JOPSS - Search Results

Journal Articles

Evaluation of an ultra-thin plastic scintillator to detect alpha and beta particle contamination

Morishita, Yuki; Hoshi, Katsuya; Torii, Tatsuo

Nuclear Instruments and Methods in Physics Research A, 966, p.163795_1 - 163795_8, 2020/06

https://doi.org/10.1016/j.nima.2020.163795

To date, alpha and high beta particle emitters have been detected in the reactor buildings of the Fukushima Daiichi Nuclear Power Station (FDNPS). Since the beta radiation levels in the FDNPS buildings are extremely high, a commercial beta survey meter, such as a Geiger-Muller (GM) counter, would no longer have the ability to measure the beta contamination levels. In order to solve this issue, we utilized ultra-thin plastic scintillators to increase the detection rate of alpha and beta contamination. In this study, ultra-thin plastic scintillators with varied thicknesses of 7, 22, 24, 31, 39, and 55 um were prepared. To test their sensitivity, each scintillator was optically coupled to a glass plate and a 2-in square position-sensitive photomultiplier tube, and exposed to either an alpha, beta, or gamma source. Results from alpha spectrometry show that only the 55 um-thick plastic scintillator fully absorbed the alpha particles (5.5 MeV) with a 16.7% Full Width at Half Maximum. For alpha imaging under a high beta background, the 7 um-thick plastic scintillator was found to be the best choice, with an alpha to beta ratio of 652. This plastic scintillator also had the lowest sensitivity to beta particles, measuring only 41.74 cps when exposed to a 1 MBq $^{90}$ Sr/ $^{90}$ Y source in contact. It would therefore be possible to use the 7 um-thick plastic scintillator, to directly measure the surface contamination levels at the FDNPS site in real-time, where previous methods have fallen short. Thus, the developed detector would be a useful tool for the detection of alpha and beta contamination in the FDNPS.

Journal Articles

A Remote continuous air monitoring system for measuring airborne alpha contamination

Morishita, Yuki; Usami, Hiroshi; Furuta, Yoshihiro; Aoki, Katsunori; Tsurudome, Koji; Hoshi, Katsuya; Torii, Tatsuo

Radiation Protection Dosimetry, 189(2), p.172 - 181, 2020/04

https://doi.org/10.1093/rpd/ncaa028

Times Cited Count：0 Percentile：0.01(Environmental Sciences)

We developed a remote continuous air monitoring (RCAM) system. The RCAM system consisted of a personal air monitor and a robot. The personal air monitor (poCAMon, SARAD, Germany) had a 400 mm $^{2}$ ion-injected silicon detector and a membrane air filter with 25 mm-diameter. The personal air monitor provides the alpha energy spectra for any measurement time interval. Demonstration measurements were taken underground at the Mizunami Underground Research Laboratory (MIU) and at a poorly ventilated concrete building. The RCAM system was remotely operated and successfully measured the $^{222}$ Rn progeny even though the relative humidity (RH) was almost 100%. In the measured alpha spectra, the peaks of $^{218}$ Po (6.0 MeV alpha) and $^{214}$ Po (7.7 MeV alpha) were clearly identified. Our developed monitor is promising for alpha dust monitoring in a high gamma-ray environment or contaminated areas where a worker cannot safely physically enter.

Journal Articles

Optimization of thickness of GAGG scintillator for detecting an alpha particle emitter in a field of high beta and gamma background

Morishita, Yuki; Yamamoto, Seiichi*; Izaki, Kenji; Kaneko, Junichi*; Hoshi, Katsuya; Torii, Tatsuo

Radiation Measurements, 112, p.1 - 5, 2018/05

https://doi.org/10.1016/j.radmeas.2018.02.003

Times Cited Count：17 Percentile：85.18(Nuclear Science & Technology)

To detect plutonium isotopes ( $^{238}$ Pu, $^{239}$ Pu, and $^{240}$ Pu) in a field of high beta and background, an alpha particle detector with low beta and -ray sensitivity is required. Therefore, we optimized the thickness of the GAGG scintillator for alpha particle detection in a field of high beta and background. We prepared three GAGG scintillators with thicknesses of 0.05 mm, 0.07 mm, and 0.1 mm. Each of the GAGG scintillators was coupled optically to the SiPM array, which was used as the photodetector. Alpha, beta, and rays were irradiated onto the developed alpha particle detector, and their spectra were obtained. All GAGG scintillators used in this study were not sensitive to rays with a dose rate of 1 mSv/h. The beta count of the 0.05-mm-thick GAGG was only 1/100 that of the 0.1-mm-thick GAGG. Therefore, the 0.05-mm-thick GAGG scintillator is promising from the viewpoint of detecting plutonium contamination in a field with high beta and background.

Journal Articles

Beginning of new voyage of nuclear ship 「MUTSU」; Decommissioning of nuclear ship 「MITSU」 and research/development on nuclear ship

; ; Hoshi, Tatsuo; *

Genshiryoku Kogyo, 42(2), p.14 - 55, 1996/00

http://ci.nii.ac.jp/naid/40001074423

no abstracts in English

Journal Articles

Status on development and application of small and medium sized power reactors

Hoshi, Tatsuo

Nihon Genshiryoku Gakkai-Shi, 38(3), p.216 - 218, 1996/00

no abstracts in English

Journal Articles

MRX(marine reactor X)

Hoshi, Tatsuo

Nihon Genshiryoku Gakkai-Shi, 37(9), p.792 - 794, 1995/00

no abstracts in English

Journal Articles

Policy and regulation for decommissioning reactors in Japan

Hoshi, Tatsuo

IAEA-SR-179, 15 Pages, 1992/00

no abstracts in English

Journal Articles

Removal of JPDR biological shield concrete using diamond sawing and coring system

Hoshi, Tatsuo; ; *; *; *; *; *; *

FAPIG, 0(129), p.28 - 32, 1991/11

no abstracts in English

JAEA Reports

High intensity proton accelerator program

Kaneko, Yoshihiko; Mizumoto, Motoharu; ; Nakahara, Yasuaki; Iwamoto, Akira; Funahashi, Satoru; ; Takeda, Tatsuoki; Hoshi, Michio; Shinohara, Nobuo; et al.

JAERI-M 91-095, 137 Pages, 1991/06

JAERI-M-91-095.pdf:4.2MB