Characterization and corrosion behavior of Al-added high Mn ODS austenitic steels in oxygen-saturated lead-bismuth eutectic

Haoran, W.*; Yu, H.*; Liu, J.*; Kondo, Sosuke*; Okubo, Nariaki; Kasada, Ryuta*

Corrosion Science, 209, p.110818_1 - 110818_12, 2022/12

https://doi.org/10.1016/j.corsci.2022.110818

The corrosion behavior of newly developed AlO forming high Mn oxide dispersion strengthened (ODS) austenitic steels was examined in oxygen-saturated lead-bismuth eutectic at 450C for 430 h. Compared with non-ODS steels, the ODS steels possessed superior resistance to corrosion and spallation. The high density grain boundaries in the ODS steels acted as channels for the rapid outward diffusion of metallic elements, forming an internal continuous CrO scale at the original surface. Accelerated Al diffusion, along with oxidation prevention by the external (Fe, Mn) oxide scale and the internal CrO scale, jointly resulted in the formation of a continuous Al-rich oxide scale in ODS-7Al steel, contributing to its superior corrosion resistance.

The Activity of sulfate reducing bacteria in bentonite and the effect of hydrogen sulfide on the corrosion of candidate materials for overpacks

Taniguchi, Naoki; Kawasaki, Manabu*; Fujiwara, Kazuo*

JNC TN8400 2001-011, 62 Pages, 2001/03

JNC-TN8400-2001-011.pdf:5.67MB

The corrosion of metallic materials used in natural environment are sometimes affected by microbial action. It is apprehended that microorganism living in deep underground or brought from ground surface during excavation makes an impact on overpack material for geological disposal of high-level radioactive waste. Sulfate reducing bacteria (SRB) is known to be one of the most representative microorganism which affects the corrosion of metals. In this study, the behavior of growth of SRB was investigated at first under the presence of bentonite as a main component of buffer material which encloses the overpack. The results of the tests showed that the population of SRB after the culture in synthetic sea water mixed with bentonite decreased with increasing the ratio of bentonite/solution. SRB was hardly grown in medium whose bentonite/solution ratio exceeded 1000g/l. As a conservative case, the effects of sulfide on the corrosion of overpack materials were also studied assuming high activity of SRB. Carbon steel, copper and titanium specimens were immersed in synthetic sea water purging 0.1MPa HS gas and the corrosion behavior was compared with the results in N gas purging environment. Obvious effect of sulfide on the corrosion of carbon steel was not observed, but the corrosion rates of copper specimens were accelerated several hundred times by purging HS gas. The absorption of hydrogen into titanium specimens was not affected by purging HS gas, but the difference of hydrogen absorption between pure titanium and titanium alloy containing 0.06%-Pd was observed.

None

*; *; *; *; *; *; *

PNC TJ1010 97-002, 170 Pages, 1997/02

PNC-TJ1010-97-002.pdf:7.94MB

None

Dismantling technology for large-scale sodium components used for a long time, 1; Behavior of impurity adhesion to sodium equipment

Shimoyama, Kazuhito; Hayakawa, Masato; Suzuki, Shigeaki*; Miyakoshi, Hiroyuki; Ara, Kuniaki

no journal, , 

We are conducting dismantling inspection of large-scale sodium component that we have been using in sodium environment for a long time. It was found from the operation history etc. that the sodium compound adhesion behavior on the inner surface of each device exposed to the sodium environment for several decades from the start of use affects sodium purity. In dismantling large sodium equipment, it is important to reduce the residual sodium in the equipment as much as possible, and proposing to carry out high temperature refining operation effective for removal of these attached impurities at the end of plant operation.

Time dependence on corrosion behavior of Ta in NaOH solutions

Ishijima, Yasuhiro; Ueno, Fumiyoshi; Abe, Hitoshi

no journal, , 

In spent nuclear fuel reprocessing plant, Zr/Ta dissimilar metal joint is used for connect between different devices. And it is known that Ta corrodes in NaOH solutions. The other hand, it is not clear that the time dependency on corrosion behavior of Ta in NaOH solutions. This study aims to elucidate the effect on time dependency for corrosion behavior of Ta in NaOH solutions. Immersion tests and electrochemical measurements were carried out in NaOH solutions. Immersion test results show that corrosion rate in 6mol/L NaOH was decreased with time. And electrochemical measurement results suggested that the decrease of corrosion rate was caused by corrosion product film generation on the surface of Ta. The corrosion product was determined as NaTaO 24.5HO by Raman spectroscopy. From these results, it is considered that the decrease of corrosion rate was caused by the NaTaO 24.5HO film suppress the Ta dissolution.

Temperature dependence on corrosion behavior of Ta in NaOH solutions

Ishijima, Yasuhiro; Ueno, Fumiyoshi; Abe, Hitoshi

no journal, , 

In spent nuclear fuel reprocessing plant, SUS304/Ta/Zr dissimilar metal joint is used for connect between different devices. And it is known that Ta corrodes in NaOH solutions. The other hand, it is not clear that the temperature effect on corrosion behavior of Ta in NaOH solutions. This study aims to elucidate the effect on temperature effect for corrosion behavior of Ta in NaOH solutions. Immersion tests and electrochemical measurements were carried out in NaOH solutions. Immersion test results show that corrosion rate in 1mol/L NaOH at 353 K was decreased compared to 333 K. And also the test results show that corrosion rate increased with temperature at above 3 mol/L. From SEM observation, dence film was observed at the surface of specimen after immersion test in 1 mol/L NaOH at 353 K. From these results, it is considered that the decrease of corrosion rate in 1mol/L at 353 K was caused by the dence film suppress the Ta dissolution.

Corrosion behavior of the SUS304ULC/Ta/Zr dissimilar metal joint in NaOH-HNO alternating immersion environment

Ishijima, Yasuhiro; Ueno, Fumiyoshi; Abe, Hitoshi

no journal, , 

In order to investigate the corrosion behavior of SUS304ULC/Ta/Zr dissimilar metal joint used in nuclear fuel reprocessing plants during decontamination, alternate immersion tests with 1 to 7 mol/L NaOH and HNO were carried out for dissimilar metal joint and pure Ta. From immersion test results, surface observations, and test solutions analysis after immersion test, it was considered that the joints were corroded by Ta during immersion in sodium hydroxide. The corrosion rate of Ta in dissimilar metal joint was found to be lower than that of pure Ta in some immersion conditions. It is considered that the corrosion of Ta in such an environment was inhibited by the fact that the corrosion potential of Ta was nobler than that of pure Ta due to contact with SUS304ULC.