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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：75.48(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.
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.
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.
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.
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.
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
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.
Yamamoto, Masahiro; Ban, Yasutoshi; Kato, Chiaki; Ueno, Fumiyoshi; Nojima, Yasuo*; Fujine, Sachio*
no journal, ,
Electrochemical behavior of SUS310Nb stainless steel in nitric acid solution was investigated using specially designed electrochemical cell in which dealt with the solution containing radioactive elements. Polarization curves of SUS310Nb steel were measured the range from room temperature to boiling condition in 3N nitric acid solution containing U, Pu and Np. The results show that corrosion potentials and currents were affected by the reduced reactions of added ions and temperatures. Especially, Np(VI) ion accelerated corrosion rate dominantly. It was also discussed the effect of deduced reactions of the other ions.
Uchida, Hiroki*; Tada, Eiji*; Tsuru, Toru*; Ishijima, Yasuhiro; Ueno, Fumiyoshi; Yamamoto, Masahiro; Uchiyama, Gunzo; Nojima, Yasuo*; Fujine, Sachio*
no journal, ,
no abstracts in English
-ray irradiation on zirconium in nitric acid solutionIshijima, Yasuhiro; Ueno, Fumiyoshi; Abe, Hitoshi; Sakai, Junichi*; Nojima, Yasuo*; Hashikura, Yasuaki*
no journal, ,
Besause of good corrosion resistance in boiling nitric acid solution, some equipment in the nuclear fuel reprocessing plant has been made of zirconium (Zr). However, it is well known that Zr has susceptibility of hydrogen embrittleent by hydride formation. To evaluate radiolitic hydrogen absorption behavior, radiolytic hydrogen absorption tests and constant load tensile tests under -ray irradiation were carried out. From test results, the maximum value of absorbed hydrogen was 250 wppm. On the other hand, Zr did not failure in constant load tensile test under -ray irradiation until 1000 hr. These results shows that, Zr can absorb radiolytic hydrogen but hydride generation rate into the metal is very slow. And it is considered that it is improtant to evaluate hydride generation behavior under plant operation environment.
Ishijima, Yasuhiro; Ueno, Fumiyoshi; Yamamoto, Masahiro; Uchiyama, Gunzo; Nojima, Yasuo*; Fujine, Sachio*
no journal, ,
To obtain hydrogen embrittlement on pure titanium and titanium alloy in billing nitric acid solution, SSRT in boiling nitric acid solution with cathodic charging was carried out. From SSRT results, reduction of elongation did not observed with cathodic charging, fracture surface showed ductile surface, and micro-cracks were observed at the surface of specimens but did not propagated. These results suggest that pure titanium and titanium alloy were difficult to show hydrogen embrittlement in the test condition of this study.
Igarashi, Takahiro; Motooka, Takafumi; Ueno, Fumiyoshi; Yamamoto, Masahiro; Uchiyama, Gunzo; Nojima, Yasuo*; Fujine, Sachio*
no journal, ,
no abstracts in English
Tashiro, Shinsuke; Matsumoto, Tetsuya; Kataoka, Osamu; Amano, Yuki; Abe, Hitoshi; Yamane, Yuichi; Yoshida, Kazuo; Ishikawa, Jun; Uchiyama, Gunzo; Ueda, Yoshinori*; et al.
no journal, ,
The release behavior of radioactive materials from high-level radioactive liquid wastes (HLW) from reprocessing plants under an accidents of boiling to dryness of HLW condition has been studied. The influences of FP concentration in the simulated HLW on the release ratio of FP from the waste were measured in the laboratory-scaled experiments using non-radioactive simulated HLW which was prepared by dissolving 27 FP elements into nitric acid and adjusted to 2 M acidity. The simulated HLW was heated up to 300
C under the constant air ventilation condition. The accumulated release ratios of FP elements from samples were determined using ICP-MS analysis. It was found that the accumulated release ratio of Ru was decreased with the increase of the initial Ru concentration in the simulated HLW. However, those of Cs and Nd were not influenced by the initial concentrations of them.
Sano, Yuichi; Takeuchi, Masayuki; Hoshi, Masayuki; Sakauchi, Nobuyuki; Hirano, Hiroyasu; Uchiyama, Gunzo; Nojima, Yasuo*; Fujine, Sachio*
no journal, ,
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.
Ishijima, Yasuhiro; Motooka, Takafumi; Ueno, Fumiyoshi; Yamamoto, Masahiro; Uchiyama, Gunzo; Sakai, Junichi*; Yokoyama, Kenichi*; Tada, Eiji*; Tsuru, Toru*; Nojima, Yasuo*; et al.
no journal, ,
Titanium and Ti-5mass%Ta alloy has been utilized in nuclear fuel reprocessing plant material because of its superior corrosion resistance in nitric acid solutions. However, Ti alloy have been known to high susceptibility of hydrogen embrittlement. To evaluate properties of hydrogen absorption and hydrogen embrittlement of Ti alloys, cathodic polarization tests and slow strain rate tests (SSRT) under cathodic polarization were carried out. Results show titanium hydrides covered on the surface of metals and hydrides thickness were within 
m. Ti and Ti-5%Ta did not show hydrogen embrittlement by SSRT under cathodic charging. These results suggested that Ti and Ti-5%Ta could absorb hydrogen. But hydrogen did not penetrate inner portion of the metals more than m in depth because titanium hydrides act as barrier of hydrogen diffusion. It is considered that retardation of hydrogen diffusion hindered hydrogen embrittlement of Ti and Ti-5%Ta alloys.
