Mobile radiation measurement system by multiple small gamma-ray detectors for radioisotope detection and identification supporting responders in the field of nuclear detection and nuclear security

Kimura, Yoshiki; Yamaguchi, Tomoki

Progress in Nuclear Science and Technology (Internet), 7, p.60 - 66, 2025/03

https://doi.org/10.15669/pnst.7.60

High-temperature atomic diffusion and specific heat in quasicrystals

Nagai, Yuki; Iwasaki, Yutaka*; Kitahara, Koichi*; Takagiwa, Yoshiki*; Kimura, Kaoru*; Shiga, Motoyuki

Physical Review Letters, 132(19), p.196301_1 - 196301_6, 2024/05

https://doi.org/10.1103/PhysRevLett.132.196301

A quasicrystal is an ordered but non-periodic structure understood as a projection from a higher dimensional periodic structure. An anomalous increase in heat capacity at high temperatures has been discussed for over two decades as a manifestation of a hidden high dimensionality of quasicrystals. A theoretical study of the heat capacity of realistic quasicrystals or their approximants has yet to be conducted because of the huge computational complexity. To bridge this gap between experiment and theory, we show experiments and cutting-edge machine-learning molecular simulations on the same material, an Al-Pd-Ru quasicrystal, and its approximants. We show that at high temperatures, aluminum atoms diffuse with discontinuous-like jumps, and the diffusion paths of the aluminum can be understood in terms of jumps corresponding to hyperatomic fluctuations in six-dimensional space.

Radioisotope identification algorithm using deep artificial neural network for supporting nuclear detection and first response on nuclear security incidents

Kimura, Yoshiki; Tsuchiya, Kenichi*

Radioisotopes, 72(2), p.121 - 139, 2023/07

https://doi.org/10.3769/radioisotopes.72.121

Rapid and precise radioisotope identification in the scene of nuclear detection and nuclear security incidents is one of the challenging issues for the prompt response on the detection alarm or the incidents. A radioisotope identification algorithm using a deep artificial neural network model applicable to handheld gamma-ray detectors has been proposed in the present paper. The proposed algorithm automatically identifies gamma-emitting radioisotopes based on the count contribution ratio (CCR) from each of them estimated by the deep artificial neural network model trained by simulated gamma-ray spectra. The automated radioisotope identification algorithm can support first responders of nuclear detection and nuclear security incidents without sufficient experience and knowledge in radiation measurement. The authors tested the performance of the proposed algorithm using two different types of deep artificial neural network models in application to handheld detectors having high or low energy resolution. The proposed algorithm showed high performance in identifying artificial radioisotopes for actually measured gamma-ray spectra. It was also confirmed that the algorithm is applicable to identifying U and automated uranium categorization by analyzing estimated CCRs by the deep artificial neural network models. The authors also com-pared the performance of the proposed algorithm with a conventional radioisotope identification method and discussed promising ways to improve the performance of the algorithm using the deep artificial neural network.

Monitoring technique for detection of nuclear and radioactive materials on major public events

Mochimaru, Takanori*; Koizumi, Mitsuo; Takahashi, Tone; Hironaka, Kota; Kimura, Yoshiki; Sato, Yuki; Terasaka, Yuta; Yamanishi, Hirokuni*; Wakabayashi, Genichiro*

Dai-42-Kai Nihon Kaku Busshitsu Kanri Gakkai Nenji Taikai Kaigi Rombunshu (Internet), 4 Pages, 2021/11

no abstracts in English

Introduction to nuclear security, 4; Nuclear forensics technology supporting nuclear security

Kimura, Yoshiki

Nihon Genshiryoku Gakkai-Shi ATOMO, 62(10), p.583 - 587, 2020/10

https://doi.org/10.3327/jaesjb.62.10_583

no abstracts in English

Material discrimination analysis by particle shape of nuclear materials for nuclear forensics application

Kimura, Yoshiki; Shinohara, Nobuo; Matsumoto, Tetsuya*

Progress in Nuclear Science and Technology (Internet), 5, p.188 - 191, 2018/11

https://doi.org/10.15669/pnst.5.188

Prospective features for integration of nuclear forensics capability in national framework

Tamai, Hiroshi; Okubo, Ayako; Kimura, Yoshiki; Shinohara, Nobuo; Tazaki, Makiko; Shimizu, Ryo; Suda, Kazunori; Tomikawa, Hirofumi

Proceedings of INMM 58th Annual Meeting (Internet), 6 Pages, 2017/07

Nuclear forensics is a technical measure to analyse and collate samples of illegally used nuclear materials, etc., to clarify their origins, routes, etc. and contribute to criminal identifications. Close collaboration with police and judicial organizations is essential. The national response framework is being built up with international cooperation. Discussions on promoting technical capability and regional cooperation are presented.

Development of prototype nuclear forensics library for radioactive isotopes at Japan Atomic Energy Agency

Kimura, Yoshiki; Shinohara, Nobuo; Funatake, Yoshio

57th Annual Meeting of the Institute of Nuclear Materials Management (INMM 2016), Vol.2, p.1024 - 1029, 2016/07

Development of prototype national nuclear forensics library at Japan Atomic Energy Agency

Kimura, Yoshiki; Shinohara, Nobuo; Funatake, Yoshio

Proceedings of INMM 56th Annual Meeting (Internet), 8 Pages, 2015/07

Progress and future prospects of nuclear forensics technology development project at JAEA

Kimura, Yoshiki; Shinohara, Nobuo; Sato, Kaneaki; Toda, Nobufumi; Shinoda, Yoshiharu; Funatake, Yoshio; Watahiki, Masaru; Kuno, Yusuke

Proceedings of INMM 55th Annual Meeting (Internet), 7 Pages, 2014/07

In 2010, the Japan Government issued the national statement at Nuclear Security Summit (Washington D.C., USA) to develop technologies related to measurement and detection of nuclear materials for nuclear forensics within three-year timeframe, and to share the products with the international community in order to contribute to strengthening the nuclear security system. In response to this statement, JAEA that possesses sufficient technical capabilities to fulfil this nuclear forensics mission has started a nuclear forensics technology development project since JFY 2011. This paper will present the progress of the development project during JFY 2011 to 2013. This project includes the developments of analytical technologies such as isotope and impurity measurements, morphology analysis, age determination technique, and the prototype of national nuclear forensics library (NNFL). Some future prospects of this project will be also presented in this paper.