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Journal Articles

Analytical technique for isotope composition of nuclear micro particles

Miyamoto, Yutaka; Suzuki, Daisuke; Tomita, Ryohei; Tomita, Jumpei; Yasuda, Kenichiro

Isotope News, (786), p.22 - 25, 2023/04

no abstracts in English

Journal Articles

Variation of crystallinity and secondary ion quantity of uranium particles with heating temperature of Sample preparation

Tomita, Ryohei; Tomita, Jumpei; Yomogida, Takumi; Suzuki, Daisuke; Yasuda, Kenichiro; Esaka, Fumitaka; Miyamoto, Yutaka

KEK Proceedings 2022-2, p.108 - 113, 2022/11

Automated Particle Measurement (APM) is the first measurement of environmental sample for safeguard purpose. APM tells us the number of particles in sample, their enrichment and their location. Precision and accuracy of APM is easily affected by particle condition. We have investigated how influential baking temperature in sample preparation are for uranium secondary ion quantity, uranium hydride generation and particle crystallinity. Our experimental results showed that baking temperature of 800$$^{circ}$$C reduced uranium secondary ion quantity to 33% compared with baking at 350$$^{circ}$$C. Uranium hydride generation ratio of the sample baked at 850$$^{circ}$$C was also 4 times higher than the sample baked at 350$$^{circ}$$C. Baking at 850$$^{circ}$$C raised only crystallinity of uranium particles. Baking sample at too high temperature caused less uranium secondary ion generation and much more uranium hydride generation. It made precision and accuracy of APM worse. In our experiment, baking at 350$$^{circ}$$C is suitable for uranium particles in the safeguards sample.

Journal Articles

Preparation of the particles containing isotope reference uranium for the determination of the low abundant U isotope ratios

Tomita, Jumpei; Tomita, Ryohei; Suzuki, Daisuke; Yasuda, Kenichiro; Miyamoto, Yutaka

KEK Proceedings 2022-2, p.154 - 158, 2022/11

Precise determination of minor U isotopes ($$^{233}$$U and $$^{236}$$U) of particles from the safeguard environmental samples is powerful method for detecting the undeclared nuclear activities. In this study, preparation method of U particle was examined to utilize for the minor U isotope determination. The porous silica particles were used as the particle matrix and lutetium was mixed to the impregnation solution as U impregnation indicator for the particle picking. The result of the Scanning Electron Microscope indicated that the contacting the solution with Si particles overnight gently could produce the impregnated particles effectively rather than the mixing them with PFA stick.

Journal Articles

Optimization of SIMS-APM for high enrichment uranium particles including higher uranium hydride

Tomita, Ryohei; Tomita, Jumpei; Yomogida, Takumi; Suzuki, Daisuke; Yasuda, Kenichiro; Esaka, Fumitaka; Miyamoto, Yutaka

KEK Proceedings 2021-2, p.146 - 150, 2021/12

no abstracts in English

Journal Articles

Age determination analysis of a single uranium particle for safeguards

Suzuki, Daisuke; Tomita, Ryohei; Tomita, Jumpei; Esaka, Fumitaka; Yasuda, Kenichiro; Miyamoto, Yutaka

Journal of Radioanalytical and Nuclear Chemistry, 328(1), p.103 - 111, 2021/04

 Times Cited Count:3 Percentile:47.54(Chemistry, Analytical)

An analytical technique was developed to determine the age of uranium particles for safeguards. After the chemical separation of uranium and thorium, the $$^{230}$$Th/$$^{234}$$U ratio was measured using single-collector inductively coupled plasma mass spectrometry and a $$^{233}$$U-based reference material comprising a certain amount of $$^{229}$$Th as a progeny nuclide of $$^{233}$$U. The results allowed us to determine the purification age of two certified materials, i.e., U-850 and U-100, which was in good agreement with the reference purification age (61 y). Moreover, the age of a single U-850 particle was determined with a difference of -28 to 2 years from the reference date.

Journal Articles

Discriminative measurement of absorbed dose rates in air from natural and artificial radionuclides in Namie Town, Fukushima Prefecture

Ogura, Koya*; Hosoda, Masahiro*; Tamakuma, Yuki*; Suzuki, Takahito*; Yamada, Ryohei; Negemi, Ryoju*; Tsujiguchi, Takakiyo*; Yamaguchi, Masaru*; Shiroma, Yoshitaka*; Iwaoka, Kazuki*; et al.

International Journal of Environmental Research and Public Health, 18(3), p.978_1 - 978_16, 2021/02

 Times Cited Count:3 Percentile:70.28(Environmental Sciences)

Journal Articles

A Unique high natural background radiation area; Dose assessment and perspectives

Hosoda, Masahiro*; Nugraha, E. D.*; Akata, Naofumi*; Yamada, Ryohei; Tamakuma, Yuki*; Sasaki, Michiya*; Kelleher, K.*; Yoshinaga, Shinji*; Suzuki, Takahito*; Rattanapongs, C. P.*; et al.

Science of the Total Environment, 750, p.142346_1 - 142346_11, 2021/01

 Times Cited Count:20 Percentile:87.03(Environmental Sciences)

The biological effects of low dose-rate radiation exposures on humans remains unknown. In fact, the Japanese nation still struggles with this issue after the Fukushima Dai-ichi Nuclear Power Plant accident. Recently, we have found a unique area in Indonesia where naturally high radiation levels are present, resulting in chronic low dose-rate radiation exposures. We aimed to estimate the comprehensive dose due to internal and external exposures at the particularly high natural radiation area, and to discuss the enhancement mechanism of radon. A car-borne survey was conducted to estimate the external doses from terrestrial radiation. Indoor radon measurements were made in 47 dwellings over three to five months, covering the two typical seasons, to estimate the internal doses. Atmospheric radon gases were simultaneously collected at several heights to evaluate the vertical distribution. The absorbed dose rates in air in the study area vary widely between 50 nGy h$$^{-1}$$ and 1109 nGy h$$^{-1}$$. Indoor radon concentrations ranged from 124 Bq m$$^{-3}$$ to 1015 Bq m$$^{-3}$$. That is, the indoor radon concentrations measured exceed the reference levels of 100 Bq m$$^{-3}$$ recommended by the World Health Organization. Furthermore, the outdoor radon concentrations measured were comparable to the high indoor radon concentrations. The annual effective dose due to external and internal exposures in the study area was estimated to be 27 mSv using the median values. It was found that many residents are receiving radiation exposure from natural radionuclides over the dose limit for occupational exposure to radiation workers. This enhanced outdoor radon concentration might be as a result of the stable atmospheric conditions generated at an exceptionally low altitude. Our findings suggest that this area provides a unique opportunity to conduct an epidemiological study related to health effects due to chronic low dose-rate radiation exposure.

Journal Articles

Sequestration and oxidation of Cr(III) by fungal Mn oxides with Mn(II) oxidizing activity

Suzuki, Ryohei*; Tani, Yukinori*; Naito, Hirotaka*; Miyata, Naoyuki*; Tanaka, Kazuya

Catalysts, 10(1), p.44_1 - 44_15, 2020/01

 Times Cited Count:10 Percentile:41.25(Chemistry, Physical)

We prepared biogenic Mn oxides (BMOs) using ${it Acremonium strictum}$ strain KR21-2, and subsequently conducted single or repeated treatment experiments in Cr(NO$$_{3}$$)$$_{3}$$ at pH6.0. Under aerobic conditions, newly formed BMOs exhibited a rapid production of Cr(VI) without a significant release of Mn(II), demonstrating that newly formed BMO mediates a catalytic oxidation of Cr(III) with a self-regeneration step of reduced Mn. In anaerobic solution, newly formed BMOs showed a cessation of Cr(III) oxidation in the early stage of the reaction, and subsequently had a much smaller Cr(VI) production with significant release of reduced Mn(II).

Journal Articles

Cesium concentrations in various environmental media at Namie, Fukushima

Heged$"u$s, M.*; Shiroma, Yoshitaka*; Iwaoka, Kazuki*; Hosoda, Masahiro*; Suzuki, Takahito*; Tamakuma, Yuki*; Yamada, Ryohei; Tsujiguchi, Takakiyo*; Yamaguchi, Masaru*; Ogura, Koya*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 323(1), p.197 - 204, 2020/01

 Times Cited Count:3 Percentile:32.21(Chemistry, Analytical)

The radioactivity of cesium in the water and sediments of two major rivers was measured along with airborne radioactivity in Namie Town, after the recent partial lift on the evacuation order in 2017. The observed concentrations were up to 384 $$pm$$ 11 mBq/L for $$^{137}$$Cs in unfiltered water and 1.28 $$pm$$ 0.09 mBq/m$$^{3}$$ for $$^{137}$$Cs in air, while the sediment had a maximum of 44900 $$pm$$ 23.4 Bq/kg for $$^{137}$$Cs. The $$^{134}$$Cs/$$^{137}$$Cs ratios indicate the main origin of the cesium in the sediment to be Unit 1 in good agreement with previous reports on the accident.

Journal Articles

Comparative study on performance of various environmental radiation monitors

Tamakuma, Yuki*; Yamada, Ryohei; Suzuki, Takahito*; Kuroki, Tomohiro*; Saga, Rikiya*; Mizuno, Hiroyuki*; Sasaki, Hiroyuki*; Iwaoka, Kazuki*; Hosoda, Masahiro*; Tokonami, Shinji*

Radiation Protection Dosimetry, 184(3-4), p.307 - 310, 2019/10

 Times Cited Count:1 Percentile:11.41(Environmental Sciences)

After the Fukushima Daiichi Nuclear Power Plant accident, the radiation dose for first responders was not evaluated accurately due to lack of the monitoring data. It has been important to evaluate a radiation dose for workers in emergency response at a nuclear accident. In this study, a new device which can evaluate both of external and internal exposure doses was developed and the performance of various environmental radiation monitors including commercially available monitors were tested and compared from the viewpoint of an environmental monitoring at emergency situation. Background counts of the monitors and the ambient dose equivalent rate were measured in Fukushima Prefecture. The detection limit for beta particles was evaluated by the method of ISO11929. The sensitivity for gamma-rays of the dust monitor using a ZnS(Ag) and a plastic scintillator was high, but that of the external exposure monitor using a silicon photodiode with CsI(Tl) crystal was relatively low. The detection limit ranged 190-280 Bq m$$^{-3}$$ at 100 $$mu$$Sv h$$^{-1}$$, exceeding the detection limit of 100 Bq m$$^{-3}$$ in the minimum requirement by the National Regulation Authority in Japan. Use of the shielding with lead is necessary to achieve the minimum requirement. These results indicate that the dust monitor using a ZnS(Ag) scintillator and a plastic scintillator is suitable for the external exposure monitor and the developed internal exposure monitor is for the internal exposure monitor at emergency situation among the evaluated monitors. In the future study, the counting efficiency, the relative uncertainty and the performance of the detection for alpha particles will be evaluated, and it will be considered which type of a monitor is suitable after taking the portability into account.

Journal Articles

Feasible evaluation of neutron capture therapy for hepatocellular carcinoma using selective enhancement of boron accumulation in tumour with intra-arterial administration of boron-entrapped water-in-oil-in-water emulsion

Yanagie, Hironobu*; Kumada, Hiroaki*; Nakamura, Takemi; Higashi, Shushi*; Ikushima, Ichiro*; Morishita, Yasuyuki*; Shinohara, Atsuko*; Fujiwara, Mitsuteru*; Suzuki, Minoru*; Sakurai, Yoshinori*; et al.

Proceedings of 14th International Congress on Neutron Capture Therapy (ICNCT-14) (CD-ROM), p.157 - 160, 2010/10

Journal Articles

High thermoelectric performance of metal-substituted samples of $$alpha$$-Fe$$_{2}$$O$$_{3}$$ and computation of their electronic structures by the DV-X$$alpha$$ method

Sugihara, Sunao*; Suzuki, Chikashi; Kameya, Ryohei*

International Journal of Quantum Chemistry, 109(12), p.2788 - 2792, 2009/10

 Times Cited Count:2 Percentile:16.79(Chemistry, Physical)

no abstracts in English

Journal Articles

Measurement of the spin and magnetic moment of $$^{23}$$Al

Ozawa, Akira*; Matsuta, Kensaku*; Nagatomo, Takashi*; Mihara, Mototsugu*; Yamada, Kazunari*; Yamaguchi, Takayuki*; Otsubo, Takashi*; Momota, Sadao*; Izumikawa, Takuji*; Sumikama, Toshiyuki*; et al.

Physical Review C, 74(2), p.021301_1 - 021301_4, 2006/08

 Times Cited Count:41 Percentile:88.96(Physics, Nuclear)

no abstracts in English

Oral presentation

Recent development of the slow positron facility at institute of materials structure science, KEK

Wada, Ken*; Hyodo, Toshio*; Yagishita, Akira*; Ikeda, Mitsuo*; Osawa, Satoshi*; Shidara, Tetsuo*; Michishio, Koji*; Suzuki, Ryohei*; Tachibana, Takayuki*; Nagashima, Yasuyuki*; et al.

no journal, , 

no abstracts in English

Oral presentation

Increase in the intensity and brightness enhancement of the slow positron beam and its application at the Slow Positron Facility, KEK

Wada, Ken*; Hyodo, Toshio*; Kosuge, Takashi*; Saito, Yuki*; Yagishita, Akira*; Ikeda, Mitsuo*; Osawa, Satoshi*; Suwada, Tsuyoshi*; Furukawa, Kazuro*; Shirakawa, Akihiro*; et al.

no journal, , 

no abstracts in English

Oral presentation

Beam-line improvement and new experiment stations of KEK-IMSS slow-positron facility

Wada, Ken*; Mochizuki, Izumi*; Hyodo, Toshio*; Kosuge, Takashi*; Saito, Yuki*; Shidara, Tetsuo*; Osawa, Satoshi*; Ikeda, Mitsuo*; Shirakawa, Akihiro*; Furukawa, Kazuro*; et al.

no journal, , 

no abstracts in English

Oral presentation

Beam-line improvement and recent results of KEK-IMSS slow-positron facility

Wada, Ken*; Mochizuki, Izumi*; Hyodo, Toshio*; Kosuge, Takashi*; Saito, Yuki*; Shidara, Tetsuo*; Osawa, Satoshi*; Ikeda, Mitsuo*; Shirakawa, Akihiro*; Furukawa, Kazuro*; et al.

no journal, , 

no abstracts in English

Oral presentation

Present status of the KEK-IMSS Slow Positron Facility; A New beam-line branch and a rearrangement of the experiment stations

Wada, Ken*; Mochizuki, Izumi*; Hyodo, Toshio*; Kosuge, Takashi*; Saito, Yuki*; Nigorikawa, Kazuyuki*; Shidara, Tetsuo*; Osawa, Satoshi*; Ikeda, Mitsuo*; Shirakawa, Akihiro*; et al.

no journal, , 

no abstracts in English

Oral presentation

Recent developments and results of the KEK slow positron facility

Wada, Ken*; Mochizuki, Izumi*; Hyodo, Toshio*; Kosuge, Takashi*; Saito, Yuki*; Nigorikawa, Kazuyuki*; Shidara, Tetsuo*; Osawa, Satoshi*; Ikeda, Mitsuo*; Shirakawa, Akihiro*; et al.

no journal, , 

no abstracts in English

Oral presentation

Materials science at the KEK slow positron facility

Wada, Ken*; Mochizuki, Izumi*; Hyodo, Toshio*; Kosuge, Takashi*; Saito, Yuki*; Nigorikawa, Kazuyuki*; Shidara, Tetsuo*; Osawa, Satoshi*; Ikeda, Mitsuo*; Shirakawa, Akihiro*; et al.

no journal, , 

no abstracts in English

36 (Records 1-20 displayed on this page)