The Effects of Gas Atoms on the Formation of Voids in Neutron-irradiated Metals
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概要
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A series of experiments was carried out to study the effects of gas atoms on the formation of voids in neutron-irradiated pure Cu, Cu dilute (Al, Ni) alloys, pure Ni and SUS316L. Experiments were carried out with specimens from which dissolved residual gas atoms were removed by melting them in highly evacuated vacuum as 10^<-5> Pa. It is found that in Cu, Cu-Al and SUS316L a residual gas has significant effects on the formation of voids while in Cu-Ni and Ni no effects were observed. Substantial component of gas evaporated from molten Cu, Cu-alloy and Ni was hydrogen. A large amount of nitrogen together with hydrogen evaporated from a molten SUS316L. Both types of residual gas free and as-received specimens were irradiated at the JMTR, JOYO, FFTF and EBR-II reactors. On the irradiation of low neutron fluence below 10^<19> n/cm^2, the number density of voids decreased in a residual gas free Cu. On the neutron irradiation at FFTF to a high fluence as 10^<22> n/cm^2, it was observed in pure Cu whose surface was shiny after the irradiation that the number density of voids increased in residual gas free specimen than that in as-received specimen. In the majority of pure Cu whose surface was contaminated severely by FFTF neutron irradiation to high neutron fluence, the difference of void formation was not observed between two types of specimens. This is due to resolving of gas atoms during a neutron irradiation. In Cu-5at.%Al, the formation of voids was remarkably suppressed in specimens of residual gas atom free. In Cu-5at.%Al irradiated at FFTF, many large voids were observed in as-received specimen while no void was observed in residual gas free specimens. In Cu-5at.%Ni, difference of the void formation between two type of specimens was not observed even after a low fluence of neutron irradiation at JMTR. Voids and many tangled dislocations were observed in irradiated Cu-5at.%Ni alloys. In as-received SUS316L which was irradiated at EBR-II to 10^<22> n/cm^2, small voids whose size is 10 nm in an average diameter were observed while no voids were observed in specimens of residual gas free. In pure Ni irradiated at the JMTR and EBR-II, the density and size of voids were similar in both type of specimens. The development of dislocation structure was not so remarkable in neutron-irradiated nickel. The atomistic process of the evolution of damage structure in neutron irradiated metals is discussed including the role of residual and transmutation generated gas atoms.void formationCu alloysaustenitic alloysneutron irradiationgas atoms
- 東北大学の論文
- 1997-03-28
著者
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Mukouda Ichiro
Applied Physics And Chemistry Faculty Of Engineering Hiroshima University
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Shimomura Yoshiharu
Applied Physics And Chemistry Faculty Of Engineering Hiroshima University
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