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Oral presentation

Reaction of solvated electrons in alkylammonium based ionic liquids

Kimura, Atsushi; Kondo, Takafumi*; Yang, J.*; Nagaishi, Ryuji; Yoshida, Yoichi*; Taguchi, Mitsumasa

no journal, , 

no abstracts in English

Oral presentation

Concentration and incident energy dependences of transient species in water by H$$^{+}$$ ion irradiation

Iwamatsu, Kazuhiro; Taguchi, Mitsumasa; Sugo, Yumi; Kurashima, Satoshi; Katsumura, Yosuke

no journal, , 

no abstracts in English

Oral presentation

Radiation and thermal ageing studies of silicone rubber (SiR) used in cable insulation in nuclear power plants

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$$^{circ}$$C and $$^{60}$$Co $$gamma$$ 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).

Oral presentation

Radiation and thermal ageing studies of polyvinylchloride used in cable insulation in nuclear power plants

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 100-135$$^{circ}$$C and/or to radiation ageing by $$^{60}$$Co $$gamma$$-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).

Oral presentation

Dose response of a natural-polymer-based gel dosimeter; Effects of composition on white turbidity increase after irradiations

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 $${gamma}$$-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 $$^{60}$$ Co $${gamma}$$-irradiation.

Oral presentation

Online analysis and yield determination of H$$_{2}$$ produced in water radiolysis with $$^{60}$$Co $${gamma}$$-rays and C ion beams

Yamashita, Shinichi; Katsumura, Yosuke; Murakami, Takeshi*

no journal, , 

Main initial products of water radiolysis are e$$^{-}$$$$_{aq}$$ and $$^{bullet}$$OH, which go through intraspur/track reactions in the time regime from ps to $${mu}$$s, leading to production of H$$_{2}$$O$$_{2}$$ and H$$_{2}$$. Among the main products, only H$$_{2}$$ is not soluble in water and difficult to be accurately quantified. H$$_{2}$$ 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$$_{2}$$. Therefore, an online analysis apparatus of gaseous products arising from liquid samples has been developed to measure H$$_{2}$$ production from water. In this work, at first accuracy and sensitivity of the apparatus were improved, and then, H$$_{2}$$ yields were measured as a function of concentration of the nitrate anion, which is a scavenger not only for e$$^{-}$$$$_{aq}$$ but also for the pre-solvated electron (e$$^{-}$$$$_{pre}$$). Figure shows G(H$$_{2}$$) measured in this work in comparison with reported values. Well-established primary G value for $$^{60}$$Co $${gamma}$$-irradiation, 0.46 (100 eV)$$^{-1}$$, is obtained at low NO$$_{3}$$$$^{-}$$ concentrations. Our data with $$^{60}$$Co $${gamma}$$-irradiation were in good agreement with the reported values. In the cases of C ion irradiations G(H$$_{2}$$) values increased with increasing LET due to increasing significance of intratrack reactions. Further discussion on H$$_{2}$$ production in fast process before 1 ps necessitate measurements of G(H$$_{2}$$) at other NO$$_{3}$$$$^{-}$$ concentrations and with the usage of other scavengers of e$$^{-}$$$$_{aq}$$ and e$$^{-}$$$$_{pre}$$.

Oral presentation

Effect of $$gamma$$ ray irradiation on deoxidation in aqueous solution by hydrazine

Motooka, Takafumi; Sato, Tomonori; Yamamoto, Masahiro

no journal, , 

The effect of $$gamma$$ 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 $$gamma$$ 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 $$gamma$$ ray irradiation. Concentration of dissolved oxygen was not decreased without $$gamma$$ ray irradiation, while concentration of dissolved oxygen was markedly decreased for one hour $$gamma$$ 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.

Oral presentation

Pulse radiolysis study on aqueous solutions containing seawater components

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$$_{3}$$$$^{-}$$, through radiolysis of seawater by $$gamma$$-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$$_{3}$$$$^{-}$$ 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$$^{-3}$$ Cl$$^{-}$$ with small amounts of Br$$^{-}$$. Model calculations are required to evaluate reaction rates of the reactions occurred in the complex solutions.

Oral presentation

Ion beam pulse radiolysis study of hydroxyl radical probed with bromide ion

Iwamatsu, Kazuhiro; Taguchi, Mitsumasa; Sugo, Yumi; Kurashima, Satoshi; Yamashita, Shinichi; Katsumura, Yosuke

no journal, , 

no abstracts in English

Oral presentation

Preparation of oligosaccharide for plant growth promoter by radiation-induced degradation in presence of hydrogen peroxide

Nguyen, T. K. L.; Nagasawa, Naotsugu; Kimura, Atsushi; Hiroki, Akihiro; Taguchi, Mitsumasa

no journal, , 

The combined method of $$gamma$$ irradiation and H$$_{2}$$O$$_{2}$$ 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 $$gamma$$-rays irradiation at low dose in the presence of H$$_{2}$$O$$_{2}$$.

Oral presentation

Observation of transient species in water under pulsed heavy ion irradiation

Taguchi, Mitsumasa; Iwamatsu, Kazuhiro; Sugo, Yumi; Kurashima, Satoshi; Katsumura, Yosuke

no journal, , 

no abstracts in English

Oral presentation

Synthesis of microscopic carboxymethylcellulose gels by radiation-induced crosslinking

Nagasawa, Naotsugu; Rokita, B.*; Ulanski, P.*; Hiroki, Akihiro; Rosiak, J. M.*; Taguchi, Mitsumasa

no journal, , 

no abstracts in English

Oral presentation

Effect of $$gamma$$ radiation on carbon steel corrosion in compacted bentonite

Taniguchi, Naoki; Yamaguchi, Makoto; Naito, Morimasa; Tateishi, Tsuyoshi*

no journal, , 

Corrosion tests of carbon steel were performed to estimaste possible effect of groundwater radiolysis by $$gamma$$ radiation from vitrified waste on corrosion rate of carbon steel overpack in HLW repository. While average corrosion rates from weight loss increased by $$gamma$$ radiation (dose rate : 30-50 Gy/h) in synthetic seawater, accompanying increased corrosion potential and cathodic current density possibly due to contribution of radiolytically generated oxidants such as hydrogen peroxide participated in cathodic reaction. On the other hand, no apparent effect of $$gamma$$ radiation was observed for samples in compacted bentonite buffer. In addition, corrosion rates little affected by dry density of bentonite buffer. A plausible mechanism was considered to explain the absence of the $$gamma$$ radiation.

Oral presentation

Pulse radiolysis studies on water at elevated temperatures and supercritical water

Lin, M.; Katsumura, Yosuke*; Muroya, Yusa*; Mostafavi, M.*

no journal, , 

In light water reactors (LWRs), coolant water is under strong radiation field. The knowledge on water radiolysis at elevated temperatures is necessary for the controlling of chemical conditions of coolant water and thus for mitigating the corrosion of the structural materials and keeping the integrity of the reactors. In this review talk, the importance, the current understanding, the challenging aspects, and the future subjects of water radiolysis in elevated temperature and supercritical water, will be addressed.

Oral presentation

Water radiolysis experiments using in-pile loop in JMTR

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

no journal, , 

Water radiolysis in reactor core is one of the key issues for safe and efficient LWR operation because chemical species formed by water radiolysis dominate corrosive environment of reactor core, and strongly influence integrity of structural materials in reactor as a result. Water chemistry in irradiation field can be evaluated by theoretical method, i.e. water radiolysis calculation, and confirmed by direct measurement of ECP. For demonstrating the adequacy of theoretical method, simulative calculation of in-pile ECP measurement and comparison between calculated and measurement results is essential. In order to provide significant information on water chemistry evaluation, experiments under well quantified condition will be performed in the JMTR. This paper presents out-lines and status of the experiments.

Oral presentation

Radiation modification of polysaccharide in ionic liquids

Kimura, Atsushi; Nagasawa, Naotsugu; Taguchi, Mitsumasa

no journal, , 

no abstracts in English

Oral presentation

Water chemistry research program using an in-pile loop in the JMTR

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

no journal, , 

no abstracts in English

Oral presentation

Hydrogen production in radiolysis of the mixture of mordenite and seawater

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.

Oral presentation

Synthesis of microscopic carboxymethylcellulose gel by metal addition and radiation-induced crosslinking method

Nagasawa, Naotsugu; Kimura, Atsushi; Hiroki, Akihiro; Taguchi, Mitsumasa

no journal, , 

no abstracts in English

Oral presentation

Water radiolysis studied by positron annihilation

Hirade, Tetsuya; Oka, Toshitaka

no journal, , 

Positronium(Ps) formation in insulating materials can be explained by spur reactions at the terminal spur of the positron track, so-called positron spur. Ps formation time is probably about 1ps and the yields of Ps formation give information of the reactions of the reactive species in the terminal spur, such as the free excess electrons. Ortho-Ps annihilation lifetime is about 1-5ns by the pick-off annihilation in condensed materials. Hence the o-Ps reactions with reactive species are quite possible. The most important reactions are, probably, ortho-Ps oxidation and spin conversion by reactive species, such as OH radical. We are introducing what we can study for water radiolysis by use of positron annihilation methods.

29 (Records 1-20 displayed on this page)