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Journal Articles

Estimation of external dose for wild Japanese macaques captured in Fukushima prefecture; Decomposition of electron spin resonance spectrum

Mitsuyasu, Yusuke*; Oka, Toshitaka; Takahashi, Atsushi*; Kino, Yasushi*; Okutsu, Kenichi*; Sekine, Tsutomu*; Yamashita, Takuma*; Shimizu, Yoshinaka*; Chiba, Mirei*; Suzuki, Toshihiko*; et al.

Radiation Protection Dosimetry, 199(14), p.1620 - 1625, 2023/09

We have been conducting dose assessments for Japanese macaques captured in Fukushima to reveal radiobiological effects on the low-dose expose animals. To accurately determine the external exposure dose, it is desirable to examine the analysis of the CO$$_{2}^{-}$$ radical intensity. We examined ESR spectra of teeth of 10 macaques captured in Fukushima by two spectrum-decomposition algorithms.

Journal Articles

A Study on accuracy of analysis of the radiation-induced component in the ESR spectra of teeth

Mitsuyasu, Yusuke*; Oka, Toshitaka; Takahashi, Atsushi*; Kino, Yasushi*; Okutsu, Kenichi*; Sekine, Tsutomu*; Yamashita, Takuma*; Shimizu, Yoshinaka*; Chiba, Mirei*; Suzuki, Toshihiko*; et al.

KEK Proceedings 2022-2, p.120 - 125, 2022/11

We investigate the effect of sample's anisotropy and measurement condition to obtain the higher reproducibility for the shape of the ESR spectrum and the intensity of CO$$_{2}^{-}$$ radical.

Journal Articles

Radiation exposure and oxidative stress status of wild Japanese macaques in the ex-evacuation zone of the Fukushima Daiichi Nuclear Power Plant accident

Ishikawa, Ryoya*; Suzuki, Masatoshi*; Kino, Yasushi*; Endo, Satoru*; Nakajima, Hiroo*; Oka, Toshitaka; Takahashi, Atsushi*; Shimizu, Yoshinaka*; Suzuki, Toshihiko*; Shinoda, Hisashi*; et al.

KEK Proceedings 2022-2, p.61 - 66, 2022/11

The balance between oxidative stress and antioxidant activity, which is a defense mechanism against oxidative stress, was investigated in the liver and bladder of wild Japanese macaques captured in Fukushima Prefecture. No significant induction of oxidative stress by exposure to environmental radionuclides after the Fukushima nuclear accident was observed, suggesting that the stress defense mechanism of the organism is activated in some organs.

Journal Articles

Detection limit of electron spin resonance for Japanese deciduous tooth enamel and density separation method for enamel-dentine separation

Oka, Toshitaka; Takahashi, Atsushi*; Koarai, Kazuma; Kino, Yasushi*; Sekine, Tsutomu*; Shimizu, Yoshinaka*; Chiba, Mirei*; Suzuki, Toshihiko*; Osaka, Ken*; Sasaki, Keiichi*; et al.

Journal of Radiation Research (Internet), 63(4), p.609 - 614, 2022/07

 Times Cited Count:0 Percentile:0.01(Biology)

Electron spin resonance (ESR) dosimetry is one of the most powerful tools for radiation dose reconstruction. The detection limit of this technique using human teeth is reported to be 56 mGy or 67 mGy; however, the absorbed dose of Fukushima residents after the Fukushima Daiichi Nuclear Power Plant (FNPP) accident was estimated to be lower than this detection limit. Our aim is to assess the absorbed radiation dose of children in Fukushima Prefecture after the accident; therefore, it is important to estimate the detection limit for their teeth. The detection limit for enamel of deciduous teeth of Japanese children separated by the mechanical method is estimated to be 115.0 mGy. The density separation method can effectively separate enamel from third molars of Japanese people. As we have collected thousands of teeth from children in Fukushima, the present technique may be useful to examine their external absorbed dose after the FNPP accident.

Journal Articles

Bayesian sparse modeling of extended X-ray absorption fine structure to determine interstitial oxygen positions in yttrium oxyhydride epitaxial thin film

Kumazoe, Hiroyuki*; Igarashi, Yasuhiko*; Iesari, F.*; Shimizu, Ryota*; Komatsu, Yuya*; Hitosugi, Taro*; Matsumura, Daiju; Saito, Hiroyuki*; Iwamitsu, Kazunori*; Okajima, Toshihiko*; et al.

AIP Advances (Internet), 11(12), p.125013_1 - 125013_5, 2021/12

 Times Cited Count:1 Percentile:9.56(Nanoscience & Nanotechnology)

Journal Articles

PSTEP: Project for solar-terrestrial environment prediction

Kusano, Kanya*; Ichimoto, Kiyoshi*; Ishii, Mamoru*; Miyoshi, Yoshizumi*; Yoden, Shigeo*; Akiyoshi, Hideharu*; Asai, Ayumi*; Ebihara, Yusuke*; Fujiwara, Hitoshi*; Goto, Tadanori*; et al.

Earth, Planets and Space (Internet), 73(1), p.159_1 - 159_29, 2021/12

 Times Cited Count:6 Percentile:57.72(Geosciences, Multidisciplinary)

The PSTEP is a nationwide research collaboration in Japan and was conducted from April 2015 to March 2020, supported by a Grant-in-Aid for Scientific Research on Innovative Areas from the Ministry of Education, Culture, Sports, Science and Technology of Japan. It has made a significant progress in space weather research and operational forecasts, publishing over 500 refereed journal papers and organizing four international symposiums, various workshops and seminars, and summer school for graduate students at Rikubetsu in 2017. This paper is a summary report of the PSTEP and describes the major research achievements it produced.

Journal Articles

Development of dose estimation method using wild animal teeth for low dose exposure

Mitsuyasu, Yusuke*; Oka, Toshitaka; Takahashi, Atsushi*; Koarai, Kazuma; Kino, Yasushi*; Okutsu, Kenichi*; Sekine, Tsutomu*; Yamashita, Takuma*; Shimizu, Yoshinaka*; Chiba, Mirei*; et al.

KEK Proceedings 2021-2, p.91 - 96, 2021/12

We examined whether the ESR dose estimation method could be applied to wild Japanese macaque. In this work, we investigated the enamel preparation protocol and the analytical method of the ESR spectra.

Journal Articles

Rapid analysis of $$^{90}$$Sr in cattle bone and tooth samples by inductively coupled plasma mass spectrometry

Koarai, Kazuma; Matsueda, Makoto; Aoki, Jo; Yanagisawa, Kayo*; Terashima, Motoki; Fujiwara, Kenso; Kino, Yasushi*; Oka, Toshitaka; Takahashi, Atsushi*; Suzuki, Toshihiko*; et al.

Journal of Analytical Atomic Spectrometry, 36(8), p.1678 - 1682, 2021/08

 Times Cited Count:3 Percentile:42.8(Chemistry, Analytical)

Rapid analysis of $$^{90}$$Sr in bone and tooth samples of cattle were achieved by an inductively coupled plasma mass spectrometry (ICP-MS) coupled with mass shift and solid phase extraction techniques. Limit of detection (LOD) in the ICP-MS measurement of 0.1 g samples was lower than that of the radioactivity measurement. Analytical time of the ICP-MS method was reduced from 20 days to 11 hours, compared with the radiometric method. Therefore, the ICP-MS method can be rapid and useful procedure of $$^{90}$$Sr in small bone and tooth samples derived from terrestrial animals.

Journal Articles

Radioactivity and radionuclides in deciduous teeth formed before the Fukushima-Daiichi Nuclear Power Plant accident

Takahashi, Atsushi*; Chiba, Mirei*; Tanahara, Akira*; Aida, Jun*; Shimizu, Yoshinaka*; Suzuki, Toshihiko*; Murakami, Shinobu*; Koarai, Kazuma; Ono, Takumi*; Oka, Toshitaka; et al.

Scientific Reports (Internet), 11(1), p.10355_1 - 10355_11, 2021/05

 Times Cited Count:5 Percentile:40.82(Multidisciplinary Sciences)

Journal Articles

External exposure dose estimation by electron spin resonance technique for wild Japanese macaque captured in Fukushima Prefecture

Oka, Toshitaka; Takahashi, Atsushi*; Koarai, Kazuma; Mitsuyasu, Yusuke*; Kino, Yasushi*; Sekine, Tsutomu*; Shimizu, Yoshinaka*; Chiba, Mirei*; Suzuki, Toshihiko*; Osaka, Ken*; et al.

Radiation Measurements, 134, p.106315_1 - 106315_4, 2020/06

 Times Cited Count:4 Percentile:48.93(Nuclear Science & Technology)

The relationship between the CO$$_{2}$$ radical intensity and the absorbed dose (dose response curve) of tooth enamel of Japanese macaque was observed by electron spin resonance and the detection limit of our system was estimated to be 33.5 mGy, which is comparable to the detection limit for human molar teeth. Using the dose response curve, external exposure dose for seven wild Japanese macaques captured in Fukushima prefecture were examined. The results suggest that the external exposure dose for the wild Japanese macaques were ranged between 45 mGy to 300 mGy.

Journal Articles

High spatial resolution ZnO scintillator for an in situ imaging device in EUV region

Arita, Ren*; Nakazato, Tomoharu*; Shimizu, Toshihiko*; Yamanoi, Kohei*; Empizo, M.*; Hori, Tatsuhiro*; Fukuda, Kazuhito*; Minami, Yuki*; Sarukura, Nobuhiko*; Maruyama, Momoko; et al.

Optical Materials, 36(12), p.2012 - 2015, 2014/10

 Times Cited Count:8 Percentile:42.63(Materials Science, Multidisciplinary)

A single shot image of a ZnO crystal excited by the EUV laser of Kansai Photon Science Institute was captured. The evaluated EUV beam waist radii from the ZnO emission pattern along the horizontal and vertical axes are 5.0 and 4.7$$mu$$m, respectively. The expected focal spot size of EUV laser and the spatial resolution of the magnifier (including the Schwarzschild objectives and lenses) are however 1 and 4$$mu$$m, respectively. The discrepancy on the spatial resolutions is attributed to exciton diffusion. We estimated the ZnO exciton diffusion length from the effective decay time which is shortened by exciton-exciton collision quenching and which is dependence on excitation energy density. Our results indicate that the short lifetime of ZnO is required to improve the spatial resolution.

Journal Articles

Evaluation of soft X-ray laser with ${it in situ}$ imaging device of high spatial resolution ZnO scintillator

Nakazato, Tomoharu*; Shimizu, Toshihiko*; Yamanoi, Kohei*; Sakai, Kohei*; Takeda, Kohei*; Nishi, Ryosuke*; Minami, Yuki*; Cadatal-Raduban, M.*; Sarukura, Nobuhiko*; Nishimura, Hiroaki*; et al.

Japanese Journal of Applied Physics, 50(12), p.122202_1 - 122202_4, 2011/12

 Times Cited Count:9 Percentile:38.42(Physics, Applied)

We demonstrate the potential of a hydrothermal method-grown ZnO as a high-spatial resolution imaging device for in-situ soft X-ray laser diagnostics by characterizing the exciton emission patterns. By plotting the emission pattern radii at each position, we estimated the evolution of the beam radius around the focal point. The beam profile of the Ni-like Ag ion plasma laser was estimated from the waist radii as 29 and 21$$mu$$m, the divergence angle as 7.2 and 11 mrad and the M2 factor as 47 and 50 in the horizontal- and vertical-axis, respectively. Spatial resolution of the magnifier was estimated to be 6$$mu$$m and is expected to improve by optimizing the optics of the magnifier and using a telescope. Our results would enhance the use of ZnO as an imaging device that would play a crucial role in the development and application of soft X-ray light sources.

Journal Articles

Evaluation of ZnO fast scintillator spatial resolution using the FZP-focused X-ray laser

Tanaka, Momoko; Nakazato, Tomoharu*; Shimizu, Toshihiko*; Yamanoi, Kohei*; Sakai, Kohei*; Sarukura, Nobuhiko*; Nishikino, Masaharu; Oba, Toshiyuki; Kaihori, Takeshi; Ochi, Yoshihiro; et al.

JAEA-Conf 2011-001, p.126 - 128, 2011/03

The spatial resolution of hydrothermal method grown zinc oxide (ZnO) scintillator was evaluated using X-ray laser focused with Fresnel zone plate. The fluorescence image of the ZnO scintillator was measured to be less than 10um using CCD camera coupled with a Schbartzchild expander mirror. The availability of large size ZnO crystal up to 3-inch is quite attractive for future lithography and imaging applications.

Journal Articles

X-ray imaging by using ZnO crystal

Sarukura, Nobuhiko*; Nakazato, Tomoharu*; Shimizu, Toshihiko*; Yamanoi, Kohei*; Sakai, Kohei*; Ehrentraut, D.*; Fukuda, Tsuguo*; Tanaka, Momoko; Nishikino, Masaharu; Kawachi, Tetsuya

Reza Kenkyu, 39(3), p.193 - 196, 2011/03

Development of light sources in the soft X-ray/X-ray region, such as laser induced plasma emission and XFEL, is in demand for applications in various fields of science, medicine, and industry, among others. To promote this endeavor, development of imaging devices as diagnostic tools in this wavelength region is required. ZnO is a prominent candidate material for high spatial and temporal resolution imaging devices because of its emission at 380 nm, lifetime of less than 1 ns, and availability of large and cheap but high quality crystals. We obtained a single shot image of ZnO emission pattern excited by an X-ray laser at the Advanced Photon Research Center, Japan Atomic Energy Agency. The spatial resolution was estimated to be around 10 $$mu$$m. This result shows that ZnO can be used as a powerful imaging device for applications such as EUV lithography.

JAEA Reports

Conceptual design of the SlimCS fusion DEMO reactor

Tobita, Kenji; Nishio, Satoshi*; Enoeda, Mikio; Nakamura, Hirofumi; Hayashi, Takumi; Asakura, Nobuyuki; Uto, Hiroyasu; Tanigawa, Hiroyasu; Nishitani, Takeo; Isono, Takaaki; et al.

JAEA-Research 2010-019, 194 Pages, 2010/08


This report describes the results of the conceptual design study of the SlimCS fusion DEMO reactor aiming at demonstrating fusion power production in a plant scale and allowing to assess the economic prospects of a fusion power plant. The design study has focused on a compact and low aspect ratio tokamak reactor concept with a reduced-sized central solenoid, which is novel compared with previous tokamak reactor concept such as SSTR (Steady State Tokamak Reactor). The reactor has the main parameters of a major radius of 5.5 m, aspect ratio of 2.6, elongation of 2.0, normalized beta of 4.3, fusion out put of 2.95 GW and average neutron wall load of 3 MW/m$$^{2}$$. This report covers various aspects of design study including systemic design, physics design, torus configuration, blanket, superconducting magnet, maintenance and building, which were carried out increase the engineering feasibility of the concept.

Journal Articles

Compact DEMO, SlimCS; Design progress and issues

Tobita, Kenji; Nishio, Satoshi; Enoeda, Mikio; Kawashima, Hisato; Kurita, Genichi; Tanigawa, Hiroyasu; Nakamura, Hirofumi; Honda, Mitsuru; Saito, Ai*; Sato, Satoshi; et al.

Nuclear Fusion, 49(7), p.075029_1 - 075029_10, 2009/07

 Times Cited Count:135 Percentile:97.77(Physics, Fluids & Plasmas)

Recent design study on SlimCS focused mainly on the torus configuration including blanket, divertor, materials and maintenance scheme. For vertical stability of elongated plasma and high beta access, a sector-wide conducting shell is arranged in between replaceable and permanent blanket. The reactor adopts pressurized-water-cooled solid breeding blanket. Compared with the previous advanced concept with supercritical water, the design options satisfying tritium self-sufficiency are relatively scarce. Considered divertor technology and materials, an allowable heat load to the divertor plate should be 8 MW/m$$^{2}$$ or lower, which can be a critical constraint for determining a handling power of DEMO (a combination of alpha heating power and external input power for current drive).

Journal Articles

Hydrothermal-method-grown ZnO single crystal as fast EUV scintillator for future lithography

Nakazato, Tomoharu*; Furukawa, Yusuke*; Tanaka, Momoko; Tatsumi, Toshihiro*; Nishikino, Masaharu; Yamatani, Hiroshi*; Nagashima, Keisuke; Kimura, Toyoaki*; Murakami, Hidetoshi*; Saito, Shigeki*; et al.

Journal of Crystal Growth, 311(3), p.875 - 877, 2009/01

 Times Cited Count:24 Percentile:86.32(Crystallography)

The temperature dependence of scintillation properties of a hydrothermal-method-grown zinc oxide (ZnO) emission is investigated using a nickel-like silver laser emitting at 13.9 nm. A broad peak at 386 nm with a full-width at half-maximum (FWHM) of 15 nm at room temperature (298 K) is obtained. The peak position tends to be blue shifted while the FWHM becomes narrower when the crystal temperature is decreased to 25 K. Streak images fitted by a double exponential decay reveal that the measured emission decay at 105 K was $$tau$$$$_{1}$$ = 0.88 ns and $$tau$$$$_{2}$$ = 2.7 ns. This decay time of a few nanoseconds is suitable for lithographic applications and is sufficiently short for the characterization of laser plasma extreme ultraviolet (EUV) sources with nanosecond durations.

Journal Articles

Time-resolved fluorescence spectrum of wide-gap semiconductors excited by 13.9 nm X-ray laser

Tanaka, Momoko; Furukawa, Yusuke*; Nakazato, Tomoharu*; Tatsumi, Toshihiro*; Murakami, Hidetoshi*; Shimizu, Toshihiko*; Sarukura, Nobuhiko*; Nishikino, Masaharu; Kawachi, Tetsuya; Kagamitani, Yuji*; et al.

X-Ray Lasers 2008; Springer Proceedings in Physics, Vol.130, p.501 - 505, 2009/00

We measured the time-resolved fluorescence spectra of ZnO and GaN single crystals excited by an X-ray laser operating at 13.9 nm and evaluated their scintillation properties for EUV excitation as compared with UV excitation case. For ZnO, a clear fluorescence peak of excitonic origin was observed at around 380 nm and the decay lifetime of less than 3 ns is found to be almost similar to the UV excitation case. The fluorescence at 380 nm is ideal for scintillator device design in the EUV and further applications. For GaN, the lifetimes are much longer than ZnO and the temporal profile of the EUV-excited fluorescence differs with the UV excitation case. As such, the EUV scintillation properties of ZnO is said to be more favorable than GaN. Finally, it is also demonstrated that an X-ray laser is an excellent tool for spectroscopic characterization of materials intended for next-generation lithography applications.

JAEA Reports

Report of investigation on malfunction of reserved shutdown system in HTTR

Hamamoto, Shimpei; Iigaki, Kazuhiko; Shimizu, Atsushi; Sawahata, Hiroaki; Kondo, Makoto; Oyama, Sunao; Kawano, Shuichi; Kobayashi, Shoichi; Kawamoto, Taiki; Suzuki, Hisashi; et al.

JAEA-Technology 2006-030, 58 Pages, 2006/03


During normal operation of High Temperature engineering Test Reactor (HTTR) in Japan Atomic Energy Agency (JAEA), the reactivity is controlled by the Control Rods (CRs) system which consists of 32 CRs (16 pairs) and 16 Control Rod Drive Mechanisms (CRDMs). The CR system is located in stand-pipes accompanied by the Reserved Shutdown System (RSS). In the unlikely event that the CRs fail to be inserted, the RSS is provided to insert B$$_{4}$$C/C pellets into the core. The RSS shall be designed so that the reactor should be held subcriticality from any operation condition by dropping in the pellets. The RSS consists of B$$_{4}$$C/C pellets, hoppers which contain the pellets, electric plug, driving mechanisms, guide tubes and so on. In accidents when the CRs cannot be inserted, an electric plug is pulled out by a motor and the absorber pellets fall into the core by gravity. A trouble, malfunction of one RSS out of sixteen, occurred during a series of the pre-start up checks of HTTR on February 21, 2005. We investigated the cause of the RSS trouble and took countermeasures to prevent the issue. As the result of investigation, the cause of the trouble was attributed to the following reason: In the motor inside, The Oil of grease of the multiplying gear flowed down from a gap of the oil seal which has been deformed and was mixed with abrasion powder of brake disk. Therefore the adhesive mixture prevented a motor from rotating.

Oral presentation

Overhaul of reserved shutdown system in HTTR

Shimizu, Atsushi; Hamamoto, Shimpei; Kobayashi, Shoichi; Ishii, Yoshiki; Iigaki, Kazuhiko; Inoi, Hiroyuki; Kawamoto, Taiki; Mizushima, Toshihiko; Nakazawa, Toshio

no journal, , 

no abstracts in English

38 (Records 1-20 displayed on this page)