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Journal Articles

Change in magnetic properties induced by swift heavy ion irradiation in CeO$$_{2}$$

Shimizu, Hirotaka*; Kosugi, Shinya*; Tahara, Yuki*; Yasunaga, Kazufumi*; Kaneta, Yasunori*; Ishikawa, Norito; Hori, Fuminobu*; Matsui, Toshiyuki*; Iwase, Akihiro*

Nuclear Instruments and Methods in Physics Research B, 286, p.291 - 294, 2012/09

 Times Cited Count:26 Percentile:87.59(Instruments & Instrumentation)

We have studied the magnetic properties of pure CeO$$_{2}$$ irradiated with swift heavy ions. Experiment a results showed that the ferromagnetism was induced even at room temperature by 200 MeV Xe ion irradiation. The value of saturation magnetization, Ms, systematically changes as a function of ion-fluence. The X-ray diffraction (XRD) spectra show that the lattice constant of CeO$$_{2}$$ increases with increasing ion-fluence. This result and our previous XPS result show that the ion-irradiation produced oxygen vacancies. The present study implies that the ferromagnetic behavior of the ion-irradiated CeO$$_{2}$$ is attributed to the magnetic moments of localized 4f electrons on Ce$$^{3+}$$ atoms, which are related to oxygen vacancies.

Journal Articles

Temperature accelerated dynamics study of migration process of oxygen defects in UO$$_{2}$$

Ichinomiya, Takashi*; Uberuaga, B. P.*; Sickafus, K. E.*; Nishiura, Yasumasa*; Itakura, Mitsuhiro; Chen, Y.*; Kaneta, Yasunori*; Kinoshita, Motoyasu

Journal of Nuclear Materials, 384(3), p.315 - 321, 2009/02

 Times Cited Count:31 Percentile:88.62(Materials Science, Multidisciplinary)

We studied the migration dynamics of oxygen point defects in UO$$_{2}$$ which is the primary ceramic fuel for light-water reactors. Temperature accelerated dynamics simulations are performed for several initial conditions. Though the migration of the single interstitial is much slower than that of the vacancy, clustered interstitial shows faster migration than those. This observation gives us important insight on the formation mechanism of high-burnup restructuring, including planar defects and grain sub-division (the rim structure), found in UO$$_{2}$$.

Journal Articles

Study of irradiation induced restructuring of high burnup fuel; The New cross-over project (NXO) to study rim-structure formation

Kinoshita, Motoyasu*; Geng, H. Y.*; Chen, Y.*; Kaneta, Yasunori*; Iwasawa, Misako*; Onuma, Toshiharu*; Sonoda, Takeshi*; Yasunaga, Kazufumi*; Matsumura, Sho*; Yasuda, Kazuhiro*; et al.

Proceedings of 2006 International Meeting on LWR Fuel Performance (TopFuel 2006) (CD-ROM), p.248 - 254, 2006/10

The New Crossover Project (NXO) is studying effect of fission irradiation on fuel material that research activity is crossing over universities, national and private laboratories. Simulation studies are being performed to find principal and triggering processes of the rim-structure formation in high burnup LWR fuel pellet, using accelerator irradiation and computational calculations. Accelerator irradiation, high energy electron irradiation, fission energy particle beam and ion implantation (ragegas atoms) and combined overlapping irradiations are being performed. For the target of irradiation, CeO$$_{2}$$ isused as simulation of nuclear fuel. The initial results were such as planar structure made by Oxygen defects created by high energy electrons, and surface modification similar to grain-sub-division created by high fluence high energy particle irradiations.

Oral presentation

Properties of interatomic potentials for CeO$$_{2}$$ and UO$$_{2}$$

Nakamura, Jinichi; Kaneta, Yasunori*; Chen, Y.*; Geng, H.*; Iwasawa, Misako*; Onuma, Toshiharu*; Kinoshita, Motoyasu

no journal, , 

no abstracts in English

Oral presentation

First principles study on formation enegitics of point defects in UO$$_{2}$$ and CeO$$_{2}$$

Nakamura, Jinichi; Chen, Y.*; Iwasawa, Misako*; Onuma, Toshiharu*; Kaneta, Yasunori*; Geng, H.*; Kinoshita, Motoyasu

no journal, , 

no abstracts in English

Oral presentation

Oxygen defects configration in UO$$_{2}$$; Dimer and planar ordering

Nakamura, Jinichi; Geng, H.*; Chen, Y.*; Kaneta, Yasunori*; Iwasawa, Misako*; Onuma, Toshiharu*; Kinoshita, Motoyasu

no journal, , 

Oral presentation

Study of fission and high-burnup induced restructuring of nuclear fuel ceramics; Applying computer science to investigate kinetic process

Kinoshita, Motoyasu; Chen, Y.*; Kaneta, Yasunori*; Geng, H. Y.*; Iwasawa, Misako*; Onuma, Toshiharu*; Ichinomiya, Takashi*; Nishiura, Yasumasa*; Itakura, Mitsuhiro; Nakamura, Jinichi; et al.

no journal, , 

no abstracts in English

Oral presentation

First principles study of lattice defects in UO$$_{2}$$ and CeO$$_{2}$$

Chen, Y.*; Kaneta, Yasunori*; Geng, H. Y.*; Kinoshita, Motoyasu; Iwasawa, Misako*; Onuma, Toshiharu*; Nakamura, Jinichi

no journal, , 

no abstracts in English

Oral presentation

Recovery and restructuring induced by fission energy ions in high burnup nuclear fuel

Kinoshita, Motoyasu; Yasunaga, Kazufumi*; Sonoda, Takeshi*; Iwase, Akihiro*; Ishikawa, Norito; Sataka, Masao; Yasuda, Kazuhiro*; Matsumura, Sho*; Geng, H. Y.*; Ichinomiya, Takashi*; et al.

no journal, , 

We show the outline of achievements of New Cross Over (NXO) project. Concerning the grain subdivision of ceramics fuel at high burnup, we are trying to clarify the mechanisms and to develop the simulation methods. The main high lights are as follow as: (1) We have reproduced the grain subdivision of CeO$$_{2}$$, by means of ion implanter and TUNDEM accelerator. (2) We performed computational science study concerning the relocation of oxygen. In case of oxygen exess conditions, first principal calculation reproduced the orderring structure. TAD calculation shows that the exess oxygen compose clusters and diffuses rapidly even if low temperature.

Oral presentation

New cross over project study, 9; Review on simulation of grain-subdivision and rim-structure formation of fuel at high burnup

Chen, Y.*; Kaneta, Yasunori*; Geng, H. Y.*; Shang, J. C.*; Iwasawa, Misako*; Onuma, Toshiharu*; Sonoda, Takeshi*; Ichinomiya, Takashi*; Suzudo, Tomoaki; Itakura, Mitsuhiro; et al.

no journal, , 

The outcome of the New Crossover Project Study is outlined. The computational results includes the ab-initio study, molecular dynamics, statistical dynamics/thermal dynamics and meso-scopic modeling, and the experimental results given by an accelerator is also mentioned. Finally, we mention the future plans and the problems.

Oral presentation

New cross over project study, 6; Study on interatomic potential properties for CeO$$_{2}$$ and UO$$_{2}$$

Kaneta, Yasunori*; Geng, H. Y.*; Chen, Y.*; Iwasawa, Misako*; Onuma, Toshiharu*; Kinoshita, Motoyasu

no journal, , 

no abstracts in English

Oral presentation

Modification of magnetic properties of CeO$$_{2}$$ by using swift ion beam

Iwase, Akihiro*; Shimizu, Hirotaka*; Hori, Fuminobu*; Matsui, Toshiyuki*; Ishikawa, Norito; Kaneta, Yasunori*

no journal, , 

CeO$$_{2}$$ is irradiated with 200 MeV Xe, and we found that it becomes ferromagnetic after the irradiation. This may be due to 4f electrons lacalized in Ce$$^{3+}$$ atoms created by the irradiation.

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