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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

Reactivity of an antioxidant, edaravone, with reactive oxygen species and its chemical repair properties against oxidative damage on DNA

Hata, Kuniki; Lin, M.*; Yokoya, Akinari*; Fujii, Kentaro*; Yamashita, Shinichi*; Muroya, Yusa*; Katsumura, Yosuke*

Hoshasen Kagaku (Internet), (103), p.29 - 34, 2017/04

Reactivity of edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one), which is known to show high antioxidative properties, with oxidative species, such as hydroxyl radical ($${}^{bullet}$$OH) and azide radical (N$$^{bullet}$$$$_{3}$$), was investigated by a pulse radiolysis experiment, and generation behavior of edaravone radicals produced through these reactions were observed. It was shown that OH-adducts are produced by the reaction with $${}^{bullet}$$OH in contrast to the other oxidative radicals, which react with edaravone by an electron transfer reaction. Chemical repair properties of edaravone against DNA lesions produced by reactions of DNA with oxidative species were also investigated by a pulse radiolysis experiment with deoxyguanosine monophosphate (dGMP) and a $$gamma$$-radiolysis experiment with plasmid DNA solutions. It was observed that edaravone reduced dGMP radicals just after produced in a dilute aqueous solution and inhibited some base lesions on plasmid DNA more effectively than single strand breaks. These results show that edaravone may protect living system from oxidative stress, such as radiation, by not only scavenging oxidative species but also reducing precursors of DNA leisons.

Journal Articles

Report on the stay in Norway as a secondee of OECD Halden Reactor Project

Hata, Kuniki

Hoshasen Kagaku (Internet), (103), P. 65, 2017/04

no abstracts in English

Journal Articles

Evaluation of ECP measured in in-pile environment

Hanawa, Satoshi; Uchida, Shunsuke; Hata, Kuniki; Chimi, Yasuhiro; Kasahara, Shigeki*; Nishiyama, Yutaka

Proceedings of 20th Nuclear Plant Chemistry International Conference (NPC 2016) (USB Flash Drive), 11 Pages, 2016/10

ECP is the exclusive index to evaluate corrosion condition directly at the points of interest in the mixing of neutron and $$gamma$$-ray environment. ECP can be calculated through the combination of water radiolysis and ECP model. A water radiolysis model have been applied to experiments performed in in-pile loops in the experimental reactors and applicability was confirmed. An ECP model based on the Butler-Volmer equation was also prepared. ECP of stainless steel was measured under well controlled water chemistry condition in in-pile loop in the Halden reactor, and the model was applied to evaluate ECP measured in the Halden reactor. The measured data were well explained by the water radiolysis calculation and ECP model. Accumulation of in-pile ECP data are expected for further validation of the models.

Journal Articles

Study of irradiation effect on ECP using in-pile loops in the JMTR

Hanawa, Satoshi; Uchida, Shunsuke; Hata, Kuniki; Chimi, Yasuhiro; Kasahara, Shigeki*; Nishiyama, Yutaka

Proceedings of 20th Nuclear Plant Chemistry International Conference (NPC 2016) (USB Flash Drive), 10 Pages, 2016/10

The authors proposed and ECP evaluation model introducing irradiation-induced diffusion in the oxide layer to simulate neutron irradiation effect, and predicted with this model that ECP is started to depress from the neutron flux of about ten to the fourteenth per square meter. As the JMTR has in-pile loops applicable to water chemistry experiments, degree of irradiation effect on ECP appears in the in-pile loop was estimated by the model. Under oxygen injected condition, ECP in a capsule becomes constant along the vertical direction due to the presence of high amount of oxygen and hydrogen peroxide in a capsule. However, if neutron irradiation depress ECP, ECP in a capsule along vertical direction wouldn't become constant, and the degree to the decrement is detectable by experiments.

Journal Articles

Simulation for radiolytic products of seawater; Effects of seawater constituents, dilution rate, and dose rate

Hata, Kuniki; Sato, Tomonori; Motooka, Takafumi; Ueno, Fumiyoshi; Hanawa, Satoshi; Kasahara, Shigeki; Tsukada, Takashi

Journal of Nuclear Science and Technology, 53(8), p.1183 - 1191, 2016/08

 Times Cited Count:1 Percentile:76.09(Nuclear Science & Technology)

Journal Articles

Effects of constituents of seawater on formation of volatile iodine by aqueous phase radiation chemistry

Hata, Kuniki; Kido, Kentaro; Nishiyama, Yutaka; Maruyama, Yu

NEA/CSNI/R(2016)5 (Internet), p.196 - 203, 2016/05

Journal Articles

Formation and release of molecular iodine in aqueous phase chemistry during severe accident with seawater injection

Kido, Kentaro; Hata, Kuniki; Maruyama, Yu; Nishiyama, Yutaka; Hoshi, Harutaka*

NEA/CSNI/R(2016)5 (Internet), p.204 - 212, 2016/05

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

Effect of chloride and bromide ion on the concentration of hydrogen peroxide produced from seawater radiolysis

Hata, Kuniki; Hanawa, Satoshi; Motooka, Takafumi; Tsukada, Takashi

JAEA-Review 2014-050, JAEA Takasaki Annual Report 2013, P. 22, 2015/03

Fukushima Daiichi Nuclear Power Plants experienced seawater injection into the cores and spent fuel pools as an emergent measure for a short period after the accident. The injected seawater was exposed to radiation, and radiolytic species were produced. Especially, hydrogen peroxide (H$$_{2}$$O$$_{2}$$) is known as an oxidant which affects corrosion of materials. In order to identify the important factor which results in the high concentration of H$$_{2}$$O$$_{2}$$ in seawater radiolysis, the concentrations of H$$_{2}$$O$$_{2}$$ in $$gamma$$-irradiated artificial seawater was measured and compared with the result of radiolysis calculation. Solutions containing some constituents of seawater were also measured to identify which ion affects H$$_{2}$$O$$_{2}$$ production of seawater radiolysis. The experimental results showed that the H$$_{2}$$O$$_{2}$$ production from seawater radiolysis is mainly attributed to reactions of Cl$$^{-}$$ and Br$$^{-}$$ in water radiolysis, though many kinds of ions are dissolved in seawater.

Journal Articles

Sequential radiation chemical reactions in aqueous bromide solutions; Pulse radiolysis experiment and spur model simulation

Yamashita, Shinichi*; Iwamatsu, Kazuhiro; Maehashi, Yuki*; Taguchi, Mitsumasa; Hata, Kuniki; Muroya, Yusa*; Katsumura, Yosuke*

RSC Advances (Internet), 5(33), p.25877 - 25886, 2015/02

 Times Cited Count:10 Percentile:46.57(Chemistry, Multidisciplinary)

Pulse radiolysis experiments were carried out to observe transient absorptions of reaction intermediates produced in N$$_{2}$$O$$^{-}$$ and Ar-saturated aqueous solutions containing 0.9-900 mM NaBr. The most important species among the reaction intermediates are BrOH $$^{cdot -}$$ and Br$$_{2}$$ $$^{cdot -}$$, which commonly have absorption peaks around 360 nm. The experimental results were compared with the results of simulation based on a spur diffusion model. Each of several complicated sequential radiation-induced chemical reactions was carefully considered, optimizing its rate constant within a range of reported values. All the experimental results were able to be universally reproduced by the simulation, assuming a reaction not yet reported, 2BrOH$$^{cdot -}$$ $$rightarrow$$ Br$$_{2}$$ + 2OH$$^{-}$$, with a rate constant of 3.8 $$times$$ 10$$^{9}$$ M$$^{-1}$$ s$$^{-1}$$, which is significant only within 10 micro-s for rather high bromide concentrations ($$>$$ 10 mM). Primary $$G$$ values, which are yields after sufficient diffusion from the spur to the perimeter region during 100 ns, of major water decomposition products, as well as of the reaction intermediates, were calculated for N$$_{2}$$O$$^{-}$$ and Ar-saturated conditions as a function of NaBr concentration.

Journal Articles

Chemical repair activity of free radical scavenger edaravone; Reduction reactions with dGMP hydroxyl radical adducts and suppression of base lesions and AP sites on irradiated plasmid DNA

Hata, Kuniki; Urushibara, Ayumi*; Yamashita, Shinichi*; Lin, M.*; Muroya, Yusa*; Shikazono, Naoya; Yokoya, Akinari; Fu, H.*; Katsumura, Yosuke*

Journal of Radiation Research, 56(1), p.59 - 66, 2015/01

AA2014-0383.pdf:0.93MB

 Times Cited Count:2 Percentile:75.84(Biology)

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

Water chemistry experiment using in-pile loop in the JMTR

Hanawa, Satoshi; Hata, Kuniki; Chimi, Yasuhiro; Nishiyama, Yutaka

Proceedings of Symposium on Water Chemistry and Corrosion in Nuclear Power Plants in Asia 2013 (USB Flash Drive), 7 Pages, 2013/10

Water chemistry experiments will be carried out by using an in-pile loop newly installed in the JMTR. Concentrations of chemical species of O$$_{2}$$, H$$_{2}$$ and H$$_{2}$$O$$_{2}$$ are measured at the inlet and the outlet of the irradiation field. Electrochemical corrosion potential (ECP) at the irradiation field is also monitored. These experimental data will be obtained under wide range of experimental conditions such as absorption dose rate, H$$_{2}$$ or O$$_{2}$$ concentration in the feeding water and water temperature. As a result of preliminary calculations, it became clear that the in-pile loop in the JMTR is capable for water chemistry experiment. Although the operation of the JMTR is being delayed because of the Tohoku district off the Pacific Ocean earthquake, construction of the loops and installation of the instrumentation for the loops have been carried out almost on schedule. The experiments will be started after JMTR restart.

Journal Articles

Chemical repair of base lesions, AP sites, and strand breaks on plasmid DNA in dilute aqueous solution by ascorbic acid

Hata, Kuniki; Urushibara, Ayumi; Yamashita, Shinichi; Shikazono, Naoya; Yokoya, Akinari; Katsumura, Yosuke*

Biochemical and Biophysical Research Communications, 434(2), p.341 - 345, 2013/05

 Times Cited Count:4 Percentile:81.59(Biochemistry & Molecular Biology)

Journal Articles

Radiation-induced reactions of Cl$$^{-}$$, CO$$_{3}$$$$^{2-}$$ and Br$$^{-}$$ in seawater; Model calculation of $$gamma$$ radiolysis of seawater

Hata, Kuniki; Hanawa, Satoshi; Kasahara, Shigeki; Muroya, Yusa*; Katsumura, Yosuke*

Proceedings of 2012 Nuclear Plant Chemistry Conference (NPC 2012) (CD-ROM), 6 Pages, 2012/09

Fukushima Daiichi Power Plants experienced seawater injection as emergent measure for a short period after the accident. As a result of seawater injection, structural materials in the reactors are exposed to unexpected corrosion environment due to Cl$$^{-}$$ as well as radiolytic products by $$gamma$$-rays from fuels. In the present study, a model calculation on seawater radiolysis was carried out to estimate concentration of radiolytic products under $$gamma$$-irradiation. Radiolytic products, H$$_{2}$$, O$$_{2}$$ and H$$_{2}$$O$$_{2}$$, in seawater monotonically increased with dose. H$$_{2}$$ production was especially distinguished, and its yield was 4.4 $$times$$ 10$$^{-8}$$ mol J$$^{-1}$$. As similar result was obtained from the calculation of NaBr solution, the main species which increased these products in seawater was thought to be Br$$^{-}$$. On the other hand, Cl$$^{-}$$ and HCO$$_{3}$$$$^{-}$$ in seawater hardly affected the concentrations of these radiolytic products.

Journal Articles

Irradiation capability of Japanese materials test reactor for water chemistry experiments

Hanawa, Satoshi; Hata, Kuniki; Chimi, Yasuhiro; Nishiyama, Yutaka; Nakamura, Takehiko

Proceedings of 2012 Nuclear Plant Chemistry Conference (NPC 2012) (CD-ROM), 9 Pages, 2012/09

no abstracts in English

Journal Articles

Pulse radiolysis study on free radical scavenger edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one), 2; A Comparative study on edaravone derivatives

Hata, Kuniki; Lin, M.; Katsumura, Yosuke*; Muroya, Yusa*; Fu, H. Y.*; Yamashita, Shinichi; Nakagawa, Hidehiko*

Journal of Radiation Research, 52(1), p.15 - 23, 2011/01

 Times Cited Count:15 Percentile:34.23(Biology)

Journal Articles

Temperature and density effects on the absorption maximum of solvated electrons in sub- and super-critical methanol

Yan, Y.*; Lin, M.; Katsumura, Yosuke*; Muroya, Yusa*; Yamashita, Shinichi; Hata, Kuniki; Meesungnoen, J.*; Jay-Gerin, J.-P.*

Canadian Journal of Chemistry, 88(10), p.1026 - 1033, 2010/10

 Times Cited Count:1 Percentile:91.1(Chemistry, Multidisciplinary)

The optical absorption spectra of the solvated electron (e$$_{rm sol}^-$$) in sub- and super-critical methanol are measured by both electron pulse radiolysis and laser photolysis techniques, at temperatures in the range 220-270 $$^{circ}$$C. Over the density range studied ($$sim$$0.45-0.59 g/cm$$^{3}$$), the position of the absorption maximum ($$E$$$$_{rm Amax}$$) of e$$_{rm sol}^-$$ is found to shift only slightly to the red with decreasing density. In agreement with our previous work in water, at a fixed pressure, $$E$$$$_{rm Amax}$$ decreases monotonically with increasing temperature in passing through the phase transition at $$T$$$$_{rm c}$$ (239.5 $$^{circ}$$C). By contrast, at a fixed density, $$E$$$$_{rm Amax}$$ exhibits a minimum as the solvent passes above the critical point into the supercritical state. These behaviors are discussed in terms of microscopic arguments based on the changes that occur in the methanol properties and methanol structure in the sub- and supercritical regimes.

Journal Articles

Protective effects of silybin and analogues against X-ray radiation-induced damage

Fu, H. Y.*; Lin, M.; Katsumura, Yosuke*; Yokoya, Akinari; Hata, Kuniki; Muroya, Yusa*; Fujii, Kentaro; Shikazono, Naoya

Acta Biochimica et Biophysica Sinica, 42(7), p.489 - 495, 2010/07

 Times Cited Count:9 Percentile:68.89(Biochemistry & Molecular Biology)

Silybin (SLB) and similar analogues, namely, hesperetin (HESP), naringenin (NAN) and naringin (NAR), are believed to be active constituents of natural flavonoids that have been reported as chemopreventive agents for certain cancers. Moreover, SLB and analogues have been determined to fast repair DNA bases from oxidative damage by pulse radiolysis techniques. The present study was designed to evaluate the protective effects of SLB and analogues on soft X-ray-induced damage to plasmid DNA in vitro. Among the compounds tested, HESP and SLB were the most effective in preventing X-ray-induced formation of DNA single-strand breaks (SSB). A comparison of these results with other experiments showed that the ability of SLB and analogues to inhibit DNA damage in vitro correlated with the ability of the compounds to scavenge free radicals. Our work revealed that natural flavonoids, SLB and analogues may be used as potent protectors against radiation damage.

93 (Records 1-20 displayed on this page)