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Journal Articles

Radiolysis of mixed solutions of Cl$$^{-}$$ and Br$$^{-}$$ and its effect on corrosion of a low-alloy steel

Hata, Kuniki; Inoue, Hiroyuki*; Kojima, Takao*; Kasahara, Shigeki; Hanawa, Satoshi; Ueno, Fumiyoshi; Tsukada, Takashi; Iwase, Akihiro*

Proceedings of Symposium on Water Chemistry and Corrosion in Nuclear Power Plants in Asia 2017 (AWC 2017) (USB Flash Drive), p.304 - 314, 2017/09

A model simulation of $$gamma$$ radiolysis of mixed solutions of NaCl and NaBr was carried out. The simulation result agreed well with the experimental result, and Br$$^{-}$$ played an important role in determining the amounts of products from water radiolysis. The simulation result also showed that, in highly pure NaCl solutions, the steady-state concentration of a radolytic product, H$$_{2}$$O$$_{2}$$, was mainly controlled by three reactions (Cl$$^{-}$$ + $$^{.}$$OH $$rightarrow$$ ClOH$$^{.-}$$, ClOH$$^{.-}$$ $$rightarrow$$ Cl$$^{-}$$ + $$^{.}$$OH, and ClOH$$^{.-}$$ + H$$^{+}$$ $$rightarrow$$ Cl$$^{.}$$ + H$$_{2}$$O), which indicated that accurate evaluation of the rate constants of these reactions was very important in improving the radiolysis simulation of solutions containing Cl$$^{-}$$. An immersion test using a low-alloy steel, SQV2A, in the mixed solutions was also carried out under irradiation. The corrosion rate increased or decreased depending on the pH or the concentrations of the halide ions in a similar way to the change in concentration of H$$_{2}$$O$$_{2}$$ produced from water radiolysis, which is affected by the presence of Cl$$^{-}$$ and Br$$^{-}$$. However, at high pH values ($$>$$12), the corrosion rate was almost zero even though the concentration of H$$_{2}$$O$$_{2}$$ was high. This could be attributed to enhancement of the passivity of test specimens at higher pH values.

Journal Articles

Ion species/energy dependence of irradiation-induced lattice structure transformation and surface hardness of Ni$$_{3}$$Nb and Ni$$_{3}$$Ta intermetallic compounds

Kojima, Hiroshi*; Kaneno, Yasuyuki*; Ochi, Masaaki*; Semboshi, Satoshi*; Hori, Fuminobu*; Saito, Yuichi*; Ishikawa, Norito; Okamoto, Yoshihiro; Iwase, Akihiro*

Materials Transactions, 58(5), p.739 - 748, 2017/05

 Times Cited Count:1 Percentile:76.21(Materials Science, Multidisciplinary)

Bulk samples of Ni$$_{3}$$Nb and Ni$$_{3}$$Ta intermetallic compounds were irradiated with 16 MeV Au, 4.5 MeV Ni, 4.5 MeV Al, 200 MeV Xe and 1.0 MeV He ions, and the change in near-surface lattice structure was investigated by means of the grazing incidence X-ray diffraction (GIXD)and EXAFS. The Ni$$_{3}$$Nb and Ni$$_{3}$$Ta lattice structures transform from the ordered structures (orthorhombic and monoclinic structures for Ni$$_{3}$$Nb and Ni$$_{3}$$Ta, respectively) to the amorphous state by the Au, Ni, Al and Xe ion irradiations. Irrespective of such heavy ion species or energies, the lattice structure transformation to the amorphous state almost correlate with the density of energy deposited through elastic collisions.

Journal Articles

Corrosion behavior of pure titanium in high pH solution under $$gamma$$ irradiation

Yukawa, Takuji*; Inoue, Hiroyuki*; Kojima, Takao*; Iwase, Akihiro*; Taniguchi, Naoki; Tachikawa, Hirokazu*

Zairyo To Kankyo 2016 Koenshu (CD-ROM), p.359 - 362, 2016/05

The immersion tests of pure titanium were carried out in aqueous solution containing carbonate/bicarbonate with 50 mM-chloride ion under gamma irradiation. The effect of pH on general corrosion rate of titanium were studied. The experimental results showed that the concentration of hydrogen preoxide was increased with pH, and the corrosion rate increased with the hydrogen preoxide concentration. The corrosion rate in pH12 and 13 were 5 to10 times larger than those under unirradiated conditions.

Journal Articles

Lattice structure transformation and change in surface hardness of Ni$$_3$$Nb and Ni$$_3$$Ta intermetallic compounds induced by energetic ion beam irradiation

Kojima, Hiroshi*; Yoshizaki, Hiroaki*; Kaneno, Yasuyuki*; Semboshi, Satoshi*; Hori, Fuminobu*; Saito, Yuichi; Okamoto, Yoshihiro; Iwase, Akihiro*

Nuclear Instruments and Methods in Physics Research B, 372, p.72 - 77, 2016/04

 Times Cited Count:3 Percentile:42.29(Instruments & Instrumentation)

Ni$$_3$$Nb and Ni$$_3$$Ta intermetallic compounds, which show the complicated lattice structures were irradiated with 16 MeV Au$$^{5+}$$ ions at room temperature. The X-ray diffraction measurement revealed that the lattice structure of these intermetallic compounds changed from the ordered structures to the amorphous state by the ion irradiation. The irradiation-induced amorphization caused the increase in Vickers hardness. The result was compared with our previous results for Ni$$_3$$Al and Ni$$_3$$V, and was discussed in terms of the intrinsic lattice structures of the samples.

Journal Articles

Hydrogen peroxide production by $$gamma$$ radiolysis of sodium chloride solutions containing a small amount of bromide ion

Hata, Kuniki; Inoue, Hiroyuki*; Kojima, Takao*; Iwase, Akihiro*; Kasahara, Shigeki; Hanawa, Satoshi; Ueno, Fumiyoshi; Tsukada, Takashi

Nuclear Technology, 193(3), p.434 - 443, 2016/03

 Times Cited Count:2 Percentile:57.25(Nuclear Science & Technology)

Journal Articles

In-situ monitoring of ion-beam luminescence of Si-O-C(-H) ceramics under proton-beam irradiation

Narisawa, Masaki*; Koka, Masashi; Takeyama, Akinori; Sugimoto, Masaki; Idesaki, Akira; Sato, Takahiro; Hokazono, Hiroki*; Kawai, Taketoshi*; Iwase, Akihiro*

Journal of the Ceramic Society of Japan, 123(9), p.805 - 808, 2015/09

Journal Articles

Hardness modification of Al-Mg-Si alloy by using energetic ion beam irradiation

Ueyama, Daichi*; Saito, Yuichi; Ishikawa, Norito; Omura, Takahito*; Semboshi, Satoshi*; Hori, Fuminobu*; Iwase, Akihiro*

Nuclear Instruments and Methods in Physics Research B, 351, p.1 - 5, 2015/05

 Times Cited Count:3 Percentile:53.75(Instruments & Instrumentation)

Journal Articles

Zirconia membrane ECP electrode for water chemistry experiments in the JMTR

Hanawa, Satoshi; Hata, Kuniki; Shibata, Akira; Chimi, Yasuhiro; Kasahara, Shigeki; Tsutsui, Nobuyuki*; Iwase, Akihiro*; Nishiyama, Yutaka

Proceedings of 2014 Nuclear Plant Chemistry Conference (NPC 2014) (USB Flash Drive), 9 Pages, 2014/10

no abstracts in English

Journal Articles

Effects of irradiation induced Cu clustering on vickers hardness and electrical resistivity of Fe-Cu model alloys

Tobita, Toru; Nakagawa, Sho*; Takeuchi, Tomoaki; Suzuki, Masahide; Ishikawa, Norito; Chimi, Yasuhiro; Saito, Yuichi; Soneda, Naoki*; Nishida, Kenji*; Ishino, Shiori*; et al.

Journal of Nuclear Materials, 452(1-3), p.241 - 247, 2014/09

 Times Cited Count:8 Percentile:25.95(Materials Science, Multidisciplinary)

Three kinds of Fe-based model alloys, Fe-0.018 atomic percent (at.%) Cu, Fe-0.53at.%Cu, and Fe-1.06at.%Cu were irradiated with 2 MeV electrons up to the dose of 2$$times$$10$$^{-5}$$ dpa at 250$$^{circ}$$C. After the irradiation, the increase in Vickers hardness and the decrease in electrical resistivity were observed. The increase in hardness by electron irradiation is proportional to the product of the Cu contents and the square root of the electron dose. The decrease in electrical resistivity is proportional to the product of the square of Cu contents and the electron dose. Cu clustering in the materials with electron irradiation and thermal aging was observed by means of the three dimensional atom probes (3D-AP). The change in Vickers hardness and electrical resistivity is well correlated with the volume fraction of Cu clusters.

Journal Articles

Hardening induced by energetic electron beam for Cu-Ti alloys

Ueyama, Daichi*; Semboshi, Satoshi*; Saito, Yuichi; Ishikawa, Norito; Nishida, Kenji*; Soneda, Naoki*; Hori, Fuminobu*; Iwase, Akihiro*

Japanese Journal of Applied Physics, 53(5S1), p.05FC04_1 - 05FC04_5, 2014/05

 Times Cited Count:2 Percentile:85.43(Physics, Applied)

In our previous research, it was found that the hardness of Cu-Ti alloy increased by energetic heavy ion irradiation at room temperature. In the conference, we will show the result of electron beam irradiation on the hardness of Cu-Ti alloys. We used CuTi sheets with the dimension of 10 $$times$$ 10 $$times$$ 0.250 mm$$^{3}$$. The specimens were irradiated at 473 K and 523 K with 2 MeV electrons. For comparison, we thermally aged some specimens at the same temperatures as that for the irradiation. The electron fluence of 8.0 $$times$$ 10$$^{17}$$/cm$$^{2}$$ corresponds to the processing time of about 10 h. As a result, the thermal aging for 10 h increases the hardness by 5 or less, which is much smaller than that by the irradiation (about 20). The hardness of the reverse side of irradiated surface is almost the same as that of the irradiated surface. The present result implies that energetic electron irradiation can be a useful tool for controlling the hardness of the "bulk" Cu-Ti alloy.

Journal Articles

Magnetic patterning of FeRh thin films by energetic light ion microbeam irradiation

Koide, Tetsuya*; Sato, Takahiro; Koka, Masashi; Saito, Yuichi; Kamiya, Tomihiro; Okochi, Takuo*; Kotsugi, Masato*; Kinoshita, Toyohiko*; Nakamura, Tetsuya*; Iwase, Akihiro*; et al.

Japanese Journal of Applied Physics, 53(5S1), p.05FC06_1 - 05FC06_4, 2014/05

 Times Cited Count:6 Percentile:58.9(Physics, Applied)

We previously reported that the magnetic state of FeRh can be controlled by irradiation with ion beams. In this paper, we evaluate possibility of magnetic patterning on FeRh thin films using energetic light ion microbeam irradiation with various shapes and dimensions. Proton microbeam irradiation with 2 MeV was performed at JAEA-Takasaki to produce micron-sized magnetic patterns. XMCD-PEEM observation was performed at SPring8 to confirm the synthesized magnetic patterns. As a result, the XMCD-PEEM images of the various micrometer sized patters in FeRh film were observed using 2 MeV H ion beam. The observed bright regions are considered to have ferromagnetic spin orders, in contrast that the gray areas have anti-ferromagnetic spin order. Since the brightness of the PEEM images is strongly correlated with the magnetization of the samples, we reveal that the magnetic state in local regions of the FeRh thin films can be controlled by changing the ion fluences.

Journal Articles

Activation detector measurements at the hadron absorber of the NuMI neutrino beamline at Fermilab

Matsuda, Norihiro; Kasugai, Yoshimi; Matsumura, Hiroshi*; Iwase, Hiroshi*; Toyoda, Akihiro*; Yashima, Hiroshi*; Sekimoto, Shun*; Oishi, Koji*; Sakamoto, Yukio*; Nakashima, Hiroshi; et al.

Progress in Nuclear Science and Technology (Internet), 4, p.337 - 340, 2014/04

The Neutrinos at the Main Injector (NuMI) at Fermilab produces intense neutrino beam to investigate the phenomena of the neutrino mixing and oscillation. The Hadron Absorber, consists of thick blocks of aluminum, iron and concrete, is placed at the end of decay volume as a dump for primary proton and secondary particles generated in NuMI. In order to estimate the shielding effect, the reaction rate measurements with activation detector were carried out on the back surface of the absorber. The induced activities in the detectors were measured by analyzing their $$gamma$$-ray spectra using HPGe detectors. Two kind of peak was showed on two-dimensional distributions of obtained reaction rates at right angle to the beam direction. One was strong peaks at the both horizontal side. And, another smaller was at the top. It was concluded that these peaks were the results of particles streaming through the gaps in the Hadron Absorber shielding.

Journal Articles

Molecular dynamics simulation of fast particle irradiation to the Gd$$_{2}$$O$$_{3}$$-doped CeO$$_{2}$$

Sasajima, Yasushi*; Ajima, Naoki*; Osada, Takuya*; Ishikawa, Norito; Iwase, Akihiro*

Nuclear Instruments and Methods in Physics Research B, 316, p.176 - 182, 2013/12

 Times Cited Count:1 Percentile:84.29(Instruments & Instrumentation)

The structural relaxation caused by the high-energy-ion irradiation of CeO$$_{2}$$ with Gd$$_{2}$$O$$_{3}$$ addition was simulated by the molecular dynamics method. The amount of Gd$$_{2}$$O$$_{3}$$ was changed. As the initial condition, high thermal energy was supplied to the individual atoms within a cylindrical region of nanometer-order radius located in the center of the specimen. The potential proposed by Inaba et al. was utilized to calculate interaction between atoms. The supplied thermal energy was first spent to change the crystal structure into an amorphous one within a short period of about 0.3 ps, then it dissipated in the specimen. By increasing the concentration of Gd$$_{2}$$O$$_{3}$$, more structural disorder was observed in the sample, which is consistent to the actual experiment.

Journal Articles

Development of dual-beam system using an electrostatic accelerator for in-situ observation of swift heavy ion irradiation effects on materials

Matsuda, Makoto; Asozu, Takuhiro; Sataka, Masao; Iwase, Akihiro*

Nuclear Instruments and Methods in Physics Research B, 314, p.43 - 46, 2013/11

 Percentile:100(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Study on ferromagnetic ordering of FeRh thin films induced by energetic heavy ion irradiation by means of X-ray magnetic circular dichroism

Aiko, Kazuma*; Toki, Atsushi*; Okuda, Shuichi*; Saito, Yuichi; Kamiya, Tomihiro; Nakamura, Tetsuya*; Kinoshita, Toyohiko*; Iwase, Akihiro*; Matsui, Toshiyuki*

Nuclear Instruments and Methods in Physics Research B, 314, p.99 - 102, 2013/11

 Times Cited Count:1 Percentile:84.29(Instruments & Instrumentation)

Journal Articles

Electrical resistivity change due to high-energy X-ray irradiation of oxygen-deficient EuBa$$_{2}$$Cu$$_{3}$$O$$_{y}$$

Ishikawa, Norito; Chimi, Yasuhiro; Michikami, Osamu*; Iwase, Akihiro*

Nuclear Instruments and Methods in Physics Research B, 315, p.201 - 205, 2013/11

 Percentile:100(Instruments & Instrumentation)

High-energy X-ray was irradiated to EuBa$$_{2}$$Cu$$_{3}$$O$$_{y}$$, which is one of the REBa$$_{2}$$Cu$$_{3}$$Oy (RE=rare earth) compounds, at low temperature (100 K), and the electrical resistivity was measured in situ at the same temperature (100 K). The X-ray energy was chosen near Cu K-edge (9.0 keV), Eu L3-edge (7.0 keV) and Ba L3-edge (5.2 keV) so that the effect of inner-shell excitation can be detected, if any. The irradiation-induced increase in the electrical resistivity is observed during the irradiations with X-ray in the energy range of 5-9 keV. The electrical resistivity monotonically increases as increasing photon dose. Even if the X-ray is switched off, the irradiation-induced effect remains unchanged. The observed effect has an opposite trend compared with that observed for the visible light irradiation which causes persistent photoconductivity. It is also found that the irradiation-induced increase in resistivity scales with the energy absorbed by EuBa$$_{2}$$Cu$$_{3}$$O$$_{y}$$.

Journal Articles

Computer simulation of structural modifications induced by highly energetic ions in uranium dioxide

Sasajima, Yasushi*; Osada, Takuya*; Ishikawa, Norito; Iwase, Akihiro*

Nuclear Instruments and Methods in Physics Research B, 314, p.195 - 201, 2013/11

 Times Cited Count:2 Percentile:72.96(Instruments & Instrumentation)

The structural modification caused by the high-energy-ion irradiation of single-crystalline uranium dioxide was simulated by the molecular dynamics method. As the initial condition, high kinetic energy was supplied to the individual atoms within a cylindrical region of nanometer-order radius located in the center of the specimen. The potential proposed by Basak et al. was utilized to calculate interaction between atoms. The supplied kinetic energy was first spent to change the crystal structure into an amorphous one within a short period of about 0.3 ps, then it dissipated in the specimen. The amorphous track radius $$R_{rm a}$$ was determined as a function of the effective stopping power $$g$$$$S_{rm e}$$, i.e., the kinetic energy of atoms per unit length created by ion irradiation ($$S_{rm e}$$: electronic stopping power, $$g$$: energy transfer ratio from stopping power to lattice vibration energy).

Journal Articles

Molecular dynamics simulation of fast particle irradiation on the single crystal CeO$$_{2}$$

Sasajima, Yasushi*; Ajima, Naoki*; Osada, Takuya*; Ishikawa, Norito; Iwase, Akihiro*

Nuclear Instruments and Methods in Physics Research B, 314, p.202 - 207, 2013/11

 Times Cited Count:5 Percentile:46.51(Instruments & Instrumentation)

We used a molecular dynamics method to simulate structural relaxation caused by the high-energy-ion irradiation of single crystal CeO$$_{2}$$. As the initial condition, we assumed high thermal energy was supplied to the individual atoms within a cylindrical region of nanometer-order diameter located in the center of the single crystal. The potential proposed by Inaba et al. was utilized to calculate interactions between atoms.

Journal Articles

Irradiation effect of swift heavy ion for Zr$$_{50}$$Cu$$_{40}$$Al$$_{10}$$ bulk glassy alloy

Onodera, Naoto*; Ishii, Akito*; Ishii, Koji*; Iwase, Akihiro*; Yokoyama, Yoshihiko*; Saito, Yuichi; Ishikawa, Norito; Yabuuchi, Atsushi*; Hori, Fuminobu*

Nuclear Instruments and Methods in Physics Research B, 314, p.122 - 124, 2013/11

 Times Cited Count:1 Percentile:84.29(Instruments & Instrumentation)

It has been reported that heavy ion irradiation causes softening in some cases of Zr-based bulk metallic glass alloys. However, the fundamental mechanisms of such softening have not been clarified yet. In this study, Zr$$_{50}$$Cu$$_{40}$$Al$$_{10}$$ bulk glassy alloys were irradiated with heavy ions of 10 MeV I at room temperature. Positron annihilation measurements have performed before and after irradiation to investigate changes in free volume. We discuss the relationship between the energy loss and local open volume change after 10 MeV I irradiation compared with those obtained for 200 MeV Xe and 5 MeV Al. The energy loss analysis in ion irradiation for the positron lifetime has revealed that the decreasing trend of positron lifetime is well expressed as a function of total electronic energy deposition rather than total elastic energy deposition. It means that the positron lifetime change by the irradiation has a relationship with the inelastic collisions with electrons during heavy ion irradiation.

Journal Articles

Magnetic Compton scattering studies of magneto-dielectric Ba(Co$$_{0.85}$$Mn$$_{0.15}$$)O$$_{3-delta}$$

Shinoda, Ryoichi*; Ito, Masayoshi*; Sakurai, Yoshiharu*; Yamamoto, Hiroyuki; Hirao, Norie; Baba, Yuji; Iwase, Akihiro*; Matsui, Toshiyuki*

Journal of Applied Physics, 113(17), p.17E307_1 - 17E307_3, 2013/05

 Times Cited Count:6 Percentile:67.17(Physics, Applied)

We revealed that the Ba(Co$$_{0.85}$$Mn$$_{0.15}$$)O$$_{3-delta}$$ (BCMO) ceramic samples exhibited ferromagnetic-dielectric behavior below the magnetic transition temperature of about 35 K. The origin of their magnetic ordering was expected to super-exchange coupling of Co$$^{4+}$$($$d^5$$)-O$$^{2-}$$-Mn$$^{4+}$$ ($$d^3$$) with bonding angle of 180$$^{circ}$$. and/or Mn$$^{4+}$$($$d^3$$)-O$$^{2-}$$-Mn$$^{4+}$$ ($$d^3$$) with bonding angle of 90$$^{circ}$$. The magnetic spin momentum estimated by the magnetic Compton profiles (MCP) of the samples had similar temperature dependence as that determined by the SQUID measurement, which meant that the observed magnetic moments could be ascribed to the spin moment. The shapes of the MCPs of the samples were completely same regardless of the temperature measured. This result indicates that there are no changes of the momentum space distribution of spin density between ferromagnetic and paramagnetic states. So, this magnetic transition is simply caused by a thermal fluctuation of the spin.

187 (Records 1-20 displayed on this page)