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-ray irradiation on pitting corrosion of fuel cladding in water containing sea saltMotooka, Takafumi; Tsukada, Takashi
Proceedings of 2014 Nuclear Plant Chemistry Conference (NPC 2014) (USB Flash Drive), 9 Pages, 2014/10
In Fukushima Daiichi Nuclear Power Station (1F), seawater was injected into spent fuel pools in March 2011. Zircaloy-2 is adopted for the fuel cladding at 1F. Zirconium alloys including Zircaloy-2 are susceptible to pitting corrosion in oxidizing chloride solutions. In this study, we investigated the effect of oxide film formed during -ray irradiation on pitting corrosion of fuel cladding in water containing sea salt. The pitting potentials of Zircaloy-2 were measured using the water containing artificial sea salt. Changes in the composition of water containing sea salt were analyzed before and after -ray irradiation. The characteristics of the oxide films formed on Zircaloy-2 were evaluated by X-ray photoelectron spectroscopy. Solution analyses for water containing sea salt showed that hydrogen peroxide was generated by the irradiation. The pitting potential of Ziracloy-2 with oxide film formed under -ray irradiation was higher than that with oxide film formed without irradiation. X-ray photoelectron spectroscopy indicated that the oxide film was composed of zirconium oxide and the growth of oxide film was enhanced during the irradiation. It could thus be explained that the enhanced growth of oxide film under -ray irradiation caused the higher pitting potential.
Kumagai, Yuta; Kimura, Atsushi; Taguchi, Mitsumasa
Proceedings of 2014 Nuclear Plant Chemistry Conference (NPC 2014) (USB Flash Drive), 9 Pages, 2014/10
Hidaka, Akihide
Proceedings of 2014 Nuclear Plant Chemistry Conference (NPC 2014) (USB Flash Drive), 12 Pages, 2014/10
During core cooling at Fukushima Daiichi NPP accident, large amount of contaminated water was accumulated in the basements of reactor buildings at Units 1 to 4. The estimated ratios of I-131 and Cs-137 quantities in water to the core inventories are 0.51%, 0.85% at Unit 1, 74%, 38% at Unit 2 and 26%, 18% at Unit 3, respectively. According to the Henry's law, certain fraction of iodine in water could be released to atmosphere. Many evaluations for I-131 release have been performed so far by MELCOR or the reverse estimation with SPEEDI. The SPEEDI reverse predicted significant release until March 26 while no prediction in MELCOR after March 17. The present study showed that iodine release from accumulated water due to radiolytic conversion from I
to I
and gas-liquid partition of I may explain the release between March 17 and 26. This strongly suggests a need for improvement of current MELCOR approach which treats the release only from containment breaks.
Otobe, Haruyoshi; Kitatsuji, Yoshihiro; Kurata, Masaki; Takano, Masahide
Proceedings of 2014 Nuclear Plant Chemistry Conference (NPC 2014) (USB Flash Drive), 11 Pages, 2014/10
The chemical and transport behaviors of Pu and U in the corroded debris must be understood for the criticality safety control of Pu and U in the debris, especially for the removal operations and storage. Therefore, the chemical changes of UO and PuO powders, disks and U and Pu metal disks in HO aqueous solution have been checked, where HO is formed by the radiolysis of HO. As a result, UO changed to hydrated uranium peroxide, whereas the PuO remained unchanged. U metal was more reactive with HO aqueous solution than Pu metal. The chemical changes of the mixed UO/PuO powders in HO aqueous solution have been investigated. The dried slurry of the middle zone of HO aqueous solution was mainly composed of hydrated uranium peroxide, whereas the dried powder of the bottom zone was mainly composed of PuO.
Morita, Keisuke; Yamagishi, Isao; Nishihara, Kenji; Tsubata, Yasuhiro
Proceedings of 2014 Nuclear Plant Chemistry Conference (NPC 2014) (USB Flash Drive), 11 Pages, 2014/10
Sekio, Yoshihiro; Yamagata, Ichiro; Yamashita, Shinichiro; Inoue, Masaki; Maeda, Koji
Proceedings of 2014 Nuclear Plant Chemistry Conference (NPC 2014) (USB Flash Drive), 10 Pages, 2014/10
In the Fukushima Dai-ichi Nuclear Power Plant accident, seawater was temporarily injected into the spent fuel pools since water cooling and feeding functions were lost. For fuel assemblies which experienced seawater immersion, surface corrosion due to seawater constituents and the resultant degradation of mechanical property are of concern. Therefore, in order to assess the integrity of fuel assemblies (especially cladding tubes), the effects of seawater immersion on corrosion behavior and mechanical properties for as-recieved and irradiated Zircaloy-2 cladding tubes were investigated in the present study. As a result, no obvious surface corrosion and no significant degradation in the tensile strength property were observed after both artificial and natural seawater immersion tests for both steels. This suggests that the effects of seawater immersions on corrosion behavior and mechanical property (especially tensile property) for Zircaloy-2 cladding tubes are probably negligible.
Yamamoto, Masahiro; Katayama, Hideki*; Sato, Tomonori; Tsukada, Takashi
Proceedings of 2014 Nuclear Plant Chemistry Conference (NPC 2014) (USB Flash Drive), 6 Pages, 2014/10
In the Fukushima Dai-ichi Nuclear Power Plant, seawater and natural river water were poured for emergency cooling. Corrosion of materials was worried because of high chloride ion concentration from seawater. The chloride ion concentration was decreased by de-chlorination operation. However, the water was not treated in the viewpoint of microbial breeding, so that many microbes could be alive and microbially induced corrosion (MIC) was worried. So, we attempted to examine the ability of MIC occurrence by using of corrosion potential analysis. Corrosion potentials of samples rose to about 300 mV nobler than the initial values in the NB added solution. The potentials of the welded samples more easily rose than the simple plate. These potential changes are attributed to the biofilms formed on the sample surface. After about 100 days' immersion, evidence of localized corrosion was not observed. More immersion time is needed to clarify the MIC ability.
Arai, Yoichi; Watanabe, So; Takahatake, Yoko; Nakamura, Masahiro; Nakajima, Yasuo
Proceedings of 2014 Nuclear Plant Chemistry Conference (NPC 2014) (USB Flash Drive), 8 Pages, 2014/10
no abstracts in English
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
Nagaishi, Ryuji; Morita, Keisuke; Yamagishi, Isao; Hino, Ryutaro; Ogawa, Toru
Proceedings of 2014 Nuclear Plant Chemistry Conference (NPC 2014) (USB Flash Drive), 9 Pages, 2014/10
Two years after Three Mile Island Unit 2 (TMI-2) loss-of-coolant accident, radioactive contaminated water has been processed by Submerged Demineralizer System (SDS) with two types of zeolite adsorbents to remove radioactive nuclides. During and after the process, adsorption amount and distribution of nuclides on the zeolites, residual water content and thermal conductivity in the SDS vessels have been measured or estimated for verification of safety in the process, subsequent transportation and disposal. Hydrogen generation has been also evaluated mainly by direct monitoring in the large-scale of vessel after the process. In this work, the revaluation of hydrogen generation was demonstrated on the basis of the open information of vessel, and the latest experimental data obtained in adsorption and radiolysis occurring in small-scale of zeolite-water mixtures. As a result, the evaluated data was found to be comparable with the reported data obtained in the large-scale of real vessel.
Nagaishi, Ryuji; Inoue, Masao; Hino, Ryutaro; Ogawa, Toru
Proceedings of 2014 Nuclear Plant Chemistry Conference (NPC 2014) (USB Flash Drive), 9 Pages, 2014/10
Since seawater has been used as a coolant for reactors and spent fuel pools in broken reactor buildings at Fukushima Daiichi NPS accident, radioactive contaminated water emitted following the accident has contained salt content of seawater at high concentrations, different from that at TMI-2 accident. Radiolysis of seawater leading to hydrogen generation and corrosion has been simulated and reported by several groups. However, the proposed radiolysis models cannot be always applied to water radiolysis at the wide range of salt concentrations present in the NPS, mainly because primary yields of radiolysis products of water and radiation-induced reactions are dependent on the salt concentration. In this study, the radiolytic behavior in diluted and concentrated systems of seawater was considered on the basis of results in steady state and pulse radiolysis experiments, in which the above salt effects were demonstrated from the obtained results.
-ray irradiationKato, Chiaki; Sato, Tomonori; Nakano, Junichi; Ueno, Fumiyoshi; Yamagishi, Isao
Proceedings of 2014 Nuclear Plant Chemistry Conference (NPC 2014) (USB Flash Drive), 9 Pages, 2014/10
As a part of consideration for long-term storage of spent zeolite adsorption vessels in the Fukushima Daiichi Nuclear Power Station, corrosion of vessel material in the spent zeolite adsorption vessel is one of important issue. We performed electrochemical tests of stainless steel (type 316L) in the zeolite containing artificial seawater under -ray irradiation. Steady spontaneous potential (Esp) and pitting potential (VC), of type 316L was measurement. 
Co -rays source was used under irradiation. Dose rate of -ray irradiation was controlled for 5 kGy/h and 400 Gy/h. In anode polarization curves, there was no clear difference under irradiation and non-irradiation. The corrosion potential of type 316L increased with increasing time after -ray irradiation. The Esp was shifted to nobler by -rays irradiation, while increasing Esp was suppressed by contacted with zeolite.
Hata, Kuniki; Hanawa, Satoshi; Kasahara, Shigeki; Motooka, Takafumi; Tsukada, Takashi; Muroya, Yusa*; Yamashita, Shinichi*; Katsumura, Yosuke*
no journal, ,
no abstracts in English
Oyaizu, Makoto; Isobe, Kanetsugu; Hayashi, Takumi
no journal, ,
The corrosion behavior of SUS304 stainless steel and tritium effects of tritiated water on it were studied by means of electrochemical techniques. As the results, the self-passivation of SUS304 stainless steel in 1N sulfuric acid solution by dissolved oxygen was inhibited in tritiated water solution. It was also indicated that the self-passivation inhibitory effect could be induced by elution of chromium by further oxidation of trivalent chromium, which is one of the main components of passive layer, by highly oxidative radiolysis products.
Onishi, Takashi; Tanaka, Kosuke; Suto, Mitsuo; Akutsu, Yoko; Yamashita, Shinichiro; Koyama, Shinichi
no journal, ,
no abstracts in English
