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Tomita, Ryohei; Tomita, Jumpei; Suzuki, Daisuke; Miyamoto, Yutaka; Yasuda, Kenichiro
Journal of Nuclear Science and Technology, 10 Pages, 2025/05
A new automated particle measurement (APM) combined with micromanipulation using large geometry secondary ion mass spectrometry instrument was proposed and demonstrated to remove the particle mixing effect, which indicated that the aggregation of uranium particles was detected as a single uranium particle, from APM results. The results showed that the new APM method was more effective than the traditional APM method in removing the particle mixing effect from the APM results and determining the existence of minor uranium isotopes in the samples.
U/
U isotopic analysis of trace uranium in safeguards environmental samples using multicollector inductively coupled plasma mass spectrometryTomita, Jumpei; Tomita, Ryohei; Suzuki, Daisuke; Yasuda, Kenichiro; Miyamoto, Yutaka
Journal of the American Society for Mass Spectrometry, 35(6), p.1178 - 1183, 2024/05
Times Cited Count：0 Percentile：0.00(Biochemical Research Methods)A sensitive analytical technique was investigated in order to determine 10
order of U/U ratio in the sub-ng of uranium using a multi-collector ICP-MS. First, the solution volume was concentrated to one tenth to obtain higher intensities. Next, data acquisition was started from the beginning of the solution uptake and continued until all solution was exhausted. Taking advantage of multi-collector measurement, all data were used with excepting the portion affected by air mixing at the beginning and end of sample introduction. The isotope ratios were calculated from the total counts of each isotope. This technique was applied to U isotope standard (IRMM-184) to measure the 10 order of U/U ratio in the sub-ng of uranium. Measured values were in good agreement with the certified value within the uncertainity (
=2). The uncertainties obtained with this new technique (32% on average) were revised to be 10 times smaller than those obtained with the conventionalmethod.
Tomita, Ryohei; Tomita, Jumpei; Suzuki, Daisuke; Yasuda, Kenichiro; Miyamoto, Yutaka
Hosha Kagaku, (48), p.1 - 15, 2023/09
Secondary Ion Mass Spectrometry (SIMS) is the method to detect secondary ions produced by the sputtering of primary ions. SIMS is one of effective method to measure isotopic composition of particles containing nuclear material in environmental sample for safeguards. We are a group member of the International Atomic Energy Agency (IAEA)'s network of analytical laboratories and have developed analytical techniques using SIMS and other mass spectrometers for nuclear safeguards. We will introduce the principle of SIMS and analytical techniques developed by our group to measure isotopic composition of uranium particles which having a particle diameter of micron order in environmental sample for safeguards.
Miyamoto, Yutaka; Suzuki, Daisuke; Tomita, Ryohei; Tomita, Jumpei; Yasuda, Kenichiro
Isotope News, (786), p.22 - 25, 2023/04
no abstracts in English
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
C reduced uranium secondary ion quantity to 33% compared with baking at 350C. Uranium hydride generation ratio of the sample baked at 850C was also 4 times higher than the sample baked at 350C. Baking at 850C 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 350C is suitable for uranium particles in the safeguards sample.
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 (
U and 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.
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
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：5 Percentile：49.08(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 
Th/
U ratio was measured using single-collector inductively coupled plasma mass spectrometry and a U-based reference material comprising a certain amount of 
Th as a progeny nuclide of 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.
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：8 Percentile：57.10(Environmental Sciences)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：35 Percentile：85.36(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
and 1109 nGy h. Indoor radon concentrations ranged from 124 Bq m
to 1015 Bq m. That is, the indoor radon concentrations measured exceed the reference levels of 100 Bq m 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.
Suzuki, Ryohei*; Tani, Yukinori*; Naito, Hirotaka*; Miyata, Naoyuki*; Tanaka, Kazuya
Catalysts, 10(1), p.44_1 - 44_15, 2020/01
Times Cited Count：12 Percentile：37.36(Chemistry, Physical)We prepared biogenic Mn oxides (BMOs) using 
strain KR21-2, and subsequently conducted single or repeated treatment experiments in Cr(NO
) 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).
Heged
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：4 Percentile：34.09(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 
11 mBq/L for 
Cs in unfiltered water and 1.28 0.09 mBq/m
for Cs in air, while the sediment had a maximum of 44900 23.4 Bq/kg for Cs. The 
Cs/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.
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：8.85(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 at 100 
Sv h, exceeding the detection limit of 100 Bq m 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.
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
-Fe
O and computation of their electronic structures by the DV-X methodSugihara, Sunao*; Suzuki, Chikashi; Kameya, Ryohei*
International Journal of Quantum Chemistry, 109(12), p.2788 - 2792, 2009/10
Times Cited Count：3 Percentile：22.22(Chemistry, Physical)no abstracts in English
AlOzawa, 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：44 Percentile：88.63(Physics, Nuclear)no abstracts in English
Tomita, Ryohei; Esaka, Fumitaka; Yasuda, Kenichiro; Suzuki, Daisuke; Miyamoto, Yutaka
no journal, ,
The research group for safeguards analytical chemistry which belong to Japan Atomic Energy Agency (JAEA) introduced new Large Geometry Secondary Ion Mass Spectrometry (LG-SIMS) instrument (1300-HR, CAMECA) to update our capability. LG-SIMS instrument has higher mass resolving power (MRP) than small geometry SIMS (SG-SIMS) instrument we had used. We hope molecular interferences (e.g. Pb, Al, Fe) are removed by LG-SIMS instrument when we analyze uranium bearing particles in environmental sample. In order to obtain the bes LG-SIMS condition for uranium particle analysis, we investigated a relationship between MRP, secondary ion's intensity and peak shape of uranium. One of the most famous molecular interferences of uranium SIMS analysis is PbAl
(mass number: 234, 235). If we attempt to remove molecular interferences of the PbAl from uranium mass regions, MRP value of 2741 is required. The MRP of LG-SIMS instrument is defined by entrance and exit slit. We need to keep balance between MRP, secondary ion's intensity and flat-top peak rate. We compared some combination of entrance and exit slit to get better balance. We found the best combination of entrance and exit slit is sized 200 m and 500 m, respectively. LG-SIMS can almost remove PbAl from uranium secondary ions in this condition. This research is part of investigation into safeguards analysis techniques commissioned by nuclear regulatory agency.
Sasaki, Jun; Okuda, Eiji; Suzuki, Nobuhiro; Ota, Katsu; Owada, Ryohei; Takamatsu, Misao
no journal, ,
no abstracts in English
Li ion beamsNishinaka, Ichiro; Yokoyama, Akihiko*; Washiyama, Koshin*; Amano, Ryohei*; Maeda, Eita*; Taniguchi, Takumi*; Murakami, Kento*; Watanabe, Shigeki; Suzuki, Hiroyuki; Ishioka, Noriko; et al.
no journal, ,
In general, an -emitter 
At which is a prospective candidate for utilization in targeted alpha radiotherapy is produced through the 
Bi(
He, 2n)At reaction. In contrast, our project is focusing on the production in the Bi(Li, 5n)Rn reaction. This enables us to supply At in a Rn/At generator system. The daughter At (7.2 h half-life) is extracted from the parent Rn (14h), expanding time-frame for transportation and use of At. To use astatine and iodine radioisotopes in our project, the excitation functions of Bi(Li, xn)
Rn, 
Pb(Li, xn)
At and Sn(Li, xn)I reactions have been measured. In addition to that, separation techniques have been developed. We report not only on the production and separation of astatine and iodine radioisotopes in the reactions but also on the utilization of those radioisotopes.
Tomita, Jumpei; Tomita, Ryohei; Suzuki, Daisuke; Yasuda, Kenichiro; Miyamoto, Yutaka
no journal, ,
no abstracts in English
