Local environmental effects on cosmic ray observations at Syowa Station in the Antarctic; PARMA-based snow cover correction for neutrons and machine learning approach for neutrons and muons

Kataoka, Ryuho*; Sato, Tatsuhiko; Kato, Chihiro*; Kadokura, Akira*; Kozai, Masayoshi*; Miyake, Shoko*; Murase, Kiyoka*; Yoshida, Rihito*; Tomikawa, Yoshihiro*; Munakata, Kazuoki*

Journal of Space Weather and Space Climate (Internet), 12, p.37_1 - 37_11, 2022/11

https://doi.org/10.1051/swsc/2022033

Solar modulation of galactic cosmic rays around the solar minimum in 2019-2020 looks different in the secondary neutrons and muons observed at the ground. To compare the solar modulation of primary cosmic rays in detail, we have to remove the possible seasonal variations caused by the atmosphere and surrounding environment. As such surrounding environment effects, we evaluate the snow cover effect on neutron count rate and the atmospheric temperature effect on muon count rate both simultaneously observed at Syowa Station in the Antarctic (69.01 S, 39.59 E). The corrected muon count rate starts decreasing in late 2019, earlier than the corrected neutron count rate which starts decreasing in early 2020, possibly indicating the rigidity dependent solar modulation in the heliosphere.

Shell structure of the neutron-rich isotopes Co

Lokotko, T.*; Leblond, S.*; Lee, J.*; Doornenbal, P.*; Obertelli, A.*; Poves, A.*; Nowacki, F.*; Ogata, Kazuyuki*; Yoshida, Kazuki; Authelet, G.*; et al.

Physical Review C, 101(3), p.034314_1 - 034314_7, 2020/03

https://doi.org/10.1103/PhysRevC.101.034314

The structures of the neutron-rich Co isotopes were investigated via () knockout reactions at the Radioactive Isotope Beam Factory, RIKEN. Level schemes were reconstructed using the coincidence technique, with tentative spin-parity assignments based on the measured inclusive and exclusive cross sections. Comparison with shell-model calculations suggests coexistence of spherical and deformed shapes at low excitation energies in the Co isotopes.

Enhancement of element production by incomplete fusion reaction with weakly bound deuteron

Wang, H.*; Otsu, Hideaki*; Chiga, Nobuyuki*; Kawase, Shoichiro*; Takeuchi, Satoshi*; Sumikama, Toshiyuki*; Koyama, Shumpei*; Sakurai, Hiroyoshi*; Watanabe, Yukinobu*; Nakayama, Shinsuke; et al.

Communications Physics (Internet), 2(1), p.78_1 - 78_6, 2019/07

https://doi.org/10.1038/s42005-019-0165-1

Searching for effective pathways for the production of proton- and neutron-rich isotopes through an optimal combination of reaction mechanism and energy is one of the main driving forces behind experimental and theoretical nuclear reaction studies as well as for practical applications in nuclear transmutation of radioactive waste. We report on a study on incomplete fusion induced by deuteron, which contains one proton and one neutron with a weak binding energy and is easily broken up. This reaction study was achieved by measuring directly the cross sections for both proton and deuteron for Pd at 50 MeV/u via inverse kinematics technique. The results provide direct experimental evidence for the onset of a cross-section enhancement at high energy, indicating the potential of incomplete fusion induced by loosely-bound nuclei for creating proton-rich isotopes and nuclear transmutation of radioactive waste.

Decreasing trend of ambient dose equivalent rates over a wide area in eastern Japan until 2016 evaluated by car-borne surveys using KURAMA systems

Ando, Masaki; Mikami, Satoshi; Tsuda, Shuichi; Yoshida, Tadayoshi; Matsuda, Norihiro; Saito, Kimiaki

Journal of Environmental Radioactivity, 192, p.385 - 398, 2018/12

https://doi.org/10.1016/j.jenvrad.2018.07.009

Car-borne surveys using KURAMA systems have been conducted over a wide area in eastern Japan since 2011. The measurement data collected until 2016 was analyzed, and decreasing trend of the dose rates in regions within 80 km of Fukushima Dai-ichi Nuclear Power Plant were examined. The averaged dose rates tended to decrease considerably with respect to the physical decay of radiocaesium, and the ecological half-lives of the fast and slow decay components were estimated. The decrease of the dose rate in the forest was slower than its decrease in other regions, and the decrease of the dose rate in urban area was the fastest. The decrease in the dose rates obtained via the car-borne survey was larger than that obtained on flat ground with few disturbances using survey meters approximately 1.5 y after the accident; hereafter, the decrease in the dose rates obtained via the car-borne survey was same as the latter measurement.

Measurement of air dose rates over a wide area around the Fukushima Dai-ichi Nuclear Power Plant through a series of car-borne surveys

Ando, Masaki; Nakahara, Yukio; Tsuda, Shuichi; Yoshida, Tadayoshi; Matsuda, Norihiro; Takahashi, Fumiaki; Mikami, Satoshi; Kinouchi, Nobuyuki; Sato, Tetsuro*; Tanigaki, Minoru*; et al.

Journal of Environmental Radioactivity, 139, p.266 - 280, 2015/01

https://doi.org/10.1016/j.jenvrad.2014.05.014

A series of car-borne surveys using the KURAMA and KURAMA-II systems was conducted in a wide area in eastern Japan from June 2011 to December 2012 to evaluate the distribution of air dose rates around the Fukushima Dai-ichi Nuclear Power Plant, and to determine the time-dependent trend of decrease in air dose rates. An automated data processing system was established, which enables analyses of large amounts of data obtained with the use of about 100 units of the measurement system in a short time. The initial data for studying the migration status of radioactive cesium was obtained in the first survey, followed by the other car-borne surveys having wider measurement ranges. Comparing the measured air dose rates obtained in each survey, it was found that the decreasing trend of air dose rates measured through car-borne surveys was larger than that expected from the physical decay of radioactive cesium and that measured using NaI (Tl) survey meters around the road.

JAEA thermodynamic database for performance assessment of geological disposal of high-level radioactive and TRU wastes

Kitamura, Akira; Fujiwara, Kenso; Doi, Reisuke; Yoshida, Yasushi*; Mihara, Morihiro; Terashima, Motoki; Yui, Mikazu

JAEA-Data/Code 2009-024, 84 Pages, 2010/03

JAEA-Data-Code-2009-024.pdf:2.84MB

A thermodynamic database was established to develop a thermodynamic database for performance assessment of geological disposal of high-level and TRU wastes. Twenty-four elements (actinides, fission products and their daughters) which are of importance for the performance assessment of geological disposal have been selected. The fundamental plan was in principle based on the guidelines established by the Nuclear Energy Agency in the Organisation for Economic Co-operation and Development (OECD/NEA). Additional unique guidelines were established due to a requirement from the performance assessment to select tentative thermodynamic values obtained from chemical analogues and/or models for elements with insufficient thermodynamic values. Selected thermodynamic data were compiled for geochemical calculation programs.

Mizunami Underground Research Laboratory Project, Annual report for fiscal year 2006

Nishio, Kazuhisa; Matsuoka, Toshiyuki; Mikake, Shinichiro; Tsuruta, Tadahiko; Amano, Kenji; Oyama, Takuya; Takeuchi, Ryuji; Saegusa, Hiromitsu; Hama, Katsuhiro; Yoshida, Haruo*; et al.

JAEA-Review 2009-001, 110 Pages, 2009/03

JAEA-Review-2009-001.pdf:49.84MB

Japan Atomic Energy Agency (JAEA) at Tono Geoscience Center (TGC) is developing a geoscientific research project named Mizunami Underground Research Laboratory (MIU) project in crystalline rock environment in order to establish scientific and technological basis for geological disposal of HLW. Geoscientific research at MIU is planned to be carried out in three phases over a period of 20 years; Surface-based Investigation Phase (Phase 1), Construction Phase (Phase 2) and Operation Phase (Phase 3). Currently, the project is under the Construction Phase. This document presents the following results of the research and development performed in 2006 fiscal year, as a part of the Construction Phase based on the MIU Master Plan updated in 2002, (1) Investigation at the MIU Construction Site, (2) Construction at the MIU Construction Site, (3) Research Collaboration.

Measurement of the spin and magnetic moment of Al

Ozawa, Akira*; Matsuta, Kensaku*; Nagatomo, Takashi*; Mihara, Mototsugu*; Yamada, Kazunari*; Yamaguchi, Takayuki*; Otsubo, Takashi*; Momota, Sadao*; Izumikawa, Takuji*; Sumikama, Toshiyuki*; et al.

Physical Review C, 74(2), p.021301_1 - 021301_4, 2006/08

https://doi.org/10.1103/PhysRevC.74.021301

no abstracts in English

Current status of system development to provide the databases of nuclides migration

Sasamoto, Hiroshi; Yoshida, Yasushi*; Isogai, Takeshi*; Suyama, Tadahiro*; Jintoku, Takashi*; Shibata, Masahiro; Yui, Mikazu

Saikuru Kiko Giho, (28), p.27 - 33, 2005/09

https://rdreview.jaea.go.jp/gihou/pdf3/n28-04.pdf

JNC has developed the databases of nuclides migration for safety assessment of high-level radioactive waste (HLW), and the databases have been used in the second progress report to present the technical reliability of HLW geological disposal in Japan. The technical level and applicability of databases developed by JNC have been evaluated highly not only in Japan but also in overseas. Thus we have performed the followings in order to provide the databases broadly in the word and to promote the use of databases; 1) development of tools to convert the database format from geochemical code PHREEQE to PHREEQC, GWB and EQ3/6, 2) open the web site including the databases to the public. As a result, a down-load system of databases from web site has been applied and the database users have significantly increased. Additionally it has been performed that we consider the useful comments from database user for modification and/or update of databases.

Development of Thermodynamic Databases for Hyperalkaline, Argillaceous Systems

Arthur, R. C,*; Sasamoto, Hiroshi; Oda, Chie; Honda, Akira; Shibata, Masahiro; Yoshida, Yasushi*; Yui, Mikazu

JNC TN8400 2005-010, 234 Pages, 2005/07

JNC-TN8400-2005-010.pdf:11.24MB

This report describes three thermodynamic databases for minerals, gases, aqueous species and reactions of relevance to bentonite and cement barriers in geologic repositories for transuranic (TRU) and other nuclear wastes. The databases support calculations using the SUPCRT, PHREEQC and GWB geochemical codes, and are referred to as SPRONS.TRU (SUPCRT), JNC-TDB.TRU (PHREEQC) and THERMO_ JNCTRU (GWB). The reliability of these databases should be considered in the context of basic limitations in current conceptual models of clay-bearing, high-pH systems. Minerals that are important in such systems tend to be complex, possibly metastable solid solutions having highly variable compositions that have not been well characterized experimentally or thermodynamically. There is also considerable uncertainty regarding important aqueous species in such systems due to the paucity of relevant experimental data presently available. With these limitations in mind, the databases developed in this study are considered to be reliable insofar as they include data for minerals that are known to be important or representative of hyperalkaline, argillaceous systems, and because the data are in general demonstrably accurate in cases where comparisons can be made between calculated values and their experimental counterparts. The databases may not meet the ideal standard of an internally consistent database because more weight has been given in this study to the accuracy and completeness of the data than to their internal consistency. An approach recommended for future improvements and revisions of the databases described in this report includes the development of a consistent set of empirical methods permitting routine estimation of thermodynamic properties in cases where reliable experimental data are lacking, combined with uncertainty analyses to assess the importance of conceptual and parameter uncertainties on models of the long-term behavior of bentonite and cementitious barriers.