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.

In-beam -ray spectroscopy of Cf by neutron-transfer reactions using a Cf target

Takahashi, Ryuta; Ishii, Tetsuro; Asai, Masato; Nagae, Daisuke*; Makii, Hiroyuki; Tsukada, Kazuaki; Toyoshima, Atsushi; Ishii, Yasuo; Matsuda, Makoto; Makishima, Akiyasu*; et al.

Physical Review C, 81(5), p.057303_1 - 057303_4, 2010/05

https://doi.org/10.1103/PhysRevC.81.057303

The ground-state bands of Cf have been established up to 10, 12, and 10 states, respectively, by in-beam -ray spectroscopy using neutron-transfer reactions with a O beam and a highly radioactive Cf target. The deexcitation rays in Cf were identified by taking coincidences with outgoing particles of O measured with Si - detectors, and by selecting their kinetic energies. This is the first in-beam -ray spectroscopy for Cf isotopes.

Research and development for treatment and disposal technologies of TRU waste; JFY 2007 annual report

Kamei, Gento; Honda, Akira; Mihara, Morihiro; Oda, Chie; Murakami, Hiroshi; Masuda, Kenta; Yamaguchi, Kohei; Matsuda, Setsuro; Ichige, Satoru; Takahashi, Kuniaki; et al.

JAEA-Research 2008-082, 84 Pages, 2008/11

JAEA-Research-2008-082.pdf:2.52MB
JAEA-Research-2008-082(errata).pdf:0.15MB

Based on Japanese governmental policy and general scheme, research and development of geological disposal technology for TRU waste has been proceeding to improve reliability of the safety assessment of the co-locational disposal of TRU waste and of HLW, to expand the basement of generic safety assessment, and to develop the alternative technology to cope with the broad geologic environment of Japan. Japan Atomic Energy Agency is dealing with the assignments in the governmental generic scheme. We report here the progress of the studies at the end of H19 (2007) fiscal year, which are (1) treatment and packaging of TRU waste including applicability of calcination for unpacking and sorting of wastes, characterization and inspection methodology of TRU waste, (2) mechanical assessment for the near-field structure including model development and preparation, introduction of hostrock creep model and coupling analysis of deformation of hostrock and engineered barrier. (3) performance assessment of the disposal system including data acquisition and preparation on radionuclides migration, cementitious material alteration, bentonite and hostrock alteration with alkaline solution and nitrate effect, and (4) alternative technology development including decomposition of nitrate.

Acoustic emission and disturbances in central solenoid model coil for international thermonuclear experimental reactor

Arai, K.*; Ninomiya, Akira*; Ishigooka, Takeshi*; Takano, Katsutoshi*; Nakajima, Hideo; Michael, P.*; Vieira, R.*; Martovetsky, N.*; Sborchia, C.*; Alekseev, A.*; et al.

Cryogenics, 44(1), p.15 - 27, 2004/01

https://doi.org/10.1016/j.cryogenics.2003.07.006

no abstracts in English

Sodium Flow Test for Dummy Core Fuel Sudassemdlies of Prototype Fast Breeder Reactor MONJU (on Pressure Loss Increase of MONJU Dummy Core Fuel Subassemblies)

Fujimoto, Tetsuro*; Sato, Kazujiro*; Takahashi, June*

PNC TN951 76-14, 59 Pages, 1976/09

PNC-TN951-76-14.pdf:2.2MB

The 4,800-hours flow test for MONJU dummy core fuel subassemblies was carried out at sodium flow rate of 19.5 - 20.2 kg/sec. subassembly, sodium temperature of 600, oxygen impurities in sodium of 2 - 2.5ppm which are about the same condition as that for MONJU core fuel subassemblies. The result of this test showed that the pressure loss of dummy core fuel subassemblies increased up to 11% in 3,000 hours and became constant after that. The integrity of the dummy subassemblies is planned to be investigated by disassembling them and making a material examination. On the other hand,the pressure loss increase for these subassembkies was estimated at 5.4% in case of water flow test which was carried out before and after spdium test. The cause of this difference should be investigated hereafter.

Development of a linear ion trap at JAEA-ISOL

Nagae, Daisuke; Ishii, Tetsuro; Makii, Hiroyuki*; Takahashi, Ryuta

no journal, , 

Construction of a linear ion trap is now in progress at JAEA-ISOL. We trapped Na, Rb, and Cs ions successfully. We will talk about a development of the trap.

In-beam -ray spectroscopy of Cf using neutron-transfer reactions

Takahashi, Ryuta; Ishii, Tetsuro; Nagae, Daisuke; Asai, Masato; Tsukada, Kazuaki; Toyoshima, Atsushi; Ishii, Yasuo; Matsuda, Makoto; Shizuma, Toshiyuki; Makii, Hiroyuki*; et al.

no journal, , 

no abstracts in English

Measurement of fission probability of the compound nucleus U populated by the reaction U(O,O)

Nishio, Katsuhisa; Nishinaka, Ichiro; Mitsuoka, Shinichi; Makii, Hiroyuki; Furutaka, Kazuyoshi; Wakabayashi, Yasuo; Takahashi, Ryuta; Ishii, Tetsuro; Chiba, Satoshi; Hirose, Kentaro*; et al.

no journal, , 

no abstracts in English

Maintenance activities in Chemical Reprocessing Facility (CPF); Renewal of driving unit of negative pressure control valves

Kobayashi, Yuki; Takahashi, Tetsuro; Shinozaki, Tadahiro; Ogasawara, Koji; Koizumi, Kenji; Nakajima, Yasuo

no journal, , 

The negative pressure control valve is reliable apparatus which has been used in many nuclear facilities. In recent years, there are some troubles on those valves in CPF (Chemical Reprocessing Facility) by the aged deterioration because the valves were kept using for more than 25 years after facility had operated. Therefore, we have been carrying out renewal of driving units of the valves to assure performance of negative pressure control function and to keep stability of operation of the facility. In this presentation, we report knowledge provided through the renewal work, such as the renewal procedure, the deterioration situation of components and the cause of troubles.

- and high-resolution fine-structure spectroscopy for the heaviest nuclei

Asai, Masato; Haba, Hiromitsu*; Tsukada, Kazuaki; Sato, Nozomi; Kasamatsu, Yoshitaka*; Kaji, D.*; Morimoto, Koji*; Morita, Kosuke*; Sato, Tetsuya; Toyoshima, Atsushi; et al.

no journal, , 

Alpha-gamma and high-resolution fine-structure spectroscopy of Rf and Lr isotopes was performed to clarify the nuclear structure of superheavy nuclei. rays following the decay of Rf were observed for the first time through the - coincidence measurement, and the neutron configuration of the ground state of Rf was assigned. It was found that the ground-state configuration of Rf is different from those of the lighter N = 155 isotones Fm and Cf. For the Lr isotopes, the proton configurations of the ground and isomeric states in Lr and the ground states of Lr and Lr were definitely identified through the high-resolution fine structure spectroscopy. Theoretical calculations based on the macroscopic-microscopic model revealed that the change of the ground-state configuration in the N = 155 isotones is strongly associated with the rapidly decreasing hexadecapole deformation with increasing atomic number.