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Irisawa, Eriko
Taikabutsu, 76(8), p.326 - 332, 2024/08
Liquid lead-bismuth eutectic (LBE) alloys have been considered as coolants for nuclear reactors, and research and development for LBE reactors has been conducted for many years. One of the most serious problems in using LBE as a coolant is the corrosion degradation of metallic structural materials due to exposure to high operating temperatures and flowing LBE. In the case of austenitic steels containing metal components such as Ni that are easily dissolved in LBE, it is known that it is necessary to monitor and control the concentration of dissolved oxygen in LBE in order to evaluate the amount of corrosion. This paper focuses on the relationship between the dissolved oxygen concentration, which is an important factor in the corrosion degradation mechanism, and the corrosion evaluation of stainless steel in LBE. The relationship between dissolved oxygen concentration in LBE, corrosion behavior and corrosion rate will be introduced using the example of corrosion evaluation of austenitic stainless steels in LBE in this paper.
Irisawa, Eriko; Kato, Chiaki
Journal of Nuclear Materials, 591, p.154914_1 - 154914_10, 2024/04
Times Cited Count:3 Percentile:93.00(Materials Science, Multidisciplinary)The amount of corrosion of austenitic stainless-steel R-SUS304ULC was evaluated considering the changes in solution composition and boiling during actual concentration operations. Austenitic stainless-steel R-SUS304ULC is the structural material of the highly radioactive liquid waste concentrator in Japanese spent fuel reprocessing plant, which treats highly corrosive nitric acid solutions during enrichment operations. The study results show that it is necessary to focus on nitric acid concentrations, oxidizing metal ion concentrations, and decompression boiling as factors that accelerate the corrosion rate of stainless steel because of cathodic reaction activation.
Yamashita, Naoki; Irisawa, Eriko; Kato, Chiaki; Sano, Naruto; Tagami, Susumu
JAEA-Technology 2022-035, 29 Pages, 2023/03
In the treatment process of the current commercial reprocessing plant (Rokkasho Reprocessing Plant), the high-level liquid waste concentrator is the equipment that treats the most corrosive solution. In the high-level liquid waste concentrator, the extracted liquid waste after separation of uranium and plutonium is heated, concentrated, and reduced in volume. Therefore, the amount of gamma- rays emitted from fission products and the concentration of corrosive metal ion species such as neptunium-237 (Np) are the highest in the reprocessing process, and the amount of corrosion in the high-level liquid waste concentrate canner is expected to be large. In this study, in order to clarify the effect of gamma-rays on the corrosion reaction of stainless steel in nitric acid solutions containing
Np from the electrochemical viewpoint, the corrosion test apparatus for heat transfer surfaces in an airtight concrete cell at the Waste Safety TEsting Facility (WASTEF) of Nuclear Science Research Institute was modified to enable electrochemical measurements under gamma-ray irradiation. The effect of gamma-rays on the corrosion reaction taking place on the stainless steel surface was discussed from the electrochemical test results obtained. As a result, changes in the immersion potentials of stainless steel and the polarization curves due to chemical species caused by radiolysis of gamma-ray irradiation were confirmed.
Irisawa, Eriko; Kato, Chiaki; Yamashita, Naoki; Sano, Naruto
Zairyo To Kankyo, 71(3), p.70 - 74, 2022/03
In order to evaluate the corrosion of stainless steels used in spent nuclear fuel reprocessing facilities, the immersion corrosion tests and polarization measurements were performed using R-SUS304ULC stainless steel in nitric acid solution containing a kind of radionuclides, Np. At temperatures above 328 K, the corrosion potential was higher than that in nitric acid solution and was near the transpassive region. From the comparison between the corrosion amount calculated by the immersion corrosion tests and the polarization resistance, the values of
=0.018-0.025 V were obtained as a conversion factor, and the possibility of calculating the corrosion amount from the electrochemical measurement was examined.
Yamamoto, Masahiro; Irisawa, Eriko; Igarashi, Takahiro; Komatsu, Atsushi; Kato, Chiaki; Ueno, Fumiyoshi
Proceedings of Annual Congress of the European Federation of Corrosion (EUROCORR 2019) (Internet), 5 Pages, 2019/09
Intergranular corrosion phenomena were analysed using modified reprocessing solution. The data indicated that corrosion rates increased with time at the initial stage, and these stayed at constant value. Intergranular corrosion propagated at grain boundary in the initial stage and then attacked whole grain boundary causing drop out of grains. Corrosion rates of steady state were sum of intergranular corrosion amounts and weight losses of dropped grains. Surface appearances and cross sections of corroded samples were analyzed. The results indicated that the initial stage of intergranular corrosion was characterized by the ratio of corrosion rates between grain boundary and matrix. These ratios differed from individual grain boundaries. Total corrosion rates were affected by the distribution of these ratios. These data were based on the numerical modelling of intergranular corrosion using cellular automata. And also, calculated results were compared with these analytical data.
Irisawa, Eriko; Yamamoto, Masahiro; Kato, Chiaki; Motooka, Takafumi; Ban, Yasutoshi
Journal of Nuclear Science and Technology, 56(4), p.337 - 344, 2019/04
Times Cited Count:8 Percentile:59.98(Nuclear Science & Technology)Kondo, Masatoshi*; Okubo, Nariaki; Irisawa, Eriko; Komatsu, Atsushi; Ishikawa, Norito; Tanaka, Teruya*
Energy Procedia, 131, p.386 - 394, 2017/12
Times Cited Count:10 Percentile:97.54(Energy & Fuels)The chemical behaviors of lead (Pb) based coolants in the air ingress accident of fast reactors were investigated by means of the thermodynamic considerations and the static oxidation experiments for Pb alloys at various chemical compositions. The results of the static oxidation tests for lead-bismuth (Pb-Bi) alloys indicated that Pb was depleted from the alloy due to the preferential formation of PbO in air at 773K. Pb-Bi oxide and BiO
were formed after the enrichment of Bi in the alloys due to the Pb depletion. The oxidation rates of the alloys were much larger than that of the steels, and became larger with higher Pb concentration in the alloys. The compatibility of Pb-Bi alloys with stainless steel was worse when the Pb concentration in the alloys became low, since the dissolution type corrosion was promoted by the Bi composition in the alloy. The Pb-Li alloys were oxidized as they formed Li
PbO
and Li
CO
. Then, Li was depleted from the alloy.
Irisawa, Eriko; Kato, Chiaki; Kamoshida, Michio*; Hakamatsuka, Yasuyuki*; Ueno, Fumiyoshi; Yamamoto, Masahiro
Proceedings of European Corrosion Congress 2017 (EUROCORR 2017) and 20th ICC & Process Safety Congress 2017 (USB Flash Drive), 9 Pages, 2017/09
Matsueda, Makoto; Irisawa, Eriko; Kato, Chiaki; Matsui, Hiroki
Proceedings of 54th Annual Meeting of Hot Laboratories and Remote Handling (HOTLAB 2017) (Internet), 4 Pages, 2017/00
In the PUREX method, spent fuels are dissolved with nitric acid media. The reprocessing solution containing Fission Products derived from spent fuels is very corrosive to metal materials, the corrosion problem often appears on the surface stainless steel devices. The oxidizing metal ions such as Ruthenium (Ru) and Neptunium (Np) in the process solution is the key reason for severe corrosion of stainless steel. In order to obtain the corrosion rate of stainless steel, we installed the corrosion test apparatus inside an airtight concrete cell in a hot laboratory (the WAste Safety TEsting Facility (WASTEF) of the Japan Atomic Energy Agency), and performed the corrosion tests of stainless steel in the heated nitric acid solution containing Np. The corrosion tests were performed in the temperature range from room temperature to boiling point for 500 hours per batch. The results show that the presence of Np accelerate the stainless steel corrosion in the nitric acid solution.
Ueno, Fumiyoshi; Irisawa, Eriko; Kato, Chiaki; Igarashi, Takahiro; Yamamoto, Masahiro; Abe, Hitoshi
Proceedings of European Corrosion Congress 2016 (EUROCORR 2016) (USB Flash Drive), 7 Pages, 2016/09
In this study, we focused on the effect of the boiling of nitric acid solution on the corrosion of a stainless steel-made concentrator in reduced pressure in fuel reprocessing plant. In order to perform the simulation test in a non-radioactive condition, nitric acid solution with the addition of vanadium as an oxidizing metal ion were used. Corrosion tests were carried out under the conditions of boiling at reduced pressure, and of non-boiling at normal pressure and several temperatures. As a result, corrosion was accelerated by the solution boiling while it was not by non-boiling at the same temperature. It was found also that the temperature dependence of corrosion rate is the same in the both conditions of boiling and non-boiling. The corrosion accelerating effect will be discussed on the basis of the reaction among nitric acid, NOx and vanadium, etc.
Irisawa, Eriko; Ueno, Fumiyoshi; Kato, Chiaki; Abe, Hitoshi
Zairyo To Kankyo, 65(4), p.134 - 137, 2016/04
In order to investigate the effect of boiling under reduced pressure on corrosion of stainless steel in the nitric acid solution, the corrosion tests simulating the high-level radioactive liquid waste evaporator were performed. The results of immersion tests of stainless steels in the solution with and without boiling showed that the corrosion rates in boiling solution were larger than those in not boiling solution in case of same temperature of solution. Moreover, the cathode polarization curves showed that the corrosion potential of stainless steel in boiling solutions were shifted nobler, and the current intensity became larger than that in not boiling solutions. According to these results, it can be concluded that boiling of solution under reduced pressure accelerate the corrosion rates.
Irisawa, Eriko; Seki, Masaharu*; Ueno, Fumiyoshi; Kato, Chiaki; Motooka, Takafumi; Abe, Hitoshi
Proceedings of 21st International Conference & Exhibition; Nuclear Fuel Cycle for a Low-Carbon Future (GLOBAL 2015) (USB Flash Drive), p.1108 - 1112, 2015/09
Irisawa, Eriko; Ueno, Fumiyoshi; Uchida, Naoki; Taguchi, Katsuya
Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 3 Pages, 2015/05
入澤 恵理子; 小松 篤史; 大久保 成彰
上田 光敏*; 河村 憲一*; 林 優作*; 山口 周*
【課題】四酸化三鉄などの金属酸化物の皮膜の状態を簡便に評価・モニターするためのセンサを提供すること。 【解決手段】金属酸化物薄膜と、該薄膜上に設置された電極対を含むセンサであって、電極間に電流を流し、該薄膜上の環境変化に基づく金属酸化物薄膜の還元による電極間の電気抵抗変化を検知することを特徴とする、センサ。
Irisawa, Eriko; Suzuki, Kazunori*; Kumagai, Mikio*; Kato, Chiaki; Ueno, Fumiyoshi; Abe, Hitoshi
no journal, ,
For the corrosion of stainless steels in the nitric acid solution containing oxidizing metallic ions, it is important factor that the relation between re-oxidation of metallic ions which is reduced with the corrosion reaction and the redox reaction of nitric acid. To make clear the effect of nitrogen oxides formed from nitric acid on oxidation behavior of tetravalent vanadium, changing of concentrations of nitrogen oxide discharged to gas phase from solution and nitrous acid in solution during oxidation reaction of vanadium were measured. The results showed that the nitrogen dioxide acted as oxidant on the oxidation reaction of vanadium.
Irisawa, Eriko; Ueno, Fumiyoshi; Abe, Hitoshi
no journal, ,
no abstracts in English
Irisawa, Eriko; Ueno, Fumiyoshi; Seki, Masaharu; Abe, Hitoshi
no journal, ,
no abstracts in English
Igarashi, Takahiro; Irisawa, Eriko; Kato, Chiaki; Ueno, Fumiyoshi; Abe, Hitoshi
no journal, ,
It is known that existence of oxidizing metal ion in boiling nitric acid solution makes stainless steel more corrosive. In this study, in order to elucidate chemical species which promote oxidization of Vanadium(IV) ion, we conducted Redox reaction simulation in nitric acid solution using chemical reaction model. The results showed that nitrous acid and nitrogen dioxide affected oxidization of Vanadium(IV) ion, and rate constant of nitrogen dioxide was larger than that of nitrous acid.
Irisawa, Eriko; Yamashita, Naoki; Kato, Chiaki; Sano, Naruto
no journal, ,
In spent fuel reprocessing plants after nuclear power generation, intergranular corrosion of stainless steel components due to nitric acid solution containing metal ions derived from fuel is a problem. Although neptunium, a radioactive element, is considered to have a high contribution to corrosion, there have been few cases of systematic corrosion evaluations due to the difficulty of handling it. Therefore, the effects of solution temperature and neptunium ion concentration on the corrosion rate of stainless steel in nitric acid solution containing neptunium-237 were evaluated by immersion test and polarization measurement.
Irisawa, Eriko; Yamashita, Naoki; Kato, Chiaki; Sano, Naruto
no journal, ,
In spent nuclear fuel reprocessing facilities, nitric acid solutions containing metal components derived from spent fuel are heated and concentrated. This process solution is highly corrosive to stainless steel. According to previous studies, it was shown that the dissolution of oxidizing metal ions causes the cathodic reaction to occur in a higher potential range than in pure nitric acid solutions. And, it has been suggested that the anodic reaction is not sensitive to dissolved metal ion species, but is determined by the concentration of acid nitrate chemical species such as HNO and HNO
. On the other hand, the radiation released from the fuel-derived radionuclides can cause radiolysis of the reprocessing process solution. It is known that nitrous acid is produced by radiolysis of nitric acid media and reaction of nitric acid with radiolysis products. The formation of nitrite is thought to affect the anodic reaction among the corrosion reactions on the surface of stainless steels. In order to understand the corrosion reaction of stainless steel in reprocessing process solutions, it is necessary to evaluate the effect of gamma-rays on the anodic reaction of stainless steels in nitric acid media. In this study, the effect of gamma-rays on the corrosion potential and polarization curve of stainless steel in the nitric acid media was investigated. As a result, the increase in corrosion potential and the change in polarization curves were observed. And the causes of the obtained change of anodic polarization curves were verified from the results of nitrous acid addition and immersion time under non-irradiation.