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Takeuchi, Masayuki; Sano, Yuichi; Nakajima, Yasuo; Uchiyama, Gunzo; Nojima, Yasuo*; Fujine, Sachio*
Journal of Energy and Power Engineering, 7(6), p.1090 - 1096, 2013/06
The corrosion behavior of a titanium-5% tantalum alloy (Ti-5Ta) in hot nitric acid condensate was investigated to understand aging behavior of reprocessing equipments. On the basis of long-term immersion tests, it was determined that the corrosion of Ti-5Ta in nitric acid condensate is accelerated with an increase in the concentration. The corrosion rate was nearly constant during the immersion test and the coupons suffered from uniform corrosion. In addition, it is important to note that the nitric acid concentration in the condensate increased on addition of metal salts to the heated nitric acid solution. The larger valence of metal ions was contributed to the increase in the concentration of nitric acid condensate. Consequently, the metal salt in the heated nitric acid solution accelerates the corrosion of Ti-5Ta in the condensate. Therefore, the nitric acid condensate condition should be carefully considered for the corrosion environment of titanium and its alloys.
Kato, Chiaki; Ueno, Fumiyoshi; Yamamoto, Masahiro; Ban, Yasutoshi; Uchiyama, Gunzo; Nojima, Yasuo*; Fujine, Sachio*
ECS Transactions, 53(21), p.45 - 55, 2013/05
Times Cited Count：2 Percentile：76.38(Electrochemistry)Neptunium ion contained as one of the fission products in reprocessing solutions is known as a corrosion accelerator of the stainless steel. But it is not clear why remarkable acceleration of corrosion is caused by a slight amount of the Np ion in boiling nitric acid solution. Neptunium has several oxidation states in nitric acid solution. These changeable oxidation states of Np in nitric acid solution are regarded as the cause. Therefore an evaluation of the electrochemical behaviors on stainless steel in nitric acid solution related to the oxidation state of Np is required in order to understand the corrosion acceleration mechanism. A specially designed electrochemical test cell integrated with optical cell for spectroscopic analysis was used for this purpose. From results of electrochemical tests, cathodic reaction on stainless steel was activated by Np ions. Np(VI) ion made the corrosion potential shift nobler than Np(V) and nobler corrosion potential causes increasing corrosion current and accelerating corrosion of stainless steel in nitric acid solution. Np(V) was easily oxidized to Np(VI) in nitric acid solution and Np(VI) was the stable state in boiling 3M-HNO. It was considered that role of Np ions was that of mediator to accelerate corrosion due to activating cathodic reaction and re-oxidizing cycle in boiling 3M-HNO.
Takeuchi, Masayuki; Sano, Yuichi; Nakajima, Yasuo; Uchiyama, Gunzo; Nojima, Yasuo*; Fujine, Sachio*
Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 6 Pages, 2012/07
A long-term corrosion tendency and metal salt effect in heating nitric acid solution on corrosion behavior of titanium-5% tantalum alloy (Ti-5Ta) in hot nitric acid condensate condition were mainly researched to discuss the aging behavior of reprocessing equipments such as evaporators made of titanium or its alloy. The hot pure nitric acid solution with continuous renewing such as the nitric acid condensate condition is severe corrosion environment for their materials because of the corrosion inhibition effect from titanium ions as corrosion products or oxidizing ions in nitric acid solution. From the results of the long-term corrosion test for total 11,000 hrs, the corrosion of Ti-5Ta in the nitric acid condensate was accelerated with increase of the nitric acid concentration in the condensate. The corrosion rate was nearly constant during the immersion time and the test coupons suffered a uniform corrosion. Thus, from the viewpoints of nitric acid corrosion, the life-time of the reprocessing equipments made of titanium or its alloy will be roughly estimated based on the results of average corrosion rate in operation. It was also found that the kind and concentration of metal salt in the heating nitric acid solution gave a remarkable effect on the concentration of nitric acid vapor and the corrosion of Ti-5Ta in the hot nitric acid condensate. Most of the evaporators for reprocessing plants include metal ions in the heating nitric acid solution, so the metal salt effect is one of the corrosion factors to control the corrosion behavior of titanium alloy in condensate. The nitric acid concentration in the condensate increases by adding the metal salts in the heating nitric acid solution, in addition, the larger valence of metal ions was contributed to the increase of nitric acid concentration in the condensate. Consequently, the metal salts effect in the heating nitric acid solution accelerates the corrosion of Ti-5Ta in the nitric acid condensate.
Ueno, Fumiyoshi; Shiraishi, Hironori; Inoue, Shun; Motooka, Takafumi; Kato, Chiaki; Yamamoto, Masahiro; Uchiyama, Gunzo; Nojima, Yasuo*; Fujine, Sachio*
Proceedings of 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference (ICONE-20 & POWER 2012) (DVD-ROM), 8 Pages, 2012/07
In PUREX process for spent fuel reprocessing plants, heating portions in the components are severely corroded in the boiling solution under heat transfer (HT) conditions. In this paper, authors have focused on the effects of surface temperature and heat flux on corrosion rates (CRs) of stainless steels in boiling nitric acid under HT conditions. Two types of cells for HT and immersion conditions were applied for corrosion tests. Test solution used was 33 mol/m
vanadium added to 3 kmol/m nitric acid solution, and was heated at boiling temperature under atmospheric pressure. Additionally, a boiling curve which was indicated the relation between heat flux and degree of superheating was investigated experimentally. Surface temperatures during corrosion tests were estimated from a boiling curve. The results showed that CR did not depend on heat flux, but depended on surface temperature. Arrhenius plots on CRs indicated that CR was accelerated by solution boiling against non-boiling.
Yokoyama, Kenichi*; Murata, Yusuke*; Shiimori, Fusae*; Sakai, Junichi*; Yamamoto, Masahiro; Uchiyama, Gunzo; Nojima, Yasuo*; Fujine, Sachio*
Fushoku Boshoku Kyokai Dai-58-Kai Zairyo To Kankyo Toronkai Koenshu, p.11 - 12, 2011/09
Characteristics of hydrogen embrittlement of pure Ti and Ti-5Ta alloys were evaluated by stress loading and constant load tests. Mechanical properties of these materials were affected by hydride formation of surface layers. Although elongation was reduced by hydrogen absorption, embrittlement was observed only in the surface hydride area. It is also suggested that Ti-5Ta alloy was better susceptibility of hydrogen embrittlement than pure Ti.
Miura, Tatsuya*; Nishikata, Atsushi*; Tsuru, Toru*; Yamamoto, Masahiro; Uchiyama, Gunzo; Nojima, Yasuo*; Fujine, Sachio*
Fushoku Boshoku Kyokai Dai-58-Kai Zairyo To Kankyo Toronkai Koenshu, p.15 - 16, 2011/09
There exist some equipments made of Ti or Ti-5Ta alloy in the spent nuclear fuel reprocessing plant. These equipments are investigated for failure by hydrogen embrittlement. To evaluate the stabilities of hydrogen in the solutions using at the reprocessing plant, channel-flow-ellectrode (CFE) method was utilized. The method to determine the dissolved hydrogen concentration was considered from the results of anodic polarization curves.
Shiimori, Fusae*; Sakai, Junichi*; Yokoyama, Kenichi*; Motooka, Takafumi; Uchiyama, Gunzo; Nojima, Yasuo*; Fujine, Sachio*
Fushoku Boshoku Kyokai Dai-58-Kai Zairyo To Kankyo Toronkai Koenshu, p.13 - 14, 2011/09
In reprocessing plants, hydrogen gas was released by radiolysis of aqueous solution. The relationship of the amount of hydrogen gas and the amount of hydrogen absorption to titanium and Ti-5Ta were not clear. In this study, hydrogen was absorbed to titanium by the cathode charging and irradiation. Then, the amount of the hydrogen gas from solutions and the amount of the hydrogen absorbed to titanium was compared. It was found that a very small amount of the hydrogen by radiolysis was absorbed to titanium. It was suggested that the difference of the hydrogen absorption rate was caused by the difference of the hydrogen concentration on the metal surface.
Kato, Chiaki; Ueno, Fumiyoshi; Yamamoto, Masahiro; Hakamatsuka, Yasuyuki; Ban, Yasutoshi; Morita, Yasuji; Uchiyama, Gunzo; Nojima, Yasuo*; Fujine, Sachio*
Zairyo To Kankyo, 60(2), p.69 - 71, 2011/02
It was reported that the metric ions such as Pu and Np contained in reprocessing solutions would accelerate corrosion of stainless steals due to those ions changing higher oxidizer. It's difficult that those ions was used in laboratory test because of radioactive elements. However it's important to understand oxide stats of those ions and electrochemical behavior on stainless steals in order to estimate corrosion rate of materials in reprocessing plats. Furthermore laboratory test with very a little solution volume is demanded for handling radioactive elements. This paper shows that developed a small electrochemical cell with a spectral analysis function and those results of polarization curves on stainless steals and oxide stats of Np(IV)/Np(V) and Pu(IV)/Pu(VI) in boiling nitric acid solutions.
Kato, Chiaki; Ueno, Fumiyoshi; Yamamoto, Masahiro; Hakamatsuka, Yasuyuki; Ban, Yasutoshi; Morita, Yasuji; Uchiyama, Gunzo; Nojima, Yasuo*; Fujine, Sachio*
Fushoku Boshoku Kyokai Dai-57-Kai Zairyo To Kankyo Toronkai Koenshu, p.43 - 46, 2010/10
Reprocessing process solution including Pu and Np may accelerate corrosion of the stainless steel because of oxidizing states in boiling nitric acid. The small electrochemical test cell with a spectral analysis function was developed for the purpose of evaluating corrosion of the stainless steel and oxidizing states of Pu and Np ions in a boiling nitric acid solution. The relationship between corrosion states of the stainless steel and oxidizing states in boiling nitric acid solution can be confirmed.
Matsumoto, Kenichi*; Miyahara, Kenji; ; Asazuma, Shinichiro; Fukushima, Isao; Shoji, Kenji; Nojima, Yasuo; Kimura; Ikeda; Shibuya, Jun*; et al.
PNC TN8440 87-194, 82 Pages, 1987/08
no abstracts in English
Hirose, Fumimasa*; Nakahara, Masahiro*; Ueno, Fumiyoshi; Uchiyama, Gunzo; Nojima, Yasuo*
no journal, ,
To study aging phenomena caused by corrosion of stainless steels, commercial pure titanium and titanium alloys in chemical plants using nitric acid, corrosion incidents, experiences of materials installation, corrosion tests results under actual and simulated environments were investigated in this report. The results were compared with literatures. As the results, it was clarified that corrosion of SUS304L and SUS310ELC were accelerated at heat affected zone and weld metal, respectively. In the cases of commercial pure titanium and titanium alloys, corrosion were accelerated at the portion in the environments without Ti ion. Finally, corrosion lives and application conditions of these materials in nitric acid environment were considered.
Kim, S.-Y.; Morita, Yasuji; Hakamatsuka, Yasuyuki; Ueno, Fumiyoshi; Yamamoto, Masahiro; Uchiyama, Gunzo; Nojima, Yasuo*; Fujine, Sachio*
no journal, ,
Electrochemical data of Pu and Np at stainless steel electrode and platinum electrode are obtained as fundamental data for the effect of these elements on the material corrosion at the boiling surface. Natural electric potential became constant within 1 hour and the existence of these elements increased the potential.
Takeuchi, Masayuki; Kubota, Masahiro; Hoshi, Masayuki; Sakauchi, Nobuyuki; Nakajima, Yasuo; Uchiyama, Gunzo; Nojima, Yasuo*; Fujine, Sachio*
no journal, ,
no abstracts in English
Ueno, Fumiyoshi; Kato, Chiaki; Motooka, Takafumi; Yamamoto, Masahiro; Uchiyama, Gunzo; Nojima, Yasuo*; Fujine, Sachio*
no journal, ,
Long term corrosion of stainless steel in boiling nitric acid solution at heating portion of dissolver and concentrator was studied to investigate ageing behavior of the components in spent fuel reprocessing plant. Corrosion tests carried out more than 8,000 hours in test duration using simulated test solutions including non-radioactive V and Ru ions. As the result, several simulated corrosion data which were equivalent and accelerated about three times of corrosion rate in comparison with actual components were obtained. And it was considered that loss of thickness caused by intergranular corrosion increases as approximately constant rate in stainless steel components but acceleration of corrosion could be observed in the case of remarkable loss of thickness.
Motooka, Takafumi; Ueno, Fumiyoshi; Yamamoto, Masahiro; Uchiyama, Gunzo; Nojima, Yasuo*; Fujine, Sachio*
no journal, ,
The corrosion behavior of stainless steels under denitration condition with formaldehyde was investigated by the corrosion test etc. As a result, the decrease in nitric acid concentration and the generation of NOx gas were observed under the denitration. The corrosion rate of stainless steels has decreased greatly by the injection of formaldehyde. It was thought that NOx and nitrous acid were factors for decrease of corrosion rate in a stainless steel.
Motooka, Takafumi; Yamamoto, Masahiro; Ueno, Fumiyoshi; Ishijima, Yasuhiro; Uchiyama, Gunzo; Nojima, Yasuo*; Fujine, Sachio*; Sakai, Junichi*; Shiimori, Fusae*; Miyasaka, Yuto*
no journal, ,
As a part of studies on ageing behavior of reprocessing plants, the amount of hydrogen gas generated from nitrate solutions under 
irradiation and the amount of hydrogen absorbed to titanium alloy were measured after irradiation in order to evaluate the hydrogen degradation of instruments made of titanium alloy. The amount of hydrogen gas was decreased with increase of nitrate concentration. Only a little hydrogen was absorbed to titanium. It is necessary to consider the long-time prediction model for hydrogen adsorption to evaluate hydrogen degradation.
Ishijima, Yasuhiro; Takada, Juntaro; Ueno, Fumiyoshi; Yamamoto, Masahiro; Uchiyama, Gunzo; Nojima, Yasuo*; Fujine, Sachio*; Kimura, Kazuhiro*
no journal, ,
Effect of ageing on mechanical properties of nickel based refractory alloy was evaluated for study on ageing behavior of nuclear fuel reprocessing plants. Solution treated and aged Alloy 625 was elected to test material. Creep tests and tensile tests were carried out at 1027 K. From test results, aged alloy 625 showed linear relationship between test stress and secondary creep rate. On the other hand, solution treated alloy 625 showed deformation behavior change at 100 MPa. This result indicates that the ageing behavior of reducing furnace can evaluate by straight line extrapolation. Aged alloy 625 showed remarkable decreasing of ductility at room temperature. This result suggests that room temperature embrittlement should be considered on the ageing behavior of reducing furnace.
Ueno, Fumiyoshi; Shiraishi, Hironori; Inoue, Shun; Motooka, Takafumi; Kato, Chiaki; Yamamoto, Masahiro; Uchiyama, Gunzo; Nojima, Yasuo*; Fujine, Sachio*
no journal, ,
Effect of metal surface temperature and solution boiling on corrosion of stainless steel in boiling nitric acid solution at heating portion was studied to investigate ageing behavior of the components in spent fuel reprocessing plant. Corrosion tests under the conditions of heat transfer and immersion in atmospheric pressure were carried out using nitric acid solution including Vanadium. As the results, apparent activation energies of thermal dependences on corrosion rates of both the heat transfer and the immersion were indicated approximately 40 kJ/mol. Corrosion rate under the boiling condition were higher about 7 times for the non-boiling condition.
Sano, Yuichi; Takeuchi, Masayuki; Hoshi, Masayuki; Sakauchi, Nobuyuki; Hirano, Hiroyasu; Uchiyama, Gunzo; Nojima, Yasuo*; Fujine, Sachio*
no journal, ,
no abstracts in English
Ban, Yasutoshi; Morita, Yasuji; Hakamatsuka, Yasuyuki; Kato, Chiaki; Yamamoto, Masahiro; Uchiyama, Gunzo; Nojima, Yasuo*; Fujine, Sachio*
no journal, ,
Polarization curves, open circuit potential, optical absorption spectra were measured in nitric acid solutions containing Np and Pu using SUS310Nb as a working electrode for a study on ageing behavior of reprocessing plants. Appreciable difference was not observed between the polarization curves obtained in presence of Np only and obtained coexistence of Np and Pu.
