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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：3 Percentile：44.61(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.
-Orbital component in the Borromean nucleus 
BYang, Z. H.*; Kubota, Yuki*; Corsi, A.*; Yoshida, Kazuki; Sun, X.-X.*; Li, J. G.*; Kimura, Masaaki*; Michel, N.*; Ogata, Kazuyuki*; Yuan, C. X.*; et al.
Physical Review Letters, 126(8), p.082501_1 - 082501_8, 2021/02
Times Cited Count：45 Percentile：96.69(Physics, Multidisciplinary)A quasifree (
,
) experiment was performed to study the structure of the Borromean nucleus B, which had long been considered to have a neutron halo. By analyzing the momentum distributions and exclusive cross sections, we obtained the spectroscopic factors for 
and 
orbitals, and a surprisingly small percentage of 9(2)% was determined for . Our finding of such a small component and the halo features reported in prior experiments can be explained by the deformed relativistic Hartree-Bogoliubov theory in continuum, revealing a definite but not dominant neutron halo in B. The present work gives the smallest - or -orbital component among known nuclei exhibiting halo features and implies that the dominant occupation of or orbitals is not a prerequisite for the occurrence of a neutron halo.
F from 
O
?Tang, T. L.*; Uesaka, Tomohiro*; Kawase, Shoichiro; Beaumel, D.*; Dozono, Masanori*; Fujii, Toshihiko*; Fukuda, Naoki*; Fukunaga, Taku*; Galindo-Uribarri, A.*; Hwang, S. H.*; et al.
Physical Review Letters, 124(21), p.212502_1 - 212502_6, 2020/05
Times Cited Count：14 Percentile：73.46(Physics, Multidisciplinary)The structure of a neutron-rich F nucleus is investigated by a quasifree (
) knockout reaction. The sum of spectroscopic factors of 
orbital is found to be 1.0 
0.3. The result shows that the O core of F nucleus significantly differs from a free O nucleus, and the core consists of 
35% O
, and 65% excited O. The result shows that the O core of F nucleus significantly differs from a free O nucleus. The result may infer that the addition of the proton considerably changes the neutron structure in F from that in O, which could be a possible mechanism responsible for the oxygen dripline anomaly.
Tomita, Jumpei; Tomita, Ryohei; Suzuki, Daisuke; Yasuda, Kenichiro; Miyamoto, Yutaka
no journal, ,
no abstracts in English
Tomita, Ryohei; Tomita, Jumpei; Yomogida, Takumi; Suzuki, Daisuke; Yasuda, Kenichiro; Esaka, Fumitaka; Miyamoto, Yutaka
no journal, ,
Secondary ion mass spectrometry (SIMS) analysis of uranium particles for safeguards purpose consists of Automated Particle Measurement (APM) and Microprobe analysis. APM for safeguards sample includes 2400 measurements, each field is analyzed for short time. So, if a sample have particles which generate too much uranium hydride formation on their surface, the APM result, especially U abundance, is affected by uranium hydride formation. It causes inaccurate APM result. To investigate what percentage of the entire particle the particle surface causing ratio change account for, total evaporation measurement was implemented for standard uranium particle generating much uranium hydride formation on their surface and uranium isotopic ratio change during the total evaporation measurement was observed. Total evaporation experiment indicated that the number of secondary ions originated from particle surface accounted for 3.1% of all of number of ions sputtered from the entire particle. Based on the total evaporation result, APM conditions, primary beam intensity, measurement time and raster size, combined with the method manipulating particles under scanning electron microscope were optimized to reduce the hydride effect for APM result.
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, Jumpei; Tomita, Ryohei; Suzuki, Daisuke; Yasuda, Kenichiro; Miyamoto, Yutaka
no journal, ,
Isotopic ratios of uranium particle provide us with the information on the nuclear activities such as enrichment and reprocessing. Precise determination of U isotopic ratios is difficult due to the low intensity of U measured by Faraday cup when pico-gram quantities of uranium was measured by MC-ICP-MS. In this study, the sensitive measurement of the 1-20 pg of uranium was examined. The solution was prepared by only 0.2 mL, which was one-tenth compared to the conventional method, to increase U concentration. Data acquisition was started from the beginning of the solution uptake and continued until all solution was exhausted. The isotopic ratios of uranium were calculated from the total counts of each isotope excepting the portion affected by air mixing at the beginning and end of sample introduction. Uranium isotopic ratios of CRM U015 and IRMM184 determined by this method examined in this study were agreed with the certified values within the uncertainties (2-sigma). The uncertainties obtained by this method were smaller than those by the conventional method.
Tomita, Ryohei; Tomita, Jumpei; Suzuki, Daisuke; Yasuda, Kenichiro; Esaka, Fumitaka; Miyamoto, Yutaka
no journal, ,
It is necessary to correctly calibrate the mass bias effect of uranium isotopes using uranium standard particles in the secondary ion mass spectrometry (SIMS) analysis. The preparation of uranium standard particles is mainly carried out by drying aerosols generated from uranium standard solutions in unique equipment and facility. This is the reason why only few types of commercial uranium standard particles are available. In this study, our purpose is to propose easier way to prepare uranium standard particle by immersing porous silicon particle in the uranium standard solution. Quality of this handmade uranium standard particles were evaluated by analyzing isotopic ratios using SIMS. The uranium isotopic standard solution (U/U=0.694, 
U/U=0.922) of 2.21 ppm was concentrated to 4.48
10
ppm, and mixed with porous silicon particle. Uranium isotopic ratios of handmade particles collected on a glassy carbon planchet were analyzed using LG-SIMS (IMS-1300HR
, CAMECA). Analytical results of U/U and U/U agreed with the certified value of standard solution within the standard deviation (1
). This new particle preparation is effective to create standard particles without uranium aerosol, and the particles made by this method showed same isotopic ratios as standard solution in which porous silicon particles was immerged.
Tomita, Ryohei; Tomita, Jumpei; Suzuki, Daisuke; Yasuda, Kenichiro; Miyamoto, Yutaka
no journal, ,
We are applying a secondary ion mass spectrometer (SIMS) to measure the isotopic composition of micron-sized nuclear particles in environmental samples for safeguards purposes. International Atomic Energy Agency (IAEA) collects swipe samples taken from the walls and floors of nuclear facilities through on-site inspections, and analyzes uranium isotopic composition of these samples for confirming the absence of undeclared nuclear activity. As a member of IAEA network analytical laboratories (NWALs), our research group has not only reported the analytical results of isotopic composition of U and Pu in the inspection samples to IAEA, but also has been developed analytical techniques to precisely and accurately measure the isotopic composition of nuclear materials on the IAEA swipe samples. Our analytical activity at Clean Laboratory for Environmental Analysis and Research (CLEAR) in JAEA, and analytical techniques using SIMS are introduced.
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; 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.
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.
