Concept for a cesium-free negative ion source based on microwave heating of a low work function granular material

Matsubara, Akihiro*; Kokubu, Yoko; Nishio, Kazuhisa*; Kimura, Kenji*; Kashimura, Keiichiro*; Shimada, Koji; Fujita, Natsuko

Nuclear Instruments and Methods in Physics Research B, 568, p.165863_1 - 165863_5, 2025/11

https://doi.org/10.1016/j.nimb.2025.165863

We propose a concept for a cesium-free negative ion source based on microwave heating of granular low work function materials, which allows for both safety and high efficiency. This negative ion source features a structure where the plasma region and the negative ion generation region are adjacent within a microwave cavity. In the negative ion generation region, granular low work function materials heated by microwaves are placed. The sample gas entering the plasma region is excited, then it enters the negative ion generation region. Subsequently, it comes into contact with the surface of the low work function material, changes into negative ions, and finally, is extracted by an electric field. One advantage of this negative ion source is that, by using low work function materials in granular form, the reactive area is more than ten times larger compared to conventional negative ion sources using low work function materials.

Radiological management of air-fed suit work for glovebox dismantling activities

Asakawa, Jun; Kimura, Yasuhisa; Hirano, Hiroshi*; Kitamura, Akihiro

Hoken Butsuri (Internet), 60(1), p.63 - 73, 2025/04

https://doi.org/10.5453/jhps.60.63

Dismantlement activities of contaminated glovebox and tunnel with new sealed enclosure methods

Nagai, Yuya; Kimura, Yasuhisa; Hirano, Hiroshi*; Kitamura, Akihiro

Hoken Butsuri (Internet), 59(4), p.168 - 181, 2024/12

https://doi.org/10.5453/jhps.59.168

We have dismantled one glovebox that stood very near at the wall of a controlled room and a part of one transfer tunnel that penetrated walls of control rooms. We have developed new containment boundaries because conventional tent enclosure cannot be applied to these objects. In this report, we present the features of new containment boundaries and dismantlement procedures we have developed and the details of the dismantlement activities we have implemented.

Investigation of asbestos at hot laboratory; Investigation of asbestos in heat insulation material

Ishida, Reiya; Sonobe, Hiroshi; Kimura, Akihiro

JAEA-Review 2024-030, 75 Pages, 2024/08

JAEA-Review-2024-030.pdf:8.53MB

Department of JMTR Hot Laboratory (HL) had been construction since 1967 (concrete and lead cells have been in service since 1971 and steel cells since 1982). Because the HL is old, there is a high possibility that asbestos is used in heat insulation material wrapped around the piping installed in the HL. If asbestos is contained in that of such pipes, it may be dispersed into the air during repair, remodeling, or removal of such pipes, causing lung cancer, mesothelioma, or other health problems to workers. Therefore, it is also important to understand the status of asbestos use in the facility. The HL has been investigating the presence of asbestos in heat insulation material wrapped around piping in several systems installed in the facility. As a result, asbestos was detected in some of heat insulation material. This report describes the results of the asbestos survey conducted so far.

Present status of the JAEA-AMS-TONO (2022FY)

Fujita, Natsuko; Miyake, Masayasu; Matsubara, Akihiro*; Ishii, Masahiro*; Watanabe, Takahiro; Jinno, Satoshi; Nishio, Tomohiro*; Ogawa, Yumi; Kimura, Kenji; Shimada, Akiomi; et al.

Dai-35-Kai Tandemu Kasokuki Oyobi Sono Shuhen Gijutsu No Kenkyukai Hokokushu, p.17 - 19, 2024/03

The JAEA-AMS-TONO facility at the Tono Geoscience Center, JAEA has three accelerator mass spectrometers. We report the present status of the JAEA-AMS-TONO.

Development of irradiation capsules with adjusting neutron spectrum

Fuyushima, Takumi; Takabe, Yugo; Sayato, Natsuki; Kimura, Akihiro; Takemoto, Noriyuki

The IV International Scientific Forum "Nuclear Science and Technologies"; AIP Conference Proceedings 3020, p.040007_1 - 040007_6, 2024/01

https://doi.org/10.1063/5.0192860

We studied irradiation tests of structural materials simulating fast reactor conditions in JMTR. We fabricated capsules that can simulate fast reactor irradiation in JMTR by using He/dpa ratio as index. To simulate fast reactor, cadmium, which shield thermal neutrons, was placed inside the capsule to adjust the neutron spectrum. According to the result of irradiation tests by neutron spectrum adjusting capsule, we confirmed that it can simulate the He/dpa ratio of fast reactor. Currently, since it is impossible to conduct irradiation tests in Japan, a plan is underway to partly replace the irradiation function of JMTR with overseas reactors. The alternative irradiation will be carried out by succeeding and developing the irradiation technology accumulated in the JMTR, and as a part of this, a trial of such irradiation in which the neutron spectrum is adjusted is under consideration.

Status report of JAEA-AMS-TONO; Research and technical development in the last four years

Kokubu, Yoko; Fujita, Natsuko; Watanabe, Takahiro; Matsubara, Akihiro; Ishizaka, Chika; Miyake, Masayasu*; Nishio, Tomohiro*; Kato, Motohisa*; Ogawa, Yumi*; Ishii, Masahiro*; et al.

Nuclear Instruments and Methods in Physics Research B, 539, p.68 - 72, 2023/06

https://doi.org/10.1016/j.nimb.2023.03.005

The JAEA-AMS-TONO facility at the Tono Geoscience Center, JAEA has an accelerator mass spectrometer (JAEA-AMS-TONO-5MV). The spectrometer enabled us to use a multi-nuclide AMS of carbon-14 (C), beryllium-10, aluminium-26 and iodine-129, and we have recently been proceeding test measurement of chlorine-36. In response to an increase of samples, we installed a state-of-the-art multi-nuclide AMS with a 300 kV Tandetron accelerator in 2020. Recently, we are driving the development of techniques of isobar separation in AMS and of sample preparation. Ion channeling is applied to remove isobaric interference and we are building a prototype AMS based on this technique for downsizing of AMS. The small sample graphitization for C has been attempted using an automated graphitization equipment equipped with an elemental analyzer.

Present status of the JAEA-AMS-TONO (2022FY)

Fujita, Natsuko; Miyake, Masayasu; Matsubara, Akihiro*; Ishii, Masahiro*; Watanabe, Takahiro; Jinno, Satoshi; Nishio, Tomohiro*; Ogawa, Yumi; Yamamoto, Yusuke; Kimura, Kenji; et al.

Dai-23-Kai AMS Shimpojiumu Hokokushu, p.1 - 4, 2022/12

The JAEA-AMS-TONO facility at the Tono Geoscience Center, JAEA has three accelerator mass spectrometers. We report the present status of the JAEA-AMS-TONO.

Design and production of the valve used in Radioactive Liquid Disposal Facility

Nishimura, Arashi; Okada, Yuji; Sugaya, Naoto; Sonobe, Hiroshi; Kimura, Nobuaki; Kimura, Akihiro; Hanawa, Yoshio; Nemoto, Hiroyoshi

JAEA-Technology 2021-003, 51 Pages, 2021/05

JAEA-Technology-2021-003.pdf:5.55MB

In the Japan Materials Testing Reactor (JMTR), the leakage accidents of radioactive waste liquid were occurred from the tanks and pipes of the liquid waste disposal facility in the JMTR tank-yard building in JFY2014. In order to respond to the accident, obtain the approval of the JAEA to the design and construction method from JFY2016, the tanks and pipes were replaced from JFY2016 to 2019. In the replaced, the production of the tanks and pipes of the liquid waste disposal facility applied Japanese technical standards correspondingly. On the other hand, the valve did not fall under the category of Japanese technical standards. The manufacturing specifications when replacing the valve were decided based on the including the selecting the standards of production and inspection for valves, Fluid properties, experience in JMTR. The production proceeded while carrying out the decided inspection. The valves that passed all the inspections were installed together with the tanks and pipes of the liquid waste, and the finished inspection was performed as a systems. The construction was completed with those inspection passed. This report is summarized valve Design, production and installation.

Measurement of cesium isotopic ratio by thermal ionization mass spectrometry for neutron capture reaction studies on Cs

Shibahara, Yuji*; Nakamura, Shoji; Uehara, Akihiro*; Fujii, Toshiyuki*; Fukutani, Satoshi*; Kimura, Atsushi; Iwamoto, Osamu

Journal of Radioanalytical and Nuclear Chemistry, 325(1), p.155 - 165, 2020/07

https://doi.org/10.1007/s10967-020-07198-2

The measurements of isotopic ratios of Cs samples by thermal ionization mass spectrometry were performed for the analysis of their samples used to evaluate nuclear data obtained for Cs. To obtain a high intensity and stable ion beam, the effects of additive agents on the ionization of Cs were examined. The effect of silicotungstic acid on the ionization of Cs was the largest among the additive agents studied in the present study, while the silicotungstic acid also showed the largest isobaric interference of polyatomic ions. It was demonstrated that as small as 210 g of a Cs sample was sufficient to achieve the analytical precision required to measure the Cs/Cs ratio in the case where an additive agent of TaO/glucose was employed. After examining of the analytical conditions, such as the interference effect due to Ba, the measurements of the isotopic ratios of two Cs samples used in our study using TIMS were conducted, and it was discussed how much the ratios contributed to evaluation of the neutron capture cross-section of Cs.