Jun 25 – 29, 2023
Ole-Johan Dahls Hus
Europe/Oslo timezone

P1.4: MPPC-based gamma camera with pinhole collimator to locate Cs-137 sources at high doses for the Fukushima nuclear power plant

Jun 26, 2023, 2:48 PM
Ole-Johan Spiseri (Ole-Johan Dahls Hus)

Ole-Johan Spiseri

Ole-Johan Dahls Hus

Ole Johan Dahls Hus - Oslo Science Park Gaustadalléen 23B, 0373 Oslo


Mr Takahiro Tomoda (Kanazawa University)


The Fukushima Daiichi Nuclear Power Plant was severely damaged during the 2011 Great east Japan earthquake. Currently, investigations and various decontamination efforts are underway to de-commission the plants. However, it is difficult to perform decommissioning inside the reactor because the exact structure of the reactor is not yet known; the radiation level inside the reactor is extremely high, with a maximum of approximately 100 Sv/h. Under these circumstances, it is necessary to locate the radioactive sources to proceed with the work efficiently. Therefore, we developed a pinhole gamma camera consisting of a high-speed scintillator array (YGAG with a decay time of ~70 ns, Proterial Ltd.) and multi-pixel photon counters (MPPCs) that can detect individual gamma-ray photons to locate radioactive sources at high dose rates (~100 Sv/h). In this presentation, we report the system of the developed gamma camera and the measurement results of an extremely high dose of 137Cs (34 TBq) using the developed gamma camera. The gamma ray source position was determined with an angular size of ~4.5° at 2-m distance from the radiation source (~0.3 Sv/h). The direct gamma rays with a photoelectric peak at 662 keV and scattered gamma rays can be discriminated from the measured spectrum. We will also show that the imaging capability of the 137Cs depends on the detected gamma ray energies and the discussed details.

Primary author

Mr Takahiro Tomoda (Kanazawa University)


Mr Daichi Sato (Kanazawa University) Prof. Jun Kataoka (Waseda University) Dr Junya Ishii (National Institute of Advanced Industrial Science and Technology) Dr Makoto Arimoto (Kanazawa University) Dr Masahiro Kato (National Institute of Advanced Industrial Science and Technology) Mr Satoshi Shiota (Proterial Ltd) Mr Shinsuke Terazawa (Proterial Ltd) Mr Tomoya Mizuno (Kanazawa University)

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