Omori, Atsushi*; Akiyama, Eiji*; Abe, Hiroshi*; Hata, Kuniki; Sato, Tomonori; Kaji, Yoshiyuki; Inoue, Hiroyuki*; Taguchi, Mitsumasa*; Seito, Hajime*; Tada, Eiji*; et al.
Zairyo To Kankyo, 69(4), p.107 - 111, 2020/04
To evaluate the effect of oxidants, which are formed by radiolysis of water under gamma ray irradiation, on the corrosion of a carbon steel in humid environment, ozone was introduced as a model oxidant in to humidity-controlled air at 50C in a thermo-hygrostat chamber. Corrosion monitoring was performed by using an Atmospheric Corrosion Monitor-type (ACM) sensor consisting of a carbon steel anode and an Ag cathode. The output current of the ACM sensor was increased with the increase in relative humidity and it was obviously increased with the increase in the introduced ozone concentration at each relative humidity. The results indicate that ozone accelerates the corrosion of the carbon steel. The effect of ozone on the corrosion acceleration is attributed to the fast reduction reaction and fast dissolution reaction in to water compared to that of oxygen.
Kumagai, Yuta; Kimura, Atsushi*; Taguchi, Mitsumasa*; Watanabe, Masayuki
Journal of Radioanalytical and Nuclear Chemistry, 316(1), p.341 - 348, 2018/04
We studied effect of adsorption and condensation by zeolites on radiation-induced degradation of aqueous 2-chlorophenol (2-ClPh). This study aims to demonstrate that the solid-phase extraction using zeolites has potential advantage in treatments of aqueous organic pollutants. Among three zeolites examined in this study, a mordenite type zeolite (HMOR) that has a high Si to Al ratio (127 3) exhibited preferable performance as the matrix for the 2-ClPh degradation. HMOR adsorbed far more 2-ClPh than the other zeolites, which have lower Si/Al ratios. The irradiation of HMOR induced degradation of adsorbed 2-ClPh into Cl and organic by-products. We found a significant increase in Cl production by HMOR. The yield of Cl production in the presence of HMOR was as high as the yield in aqueous solution of 2-ClPh at a concentration 10 times higher. The increased Cl production indicates that the high concentration of adsorbed 2-ClPh led to effective use of the adsorbed energy of HMOR.
Kumagai, Yuta; Kimura, Atsushi*; Taguchi, Mitsumasa*; Watanabe, Masayuki
Journal of Physical Chemistry C, 121(34), p.18525 - 18533, 2017/08
H production by irradiation of zeolite-water mixtures was studied, to investigate effect of zeolites in the reaction process for H. Four different types of zeolites were examined comparatively under anoxic and under aerated conditions. High production yields of H were observed for the zeolites of high Al contents at low water fraction and under anoxic condition, compared to zeolites having lower Al contents. A comparison of the H yields in connection with chemical analysis of the zeolites suggests that extraframework Al species in the zeolites are involved in a reaction pathway for H. Meanwhile, under aerated condition and at high mixing ratio of water, the difference in H yield among the zeolites was suppressed and the yields of H were lower than those under anoxic condition probably due to HO produced by water radiolysis. The comparable H yields suggest another reaction pathway for H which is less dependent on the structure and composition of the zeolites.
Yang, S.*; Katsumura, Yosuke*; Yamashita, Shinichi*; Matsuura, Chihiro*; Hiroishi, Daisuke*; Lertnaisat, P.*; Taguchi, Mitsumasa
Radiation Physics and Chemistry, 123, p.14 - 19, 2016/06
-radiolysis of boiling water has been investigated. The G-value of H evolution was found to be very sensitive to the purity of water. In high-purity water, both H and O gases were formed in the stoichiometric ratio of 2:1; a negligible amount of HO remained in the liquid phase. The G-values of H and O gas evolution depend on the dose rate: lower dose rates produce larger yields. To clarify the importance of the interface between liquid and gas phase for gas evolution, the gas evolution under Ar gas bubbling was measured. A large amount of H was detected, similar to the radiolysis of boiling water. The evolution of gas was enhanced in a 0.5 M NaCl aqueous solution. Deterministic chemical kinetics simulations elucidated the mechanism of radiolysis in boiling water.
Iwamatsu, Kazuhiro*; Muroya, Yusa*; Yamashita, Shinichi*; Kimura, Atsushi; Taguchi, Mitsumasa; Katsumura, Yosuke*
Radiation Physics and Chemistry, 119, p.213 - 217, 2016/02
A quick measurement system of a continuous absorption spectrum covering a wide range from 200 to 950 nm was constructed by employing an optical multi-channel detector. Ion beam pulse radiolysis with 12.5 MeV/u He, 18.3 MeV/u C and 17.5 MeV/u Ne ions were performed with the measurement system. Transient absorption spectrum of (SCN) was clearly observed in KSCN aqueous solutions within a few minutes in spite of their very small absorbance, demonstrating high sensitivity of 0.001-0.003 in absorbance in the range from 260 to 660 nm as well as short measurement time of a few minutes. Two different absorption peaks attributed to Br and Br were observed simultaneously in NaBr aqueous solutions, showing powerfulness of the measurement system in overviewing chemical kinetics under ion beam irradiation especially in not well investigated chemical systems.
Koshimizu, Masanori*; Iwamatsu, Kazuhiro*; Taguchi, Mitsumasa; Kurashima, Satoshi; Kimura, Atsushi; Yanagida, Takayuki*; Fujimoto, Yutaka*; Watanabe, Kenichi*; Asai, Keisuke*
Journal of Luminescence, 169(Part B), p.678 - 681, 2016/01
We analyzed the effects of linear energy transfer (LET) on the scintillation properties of a Li glass scintillator, GS20. The scintillation time profiles were measured by using pulsed ion beams having different LETs. The rise in the scintillation time profiles was faster for higher LET, whereas the decay part was not significantly different for largely different LETs. The LET effects in the rise was ascribed to the effects of excited states interaction during the energy transfer process from the host glass to the luminescent centers, Ce ions. Supposing that the light yield decreases with LET, the fast rise at high LET was explained in terms of the competition between the energy transfer and the quenching due to the excited states interaction.
Hiroki, Akihiro; Yamashita, Shinichi*; Kimura, Atsushi; Nagasawa, Naotsugu; Taguchi, Mitsumasa
Nuclear Instruments and Methods in Physics Research B, 365(Part B), p.583 - 586, 2015/12
Effects of liner energy transfer (LET) and dose rate on the optical property of polymer gel dosimeters were investigated. The dosimeter prepared by using a radiation-crosslinked hydroxypropyl cellulose gel and methacrylate monomers such as 2-hydroxyethyl methacrylate and nonaethylene glycol dimethacrylate showed the color change from colorless to white with the He, C, Fe ions irradiation. Absorbance of the irradiated dosimeters increased with the dose up to 10 Gy. The absorbance of the dosimeters at the same total dose decreased with increasing dose rate in the range of 0.1 to 6.8 Gy/min. The absorbance decreased in order of He, C, Fe ions, which was in agreement with a change of LET. The increase in LET affected the decrease in the number of polymerization initiator such as OH radical and hydrated electron, resulting in the reduction of the absorbance of the dosimeters.
Yanagida, Takayuki*; Koshimizu, Masanori*; Kurashima, Satoshi; Iwamatsu, Kazuhiro*; Kimura, Atsushi; Taguchi, Mitsumasa; Fujimoto, Yutaka*; Asai, Keisuke*
Nuclear Instruments and Methods in Physics Research B, 365(Part B), p.529 - 532, 2015/12
We measured temporal profiles of scintillation of Ce-doped LiCaAlF scintillator crystals at different linear energy transfers (LETs). Based on the comparison of the high-LET temporal profiles with those at low LET, we found that a fast component was observed only at low LET. The disappearance of the fast component at high LET is tentatively ascribed to quenching of excited states at defects owing to the interaction between excited states via Auger process. In addition, the rise and the initial decay behavior was dependent on the LET. This LET-dependent behavior is explained by a seeming acceleration process and a slowing down process in energy transfer at high LET. The LET-dependent temporal profiles provide a basis of discrimination technique of -ray and neutron detection events using these scintillators based on the nuclear reaction, Li(n,)t.
Nagasawa, Naotsugu; Taguchi, Mitsumasa
Isotope News, (736), p.47 - 50, 2015/08
no abstracts in English
Kurashima, Satoshi; Miyawaki, Nobumasa; Kashiwagi, Hirotsugu; Okumura, Susumu; Taguchi, Mitsumasa; Fukuda, Mitsuhiro*
Review of Scientific Instruments, 86(7), p.073311_1 - 073311_8, 2015/07
The single-pulse formation technique using a beam chopping system consisting of two types of high-voltage beam kickers was modified to improve the quality and intensity of the single-pulse beam with pulse intervals over 1 s at TIARA cyclotron facility of Japan Atomic Energy Agency. Reduction of the multi-turn extraction number for suppressing the neighboring beam bunch contamination was achieved by restriction of a beam phase width and precise optimization of a particle acceleration phase. In addition, the single-pulse beam intensity was increased by a factor of two or more by a combination of two types of beam bunchers using sinusoidal and saw-tooth voltage waveforms. As a result, a contamination rate of neighboring beam bunches in the single-pulse beam was reduced to less than 0.1 %. Long-term purification of the single pulse beam was guaranteed by the well-controlled magnetic field stabilization system for the TIARA cyclotron magnet. Provision of the high quality intense single-pulse beam contributes to improve the accuracy of experiments for investigation of scintillation light time-profile and for neutron energy measurement by a time-of-flight method.
Sugo, Yumi; Sasaki, Yuji; Taguchi, Mitsumasa; Ishioka, Noriko
Journal of Radioanalytical and Nuclear Chemistry, 303(2), p.1381 - 1384, 2015/02
Yamashita, Shinichi*; Iwamatsu, Kazuhiro; Maehashi, Yuki*; Taguchi, Mitsumasa; Hata, Kuniki; Muroya, Yusa*; Katsumura, Yosuke*
RSC Advances (Internet), 5(33), p.25877 - 25886, 2015/02
Pulse radiolysis experiments were carried out to observe transient absorptions of reaction intermediates produced in NO and Ar-saturated aqueous solutions containing 0.9-900 mM NaBr. The most important species among the reaction intermediates are BrOH and Br , 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 Br + 2OH, with a rate constant of 3.8 10 M s, which is significant only within 10 micro-s for rather high bromide concentrations ( 10 mM). Primary 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 NO and Ar-saturated conditions as a function of NaBr concentration.
Hiroki, Akihiro; Yamashita, Shinichi*; Taguchi, Mitsumasa
Journal of Physics; Conference Series, 573(1), p.012028_1 - 012028_4, 2015/01
Polymer gel dosimeters based on radiation-crosslinked hydroxypropyl cellulose gel were prepared, which comprised 2-hydroxyethyl methacrylate (HEMA) and polyethylene glycol dimethacrylate (9G) as less toxic monomers and tetrakis (hydroxymethyl) phosphoniumu chloride (THPC) as an antioxidant. The dosimeters exposed to Co -rays became cloudy at only 1 Gy. The irradiated dosimeters were optically analyzed by using a UV-vis spectrophotometer to evaluate dose response. Absorbance of the dosimeters linearly increased in the dose range from 0 to 10 Gy. The dose sensitivity increased with increasing 9G concentration. The dosimeter with 2 wt% HEMA, 3 wt% 9G, and 0.16 wt% THPC exhibited about 0.04 Abs Gy of the dose sensitivity. The dose sensitivity of the dosimeters was also enhanced by increment in THPC, reached about 0.06 Abs Gy at 0.40 wt% THPC.
Koshimizu, Masanori*; Kurashima, Satoshi; Taguchi, Mitsumasa; Iwamatsu, Kazuhiro; Kimura, Atsushi; Asai, Keisuke*
Review of Scientific Instruments, 86(1), p.013101_1 - 013101_5, 2015/01
We have developed a system for measuring the temporal profiles of scintillation at high linear energy transfer (LET) by using pulsed ion beams from a cyclotron. The half width at half maximum time resolution was estimated to be 1.5-2.2 ns, which we attributed mainly to the duration of the pulsed ion beam and timing jitter between the trigger signal and the arrival of the ion pulse. The temporal profiles of scintillation of BaF at different LETs were successfully observed. These results indicate that the proposed system is a powerful tool for analyzing the LET effects in temporal profiles of scintillation.
Kumagai, Yuta; Kimura, Atsushi; Taguchi, Mitsumasa
Proceedings of 2014 Nuclear Plant Chemistry Conference (NPC 2014) (USB Flash Drive), 9 Pages, 2014/10
Kimura, Atsushi; Nagasawa, Naotsugu; Taguchi, Mitsumasa
Radiation Physics and Chemistry, 103, p.216 - 221, 2014/10
Large quantities of polysaccharide-based biomass are ubiquitous on Earth, and they possess unique structures, distinctive properties, and offer the advantages of being non-toxic and biodegradable. Ionizing radiation is widely used as a convenient tool for the modification of the polysaccharides via decomposition, grafting, and cross-linking. Until now, radiation cross-linked materials have only been produced either from polysaccharide derivatives or using cross-linking reagents, as certain natural polysaccharides have poor solubility in water and organic solvents as well as low chemical reactivity. These limitations could possibly be circumvented by the use of room temperature ionic liquids (RTILs), which can cleave the hydrogen bonds of the polysaccharides to form solutions. In this study, we focus on the application of RTILs as "specific solvents for the dissolution of polysaccharides," and their use in establishing a "proper reaction field for radiation cross-linking." For the first time in this study, we have demonstrated the possibility of producing cellulose gels by -ray irradiation of cellulose in RTILs under humid conditions. The gel fraction could be controlled by adept regulation of following conditions: initial concentration of cellulose, irradiation temperature, water content, and the absorbed dose. The cellulose gel thus obtained had an electronic conductivity of 3.0 mS cm, showing great potential for applications in optoelectronic and medical devices.
Haema, K.*; Oyama, Tomoko; Kimura, Atsushi; Taguchi, Mitsumasa
Radiation Physics and Chemistry, 103, p.126 - 130, 2014/10
For biological and medical applications, radiation sterilization of gelatin was evaluated in terms of radiation stability. It was found that electron beam irradiation decomposed the gelatin and that the weight-averaged molar mass decreased by approximately 7-10% with sterilization doses in the range of 5-25 kGy. Also, we found that the hydrolysis rate in 37C water was affected by the irradiation. On the other hand, crosslinking was predominantly induced when the gelatin was irradiated in water solution and radiation-crosslinked (RX) gelatin hydrogel was fabricated. Using gel fraction and gel permeation chromatography analysis of the eluted sol, it was determined that the RX-gelatin hydrogel was stable for 7 days in water at 37C.
Nakagawa, Seiko*; Taguchi, Mitsumasa; Kimura, Atsushi; Nagasawa, Naotsugu; Hiroki, Akihiro
Nuclear Instruments and Methods in Physics Research B, 334, p.64 - 68, 2014/09
N-saturated 2-propanol solutions containing styrene and maleimide were gelled by the addition of hydroxypropylcellulose and irradiated by proton, He and C-ion beams. The trend in the dose rate and LET effects on the yield and molecular weight distribution of the polymer produced in the gel was almost the same in the solution. On the contrary, the dose rate effect in the gel was higher than that in the solution. This effect was accelerated for irradiations by proton as well as heavier ion with a higher LET value.
Yamashita, Shinichi*; Hiroki, Akihiro; Taguchi, Mitsumasa
Radiation Physics and Chemistry, 101, p.53 - 58, 2014/08
Aino, Masataka*; Sato, Katsuya; Narumi, Issey*; Nagasawa, Naotsugu; Yoshii, Fumio; Taguchi, Mitsumasa
JAEA-Review 2013-059, JAEA Takasaki Annual Report 2012, P. 113, 2014/03