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Journal Articles

Effect of Sn and Nb on generalized stacking fault energy surfaces in zirconium and $$gamma$$ hydride habit planes

Udagawa, Yutaka; Yamaguchi, Masatake; Tsuru, Tomohito; Abe, Hiroaki*; Sekimura, Naoto*

Philosophical Magazine, 91(12), p.1665 - 1678, 2011/04

 Times Cited Count:15 Percentile:63.86(Materials Science, Multidisciplinary)

We have investigated the effects of Sn and Nb on dislocation properties in a Zr lattice in order to elucidate the role of these alloying elements in hydride nucleation processes. According to experimental observations, $$gamma$$-hydride habit planes are close to the prismatic plane in pure Zr and close to the basal plane in zircaloy. Dislocation loops are observed around hydride precipitates, implying they play a part in hydride formation. Our ab initio generalized-stacking-fault energy calculations showed remarkable effects of Sn on unstable-stacking energy and stacking-fault energy: these parameters for basal slip were considerably reduced while those for prismatic slip were increased in the presence of Sn. These results suggest selective stabilization and enhancement of dislocation spreading in the basal plane, promoting possible elementary processes of hydride precipitation with basal habit plane, i.e. screw-dislocation spreading and edge-dislocation emission in the basal plane.

Journal Articles

Ab initio study on plane defects in zirconium-hydrogen solid solution and zirconium hydride

Udagawa, Yutaka; Yamaguchi, Masatake; Abe, Hiroaki*; Sekimura, Naoto*; Fuketa, Toyoshi

Acta Materialia, 58(11), p.3927 - 3938, 2010/06

 Times Cited Count:96 Percentile:96.47(Materials Science, Multidisciplinary)

Journal Articles

${it In situ}$ TEM observation of growth process of zirconium hydride in zircaloy-4 during hydrogen ion implantation

Shinohara, Yasunari*; Abe, Hiroaki*; Iwai, Takeo*; Sekimura, Naoto*; Kido, Toshiya*; Yamamoto, Hiroyuki; Taguchi, Tomitsugu

Journal of Nuclear Science and Technology, 46(6), p.564 - 571, 2009/06

 Times Cited Count:30 Percentile:87.36(Nuclear Science & Technology)

${it In situ}$ observation during hydrogen ion implantation was performed with a TEM installed in an ion accelerator to investigate the growth process of Zr hydride in Zicaloy-4. To clarify the effect of radiation damage, some samples were irradiated with 4 MeV Ni$$^{3+}$$ ions prior to hydrogen implantation. Growth processes of Zr hydrides accompanying the formation of dislocations were observed. The crystallographic relationship between the Zr matrix and Zr hydrides was identical with that found in previous studies: inter- and intragranular hydrides exhibiting a tendency to grow in the $$<$$11$$bar{2}$$0$$>$$ direction. This growth can be attributed to a shear mechanism. In specimens preirradiated with Ni ions, the growth rate of hydrides was suppressed, but the growth direction was not affected by radiation defects. It was also confirmed that the black spots induced by Ni$$^{3+}$$ ion irradiation grew during hydrogen ion implantation, suggesting the formation of hydrides at the defects.

Journal Articles

Influence of H and He on corrosion behavior of ion irradiated stainless steel

Nemoto, Yoshiyuki; Miwa, Yukio; Tsuji, Hirokazu; Tsukada, Takashi; Abe, Hiroaki*; Sekimura, Naoto*

JAERI-Review 2003-033, TIARA Annual Report 2002, p.171 - 173, 2003/11

The aim of this work is to evaluate corrosion behavior of irradiated materials for mechanistic understanding of irradiation assisted stress corrosion cracking (IASCC). Solution annealed high purity Fe-18Cr-12Ni specimens were used in this study. H and He were implanted during irradiation with 12MeV Ni$$^{3+}$$ ion at 573K. After corrosion procedure, the specimens were examined with atomic force microscope (AFM) to evaluate corrosion behavior. It was shown that the corroded volume of irradiated area increased with radiation damage. H implantation at lower temperature accelerated corrosion. He implantation suppressed corrosion.

Journal Articles

Reweldability tests of irradiated inconel 625 by TIG welding method

Tsuchiya, Kunihiko; Sekimura, Naoto*; *; G.Kalinin*; ; Kawamura, Hiroshi

Fusion Technology 1998, 2, p.1297 - 1300, 1998/00

no abstracts in English

Journal Articles

Present status of radiation damage mechanism study on reactor pressure vessels based on irradiation correlatin concept

Ishino, Shiori*; Sekimura, Naoto*; Suzuki, Masahide; *; *; Shibahara, Itaru*

Nihon Genshiryoku Gakkai-Shi, 36(5), p.396 - 404, 1994/00

 Times Cited Count:1 Percentile:17.88(Nuclear Science & Technology)

no abstracts in English

Oral presentation

Ab initio study on plane defects in Zirconium hydrogen solution and hydride

Udagawa, Yutaka; Yamaguchi, Masatake; Abe, Hiroaki*; Asari, Keisuke*; Shinohara, Yasunari*; Murakami, Kenta*; Nakazono, Yoshihisa*; Mihara, Takeshi*; Sawayama, Yohei*; Sekimura, Naoto*; et al.

no journal, , 

no abstracts in English

Oral presentation

Study on hydrogenation and radiation effects in Zr-Nb alloys, 4; Modelling; First-principles calculations for the energies of lattice defects in Zr

Yamaguchi, Masatake; Udagawa, Yutaka; Abe, Hiroaki*; Sekimura, Naoto*

no journal, , 

no abstracts in English

Oral presentation

Study on hydrogenation and radiation effects in Zr-Nb alloys; Development of an interatomic potential for Zr-H binary systems

Udagawa, Yutaka; Yamaguchi, Masatake; Abe, Hiroaki*; Sekimura, Naoto*

no journal, , 

no abstracts in English

Oral presentation

Study on hydrogenation and radiation effects in Zr-Nb alloys, 2; First-principles study on the behavior of solute elements (Nb, Fe, Cr, etc.) inhcp Zr

Yamaguchi, Masatake; Udagawa, Yutaka; Abe, Hiroaki*; Sekimura, Naoto*

no journal, , 

no abstracts in English

Oral presentation

Study on corrosion, hydrogenation and radiation effects in Zr-Nb Alloys, 5; Simulations

Yamaguchi, Masatake; Udagawa, Yutaka; Abe, Hiroaki*; Sekimura, Naoto*

no journal, , 

From first-principles calculations, we investigate solute segregation energy and defect formation energy in hcp Zirconium. We found that segregation energies of some solute elements (Fe, Cr, etc.) are large enough to segregate at Zr grain boundary.

Oral presentation

Development of nuclear safety research roadmap and efforts at Nuclear Safety Research Center in JAEA

Sekimura, Naoto*; Nakamura, Hideo

no journal, , 

no abstracts in English

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