Study of rational safeguards for the treatment of radioactive waste containing nuclear materials

Nakatani, Takayoshi; Shimizu, Ryo; Tazaki, Makiko; Kimura, Takashi; Tamai, Hiroshi; Suda, Kazunori

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

Currently, JAEA is in the advancing of decommissioning own nuclear facilities, and some facilities have been handling nuclear materials. In decommissioning, it is necessary to consider rational methods while keeping nuclear non-proliferation and transparency, including treatment of radioactive waste generated from these facilities and methods for terminating safeguards. In this study, we considered the above issues regarding waste treatment with reference to the guidance of Safeguards by Design (SBD) published by the International Atomic Energy Agency (IAEA).

Research on factor analysis for achieving denuclearization, 10; Summary of research; Analysis of denuclearization factors of target countries and lessons learned from the analysis

Tazaki, Makiko; Shimizu, Ryo; Kimura, Takashi; Nakatani, Takayoshi; Tamai, Hiroshi; Suda, Kazunori

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

no abstracts in English

Three-dimensional bulk Fermi surfaces and Weyl crossings of CoMnGa thin films underneath a protection layer

Kono, Takashi*; Kakoki, Masaaki*; Yoshikawa, Tomoki*; Wang, X.*; Sumida, Kazuki; Muro, Takayuki*; Goto, Kazuki*; Sakuraba, Yuya*; Umetsu, Rie*; Kimura, Akio*

Physical Review B, 104(19), p.195112_1 - 195112_8, 2021/11

https://doi.org/10.1103/PhysRevB.104.195112

Angle-resolved photoelectron spectroscopy utilizing soft X-ray synchrotron radiation was applied to Heusler-type CoMnGa thin films that have a 1-nm Al capping layer. The bulk Fermi surfaces and band structures varied along the out-of-plane momentum, stemming from the three-dimensional crystal structure, in the absence of any in situ surface treatment. In addition, there were characteristic intersecting bands (Weyl cones), with crossing points near the Fermi level, which were consistent with computed results. The Weyl cones are of bulk origin and are responsible for the high anomalous Nernst and the anomalous Hall coefficients. A close comparison of the experimental band structures in CoMnGe and CoMnGa indicated that the rigid band picture is valid in both alloys and that fine carrier tuning is possible by replacing Ga with Ge to improve the anomalous conductivity.

Quasifree neutron knockout reaction reveals a small -Orbital component in the Borromean nucleus B

Yang, 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

https://doi.org/10.1103/PhysRevLett.126.082501

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.

Spin-polarized Weyl cones and giant anomalous Nernst effect in ferromagnetic Heusler films

Sumida, Kazuki; Sakuraba, Yuya*; Masuda, Keisuke*; Kono, Takashi*; Kakoki, Masaaki*; Goto, Kazuki*; Zhou, W.*; Miyamoto, Koji*; Miura, Yoshio*; Okuda, Taiichi*; et al.

Communications Materials (Internet), 1, p.89_1 - 89_9, 2020/11

https://doi.org/10.1038/s43246-020-00088-w

Research on factor analysis for achieving denuclearization, 6; Denuclearization of former republics of the Soviet Union

Kimura, Takashi; Tazaki, Makiko; Nakatani, Takayoshi; Shimizu, Ryo; Tamai, Hiroshi; Suda, Kazunori

Dai-41-Kai Nihon Kaku Busshitsu Kanri Gakkai Nenji Taikai Kaigi Rombunshu (Internet), 3 Pages, 2020/11

Following the collapse of the Soviet Union in 1991, Ukraine, Kazakhstan, and Belarus (the former three Soviet Union countries) unintentionally deployed nuclear weapons within their territory. The former three Soviet Union countries achieved denuclearization by transferring the deployed warheads and the delivery system of the nuclear weapons to Russia for disposal. This report gives our analysis of the success factors for achieving denuclearization by investigating the efforts towards denuclearization of such countries, the relevant frameworks such as the Treaty on the Reduction of Strategic Arms, etc.

Research on factor analysis for achieving denuclearization, 7; Framework on the non-proliferation of weapons scientists and engineers

Suda, Kazunori; Kimura, Takashi; Nakatani, Takayoshi; Shimizu, Ryo; Tazaki, Makiko; Tamai, Hiroshi

Dai-41-Kai Nihon Kaku Busshitsu Kanri Gakkai Nenji Taikai Kaigi Rombunshu (Internet), 3 Pages, 2020/11

The disintegration of central control in the former Soviet Union (FSU) prompted concerns among western countries that weapons scientists and engineers would flee to countries to acquire know-hows of weapons of mass destruction. To reduce this threat, the International Science and Technology Center (ISTC) was established at Moscow aimed at engaging weapons scientists and engineers from the FSU in peaceful use of nuclear technologies. In order to contribute the denuclearization study, it was discussed on contributions and good practice of the ISTC including non-proliferation measures of weapons scientists and engineers, deploying research results.

Introduction to nuclear security, 2; Efforts to strengthen nuclear security

Suda, Kazunori; Kimura, Takashi

Nihon Genshiryoku Gakkai-Shi ATOMO, 62(6), p.334 - 338, 2020/06

https://doi.org/10.3327/jaesjb.62.6_334

Amid growing concerns about potential nuclear terrorism, discussions have been conducted internationally to strengthen the nuclear security. In this series, we will explain the efforts of the international community to strengthen the nuclear security and the reflection of the treaty for the nuclear security and the IAEA nuclear security recommendations in the domestic laws.

Measurement of the angular distribution of -rays after neutron capture by La for a T-violation search

Okudaira, Takuya; Shimizu, Hirohiko*; Kitaguchi, Masaaki*; Hirota, Katsuya*; Haddock, C. C.*; Ito, Ikuya*; Yamamoto, Tomoki*; Endo, Shunsuke*; Ishizaki, Kohei*; Sato, Takumi*; et al.

EPJ Web of Conferences, 219, p.09001_1 - 09001_6, 2019/12

https://doi.org/10.1051/epjconf/201921909001

Parity violating effects enhanced by up to 10 times have been observed in several neutron induced compound nuclei. There is a theoretical prediction that time reversal (T) violating effects can also be enhanced in these nuclei implying that T-violation can be searched for by making very sensitive measurements. However, the enhancement factor has not yet been measured in all nuclei. The angular distribution of the (n,) reaction was measured with La by using a germanium detector assembly at J-PARC, and the enhancement factor was obtained. From the result, the measurement time to achieve the most sensitive T-violation search was estimated as 1.4 days, and a 40% polarized La target and a 70% polarized He spin filter whose thickness is 70 atmcm are needed. Therefore high quality He spin filter is developed in JAEA. The measurement result of the (n,) reaction at J-PARC and the development status of the He spin filter will be presented.

Research on factor analysis for achieving denuclearisation, 3; Denuclearisation at Libya: Process and success factors

Tamai, Hiroshi; Shimizu, Ryo; Tazaki, Makiko; Kimura, Takashi; Nakatani, Takayoshi; Suda, Kazunori

Nihon Kaku Busshitsu Kanri Gakkai Dai-40-Kai Nenji Taikai Puroshidhingusushu, p.89 - 92, 2019/11

Libya's denuclearisation, named "the Libya model", is regarded as one of good practices in cooperation of the international community and measures that have a sense of speed with the countries and institutions involved. Success factors of the denuclearisation are the Libya's relatively low technological progress despite the procurement of extensive nuclear materials and components due to the delay of detecting the nuclear programme, prompt implementation with the close collaboration of countries concerned, and Libya's cooperation facing to the economic sanctions and the regime collapse by the Iraq war. Precious lessons will be learned towards the prevention and the denuclearisation in other countries.