Feasibility study of PGAA for boride identification in simulated melted core materials

Tsuchikawa, Yusuke; Abe, Yuta; Oishi, Yuji*; Kai, Tetsuya; Toh, Yosuke; Segawa, Mariko; Maeda, Makoto; Kimura, Atsushi; Nakamura, Shoji; Harada, Masahide; et al.

JPS Conference Proceedings (Internet), 33, p.011074_1 - 011074_6, 2021/03

https://doi.org/10.7566/JPSCP.33.011074

In the decommissioning of the Fukushima-Daiichi (1F) Nuclear Power Plant, it is essential to understand characteristics of the melted core materials. The estimation of boride in the real debris is of great importance to develop safe debris removal plans. Hence, it is required to investigate the amount of boron in the melted core materials with nondestructive methods. Prompt gamma-ray activation analysis (PGAA) is one of the useful techniques to determine the amount of borides by means of the 478 keV prompt gamma-ray from neutron absorption reaction of boron. Moreover, it is well known that the width of the 478 keV gamma-ray peak is typically broadened due to the Doppler effect. The degree of the broadening is affected by coexisting materials, and can be recognized by the width of the prompt gamma-ray peak. As a feasibility study, the prompt gamma-ray from boride samples were measured using the ANNRI, NOBORU, and RADEN beamlines at the Materials and Life Science Experimental Facility (MLF) of Japan Proton Accelerator Complex (J-PARC).

Penetration behavior of water solution containing radioactive species into dried concrete/mortar and epoxy resin materials

Sato, Isamu; Maeda, Koji; Suto, Mitsuo; Osaka, Masahiko; Usuki, Toshiyuki; Koyama, Shinichi

Journal of Nuclear Science and Technology, 52(4), p.580 - 587, 2015/04

https://doi.org/10.1080/00223131.2014.963725

Penetration behavior of radionuclides such as Cs into dried concrete material, dried mortar material and epoxy paint for a few dozen days was observed using a solution containing fission products extracted from irradiated fuels to obtain fundamental information on the radionuclide penetration rate and depth. Hardly any radionuclides could penetrate into the epoxy paint. The radionuclide solution penetrated into concrete and mortar materials to a depth of a few millimeters for a few dozen days. The penetration behavior observed near the surface of concrete and mortar materials was similar to the diffusion of nuclides in media such as water-saturated concrete, bentonite and cement materials.

Penetration behavior of solution containing radioactive nuclides into floor and wall materials

Usuki, Toshiyuki; Sato, Isamu; Suto, Mitsuo; Maeda, Koji; Osaka, Masahiko; Koyama, Shinichi; Tokoro, Daishiro*; Sekioka, Ken*; Ishigamori, Toshio*

JAEA-Testing 2014-001, 29 Pages, 2014/05

JAEA-Testing-2014-001.pdf:5.33MB

The penetration tests with solution containing radioactive nuclides were experimented to understand basic data for floor and wall materials of Fukushima Daiichi reactor buildings. The solution prepared from irradiated fuels was used as solution containing radioactive nuclides. The solution was applied to surface of epoxy paint, dried concrete and mortar used as specimens. Dose-rate profiles of direction of depth were given by radiation measurement and grinding of the specimens. The penetrations of radioactive nuclides for epoxy paint specimens were not clearly observed and the penetration depths would be within 0.4 mm. The penetrations of radioactive nuclides for dried concrete specimens proceeded. The penetration rates were substantially decreased when 16 days have elapsed from start. The dose rates of penetrated dried concrete specimens were reduced to background by grinding-2.0 mm. -ray spectrometry measurement showed that penetration behavior of near surface concrete are different among nuclides and the penetration behavior of radioactive nuclides into dried concrete and mortar materials through solution is similar to migration behavior of ions into those water-saturated materials.

Results of detailed analyses performed on boring cores extracted from the concrete floors of the Fukushima Daiichi Nuclear Power Plant reactor buildings

Maeda, Koji; Sasaki, Shinji; Kumai, Misaki; Sato, Isamu; Osaka, Masahiko; Fukushima, Mineo; Kawatsuma, Shinji; Goto, Tetsuo*; Sakai, Hitoshi*; Chigira, Takayuki*; et al.

Proceedings of International Nuclear Fuel Cycle Conference; Nuclear Energy at a Crossroads (GLOBAL 2013) (CD-ROM), p.272 - 277, 2013/09

Energy dependence of nonlinear effects of sputtering yields of Si bombarded with 10-540-keV C ions

Narumi, Kazumasa; Naramoto, Hiroshi*; Yamada, Keisuke; Saito, Yuichi; Chiba, Atsuya; Takahashi, Yasuyuki*; Maeda, Yoshihito

JAEA-Review 2011-043, JAEA Takasaki Annual Report 2010, P. 155, 2012/01

https://doi.org/10.11484/jaea-review-2011-043

no abstracts in English

Composition dependence of magnetic and magnetotransport properties in C-Co granular thin films

Sugai, Isamu*; Sakai, Seiji; Matsumoto, Yoshihiro; Naramoto, Hiroshi*; Mitani, Seiji*; Takanashi, Koki; Maeda, Yoshihito

Journal of Applied Physics, 108(6), p.063920_1 - 063920_7, 2010/09

https://doi.org/10.1063/1.3471800

The Electronic structures of fullerene/transition-metal hybrid material

Matsumoto, Yoshihiro; Sakai, Seiji; Naramoto, Hiroshi*; Hirao, Norie*; Baba, Yuji; Shimada, Toshihiro*; Sugai, Isamu; Takanashi, Koki; Maeda, Yoshihito

Materials Research Society Symposium Proceedings, Vol.1081 (Internet), 6 Pages, 2008/03

Recently, we have found the appearance of substantial MR ratio (80%) in a C/Co hybrid material. Such the MR ratio cannot be explained enough only by tunnel conduction through Co grains. Therefore, to obtain information about electronic structures of C/Co hybrid material is necessary. Absorption spectra of CCo are different from that of pristine C. In particular, peak intensity corresponding to (LUMO) C 1s excitation of CCo is clearly attenuated. In addition, C 1s photoelectron peak of CCo slightly shifted to lower binding energy compared to that of pristine C. These results indicate that 3d electron of Co transfers to orbital of C and new electronic states are formed in the C-Co compound. In fact, XPS spectra of valence excitation region also demonstrate the formation of hybrid orbital near the Fermi level due to the coupling of C and Co.

Magnetic and magnetotransport properties in nanogranular Co/C-Co film with high magnetoresistance

Sakai, Seiji; Yakushiji, Kei*; Mitani, Seiji*; Sugai, Isamu; Takanashi, Koki*; Naramoto, Hiroshi*; Avramov, P.; Lavrentiev, V.*; Narumi, Kazumasa; Maeda, Yoshihito

Materials Transactions, 48(4), p.754 - 758, 2007/04

https://doi.org/10.2320/matertrans.48.754

Magnetic properties were investigated for the alternately deposited film of C and Co which has found to exhibit tunnel magnetoresistance (MR) of 10-80 %. Magnetic field and temperature dependences of magnetization showed typical superparamagnetic behaviors with the blocking temperature of 40 K. The magnetization curve at 300 K was well fitted by the Langevin function with the size distribution of Co particles, and the mean diameter and size distribution were evaluated to be 3.1 nm and 1 nm, respectively. Based on the magnetic properties, the detailed structure and magnetotransport properties are discussed.

Initial spike pressure analysis in a large-scale sodium-water reaction test of downcomer region in SG; Large leak sodium-water reaction analysis (Report No.8)

*; *; *; *; Miyake, Osamu; *

PNC TN941 80-21, 85 Pages, 1980/02

PNC-TN941-80-21.pdf:10.52MB

Computer analysis for the downcomer water ingection test (SWAT-3, Run-7) was performed using the calculation module for initial spike pressure, SWAC-5KII which was revised the SWAC-5K module included in the large leak sodium-water reaction code "SWACS", at August, 1978. In order to verify this code, the sensitivity study for the significant parameters, such as rising time of water injection rate, H/HO conversion ratio, sonic velocity of the sodium in the vessel, initial bubble radius and number of downcomer flow pass, were carried out, and the comparison between calculation and measurements were accomplished. The suitable values of the parameters to explain the measurements of the SWAT-3, Run-7 experiment were obtained. And the availability of the calculation module, SWAC-5KII, of the SWACS has been demonstrated.

Tunneling magnetotransport in hybrid system of cobalt and C

Sakai, Seiji; Sugai, Isamu; Yakushiji, Kei*; Mitani, Seiji*; Takanashi, Koki*; Naramoto, Hiroshi; Avramov, P.; Narumi, Kazumasa; Maeda, Yoshihito

no journal, , 

We have revealed that the Co/Co-C films prepared by alt-deposition show the tunnel MR of a few 10% under low bias voltage and the further enhancement to above 80% by the voltage increase at lower temperature than 10 K. In the present study, the magnetotransport properties in the co-deposited Co/Co-C films are reported. The co-deposited film shows the remarkable tunnel MR effect (10-50%) whose ratio is significantly influenced by the applied voltage. Such a significant MR enhancement by the bias-voltage is found to take place commonly in the Co/Co-C films irrespective of the deposition method, and that is in contrast to the small extent of changes in the conventional metal/insulator systems. In the presentation, the comparative results for the co-deposited and alt-deposited Co/Co-C films are also reported in comparison with the analyzed structures by Raman spectroscopy et al..