TY - JOUR
T1 - Phase analysis of uranium oxides after reaction with stainless steel components and ZrO 2 at high temperature by XRD, XAFS, and SEM/EDX
AU - Akiyama, Daisuke
AU - Akiyama, Hidenori
AU - Uehara, Akihiro
AU - Kirishima, Akira
AU - Sato, Nobuaki
N1 - Funding Information:
This work was partially supported by the Research Program for CORE lab of “Dynamic Alliance for Open Innovation Bridging Human, Environment and Materials” in “Network Joint Research Center for Materials and Devices.” The authors gratefully acknowledge Kazuhisa Matsumoto (Chiba University), Chiya Numako (Chiba University), Yasuko Terada (Japan Synchrotron Radiation Research Institute), Toshiaki Ina (Japan Synchrotron Radiation Research Institute), and Shino Takeda-Homma (National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology) for their cooperation in the XANES measurement at SPring-8 under the 2016A1693, 2016B1805 and 2017A1725 programs.
Publisher Copyright:
© 2019
Copyright:
Copyright 2019 Elsevier B.V., All rights reserved.
PY - 2019/7
Y1 - 2019/7
N2 - In the Fukushima Daiichi nuclear power station accident in March 2011, fuel debris was formed when fuel materials reacted with various structural materials in reactor core. Fuel debris retrieval is expected to start in 2021 for decommissioning of the damaged plants. To perform this activity safely, it is necessary to know the properties of the fuel debris. In this study, we investigated the reaction of UO 2 , stainless steel (SS) components, and ZrO 2 at high temperature under oxidizing and reducing conditions, and determined the valence state of uranium in the products, such as CrUO 4 and (Fe x , Cr 1−x )UO 4 , by X-ray absorption near edge structure (XANES) spectroscopy. Mixed powders of UO 2 and SS, Fe, and/or Cr were heated in Ar + 2% O 2 (oxidizing condition) or Ar + 10% H 2 (reducing condition) at a flow rate of 20 mL/min for 2 h at 1473 or 1673 K. After heat treatment, the phase relation of the products was analyzed by powder X-ray diffraction and scanning electron microscopy with energy-dispersive X-ray spectroscopy. Under reducing conditions, UO 2 did not react with SS, Fe, Cr, or ZrO 2 . In contrast, under oxidizing conditions, UO 2 reacted with SS and Cr to form CrUO 4 or (Fe x , Cr 1−x )UO 4 at 1473 and 1673 K. When the UO 2 and Fe mixture was heated under oxidizing conditions, the Fe 2 O 3 phase coexisted with U 3 O 8 at 1473 K, whereas FeUO 4 formed at 1673 K. When the UO 2 , Fe, and Cr mixtures were heated at 1473 K under the oxidizing condition, the molar ratio of Fe/Cr in the (Fe x , Cr 1−x )UO 4 phase corresponded to the initial molar ratio in the sample. As the iron content of these samples increased, all three lattice parameters of (Fe x , Cr 1−x )UO 4 approached those of FeUO 4 . XANES spectra revealed that the oxidation state of uranium in CrUO 4 and (Fe x , Cr 1−x )UO 4 is pentavalent.
AB - In the Fukushima Daiichi nuclear power station accident in March 2011, fuel debris was formed when fuel materials reacted with various structural materials in reactor core. Fuel debris retrieval is expected to start in 2021 for decommissioning of the damaged plants. To perform this activity safely, it is necessary to know the properties of the fuel debris. In this study, we investigated the reaction of UO 2 , stainless steel (SS) components, and ZrO 2 at high temperature under oxidizing and reducing conditions, and determined the valence state of uranium in the products, such as CrUO 4 and (Fe x , Cr 1−x )UO 4 , by X-ray absorption near edge structure (XANES) spectroscopy. Mixed powders of UO 2 and SS, Fe, and/or Cr were heated in Ar + 2% O 2 (oxidizing condition) or Ar + 10% H 2 (reducing condition) at a flow rate of 20 mL/min for 2 h at 1473 or 1673 K. After heat treatment, the phase relation of the products was analyzed by powder X-ray diffraction and scanning electron microscopy with energy-dispersive X-ray spectroscopy. Under reducing conditions, UO 2 did not react with SS, Fe, Cr, or ZrO 2 . In contrast, under oxidizing conditions, UO 2 reacted with SS and Cr to form CrUO 4 or (Fe x , Cr 1−x )UO 4 at 1473 and 1673 K. When the UO 2 and Fe mixture was heated under oxidizing conditions, the Fe 2 O 3 phase coexisted with U 3 O 8 at 1473 K, whereas FeUO 4 formed at 1673 K. When the UO 2 , Fe, and Cr mixtures were heated at 1473 K under the oxidizing condition, the molar ratio of Fe/Cr in the (Fe x , Cr 1−x )UO 4 phase corresponded to the initial molar ratio in the sample. As the iron content of these samples increased, all three lattice parameters of (Fe x , Cr 1−x )UO 4 approached those of FeUO 4 . XANES spectra revealed that the oxidation state of uranium in CrUO 4 and (Fe x , Cr 1−x )UO 4 is pentavalent.
KW - Chromium
KW - Fuel debris
KW - Fukushima Daiichi nuclear power plant
KW - Iron
KW - SEM/EDX
KW - Stainless steel
KW - Uranium oxide
KW - XAFS
KW - XANES
KW - XRD
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U2 - 10.1016/j.jnucmat.2019.03.055
DO - 10.1016/j.jnucmat.2019.03.055
M3 - Article
AN - SCOPUS:85064177714
VL - 520
SP - 27
EP - 33
JO - Journal of Nuclear Materials
JF - Journal of Nuclear Materials
SN - 0022-3115
ER -