検索対象:     
報告書番号:
※ 半角英数字
 年 ~ 
 年

実機シュラウド材の3次元アトムプローブ分析(受託研究)

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

近藤 啓悦; 根本 義之; 三輪 幸夫; 加治 芳行; 塚田 隆; 永井 康介*; 長谷川 雅幸*; 大久保 忠勝*; 宝野 和博*

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

沸騰水型軽水炉(BWR)炉心シュラウドなどにおいて低炭素オーステナイト系ステンレス鋼の応力腐食割れ(SCC)発生が報告されている。機構解明のためにBWR炉心シュラウドから採取されたサンプル(SUS316L)の3次元アトムプローブ分析を行った。その結果、粒内において偏析及び析出物生成,スピノーダル分解などに伴う溶質元素の不均一分布は観察されなかった。また、結晶粒界の分析の結果、粒界において原子層レベルでも明確なCrの欠乏層が存在しなかったことから、低炭素ステンレス鋼のSCCにはCr欠乏による耐食性劣化とは異なるき裂進展機構が存在することが明確に示された。他の溶質元素についてはMo及びSiが、粒界において従来のFE-TEM/EDSによって分析された濃度値よりも高濃度で濃縮している可能性が示唆された。

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.

Access

:

- Accesses

InCites™

:

Altmetrics

:

[CLARIVATE ANALYTICS], [WEB OF SCIENCE], [HIGHLY CITED PAPER & CUP LOGO] and [HOT PAPER & FIRE LOGO] are trademarks of Clarivate Analytics, and/or its affiliated company or companies, and used herein by permission and/or license.