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JAEA Reports

Analyses of core Shroud materials by three dimensional atom probe (Contract research)

Kondo, Keietsu; Nemoto, Yoshiyuki; Miwa, Yukio; Kaji, Yoshiyuki; Tsukada, Takashi; Nagai, Yasuyoshi*; Hasegawa, Masayuki*; Okubo, Tadakatsu*; Hono, Kazuhiro*

JAEA-Research 2006-013, 39 Pages, 2006/12

JAEA-Research-2006-013.pdf:4.57MB

There has been an increasing number of stress corrosion cracking (SCC) incidents on low carbon austenitic stainless steels used in boiling water reactor (BWR) environments. To reveal the acceleration factor of intergranular crack propagation from the viewpoint of solute distribution in stainless steels, the material extracted from a core shroud of Japanese BWR was analyzed by the three dimensional atom probe (3DAP), which has the highest spatial resolution among the various microanalytical techniques. It was revealed by statistical analysis on 3DAP data that solute elements, such as Fe, Cr, Ni, Mo, Mn, Si, are randomly distributed in matrix of the shroud material. This result means that solute was not segregated or precipitated and was not form spinodal decomposition during the service. The concentration profile in the vicinity of grain boundary obtained from 3DAP dataset showed the random distribution of Cr. This result shows that degradation of the corrosion resistance induced by depletion of Cr was not responsible for the crack propagation along grain boundaries in low carbon stainless steel. On the other hand, enrichment of Mo and Si was observed at grain boundary. The width of the enriched zone was about 2 nm across the grain boundary, and the concentration of those elements could be much higher than the concentration obtained by field emission transmission electron microscopy/energy dispersive X-ray spectroscopy (FE-TEM/EDS). Therefore, it is necessary to study about the effects of enrichment of Mo and Si as a potential contributor to SCC.

JAEA Reports

Current status and future of studies on the corrosion of carbon steel in the presence of magnetite

Shibata, Toshio*; *; *; Tsuru, Toru*; Inoue, Hiroyuki*; *

JNC TJ8400 2002-060, 43 Pages, 2003/02

JNC-TJ8400-2002-060.pdf:1.58MB

It is essentially necessary to understand the effect of corrosion products on the corrosion rate of carbon steel in order to evaluate the lifetime of carbon steel overpack, Especially, effect of magnetite on the long term integrity of overpack is one of the important subjects to be solved, because some experimental results showed that the magnetite layer formed on a carbon steel overpack as a corrosion product would accelerates the corrosion rate of the overpack. Various studies have been conducted on the corrosion mechanism of carbon steel in the presence of magnetite, its effect on the overpack lifetime and the countermeasures against the corrosion acceleration. At present, however, the interpretations on the results of these studies are not always consistent each other. In this report, the current status of the studies on corrosion of carbon steel in the presence of magnetite was reviewed, and the unsolved problems and future research subjects were extracted and discussed.

JAEA Reports

Development of the corrosion models for the analysis of candidate materials for overpacks

Shibata, Toshio*; *; *; Tsuru, Toru*; Inoue, Hiroyuki*; *

JNC TJ8400 2002-059, 139 Pages, 2003/02

JNC-TJ8400-2002-059.pdf:7.07MB

A technical committee was organized in Japan Society of Corrosion Engineering (JSCE) to review and assess the study of overpack in JNC. The corrosion models for candidate materials for overpacks were developed in terms of corrosion science to contribute the selection of material, establishment of experimental methods and lifetime prediction of overpacks. It is expected that this report is used for the study of overpacks in the process of the research and development of high-level radioactive waste disposal.

JAEA Reports

Development of the corrosion models for the analysis of candidate materials for overpacks

Shibata, Toshio*; *; *; Tsuru, Toru*; Inoue, Hiroyuki*

JNC TJ8400 2001-049, 86 Pages, 2002/02

JNC-TJ8400-2001-049.pdf:3.68MB

A technical committee was organized in Japan Society of Corrosion Engineering to review and assess the study of overpacks in JNC. The corrosion models for candidate materials for overpaks were developed in terms of corrosion science to contribute the selection of material, establishment of experimental methods and life prediction of overpacks. It is expected that this report is used for the study of overpacks in the process of the research and development of high-level radioactive waste disposal.

JAEA Reports