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Hiroki, Akihiro; Sato, Toshihiro*; Nagasawa, Naotsugu; Taguchi, Mitsumasa; Tamada, Masao
no journal, ,
Radiation modification of hydroxypropyl cellulose (HPC) hydrogels by blending polyvinyl alcohol (PVA) was investigated. The blend hydrogels constructed with HPC and PVA were prepared by electron beam irradiation to high concentrated aqueous solutions. Gel fraction of the blend hydrogels increased sharply up to 10 kGy, and leveled off at 50 kGy. It was found that PVA content caused a decrease in the gel fraction. Elongation at break of the blend hydrogels obtained at 50 kGy gradually increased with the PVA content beyond 0.4 wt%, and reached 125 % at 4 wt% of PVA, which was about 1.8 times larger than that of the pure HPC hydrogel. Therefore, the HPC hydrogels with desired mechanical properties were obtained by the combination of PVA blending with the radiation crosslinking technique.
Oka, Toshitaka; Yokoya, Akinari; Fujii, Kentaro
no journal, ,
no abstracts in English
Yamashita, Shinichi; Hiroki, Akihiro; Nagasawa, Naotsugu; Murakami, Takeshi*; Taguchi, Mitsumasa
no journal, ,
A new polymer gel dosimeter was developed to overcome weakness of earlier polymer gel dosimeters. Hydroxyethyl 2-methacrylate (HEMA) and polyethylene glycol ester dimethacrylate (9G) were less toxic constituents, which polymerize with irradiations. One of cellulose derivatives, hydroxypropyl cellulose (HPC), was crosslinked by irradiations of electron beam and used as a gel matrix, which doesn't soften with increasing temperature. Hydrogel of HPC is very transparent, so light scattering and absorption of products of radiation-induced polymerization are easily observable. As a result of irradiation, white turbidity was observed inside the gel at around 1-2 Gy. Increasing behavior of white turbidity with irradiation depended on composition of constituent monomers. White turbidity appears at rather lower dose and its increase saturates at around 10 Gy of 
-irradiation when 9G is predominant. On the other hand, it becomes stronger even beyond 10 Gy when HEMA is predominant. In order to quantify the degree of white turbidity, haze measurement and UV-vis absorption spectrometry were conducted. In addition, white turbidity evolution was also confirmed after irradiations of therapeutic C ion beam although degree of white turbidity was less clear than that observed after 
Co -irradiation.
produced in water radiolysis with Co -rays and C ion beamsYamashita, Shinichi; Katsumura, Yosuke; Murakami, Takeshi*
no journal, ,
Main initial products of water radiolysis are e
and 
OH, which go through intraspur/track reactions in the time regime from ps to 
s, leading to production of HO and H. Among the main products, only H is not soluble in water and difficult to be accurately quantified. H also tends to leak even from a very small crevice where other gases do not leak. It is necessary to pay attentions to leakage and equilibrium between liquid-gas phases when ones want to accurately quantify H. Therefore, an online analysis apparatus of gaseous products arising from liquid samples has been developed to measure H production from water. In this work, at first accuracy and sensitivity of the apparatus were improved, and then, H yields were measured as a function of concentration of the nitrate anion, which is a scavenger not only for e but also for the pre-solvated electron (e
). Figure shows G(H) measured in this work in comparison with reported values. Well-established primary G value for Co -irradiation, 0.46 (100 eV)
, is obtained at low NO
concentrations. Our data with Co -irradiation were in good agreement with the reported values. In the cases of C ion irradiations G(H) values increased with increasing LET due to increasing significance of intratrack reactions. Further discussion on H production in fast process before 1 ps necessitate measurements of G(H) at other NO concentrations and with the usage of other scavengers of e and e.
Hata, Kuniki; Hanawa, Satoshi; Kasahara, Shigeki; Muroya, Yusa*; Katsumura, Yosuke*
no journal, ,
Fukushima Daiichi Nuclear Power Units 1 - 3 experienced seawater injection into the reactor cores as an emergent measure to cool the reactors for a short period after the accident. As a result, structural materials in the reactors have been exposed to unexpected corrosion environment due to anions, such as Cl, in seawater. Furthermore, strong oxidants, such as ClO and ClO, through radiolysis of seawater by 
-rays would make the corrosion environment severer. Several studies on radiolysis of seawater at ambient temperature had been performed in the field of geological disposal of high level wastes, and amount of ClO and gas products had been evaluated. However, further examination is required on radiation induced reactions among seawater components to predict precisely the corrosion environment of the structural materials exposed to seawater. In the present study, the reactions of Cl derived radicals with Br were measured by pulse radiolysis. The production of mixed radical anion, BrCl
, was observed in aqueous solutions containing 1 mol dm
Cl with small amounts of Br. Model calculations are required to evaluate reaction rates of the reactions occurred in the complex solutions.
Iwamatsu, Kazuhiro; Taguchi, Mitsumasa; Sugo, Yumi; Kurashima, Satoshi; Yamashita, Shinichi; Katsumura, Yosuke
no journal, ,
no abstracts in English
Nguyen, T. K. L.; Nagasawa, Naotsugu; Kimura, Atsushi; Hiroki, Akihiro; Taguchi, Mitsumasa
no journal, ,
The combined method of irradiation and HO oxidizing agent has showed the advantage in using low irradiation doses of 5-30 kGy to get a large scale of oligoalginate compare with early methods. It is concluded that low molecular weight AlgNa and/or oligoalginate can effectively be obtained by -rays irradiation at low dose in the presence of HO.
Kumagai, Yuta; Muroya, Yusa*; Yamada, Reiji; Nagaishi, Ryuji; Katsumura, Yosuke*
no journal, ,
Transient kinetics of hydroxyl radical and hydrated electron in aqueous solution containing colloidal silica were studied using pulse-radiolysis technique in order to understand the coexistent effect of silica on the radiation-induced reaction. Nano-sized colloidal silica prepared by Stober method allowed time-resolved optical absorption measurement in mixture of water and silica. In the presence of colloidal silica, the reaction of hydroxyl radical with ferrocyanide ion was inhibited. Change in the transient absorption in UV region was also observed and it suggests formation of a product due to a reaction of hydroxyl radical with colloidal silica. The results suggest that hydroxyl radical was scavenged by colloidal silica. On the other hand, little effect of colloidal silica on the decay of hydrated electron was observed. Therefore it is unlikely that an interaction between hydrated electron and colloidal silica significantly changes the reaction pathway of hydrated electron.
ion irradiationIwamatsu, Kazuhiro; Taguchi, Mitsumasa; Sugo, Yumi; Kurashima, Satoshi; Katsumura, Yosuke
no journal, ,
no abstracts in English
Shimada, Akihiko; Seguchi, Tadao*; Tamura, Kiyotoshi; Oshima, Takeshi; Idesaki, Akira; Kudo, Hisaaki*
no journal, ,
Silicone rubber (SiR) is used widely in cable insulation in nuclear power plants. SiR sheets with different formulation were examined on the two points, specimen's thickness and thermal and radiation combined accelerated ageing. The 0.5 and 2 mm thick sheets were aged by thermal at up to 235
C and Co rays radiation with 1 kGy/h up to 800 kGy. The degradation was measured by tensile testing and gel fraction and swelling experiments. For check the distribution of degradation in depth of sheet, the 2 mm sheet sample was sliced by 0.3 mm thickness after ageing. The results indicated that the degradation progressed uniformly throughout the 2 mm thick sheet. For the ageing combination, the degradation by three different combinations was examined, that is, (a) simultaneous ageing, (b) thermal and radiation sequential ageing, and (c) radiation and thermal reversed sequential ageing. Elongation at break indicated that the order of degradation mild to severe was reverse sequential, sequential, simultaneous ageing. The study was supported by Nuclear and Industrial Safety Agency (NISA), Japanese Minister of Economy, Trade and Industry (METI).
Idesaki, Akira; Seguchi, Tadao*; Tamura, Kiyotoshi; Oshima, Takeshi; Shimada, Akihiko; Kudo, Hisaaki*
no journal, ,
The degradation of polyvinylchloride (PVC) used in cable insulation in nuclear power plant was investigated by accelerated thermal and radiation ageing. The sheets of PVC as same formulation as cables were subjected to thermal ageing at temperature range 100-135C and/or to radiation ageing by Co -rays at a dose rate of 1 kGy/h in air. The degradation was evaluated by the tensile test and by the weight change. The relations between elongation at break and change of weight by loss of plasticizer were analyzed. At higher temperature, the plasticizer evaporates to cause the decrease of tensile properties. The study was supported by Nuclear and Industrial Safety Agency (NISA), Japanese Minister of Economy, Trade and Industry (METI).
Tago, Takanori; Nagasawa, Naotsugu; Kudo, Hisaaki*; Taguchi, Mitsumasa; Katsumura, Yosuke*
no journal, ,
Poly (L-lactic acid)(PLA) is a hard and transparent bioplastic and now widespread with a potential to replace the conventional petroleum-derived plastics. The PLA crosslinked to improve the thermal property by irradiating with triallyl isocyanurate (TAIC). The impact resistance, however, is nearly un-improved. To improve the above-mentioned two properties of PLA, we investigated a new combination method of blending of PLA with polyamide11 (PA11) having high impact resistance, which is produced from castor oil, and then crosslinking with TAIC by radiation. The crosslinking structures were formed in irradiated PLA/PA11 blends with TAIC. The gel content of PLA/PA11 blends increased with increasing the mixing ratio of PA11 and absorbed dose. At the dose of 100 kGy and more, the network was formed about 80% in the PLA / PA11 blends. The thermal properties of the blends were evaluated from the deformation at the melting-temperature (
) by the thermo-mechanical analysis. The blends with high gel contents (
80%) demonstrated very little deformation above the of PA11 around 185C. The improvement of the impact property was indicated by the Charpy impact testing. The blends (50/50wt%) irradiated with 100 kGy showed the higher impact resistance about 2.5 times of original PLA. Therefore, the applications of bioplastic will be expanded by the combination method of blending and radiation-induced crosslinking.
Kimura, Atsushi; Nagasawa, Naotsugu; Taguchi, Mitsumasa
no journal, ,
no abstracts in English
ray irradiation on deoxidation in aqueous solution by hydrazineMotooka, Takafumi; Sato, Tomonori; Yamamoto, Masahiro
no journal, ,
The effect of ray irradiation on deoxidation in aqueous solution by hydrazine was investigated using pure water and artificial sea water at room temperature. We placed the solutions with small amount of hydrazine at ray irradiation field at dose rates of 0.3-7.5 kGy/h. The concentration of dissolved oxygen in the solutions was measured before and after ray irradiation. Concentration of dissolved oxygen was not decreased without ray irradiation, while concentration of dissolved oxygen was markedly decreased for one hour ray irradiation, which is under detection limit at higher dose rate over 2 kGy/h. It is believed that the hydrazine addition to spent nuclear fuel pool water is effective as a method for decreasing concentration of dissolved oxygen.
Hanawa, Satoshi; Hata, Kuniki; Chimi, Yasuhiro; Nishiyama, Yutaka; Nakamura, Takehiko
no journal, ,
no abstracts in English
Kumagai, Yuta; Nagaishi, Ryuji; Kimura, Atsushi; Taguchi, Mitsumasa; Nishihara, Kenji; Yamagishi, Isao
no journal, ,
For decontamination of radioactive water containing salts from seawater in Fukushima Dai-ichi Nuclear Power Station, zeolite is used as adsorbent for radioactive Cs. The management of hydrogen produced by radiolysis of water in the zeolite waste is important for safe storage of the waste. Thus hydrogen production from the mixture of mordenite-type zeolite and seawater was studied. The hydrogen yield from the mixture decreased monotonically as the weight fraction of seawater was decreased. However, the measured yield was higher than the yield expected from the weight fraction of seawater, supposing that mordenite has no effect. The result suggests that hydrogen was produced in another pathway besides the direct radiolysis of seawater in the presence of mordenite but its efficiency of the hydrogen production was lower than the direct radiolysis of seawater. The radiation energy deposited to mordenite is expected to be involved in the radiolysis of the adsorbed water.
Kimura, Atsushi; Kondo, Takafumi*; Yang, J.*; Nagaishi, Ryuji; Yoshida, Yoichi*; Taguchi, Mitsumasa
no journal, ,
no abstracts in English
Taguchi, Mitsumasa; Iwamatsu, Kazuhiro; Sugo, Yumi; Kurashima, Satoshi; Katsumura, Yosuke
no journal, ,
no abstracts in English
Nagasawa, Naotsugu; Rokita, B.*; Ulanski, P.*; Hiroki, Akihiro; Rosiak, J. M.*; Taguchi, Mitsumasa
no journal, ,
no abstracts in English