Fuel-cladding chemical interaction of a prototype annular U-10Zr fuel with Fe-12Cr ferritic/martensitic HT-9 cladding

JOURNAL OF NUCLEAR MATERIALS

卷:544

Article

Liu, Xiang¹  Capriotti, Luca¹  Yao, Tiankai¹  Harp, Jason M.²  Benson, Michael T.¹  Wang, Yachun¹  Teng, Fei¹  He, Lingfeng¹ 

[1] Idaho Natl Lab, Idaho Falls, ID 83415 USA

[2] Oak Ridge Natl Lab, Oak Ridge, TN 37831 USA

关键词: Fuel-cladding chemical interaction (FCCI);    Metallic fuel;    Advanced nuclear fuel;    Transmission electron microscopy (TEM);    HT-9 cladding;    Phase transformation;   

DOI  :  10.1016/j.jnucmat.2020.152588

来源: Elsevier

【 摘 要 】

As an alternative fuel form, the annular metallic fuel design eliminates the liquid sodium bond between the fuel and the cladding, providing back-end fuel cycle and other benefits. The fuel-cladding chemical interaction (FCCI) of annular fuel also presents new features. Here, state-of-the-art electron microscopy and spectroscopy techniques were used to study the FCCI of a prototype annular U-10wt%Zr (U-10Zr) fuel with ferritic/martensitic HT-9 cladding irradiated to 3.3% fission per initial heavy atom. Compared with sodium-bonded solid fuels, negligible amounts of lanthanides were found in the FCCI layer in the investigated helium-bonded annular fuel. Instead, most lanthanides were retained in the newly formed UZr 2 phase in the fuel center region. The interdiffusion of iron and uranium resulted in tetragonal (U,Zr)(6) Fe phase (space group I4/mcm) and cubic (U,Zr)(Fe,Cr)(2) phase (space group Fd3m). The (U,Zr)(Fe,Cr)(2) phase contains a high density of voids and intergranular uranium monocarbides of NaCl-type crystal structure (space group Fm (3) over barm). At the interdiffusion zone and inner cladding interface, a porous lamellar structure composed of alternating Cr-rich layers and U-rich layers was observed. Next to the lamellar region, the unexpected phase transformation from body-centered cubic ferrite (alpha-Fe) to tetragonal binary Fe-Cr sigma phase (space group P4(2)/mnm) occurred, and tetragonal Fe-Cr-U-Si phase (space group I4/mmm) was identified. Due to the diffusion of carbon into the interdiffusion zone, carbon depletion inside the HT-9 led to the disappearance of the martensite lath structure, and intergranular U-rich carbides formed as a result of the diffusion of uranium into the cladding. These detailed new findings reveal the unique features of the FCCI behavior of annular U-Zr fuels, which could be a promising alternative fuel form for high burnup fast reactor applications. (C) 2020 Elsevier B.V. All rights reserved.

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