Accurate automatic analysis of individual uranium particles to improve the timeliness of safeguards environmental sample analysis using an LG-SIMS instrument and SEM-micromanipulation

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

Analytical Methods, 17(44), p.9017 - 9025, 2025/10

https://doi.org/10.1039/D5AY01481F

Sensitive U/U isotopic analysis of trace uranium in safeguards environmental samples using multicollector inductively coupled plasma mass spectrometry

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

Journal of the American Society for Mass Spectrometry, 35(6), p.1178 - 1183, 2024/05

https://doi.org/10.1021/jasms.4c00014

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.

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

https://www.jrias.or.jp/books/cat3/2023/786.html

no abstracts in English

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

https://lib-extopc.kek.jp/preprints/PDF/2022/2225/2225002.pdf

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.

Odd-parity autoionizing levels of uranium observed by two-color two-step photoionization optogalvanic spectroscopy

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

https://doi.org/10.1088/1361-6455/abf89f

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.

Development to measure plutonium isotope ratio of the immersed particles by secondary ion mass spectrometry

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

no journal, , 

We developed the impregnation method to make particulate materials with known isotopic ratio with the aim to develop analytical techniques for environmental sample analysis collected for nuclear safeguards purpose. In this study, we immersed a plutonium isotopic standard solution into porous silica particles by impregnation method and investigated a method to measure plutonium isotope ratio of the particles accurately by secondary ion mass spectrometry (SIMS). Pu/Pu of the particles measured by the SIMS method we investigated agreed with the certified values of the plutonium isotopic standard within 2 standard deviations. Our SIMS method showed the capability to measure plutonium isotope ratio of the particles accurately.

The Method to reduce particle mixing under automated particle measurement (APM) condition of LG-SIMS

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 (350350 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, 5080 particles were manipulated randomly from another mixed standards planchet and analyzed them by APM.

Analytical method to remove electrostatic discharge on uranium particle based by porous silicon particle and the effect of discharge for uranium isotopic ratio analysis by SIMS

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.

Distribution of I-129 in the terrestrial environment after the Fukushima Daiichi Nuclear Power Plant accident

Matsumura, Masumi*; Sasa, Kimikazu*; Matsunaka, Tetsuya*; Tomita, Ryohei; Takahashi, Tsutomu*; Matsuzaki, Hiroyuki*; Sueki, Keisuke*

no journal, , 

Preparation of uranium standard particles and isotope ratio analysis by secondary ion mass spectrometry

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 4.4810 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.