Development of a new pinhole camera for imaging in high dose-rate environments

Sueoka, Koki; Kataoka, J.; Takabe, Miho; Iwamoto, Yasuhiro; Arimoto, M.; Yoneyama, Masaki; Yoda, Isao; Torii, Tatsuo; Sato, Yuki; Kaburagi, Masaaki; Terasaka, Yuta

doi:10.1016/j.nima.2017.10.082

Cited by 10 publications

(4 citation statements)

References 5 publications

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“…where 𝐹 is radioactivity in the unit of Bq, 𝐼 is the event fraction of 662 keV gamma rays to the whole decay process of 137 Cs, 𝜀 is the detection efficiency of the YGAG scintillator for 662 keV (𝜀 = 0.24%, considering the scintillator composition, a density of 5 g/cm 3 and thickness of 1 mm), and 𝜃 is the viewing angle of the effective pinhole diameter from the source center. Table 2 shows the radioactivity calculated from the count rate of gamma rays detected by the gamma camera at different distances between the detector and source using equation (3.3).…”

Section: Estimation Of Radioactivitymentioning

confidence: 99%

“…Investigations and various decontamination efforts are underway to decommission the plants [1]. However, decommissioning inside the reactor is complicated because the exact structure of the reactor is unknown; the radiation level inside the reactor is extremely high, with a maximum of at least 100 Sv/h [2,3]. Under these circumstances, locating the radioactive sources to efficiently proceed with the decommissioning work is necessary.…”

Section: Introductionmentioning

confidence: 99%

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Multi-pixel photon counter-based gamma camera with pinhole collimator to locate Cs-137 sources at high dose rates for the Fukushima nuclear power plant

Tomoda,

Arimoto,

Mizuno

et al. 2024

J. Inst.

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The Fukushima Daiichi Nuclear Power Plant was severely damaged during the 2011 Great East Japan Earthquake. However, the ongoing decommissioning work has been limited by the complexity of the reactor's internal structure and very high radiation levels; locating radioactive sources is essential for efficient decommissioning. Conventional gamma cameras are mainly designed for low radiation dose (∼mSv/h) and using them under high radiation conditions is difficult (>Sv/h). Therefore, we developed a pinhole gamma camera with a gamma radiation detector consisting of a high-speed YGAG scintillator array and multi-pixel photon counters to locate radioactive sources at high dose rates. The gamma-ray photon signals captured by the developed two-dimensional detector array can be processed at a speed as high as >1 MHz/pixel using the developed large scale integrated circuit. Herein, we report the measurement results of an extremely high radioactivity of 137Cs (∼34 TBq) using the developed gamma camera. The gamma-ray source position was determined using an angular size of ∼4.6°, with images obtained at 2 m from the radioactive source and at a dose rate of 0.3 Sv/h. The direct gamma rays with a photoelectric peak at 662 keV and scattered component of gamma rays can be distinguished from the measured spectrum. We also characterize the imaging capability of the 137Cs depending on the detected gamma-ray energies and discuss related details.

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Section: Estimation Of Radioactivitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Multi-pixel photon counter-based gamma camera with pinhole collimator to locate Cs-137 sources at high dose rates for the Fukushima nuclear power plant

Tomoda,

Arimoto,

Mizuno

et al. 2024

J. Inst.

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show abstract

“…For the visualization of these radioactive substances, a gamma camera, which can measure a wide range of contamination at once, is promising. To date, several studies on pinhole cameras [3][4][5][6] and Compton cameras [7,8] for the visualization of radioactive substances in nuclear reactor buildings have been carried out. Pinhole cameras tend to be large and heavy because they require extensive shielding, such as lead shielding; however, due to the simplicity of the principle and structure of the device, they offer high quantitative accuracy.…”

Section: Introductionmentioning

confidence: 99%

Optimization of Shape-Variable Gamma Camera to High-Dose-Rate Regions

Miyada,

Takada,

Sato

2023

Electronics

Self Cite

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To proceed with the decommissioning of the Fukushima Daiichi Nuclear Power Station, it is necessary to visualize radioactive substances using a gamma camera in high-dose-rate regions inside a nuclear reactor building. We developed an umbrella-shaped Compton camera, whose sensitivity distribution can be adjusted by changing its shape. When used on a robot, the moving distance of the robot can be reduced compared to a pinhole camera that is sensitive only to the front surface. In addition, unlike an omnidirectional Compton camera, the sensitivity in a specific direction can be increased, which is expected to expand the degree of freedom of measurement. In this study, the characteristics of the developed system were evaluated through simulations and experiments for application in a high-level radioactive environment inside a reactor building. It is estimated that this system can operate at a dose rate of approximately 2.68 mSv/h. Furthermore, we devised a method to compensate for the effect of the dead time of the SiPM (MPPC) in the high-dose-rate region by monitoring the current of the SiPM drive power supply and evaluating its applicability to high dose rates. This correction method was validated in the case where the photoelectric peak of the energy spectra fluctuated by approximately 60 keV due to dead time.

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“…For instance, monitoring equipment, radiation source projects and weakly penetrating radiation during multiple overhauls of nuclear power plants, as well as accident simulations of heavy water reactor nuclear power plants, found that the γ radiation dose rate near the equipment and pipelines of the emergency cooling system of the reactor could exceed several hundred mGy/h [7,8]. In February 2017, the maximum gamma radiation dose rate of Unit 2 of the Fukushima Daiichi Nuclear Power Plant remained at 530 Gy/h [9,10].…”

Section: Introductionmentioning

confidence: 99%

A novel MPPC-based detection method for wide range X/γ radiation dose rate measurement

Zhang

Tong

et al. 2022

J. Inst.

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With the increasing application of nuclear technology in many fields, in order to meet the requirements for the measurement range of nuclear radiation dose rate in different fields, a new X/γ dose rate measurement method is proposed in this paper. Using MPPC to couple CsI(TI) scintillator, combined with continuous periodic charges integration electronics, a detector system was developed. It enables MPPC to work in two different regions, avalanche and proportional, and realizes a wide range of dose rate measurement through gain changes between different regions. In experiments, this method measured the γ radiation dose rate in radiation fields between 0.1 μGy/h to 400 Gy/h 60Co. Additionally, it measured an energy resolution for 137Cs at 9.4% at a dose rate of 1 mGy/h. These results demonstrate that this method is both accurate and feasible.

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Development of a new pinhole camera for imaging in high dose-rate environments

Cited by 10 publications

References 5 publications

Multi-pixel photon counter-based gamma camera with pinhole collimator to locate Cs-137 sources at high dose rates for the Fukushima nuclear power plant

Multi-pixel photon counter-based gamma camera with pinhole collimator to locate Cs-137 sources at high dose rates for the Fukushima nuclear power plant

Optimization of Shape-Variable Gamma Camera to High-Dose-Rate Regions

A novel MPPC-based detection method for wide range X/γ radiation dose rate measurement

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