Spectroscopic gamma camera for use in high dose environments

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• 作者：Yuichiro Ueno^a ; ^{yuichiro.ueno.bv@hitachi.com" class="auth_mail" title="E-mail the corresponding author} ; Isao Takahashi^a ; Takafumi Ishitsu^a ; Takahiro Tadokoro^a ; Koichi Okada^a ; Yasushi Nagumo^a ; Yasutake Fujishima^b ; Yutaka Kometani^b ; Yasuhiko Suzuki^c ; Kikuo Umegaki^d
• 关键词：Gamma camera ; Pinhole collimator ; CdTe detector
• 刊名：Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
• 出版年：2016
• 出版时间：21 June 2016
• 年：2016
• 卷：822
• 期：Complete
• 页码：48-56
• 全文大小：2727 K

文摘

We developed a pinhole gamma camera to measure distributions of radioactive material contaminants and to identify radionuclides in extraordinarily high dose regions (1000 mSv/h). The developed gamma camera is characterized by: (1) tolerance for high dose rate environments; (2) high spatial and spectral resolution for identifying unknown contaminating sources; and (3) good usability for being carried on a robot and remotely controlled. These are achieved by using a compact pixelated detector module with CdTe semiconductors, efficient shielding, and a fine resolution pinhole collimator. The gamma camera weighs less than 100 kg, and its field of view is an 8 m square in the case of a distance of 10 m and its image is divided into 256 (16×16) pixels. From the laboratory test, we found the energy resolution at the 662 keV photopeak was 2.3% FWHM, which is enough to identify the radionuclides. We found that the count rate per background dose rate was 220 cps h/mSv and the maximum count rate was 300 kcps, so the maximum dose rate of the environment where the gamma camera can be operated was calculated as 1400 mSv/h. We investigated the reactor building of Unit 1 at the Fukushima Dai-ichi Nuclear Power Plant using the gamma camera and could identify the unknown contaminating source in the dose rate environment that was as high as 659 mSv/h.