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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
Miyabe, Masabumi; Satou, Yukihiko; Wakaida, Ikuo; Terabayashi, Ryohei*; Sonnenschein, V.*; Tomita, Hideki*; Zhao, Y.*; Sakamoto, Tetsuo*
Journal of Physics B; Atomic, Molecular and Optical Physics, 54(14), p.145003_1 - 145003_8, 2021/07
Times Cited Count：1 Percentile：8.45(Optics)Two-color two-step photoionization optogalvanic spectroscopy was performed using high-repetition-rate titanium sapphire lasers and a uranium hollow cathode lamp to find the two-step resonance ionization schemes of uranium. Many ionization transitions were observed by exciting uranium atoms in a ground state into five, even parity, excited levels with the first-step laser and by scanning the second-step laser wavelengths. By blocking the first-step laser, single-color, two-photon ionization transitions were also identified. From these results, we have found more than 50 odd-parity autoionizing levels of uranium in the energy, ranging from the ionization potential (49958.4 cm
) to 51150 cm. The determined energy levels are within 1 cm of previously reported values.
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：6 Percentile：43.57(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.
Tomita, Jumpei; Tomita, Ryohei; Suzuki, Daisuke; Yasuda, Kenichiro; Miyamoto, Yutaka
no journal, ,
Formation of polyatomic interferences made of an atom of heavy element and atoms in plasma such as argon and oxygen is known to create problems for their measurements using ICP-MS. In this study, quantitative assessment of polyatomic interferences for the measurement of U and Pu isotope ratios at ultra-trace level using MC-ICP-MS was conducted. For U isotopes, significant polyatomic interferences caused by 
Ir
Ar, 
PtAr and 
PtAr were observed at the mass of 233, 234 and 236, respectively. When 1 ppb of natural uranium solution (IRMM184) containing 0.4 ppb of Pt was measured, U/U isotope ratio was roughly estimated to be two-fold higher than certified value due to the interference. For Pu isotopes, small interference from Pb (
PbAr) was observed at the mass of 244 while other obvious interferences were not found.
Tomita, Ryohei; Tomita, Jumpei; Suzuki, Daisuke; Yasuda, Kenichiro; Miyamoto, Yutaka
no journal, ,
Environmental sampling for safeguards which ensure that secret nuclear activities was organized by IAEA in 1996. Research group for safeguards analytical chemistry of Japan Atomic Energy Agency is one of a network laboratories of the IAEA with highly specialized measurement capabilities and continues to analyze the environmental samples collected by the IAEA. In our poster session, we will introduce the overview of our group and research findings about the method to make working standard particles and how to measure the particles we made accurately by secondary ion mass spectrometry.
Tomita, Ryohei*; Matsunaka, Tetsuya*; Honda, Maki*; Satou, Yukihiko; Matsumura, Masumi*; Takahashi, Tsutomu*; Sakaguchi, Aya*; Matsuzaki, Hiroyuki*; Sasa, Kimikazu*; Sueki, Keisuke*
no journal, ,
no abstracts in English
Tomita, Ryohei; Esaka, Fumitaka; Miyamoto, Yutaka
no journal, ,
In the previous study, we developed a combination method of individual uranium particle manipulation in scanning electron microscope (SEM) and secondary ion mass spectrometry (SIMS) for removing the interferences from other elements in other particles. Since the particles were selected randomly and manipulated, it caused the problem not to cover the range of 
U/U isotope ratio in the sample. In this study, we introduced pre-screening measurement into the procedure of analyzing uranium isotope ratios in individual particles by SIMS to cover the range of U/U in the sample.
Tomita, Jumpei; Tomita, Ryohei; Suzuki, Daisuke; Yasuda, Kenichiro; Miyamoto, Yutaka
no journal, ,
no abstracts in English
Tomita, Ryohei; Esaka, Fumitaka; Yomogida, Takumi; Miyamoto, Yutaka
no journal, ,
Large Geometry Secondary Ion Mass Spectrometry (LG-SIMS) is one of the strongest tools for analyzing isotope ratios of micron sized uranium particle. LG-SIMS has high spatial resolution of less than 1 
m with microprobe mode. However, this capability is bit less under automated particle measurement (APM) condition. If two or more particles are located in a quite narrow area, APM may detect the cluster as one particle. This particle mixing effect shows analytical results including false isotope ratios. In order to investigate how often particle mixing happens and how to solve this problem, we implemented APM to mixed uranium particle standard (U010, U100, U350 and U850) and try to apply particle manipulation with APM. In our experiment, each area (350
350 m
) was scanned with an O
primary beam with a current of 1.5 nA for 9 sec. Then, secondary ion images were recorded for circular area with a radius of 8500 m on the center of a sample planchet. The APM detected 5976 particles, and 1943 particles (32%) in them showed false isotope ratios. In addition to particle mixing, U850 cluster was shifted down to around 75% enrichment. The sample showed too high hydride rate, so that UH interfered U. This interference caused false U abundance and lead to false U abundance. To solve these problems, 50
80 particles were manipulated randomly from another mixed standards planchet and analyzed them by APM.
Yasuda, Kenichiro; Suzuki, Daisuke; Tomita, Jumpei; Tomita, Ryohei; Miyamoto, Yutaka
no journal, ,
The safeguards environmental sample analysis by the IAEA requires the development of efficient methods for measuring isotope ratios of ultra-trace amounts of plutonium and uranium particles. We have applied fission track and alpha track techniques to identify of discrimination between plutonium and uranium particles and have successfully measured isotope ratios of the particles using a continuous heating method with a thermal ionization mass spectrometer (TIMS). This method made it possible to find particles containing plutonium and uranium and measure them simultaneously by the TIMS without a chemical separation.
Tomita, Ryohei; Tomita, Jumpei; Suzuki, Daisuke; Yasuda, Kenichiro; Miyamoto, Yutaka
no journal, ,
Uranium standard particles are necessary to calibrate instruments and mass bias effect for analyzing isotopic ratio of uranium particles in secondary ion mass spectrometry (SIMS). In this study, we tried to make uranium particles which contain several picograms of uranium from porous silicon particles and solution of uranium standard powder (CRM U100). Quality of handmade uranium particles were evaluated by isotopic ratio analysis by Large Geometry (LG)-SIMS and mass bias factor calculated from handmade particles compared with the factor calculated from U100 particles. U atom% of handmade particles agreed with certified value of U100 within standard error (2
). However, mass bias factor calculated from handmade particles disagreed with the factor calculated from U100 particles. It is possible that electrification and uranium chemical form of handmade particles affect mass bias effect.
Tomita, Jumpei; Tomita, Ryohei; Suzuki, Daisuke; Yasuda, Kenichiro; Miyamoto, Yutaka
no journal, ,
The impact of the uranium from the process blank for a single uranium particle analysis by MC-ICP-MS was evaluated quantitatively. The synthetic uranium particles prepared by impregnating of U (NBL CRM U100) to porous silica were used in this study. A conical-bottom bottle was used to dissolve a uranium particle with a small amount of acid. The amount of U and U/U of the process blank were 0.2 pg and 0.0190, respectively. This ratio was similar to that of CRM U015 (0.0155), which was used for the detector calibration of MC-ICP-MS, indicating that the process blank was derived from ultra-trace level of uranium remining in the desolvator. The analytical results indicated that the U/U ratio could be determined accurately by MC-ICP-MS when the particle contained more than 23 pg of U.
Tomita, Jumpei; Tomita, Ryohei; Suzuki, Daisuke; Yasuda, Kenichiro
no journal, ,
no abstracts in English
Tomita, Jumpei; Tomita, Ryohei; Suzuki, Daisuke; Yasuda, Kenichiro; Miyamoto, Yutaka
no journal, ,
Plutonium isotopic standard solution was impregnated into porous silica particles to prepare the Pu particles utilized for a single particle analysis for safeguards. SEM-EDS analysis showed that the prepared silica particles contained Pu. The isotope ratios of the Pu particles were determined with a multi-collector ICP-MS after decomposing individually. 
Pu/
Pu measured ratios agreed with the certified value within the 2 of standard deviation.
Tomita, Ryohei; Tomita, Jumpei; Suzuki, Daisuke; Yasuda, Kenichiro; Miyamoto, Yutaka
no journal, ,
In this study, we tried to solve the problem of electrostatic discharge on uranium particle based by porous silicon particle and to analyze uranium isotopic ratio of the uranium particle-based silicon by SIMS with high accuracy. Experimental results showed that primary beam of negative oxygen (O
) is effective to compensate charge of uranium particle-based silicon. The negative primary beam also enable us to analyze uranium isotopic ratio of the uranium particle-based silicon within 2 range of standard deviation.
