Coexisting normal and intruder configurations in Mg

Kitamura, Noritaka*; Wimmer, K.*; Poves, A.*; Shimizu, Noritaka*; Tostevin, J. A.*; Bader, V. M.*; Bancroft, C.*; Barofsky, D.*; Baugher, T.*; Bazin, D.*; et al.

Physics Letters B, 822, p.136682_1 - 136682_7, 2021/11

AA2021-0459.pdf:1.01MB

https://doi.org/10.1016/j.physletb.2021.136682

no abstracts in English

Evaluation of source term parameters for spent fuel disposal in foreign countries, 2; Dissolution rates of spent fuel matrices and construction materials for fuel assemblies

Kitamura, Akira; Chikazawa, Takahiro*; Akahori, Kuniaki*; Tachi, Yukio

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 23(1), p.55 - 72, 2016/06

https://doi.org/10.3327/jnuce.23.1_55

The Japanese geological disposal program has started researching disposal of spent nuclear fuel (SF) in deep geological strata (hereafter "direct disposal of SF") as an alternative management option other reprocessing followed by vitrification and geological disposal of high-level radioactive waste. We conducted literature survey of dissolution rate of SF matrix and constructing materials (e.g. zircaloy cladding and control rods) selected in safety assessment reports for direct disposal of SF in Europe and United States. We also investigated basis of release rate determination and assignment of uncertainties in the safety assessment reports. Furthermore, we summarized major conclusions proposed by some European projects governed by European Commission. It was found that determined release rates are fairly similar to each other due to use of similar literature data in all countries of interest. It was also found that the determined release rates were including conservativeness because it was difficult to assign uncertainties quantitatively. It is expected that these findings are useful as fundamental information for determination of the release rates for the safety assessment of Japanese SF disposal system.

Study of annealing effect on crystal and local structures of doped zirconia using multi probe

Ito, Takanori*; Mori, Masashi*; Inukai, Manabu*; Nitani, Hiroaki*; Yamamoto, Takashi*; Miyanaga, Takashi*; Igawa, Naoki; Kitamura, Naoto*; Ishida, Naoya*; Idemoto, Yasushi*

Photon Factory News, 33(1), p.18 - 24, 2015/05

http://pfwww.kek.jp/publications/pfnews/33_1/saikin1.pdf

The effect of the annealing on the crystal and local structures of doped zirconia was investigated by multi-probe technique using synchrotron X-ray and neutron diffraction, and first principles calculation. It was revealed that the annealing process enhances the periodic distortion of some zirconia compounds by Rietveld/ maximum entropy methods applied to the SR-X-ray and neutron diffractions. In addition, the combined X-ray absorption spectroscopy and first-principles calculations results showed the ZrO polyhedra in zirconia were distorted by the annealing. Those results indicate that the degradation of oxide ionic conductivity by the annealing was related to the periodic distortion in zirconia.

Enhancement of the methodology of repository design and post-closure performance assessment for preliminary investigation stage, 3; Progress report on NUMO-JAEA collaborative research in FY2013 (Joint research)

Shibata, Masahiro; Sawada, Atsushi; Tachi, Yukio; Makino, Hitoshi; Wakasugi, Keiichiro; Mitsui, Seiichiro; Kitamura, Akira; Yoshikawa, Hideki; Oda, Chie; Ishidera, Takamitsu; et al.

JAEA-Research 2014-030, 457 Pages, 2015/03

JAEA-Research-2014-030.pdf:199.23MB

JAEA and NUMO have conducted a collaborative research work which is designed to enhance the methodology of repository design and post-closure performance assessment in preliminary investigation stage. With regard to (1) study on rock suitability in terms of hydrology, based on some examples of developing method of hydro-geological structure model, acquired knowledge are arranged using the tree diagram, and model uncertainty and its influence on the evaluation items were discussed. With regard to (2) study on scenario development, the developed approach for "defining conditions" has been reevaluated and improved from practical viewpoints. In addition, the uncertainty evaluation for the effect of use of cementitious material, as well as glass dissolution model, was conducted with analytical evaluation. With regard to (3) study on setting radionuclide migration parameters, based on survey of precedent procedures, multiple-approach for distribution coefficient of rocks was established, and the adequacy of the approach was confirmed though its application to sedimentary rock and granitic rock. Besides, an approach for solubility setting was developed including the procedure of selection of solubility limiting solid phase. The adequacy of the approach was confirmed though its application to key radionuclides.

Decontamination of school facilities in Fukushima-city

Yoshikawa, Hideki; Iijima, Kazuki; Sasamoto, Hiroshi; Fujiwara, Kenso; Mitsui, Seiichiro; Kitamura, Akira; Kurikami, Hiroshi; Tokizawa, Takayuki; Yui, Mikazu; Nakayama, Shinichi

Materials Research Society Symposium Proceedings, Vol.1518, p.269 - 275, 2013/10

https://doi.org/10.1557/opl.2013.75

Following the release of radionuclides into the environment as a result of the accident at Fukushima Daiichi Nuclear Power Plant, Japan Atomic Energy Agency (JAEA) had to develop an immediate and effective method of reducing the dose rate received by students in school facilities. A demonstration of a reducing method was carried out by JAEA at a junior high school ground and kindergarten yard in the center of Fukushima-city. Dose rates of the released radionuclides are largely controlled by the ground level contamination and accumulation of mainly cesium-137 (Cs) and cesium-134 (Cs) in populated areas. An effective means of reducing dose rate was to remove the surface soil and to bury it on-site under fresh uncontaminated soil or soil collected under deep depth at the site for shielding. The dose rate at1 m above ground level was reduced from 2.5 Sv/h to 0.15 Sv/h.

Extreme ultraviolet free electron laser seeded with high-order harmonic of Ti:sapphore laser

Togashi, Tadashi*; Takahashi, Eiji*; Midorikawa, Katsumi*; Aoyama, Makoto; Yamakawa, Koichi; Sato, Takahiro*; Iwasaki, Atsushi*; Owada, Shigeki*; Okino, Tomoya*; Yamanouchi, Kaoru*; et al.

Optics Express (Internet), 19(1), p.317 - 324, 2011/01

https://doi.org/10.1364/OE.19.000317

The 13th harmonic of a Ti:sapphire (Ti:S) laser in the plateau region was injected as a seeding source to a 250-MeV free-electron-laser (FEL) amplifier. When the amplification conditions were fulfilled, strong enhancement of the radiation intensity by a factor of 650 was observed. The random and uncontrollable spikes, which appeared in the spectra of the Self-Amplified Spontaneous Emission (SASE) based FEL radiation without the seeding source, were found to be suppressed drastically to form to a narrow-band, single peak profile at 61.2 nm. The properties of the seeded FEL radiation were well reproduced by numerical simulations. We discuss the future precept of the seeded FEL scheme to the shorter wavelength region.

Study of mechanism of mixed conduction due to electrons and oxygen ions in (LaSr)MnO and (BaSr)(CoFe)O through rietveld refinement and MEM analysis

Ito, Takanori*; Shirasaki, Saori*; Fujie, Yoshinori*; Kitamura, Naoto*; Idemoto, Yasushi*; Osaka, Keiichi*; Hirosawa, Ichiro*; Igawa, Naoki

Denki Kagaku Oyobi Kogyo Butsuri Kagaku, 77(2), p.161 - 168, 2009/02

https://doi.org/10.5796/electrochemistry.77.161

We analyzed the mechanism of mixed conduction due to electrons and oxygen ions in (LaSr)MnO and (BaSr)(CoFe)O through the Rietveld refinement and maximum entropy method analyses of neutron and synchrotron X-ray diffractions. It was found that Mn-O plane in (LaSr)MnO has a strong, isotropic covalent bond that enables conduction of electrons. The (Co, Fe)-O2 plane with a covalent bond and a low concentration of oxygen vacancies in (BaSr)(CoFe)O can also conduct electrons. On the other hand, the (Ba, Sr)-O1 plane in (BaSr)(CoFe)O, which has a high concentration of oxygen vacancies, large isotropic displacement parameter, and a strong ionic bond, is responsible for the diffusion of oxygen ions.

Research and development of minor actinide-containing fuel and target in a future integrated closed cycle system

Osaka, Masahiko; Serizawa, Hiroyuki; Kato, Masato; Nakajima, Kunihisa; Tachi, Yoshiaki; Kitamura, Ryoichi; Miwa, Shuhei; Iwai, Takashi; Tanaka, Kenya; Inoue, Masaki; et al.

Journal of Nuclear Science and Technology, 44(3), p.309 - 316, 2007/03

https://doi.org/10.3327/jnst.44.309

no abstracts in English

Acquisition of the data and their conversion to the data bases for the radionuclides migration under deep underground environment

Yoshikawa, Hideki; Shibata, Masahiro; Sasamoto, Hiroshi; Iijima, Kazuki; Sato, Haruo; Kitamura, Akira; Ishidera, Takamitsu; Fujiwara, Kenso; Kurosawa, Susumu; Xia, X.; et al.

Hoshasei Haikibutsu Anzen Kenkyu Nenji Keikaku (Heisei-13-NendoHeisei-17-Nendo) Kenkyu Seika Hokokushu, p.153 - 170, 2006/03

no abstracts in English

Development of vertical component isolation system with coned disk springs for FBR plant

Kitamura, Seiji; Okamura, Shigeki; Takahashi, Kenji; Kamishima, Yoshio*; Somaki, Takahiro*; Morishita, Masaki

Proceedings of 9th World Seminar on Seismic Isolation, Energy Dissipation and Active Vibration Control of Structures (CD-ROM), p.209 - 216, 2005/00

A structural concept of a vertical component isolation system for fast reactors, assuming a building adopting a horizontal base isolation system, has been studied. In this concept, a reactor vessel and major primary components are suspended from a large common deck supported by vertical isolation devices consisting of large coned disk springs. We designed the isolation device, which could be achieved vertical isolation frequency of 1 Hz and damping ratio of 20 %. Full scale coned disk spring and damper performance tests were carried out to verify the validity of design equations. And a series of shaking table test using a 1/8 scale model was performed. The test results fit well the simulation analysis results, so the validity of the design methods was able to be verified. The prospect that the vertical component isolation system applied to the FBR plant could technically realize was obtained.