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Journal Articles

Migration behavior of particulate radioactive cesium species generated at ground surface

Tanaka, Tadao

Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 5 Pages, 2015/05

It is necessary to confirm that there is no significant radioactivity remaining on NPP site, for the site release beforehand. Cesium 137 ($$^{137}$$Cs) is the typical radionuclide caused from NPP. In this research, generation of particulate $$^{137}$$Cs species at ground surface and its migration behavior were examined. Migration experiments were carried out by a column method, in which deionized water was fed intermittently at the drying interval for 7 days into a sand layer contaminated with $$^{137}$$Cs. A portion of the $$^{137}$$Cs in the upper surface region, which formed particulate species by sorbing on fine particles, migrated into the deeper layer. Fine particle itself also was generated at the sand surface by weathering. The sand was weathered during the drying period, so that small amount of fine particles including $$^{137}$$Cs was newly dissociated from the sand. Such particulate $$^{137}$$Cs species may be accumulated slowly by repeated cycles of rainfall and drying, during long term.

Journal Articles

X-ray absorption fine structure spectra of rust layers on Fe-based binary alloys exposed to Cl-rich environment

Konishi, Hiroyuki; Yamashita, Masato*; Uchida, Hitoshi*; Mizuki, Junichiro

Proceedings of 16th International Corrosion Congress (CD-ROM), 6 Pages, 2005/09

XANES measurements of rust layers formed on Fe, Fe-Cr alloys and Fe-Ni alloys exposed to a Cl-rich atmosphere have been performed using synchrotron radiation in order to clarify the relation between the structural properties of the rust layer on weathering steel and anticorrosive alloying elements and/or chloride ions. The XANES spectra around Cl K-edge revealed that the rust layer on the Fe-based binary alloys contains unidentified chloride in addition to akagan$'e$iteite. The Fe K-edge XANES results indicated that the rust layers are composed mainly of well-known iron oxides, goethite, akagan$'e$ite, lepidocrocite and magnetite. In particular, the mole ratio of akagan$'e$ite in the rust layers on the Fe-Ni alloys is relatively higher than that of the Fe-Cr alloys. The Cr K-edge XANES spectra of the rust layers on the Fe-Cr alloys depends on the Cr alloy content. Therefore, the local structure of Cr in the rust layer is variable with the Cr density. In contrast, the Ni K-edge XANES results show that the local structure of Ni in the rust layer are unique in a certain Ni content range.

Journal Articles

Characterization of rust layer formed on Fe, Fe-Ni and Fe-Cr alloys exposed to Cl-rich environment by Cl and Fe K-edge XANES measurements

Konishi, Hiroyuki; Yamashita, Masato*; Uchida, Hitoshi*; Mizuki, Junichiro

Materials Transactions, 46(2), p.329 - 336, 2005/02

 Times Cited Count:26 Percentile:81.12(Materials Science, Multidisciplinary)

Chloride in atmosphere considerably reduces the corrosion resistance of conventional weathering steel containing a small amount of Cr. Ni is an effective anticorrosive element for improving the corrosion resistance of steel in a Cl-rich environment. In order to clarify the structure of the protective rust layer of weathering steel, Cl and Fe K-edge X-ray absorption near edge structure (XANES) spectra of atmospheric corrosion products (rust) formed on Fe, Fe-Ni and Fe-Cr alloys exposed to Cl-rich atmosphere were measured. The Fe K-XANES measurements enable the characterization of a mixture of iron oxides such as rust. The chemical composition of the rust was determined by performing pattern fitting of the measured spectra. All the rust is composed mainly of goethite, akagan$'e$ite, lepidocrocite and magnetite. Among these iron oxides, akagan$'e$ite in particular is the major component in the rust. Additionally, the amount of akagan$'e$ite in the rust of Fe-Ni alloy is much greater than that in rust of Fe-Cr alloy. Akagan$'e$ite is generally considered to facilitate the corrosion of steel, but our results indicate that akagan$'e$ite in the rust of Fe-Ni alloy is quantitatively different from that in rust of Fe-Cr alloy and does not facilitate the corrosion of steel. The shoulder peak observed in Cl K-XANES spectra reveals that the rust contains a chloride other than akagan$'e$ite. The energy of the shoulder peak does not correspond to that of any well-known chlorides. In the measured spectra, there is no proof that Cl, by combining with the alloying element, inhibits the alloying element from acting in corrosion resistance. The shoulder peak appears only when the content of the alloying element is lower than a certain value. This suggests that the generation of the unidentified chloride is related to the corrosion rate of steel.

Journal Articles

Cl K-edge XANES spectra of atmospheric rust on Fe, Fe-Cr and Fe-Ni alloys exposed to saline environment

Konishi, Hiroyuki; Yamashita, Masato*; Uchida, Hitoshi*; Mizuki, Junichiro

Materials Transactions, 45(12), p.3356 - 3359, 2004/12

 Times Cited Count:9 Percentile:52.63(Materials Science, Multidisciplinary)

Cl K-edge XANES measurements of atmospheric corrosion products (rust) formed on Fe, Fe-Ni and Fe-Cr alloys in chloride pollution have been performed using synchrotron radiation in order to clarify roles of anticorrosive alloying elements and of Cl in the corrosion resistance of weathering steel. The spectra of binary alloys show a shoulder structure near the absorption edge. The intensity of the shoulder peak depends on the kind and amount of the alloying element, whereas the energy position is invariant. This indicates that Cl is not combined directly with alloying elements in the rust.

Journal Articles

Chraracterization of iron hydroxides in a weathered rock surface by visible microspectroscopy

Nagano, Tetsushi; Isobe, Hiroshi*; Nakashima, Satoru*; Ashizaki, Midori*

Applied Spectroscopy, 56(5), p.651 - 657, 2002/05

 Times Cited Count:8 Percentile:46.34(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Study of colors and degrees of weathering granitic rocks by visible diffuse reflectance spectroscopy

Nagano, Tetsushi;

Geochemical Journal, 23, p.75 - 83, 1989/00

 Times Cited Count:35 Percentile:68.62(Geochemistry & Geophysics)

no abstracts in English

Journal Articles

Weathering degree of granitic rocks as studied by X-ray diffractometry and diffuse reflectance spectroscopy

Nagano, Tetsushi;

Water-Rock Interaction, p.511 - 513, 1989/00

no abstracts in English

7 (Records 1-7 displayed on this page)
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