Analysis methodology of the calculation code, WRAC-JAEA, for determining major indexes of corrosive circumstance in light water reactors

Uchida, Shunsuke; Hata, Kuniki; Hanawa, Satoshi

JAEA-Data/Code 2024-003, 119 Pages, 2025/01

JAEA-Data-Code-2024-003.pdf:11.29MB
JAEA-Data-Code-2024-003-appendix(CD-ROM).zip:0.28MB

The calculation code for determining corrosive circumstance in light water reactors, WRAC-JAEA, has been developed based on water radiolysis calculation codes for BWR. The code has involved several new calculation functions to apply it for PWR, i.e., (1) high temperature pH (pH), (2) pH effects on water radiolysis, (3) electrochemical corrosion potential (ECP) based on the mixed potential theory, and (4) ECP based on the water radiolysis calculation results. Moderation of corrosive conditions in the primary cooling systems is one of the promising procedures to mitigate the loss of reliabilities of major components in the systems, especially in aging plants. However, water chemistry control for corrosive environment mitigation procedures are much different in BWRs and PWRs. In BWRs, intergranular stress corrosion cracking (IGSCC) of stainless steel is the dominant causes for determining plant reliability. It is difficult to increase pH and injected hydrogen amounts due to direct power cycle operation. So, precise control of hydrogen injection with supported by water radiolysis and ECP analyses has been carried out to keep material reliability. In PWRs, it is possible to maintain stable control of corrosive circumstances with higher pH and sufficiently large hydrogen concentration. Recently, it was pointed out that one of the major causes of primary water stress corrosion cracking (PWSCC) of nickel alloys was hydrogen. The optimal hydrogen concentration should be evaluated to mitigate ECP without increasing hydrogen concentration. For this, a combined water radiolysis and ECP analysis code is required to determine the suitable hydrogen concentration and ECP. WRAC-JAEA can contribute not only to evaluation of corrosive conditions each of BWR and PWR, but also to prepare for suitable countermeasures for both BWR and PWR by cross-talking the knowledge and experience with assistance of the code results.

Experimental and modeling study on ion concentration behavior in metal crevices in high-purity water

Soma, Yasutaka; Komatsu, Atsushi; Igarashi, Takahiro

Dai-71-Kai Zairyo To Kankyo Toronkai Koenshu (CD-ROM), p.253 - 256, 2024/11

In our previous study, we reported that Cl ions penetrating stainless steel crevices do not dissipate by diffusion, even in high-purity water (i.e., conductivity remains stable), likely due to electrochemical reactions inside and outside the crevice. This study further analyzes ion behavior by experimentally and computationally investigating ion concentration drivers in high-purity water. Results show that, at 50C, the crevice conductivity of SUS316L stainless steel reached 100 S/cm (100-1000 times bulk water). Modeling suggests this is due to metal cations and hydroxide ions from dissolved oxygen reduction. The dissolution rate was estimated at 10nA/cm.

Effect of dissolved oxygen concentration on the corrosion behavior of stainless steel in liquid lead-bismuth alloy

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.

Stress corrosion cracking induced by the combination of external and internal hydrogen in Al-Zn-Mg-Cu alloy

Tang, J.*; Wang, Y.*; Fujihara, Hiro*; Shimizu, Kazuyuki*; Hirayama, Kyosuke*; Ebihara, Kenichi; Takeuchi, Akihisa*; Uesugi, Masayuki*; Toda, Hiroyuki*

Scripta Materialia, 239, p.115804_1 - 115804_5, 2024/01

https://doi.org/10.1016/j.scriptamat.2023.115804

Stress corrosion cracking (SCC) behaviors induced by the combination of external and internal hydrogen (H) in an Al-Zn-Mg-Cu alloy were systematically investigated via in situ 3D characterization techniques. SCC of the Al-Zn-Mg-Cu alloy could initiate and propagate in the potential crack region where the H concentration exceeded a critical value, in which the nanoscopic H-induced decohesion of -MgZn precipitates resulted in macroscopic cracking. External H that penetrated the alloy from the environment played a crucial role during the SCC of the Al-Zn-Mg-Cu alloy by generating gradient-distributed H-affected zones near the crack tips, which made Al alloys in water environment more sensitive to SCC. Additionally, the pre-existing internal H was driven toward the crack tips during plastic deformation. It was involved in the SCC and made contributions to both the cracks initiation and propagation.

Effects of Cr on intergranular corrosion behavior of Fe-Cr-Ni alloys in simulated crevice environments in high temperature water

Soma, Yasutaka; Igarashi, Takahiro

Dai-70-Kai Zairyo To Kankyo Toronkai Koenshu (CD-ROM), p.199 - 202, 2023/10

Since an acidic corrosive environment (crevice environment) is formed inside the stress corrosion cracking (SCC) of stainless steel in high temperature water, it is important to understand the corrosion behavior in the crevice environment for the better understanding of crack growth behavior. In the previous study, the authors measured the electrical conductivity inside the crevice and obtained values of 380 S/cm and 1600 S/cm for the crevice with and without intergranular corrosion, respectively. In this study, we defined the crevice environment I (pH=4.41) and II (pH=3.13) corresponding the above conductivity values, and the corrosion behavior of Fe-xCr-20Ni (x=16.9, 19.8, 22.9, 24.3, 25.9) in each crevice environment was investigated. In the simulated crevice environment-I, the all alloys showed passive behavior, while in the environment-II, severe corrosion with intergranular cracking was observed for x = 16.9 and 19.8, and a thick oxide film was formed. On the other hand, above x=22.9, oxide film growth was suppressed and a clear passive region appeared on the polarization curve.

Evaluation of container using hybrid technique for thermochemical water-splitting iodine-sulfur process

Ioka, Ikuo; Kuriki, Yoshiro*; Iwatsuki, Jin; Kubo, Shinji; Yokota, Hiroki*; Kawai, Daisuke*

Proceedings of 30th International Conference on Nuclear Engineering (ICONE30) (Internet), 5 Pages, 2023/05

A thermochemical water-splitting iodine-sulfur processes (IS process) is one of candidates for the large-scale production of hydrogen using heat from solar power. Severe corrosive environment which is thermal decomposition of sulfuric acid exists in the IS process. A hybrid material with the corrosion-resistance and the ductility was made by a plasma spraying and laser treatment. The specimen had excellent corrosion resistance in the condition of 95 mass% boiling sulfuric acid. This was attributed to the formation of SiO on the surface. A corrosion test of the container was performed in 95 mass% boiling sulfuric acid until 500 hours to evaluate the corrosion characteristic of the container. No peeling was observed on the inner surface of the container after the corrosion test. The container had excellent corrosion resistance in the condition of 95 mass% boiling sulfuric acid.

Corrosion fatigue crack growth behavior of a structurally gradient steel for high-speed railway axles

Ao, N.*; Zhang, H.*; Xu, H. H.*; Wu, S. C.*; Liu, D.*; Xu, P. G.; Su, Y. H.; Kang, Q. H.*; Kang, G. Z.*

Engineering Fracture Mechanics, 281, p.109166_1 - 109166_14, 2023/03

https://doi.org/10.1016/j.engfracmech.2023.109166

Establishment of corrosion database under irradiation

Hata, Kuniki; Sato, Tomonori

Hoshasen Kagaku (Internet), (114), p.33 - 38, 2022/10

no abstracts in English

Failure estimation methods for steam generator tubes with wall-thinning or crack

Yamaguchi, Yoshihito; Mano, Akihiro; Li, Y.

Proceedings of ASME 2022 Pressure Vessels and Piping Conference (PVP 2022) (Internet), 10 Pages, 2022/07

https://doi.org/10.1115/PVP2022-84697

The steam generator (SG) tube is one of the important components in pressurized water reactors. Flaws such as wall-thinning or stress corrosion cracking have been reported in SG tubes. The burst pressure where both the internal and external pressures from the primary and secondary coolant systems are considered must be predicted to assess the structural integrity of SG tubes. Burst tests were performed by various organizations. On the basis of the test results, failure estimation methods were proposed. In this study, previous burst test data and existing failure estimation methods for SG tubes with wall-thinning or crack were investigated. As a result, the coefficient of the existing estimation method for SG tube with uniform wall-thinning was updated. In addition, failure estimation methods that are suitable for SG tubes with crack or local wall-thinning were proposed by considering the effects of the flaw shape and size on the burst pressure. The applicability of the failure estimation methods was confirmed by comparing the predicted results with the burst test data in actual SG tubes.

Effects of a corrosion inhibitor on the corrosion of steels under thin solution layers

Momma, Yuichiro*; Sakairi, Masatoshi*; Ueno, Fumiyoshi; Otani, Kyohei

Zairyo To Kankyo, 71(5), p.133 - 137, 2022/05

https://doi.org/10.3323/jcorr.71.133

The effect of the corrosion inhibitor on the corrosion of steel under a thin solution layer was investigated. As a result of forming a thin solution layer with a thickness of 1.0-0.2 mm on the specimen, adding a mixed solution of sodium molybdate and aluminum lactate as a corrosion inhibitor, and performing electrochemical measurement, the corrosion inhibitor suppresses the anodic reaction. And in the thin solution layer, it was suggested that the morphology of the protective layer structure by the corrosion inhibitor changed according to the amount of liquid as compared with the bulk immersion.