Determination of Cs/Cs isotopic ratio in soil collected near Fukushima Daiichi Nuclear Power Station through mass spectrometry

Shimada, Asako; Tsukahara, Takehiko*; Nomura, Masao*; Kim, M. S.*; Shimada, Taro; Takeda, Seiji; Yamaguchi, Tetsuji

Journal of Nuclear Science and Technology, 58(11), p.1184 - 1194, 2021/11

https://doi.org/10.1080/00223131.2021.1931520

Determining the completeness of nuclear reactor decommissioning is an important step in safely utilizing nuclear power. For example, Cs from the Fukushima Daiichi Nuclear Power Station (FDNPS) accident can be treated as background radioactivity, so determining the origin of Cs is essential. To accomplish this, measuring the Cs/Cs isotope ratio can be useful, so this study optimized a solvent extraction method, with calix[4]arene-bis(t-octylbenzo-crown-6) [BOBCalixC6] in 1-octanol, to purify radioactive Cs, radiocesium, from a solution of major environmental soil elements and mass spectrometry interference elements. This optimized method was applied to Cs purification in soil samples (40 g), and the final solutions contained a total of 10g/ml of the major soil elements and ng/ml concentrations at most of interfering elements. Soil samples collected near the FDNPS were then purified, and the Cs/Cs isotope ratios were measured, using both thermal ionization mass spectrometry (TIMS) and triple quadrupole induced coupled plasma mass spectrometry (ICP-QQQ). The results of each of these measurements were compared, and we found that Cs isotope ratios obtained by TIMS were more precise, by an order of magnitude, while the ICP-QQQ results possessed good abundance sensitivities. A slightly higher Cs/Cs ratio in the northwest area of the FDNPS was observed, while other areas exhibited similar values, all within the measurement error range, which indicated different origins of radiocesium. These results agreed with previously reported Cs/Cs activity distributions, suggesting that this ratio may be useful in identifying radiocesium origins for evaluating future nuclear reactor decommissions.

Observation of spontaneously excited waves in the ion cyclotron frequency range on JT-60U

Ichimura, Makoto*; Higaki, Hiroyuki*; Kakimoto, Shingo*; Yamaguchi, Yusuke*; Nemoto, Tatsuki*; Katano, Makoto*; Ishikawa, Masao; Moriyama, Shinichi; Suzuki, Takahiro

Nuclear Fusion, 48(3), p.035012_1 - 035012_7, 2008/03

https://doi.org/10.1088/0029-5515/48/3/035012

In this paper, experimental observations of spontaneously excited waves in the ion cyclotron range of frequency (ICRF) on JT-60U are described. The fluctuations in ICRF are driven by the presence of non-thermal ion distribution in magnetic confinement plasmas. Two types of magnetic fluctuations are detected: one is due to high energy D ions from neutral beam injections and the other is due to fusion products (FPs) of He and T ions. These fluctuations have been reported as ion cyclotron emissions (ICEs) in the burning plasma experiments on large tokamaks. This paper describes the first measurement of the spatial structures of the excited modes in the poloidal and toroidal directions. It is confirmed by using ICRF antennas as magnetic probes that all modes excited spontaneously have magnetic components and couple to the antenna straps. The modes due to D ions have small toroidal wave number and will behave as electrostatic waves. On the while, the measurement of finite in the modes due to FP ions supports the excitation of the Alfvn waves is the possible origin of FP-ICEs. It is also confirmed that the excited modes due to FP ions have different wave structures and are suggested to be in the different branch of the Alfvn waves, that is, the fast Alfvn wave and the slow Alfvn wave. Frequency peaks due to FP ions are sometimes split into doublet shape as observed in JET experiments. The phase differences of both peaks are measured and indicate that two waves are traveling in both toroidal directions. Both beam-driven ICEs and FP-ICEs are observed and those spatial structures are obtained on JT-60U.

Wave excitation in magnetically confined plasmas with an anisotropic velocity distribution

Ichimura, Makoto*; Higaki, Hiroyuki*; Kakimoto, Shingo*; Yamaguchi, Yusuke*; Nemoto, Kenju*; Katano, Makoto*; Kozawa, Isao*; Muro, Taishi*; Ishikawa, Masao; Moriyama, Shinichi; et al.

Fusion Science and Technology, 51(2T), p.150 - 153, 2007/02

https://doi.org/10.13182/FST07-A1337

In magnetically confined plasmas, fluctuations in the ion cyclotron range of frequency (ICRF) will be driven by the presence of non-thermal ion energy distribution. In strong ICRF heating experiments on the GAMMA 10 tandem mirror, plasmas with a strong temperature anisotropy have been formed. Alfven-ion-cyclotron (AIC) modes are spontaneously excited due to strong temperature anisotropy. High-energy ions are trapped in the local mirror and will form the velocity distribution with the strong anisotropy. To study the relation among the AIC modes, ICEs and beam-driven electrostatic instabilities with non-thermal energy distribution is the main purpose of this work. When the NBs are injected, the magnetic fluctuations due to injected beams and FP ions are detected by ICRF antennas used as pickup loops on JT-60U. The wave excitation near ion cyclotron and its higer harmonic frequencies are studied experimentally and theoretically in plasmas with non-thermal ion energy distribution.

Impurity release and deuterium retention properties of a ferritic steel wall in JFT-2M

Ogawa, Hiroaki; Yamauchi, Yuji*; Tsuzuki, Kazuhiro; Kawashima, Hisato; Sato, Masayasu; Shinohara, Koji; Kamiya, Kensaku; Kasai, Satoshi; Kusama, Yoshinori; Yamaguchi, Kaoru*; et al.

Journal of Nuclear Materials, 329-333(Part1), p.678 - 682, 2004/08

https://doi.org/10.1016/j.jnucmat.2004.04.192

no abstracts in English

Power flow in the negative-ion based neutral beam injection for JT-60

Kuriyama, Masaaki; Akino, Noboru; Ebisawa, Noboru; Grisham, L. R.*; Hikida, Shigenori*; Honda, Atsushi; Ito, Takao; Kawai, Mikito; Kazawa, Minoru; Kusaka, Makoto*; et al.

Review of Scientific Instruments, 71(2), p.751 - 754, 2000/02

https://doi.org/10.1063/1.1150283

no abstracts in English

Mechanistic approach to the sodium leakage and fire analysis

Yamaguchi, Akira; Muramatsu, Toshiharu; Ohira, Hiroaki; Iida, Masao

PNC TN9410 97-040, 141 Pages, 1997/04

PNC-TN9410-97-040.pdf:7.71MB

In December 1995, a thermocouple well was broken and liquid sodium leaked out of the intermediate heat transport system of the prototype fast breeder reactor Monju. In the initiating process of the incident, liquid sodium flowed out through the hollow thermocouple well, nipple and connector. As a result, liquid sodium, following ignition and combustion, was dropping from the connector to colide with the duct and gating placed below. The collision may cause fragmentation and scattering of the sodium droplet that finaly was piled up on the floor. This report deals with the development of computer programs for the phenomena based on mechanistics approach. Numerical analyses are also made for fundamental sodium leakage and combustion phenomenon, sodium combustion experiment, and Monju incident condition. The contents of this report is listed below: (1)Analysis of chemical reaction process based on molecular orbital method, (2)Thermal hydlaulic analysis of the sodium combustion experiment II performed in 1996 at O-arai Engineering Center, PNC, (3)Thermal hydlaulic analysis of room A-446 of Monju reactor when the sodium leakage took place, (4)Direct numerical simulation of sodium droplet, (5)Sodium leakage and scattering analysis using three dimensional particle method, (6)Multi-dimensional combustion analysis and multi-point approximation combustion analysis code. Subsequent to the development work of the programs, they are to be applied to the safety analysis of the Fast Breeder Reactor.

ICRF waves for plasma diagnostics in GAMMA 10 and JT-60U

Ichimura, Makoto*; Yamaguchi, Yusuke*; Nemoto, Kenju*; Katano, Makoto*; GAMMA10 Group*; Ishikawa, Masao*; Moriyama, Shinichi; Suzuki, Takahiro

no journal, , 

The measurement of fusion product (FP) ICEs will become a significant diagnostic tool for fusion reactions. The precise study of the excitation mechanism is important for future burning plasma experiments. In strong ICRF heating experiments on the GAMMA 10 tandem mirror, plasmas with a strong temperature anisotropy have been formed when the resonance layer exists near the mid-plane of the central cell. In a typical discharge, Alfven-ion-cyclotron (AIC) modes are spontaneously excited due to such a strong temperature anisotropy. On the while, the injection of low power ICRF waves into the plasma as active diagnostics has been tested in GAMMA 10. A wide band ICRF probe system was constructed. In the present experimental conditions, the inhomogeneity scale length of the plasma and the magnetic field configuration is in the same order of the wavelength. Wave excitation is strongly affected by the boundary conditions. The waves excited in the plasma are detected with a magnetic probe. In the presentation, the experimental results of the ICRF probe system in GAMMA 10 for active diagnostics and the observation of ICEs in JT-60U for passive diagnostics are reported.

Study of spontaneously excited waves on plasmas with anisotropic velocity distribution

Katano, Makoto*; Ichimura, Makoto*; Yamaguchi, Yusuke*; Motegi, Yukimi*; Muro, Taishi*; Ouchi, Toshiaki*; Oishi, Junya*; Sato, Shoichi*; Ishikawa, Masao; Moriyama, Shinichi; et al.

no journal, , 

The understanding of spontaneously excited waves in plasmas with anisotropic velocity distributions is the main purpose of this presentation. In JT-60U, the ion cyclotron emissions (ICEs) due to fusion product ions have been experimentally observed. By using the local dispersion relation in hot plasmas, the excitation of slow and fast Alfvn waves are evaluated. The excitation mechanism for ICEs due to fusion product ions are discussed.

Development of scandium recovery from KUSATSU-Spa

Seko, Noriaki; Hoshina, Hiroyuki; Kasai, Noboru; Tamada, Masao; Kiryu, Toshiyuki*; Yamaguchi, Takashi*; Yamamoto, Hideo*; Tanaka, Kazuya*; Anzai, Yasuhiro*; Anzai, Nobuhiro*; et al.

no journal, , 

no abstracts in English

Development of dose evaluation method for confirmation of completion of decommissioning, 2; Identification of radiocesium origin using Cs/Cs isotope ratio

Shimada, Asako; Tsukahara, Takehiko*; Nomura, Masao*; Kim, M. S.*; Shimada, Taro; Takeda, Seiji; Yamaguchi, Tetsuji

no journal, , 

Radiocesium from the Fukushima Daiichi Nuclear Power Station (1F) accident can be treated as background radioactivity at completion of decommissioning, so determining the origin of radiocesium is essential. Therefore, we studied identification of radiocesium origin using Cs/Cs isotope ratio. The ratio originated from 1F was 0.36280.0005. When the ratio originated from decommissioning facility was 0.050.2 larger than that originated from 1F, it is challenging to decrease the stand deviation less than 0.01 for 1 Bq/g of Cs because precision was decreased as decreasing the Cs concentration. If the ratio is able to be determined within the standard deviation of 0.0005 for 0.5 Bq/g of soil sample, the identification would be available.