitor using multiple high resolution Gd3(Al, Ga)5O12(Ce) detectors for direct thyroid measurements of small children following a nuclear accident. (April 2020)

• Record Type: Journal Article
• Authors: Yajima, Kazuaki; Kim, Eunjoo; Tani, Kotaro; Kurihara, Osamu
• Is Part Of: Radiation measurements. Volume 133(2020:Feb.)
• Publication Date: 2020-04
• Subjects: Thyroid monitor -- Nuclear accident -- HR-GAGG -- Radioiodine; Nuclear emulsions -- Periodicals; Particle tracks (Nuclear physics) -- Periodicals; Thermoluminescence -- Periodicals; Cosmic rays -- Periodicals; Radiation -- Measurement -- Periodicals; Radiometry -- Periodicals; Radiation Monitoring -- Periodicals; Émulsions nucléaires -- Périodiques; Particules (Physique nucléaire) -- Traces -- Périodiques; Thermoluminescence -- Périodiques; Rayonnement cosmique -- Périodiques; Radiométrie -- Périodiques; 539.77
• DOI: 10.1016/j.radmeas.2020.106272
• Languages: English
• ISSNs: 1350-4487

Abstract

Abstract: We developed a new thyroid monitor using multiple high energy resolution Gd3 (Al, Ga)5 O12 (Ce) (HR-GAGG) detectors (each crystal size = 1-cm 3 ), in particular with an intention of measuring small children (including infants) for their internal thyroid exposure from radioiodine following a nuclear accident. The small-sized HR-GAGG detectors allowed to be placed around the human neck at the close distance to increase the geometrical efficiency for 131 I localized in the thyroid. We tested two arrangements of the eight HR-GAGG detectors using four age-specific phantoms in each of which a thyroid-shaped container filled with standard 131 I solution was installed. The results demonstrated that the minimum detectable activity (MDA) of the new monitor reached 20–30 Bq with a counting time of 180 s, which is significantly lower than that of a conventional NaI(Tl) survey meter (crystal size: 1-inch-dia, 1-inch-thick) commonly used for measuring air dose rates. Highlights: We designed and tested a new thyroid monitor that uses multiple HR-GAGG detectors. The new monitor has higher sensitivity than the conventional NaI(Tl) survey meter used for measuring air dose rates. The feasibility of the new monitor was confirmed through experiments.