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Du, Y.*; Yoshida, Kenta*; Shimada, Yusuke*; Toyama, Takeshi*; Inoue, Koji*; Arakawa, Kazuto*; Suzudo, Tomoaki; Milan, K. J.*; Gerard, R.*; Onuki, Somei*; et al.
Materialia, 12, p.100778_1 - 100778_10, 2020/08
In order to ensure the integrity of the reactor pressure vessel in the long term, it is necessary to understand the effects of irradiation on the materials. In this study, irradiation-induced dislocation loops were observed in neutron-irradiated reactor pressure vessel specimens during annealing using our newly developed WB-STEM. It was confirmed that the proportion of loops increased with increasing annealing temperature. We also succeeded in observing the phenomenon that two loops collide into a loop. Moreover, a phenomenon in which dislocation loops decorate dislocations was also observed, and the mechanism was successfully explained by molecular dynamics simulation.
Suzuki, Masahide; Nishiyama, Yutaka
Kinzoku, 71(8), p.42 - 45, 2001/08
no abstracts in English
Momma, Yoshio*; *; ; ; ; Aoto, Kazumi
JNC TN9400 2000-044, 22 Pages, 2000/03
ln the past the microstructural observation was mostly applied to understand the materials behavior qualitatively in R&D of the new materials and the life prediction for the fast breeder reactor components. However, the correlation between the changes in properties and microstrutures must be clarified to ensure the structural integrity. Particularly we are interested in the method to correlate the long-term properties and microstructural changes at high temperatures. The current research is to quantify the changes in microstructure of the weld metal for the welded structure of the reactor vessel. ln this research we have conducted creep testing of the weld metals at 823 and 873K up to 37,000h. Two types of the weld metals (16Cr-8Ni-2Mo and 18Cr-12Ni-Mo) were subjected to the creep testing. Based on the areas of the precipitates, the microstructural characterization with time and creep damage was attempted. The creep strength of the 16Cr-8Ni-2Mo weld metal is lower than that of the 18Cr-12Ni-Mo one at higher stresses, shorter times. But there is a trend toward to become similar strength with lower stresses and increasing times. The creep-rupture ductility of the 16Cr-8Ni-2Mo weld metal is superior to that of the 18Cr-12Ni-Mo one. The creep-rupture takes place at the interface of the sigma () phases precipitated in the delta () ferrites at 823K lower stresses and 873K. The amount of precipitates in the 16Cr-8Ni-2Mo weld metal is smaller than that in the 18Cr-12Ni-Mo one at each temperature and stress. Also it is apparent that the amount of the precipitates is primarily responsible to the decomposition of the phase, because the amount of the residual ferrites measured by the Magne-Gauge reduces with times. Using the Larson-Miller parameter it was possible to correlate the amount of the precipitates linearly with the LMP values.
Kawanishi, Hiroshi*; Suzuki, Masahide
Effects of Radiation on Materials (ASTM STP 1366), p.492 - 515, 2000/03
Times Cited Count:1 Percentile:65.22(Materials Science, Multidisciplinary)no abstracts in English
Sato, Haruo
JNC TN8400 99-064, 22 Pages, 1999/10
Four kinds of diffusion experiments; (1)through-diffusion(T-D) experiments for compaction direction dependency, (2)in-diffusion(I-D) experiments for composition dependency of silica sand in bentonite, (3)I-D experiments for initial bentonite gain size dependency, and (4)I-D experiments for the restoration property of an artificial single fracture in compacted bentonite, were carried out using tritiated water which is a non-sorbing nuclide to evaluate the effect of pore structural factors for eompacted bentonite on diffudion. For(1), effective diffusivities (De) in Na-bentonites, Kunigel-V1 and Kunipia-F were measured for 1.0 and 1.5 Mgm. For(2), apparent diffusivities (Da) in Kunigel-V1 were measured for 0.8, 1.4 and 1.8 Mgm with silica sand of 30 and 50 wt%. For(3), Da values for 0.8, 1.4 and 1.8 Mgm were measured for a granulated Na-bentonite, OT-9607 which grain-size distribution is in a rang between 0.1 and 5 mm. For (4), Da values in Kunigel-V1 which a single fracture was artificially reproduced and was immersed in distilled water for 7 or 28 days for the restoration of the fracture, were measured for 1.8 Mgm. Although De values in Kunigel-V1 were approximately the same for both compacted directions over the density, De values for perpendicular direction to compacted direction were higher than those for the same direction as compacted direction in Kunipia-F. For composition dependency of silica sand in bentonite, no significant effect of the mixure of silica sand in bentonite on Da was found. For initial bentonite grain size dependency, Da values obtained for OT-960 were approximately the same as those for Kunigel-V1 and no effect of initial grain size of bentonite on diffusion was found. For the restoration property of a single fracture in compacted bentonite, no restoration period dependency on Da was found. Based on this, it may be said that diffusion of nuclides in compacted bentonite, ...
Morinaga, Masahiko*; *; *
PNC TJ9603 98-002, 48 Pages, 1998/03
[PURPOSE]Both the Nb-based and Mo-based alloys have been designed and developed in order to establish the frontier technique for super-heat-resisting materials used in the liquid alkali metal environment at high temperatures. In this study, mechanical properties of the designed Nb-1Hf alloy were experimentally evaluated. In addition, the brittleness of Nb-based alloys observed at 1073K were discussed. Moreover, characteristics of both the designed Nb-based and the Mo-based alloys were summarized in a consistent way. [EXPERIMENTAL METHODS] (1)Tensile test : The tensile test was performed at room temperature and 1473K in an Ar gas atmosphere for the designed Nb-1Hf alloy and also for commercial Nb-1Zr alloy. (2)High temperature creep test:The creep test of the designed Nb-1Hf alloy was carried out at 1473K in an Ar gas atmosphere under several applied stress levels. (3)TEM observation : The TEM observation was performed with the creep specimens tested at both 1073K and 1273K in order to get information for the 1073K brittleness of the Nb-1Zr alloy. [RESULTS AND DISCUSSIONS] (1)Tensile test : The tensile stress and the proof stress of the designed Nb-1Hf alloy were slightly lower than those of commercial Nb-1Zr alloy at room tempetarure. But the alloy was superior in the elongation to the Nb-1Zr alloy. High temperature tensile properties were not able to be evaluated properly because of the large grain size of the specimens. (2)High temperature creep test : The Nb-1Hf alloy was superior in the ereep resistance to other solid solution hardened Nb-based alloys. (3)TEM observation : A modulated structure with about 1nm preiod was observed in the specimen which was brittle at 1073K. This was supposed to cause the 1073K brittleness of the Nb-1Zr alloy. [CONCLUSION] The tensile strength of the designed Nb-1Hf alloy was slightly lower at room temperature than that of the commercial Nb-1Zr alloy. But, the designed alloy was superior in high temperature creep properties to any
Tokuoka, Naochika*; Kobayashi, Mamoru*; Koyama, Takashi*
PNC TJ1636 96-001, 64 Pages, 1996/03
None
Ono, K.*; Furuno, Shigemi; Hojo, Kiichi; *
Microstructures and Functions of Materials (ICMFM 96), 0, p.273 - 276, 1996/00
no abstracts in English
Aruga, T.; Katano, Y.; ; ; ; Shiraishi, K.
Journal of Nuclear Materials, 133-134, p.667 - 670, 1985/00
Times Cited Count:0 Percentile:0.02(Materials Science, Multidisciplinary)no abstracts in English
Shiraishi, K.; ; Katano, Y.
Radiat.Eff., 21(3), p.161 - 164, 1974/03
no abstracts in English
Terauchi, Masami*; Takahashi, Hideyuki*; Murano, Takanori*; Koike, Masato; Imazono, Takashi; Koeda, Masaru*; Nagano, Tetsuya*
no journal, ,
The emission spectra of Ti resulting from the electron transition from valance band to the core holes were observed. These reflect the chemical bonding states for the covalent bonding between Ti and O atoms. The peak position of the band is found to be placed on the lower energy side than that of metal-Ti, but which is opposite to the theoretical prediction. This means that the intensity profile is not suitable for probing the chemical shift due to the influence from the density of states of the valence band. On the contrary, the peak shift of the band caused by transitions between inner-shell levels is on the higher energy side. It is found to be reasonable for the cation chemical shift.
Takahashi, Hideyuki*; Asahina, Shunsuke*; Murano, Takanori*; Takakura, Yu*; Terauchi, Masami*; Koike, Masato; Imazono, Takashi; Koeda, Masaru*; Nagano, Tetsuya*; Sasai, Hiroyuki*; et al.
no journal, ,
We developed a soft X-ray emission spectrometer (SXES) with a detection range of 50-210 eV to be able to be installed in commercially available EMPAs and FE-SEMs. This SXES has the spectral resolution of 0.2 eV comparably high with X-ray photo emission spectrometers (XPSs) and electron energy-loss spectrometers (EELSs). In addition, it allows us to perform trace light element analysis with high sensitivity because of high peak-to-background ratio (P/B). Therefore, it is shown that the SXES installed in a FE-SEM can detect trace carbon in steel at the level of 100 ppm and below.
Shinohara, Nobuo; Kimura, Yoshiki; Okubo, Ayako
no journal, ,
Nuclear forensics is the analysis of intercepted illicit nuclear or radioactive material and any associated material to provide evidence for nuclear attribution by determining origin, history, transit routes and purpose involving such material. Because the nuclear forensics methodologies provide hints of the origin of the nuclear materials used in illegal dealings or nuclear terrorism, it contributes to identify and indict offenders, hence to enhance deterrent effect against such terrorism. In the 59th Symposium on Radiochemistry, the results of research and development of fundamental nuclear forensics technologies (analysis of isotopic composition, impurity analysis, age dating of nuclear material, particle shape analysis by electron microscope, and nuclear forensics library) performed in Japan Atomic Energy Agency are reported. Japan's capability and the role of radiochemistry on nuclear forensics are also discussed in the Symposium.