Microstructure and fission products in the UCO kernel of an AGR-1 TRISO fuel particle after post irradiation safety testing

JOURNAL OF NUCLEAR MATERIALS

卷:528

Article

Fu, Zhenyu¹  van Rooyen, Isabella J.^1,2  Bachhav, Mukesh³  Yang, Yong¹ 

[1] Univ Florida, Dept Mat Sci & Engn, Nucl Engn Program, Gainesville, FL 32611 USA

[2] Idaho Natl Lab, Fuel Performance & Design Dept, Idaho Falls, ID 83415 USA

[3] Idaho Natl Lab, Adv Characterizat Dept, Idaho Falls, ID 83415 USA

关键词: TRISO fuel;    Fission products;    Kernel;    UCO fuel;    Post irradiation examination;   

DOI  :  10.1016/j.jnucmat.2019.151884

来源: Elsevier

【 摘 要 】

Tristructural isotropic (TRISO) coated particle fuel, as a key fuel concept for the high-temperature gascooled reactors and a candidate accident-tolerant fuel, has been investigated under the US-DOE Advanced Gas Reactor Fuel Development and Qualification Program. Extensive studies have been conducted to evaluate the fission-product release, diffusion of Ag, Pd, and Cd in the SiC layer and the TRISO coating system, and safety-test performance. However, to date there are limited reported results on the fuel kernels' response to irradiation with or without post irradiation safety testing. To incrementally fill this knowledge gap, extensive studies using transmission electron microscopy (TEM) and atom probe tomography (APT) were conducted on a TRISO fuel-particle kernel with a 19.74% U-235 enrichment, irradiated to 18.63% FIMA and subsequently subjected to safety testing at 1600 degrees C for 300 h. Microstructural characterizations, elemental analysis, and phase identification were conducted using conventional TEM and scanning TEM imaging, energy-dispersive X-ray spectroscopy, selected-area electron diffraction and APT. The following findings were made: (1) significant reconstructions and phase evolutions occurred in the irradiated and post safety-tested fuel kernel, and its microstructure consists of two primary phases, namely a higher-Z (atomic mass) UC phase and a lower-Z UO phase, (2) no fissiongas bubbles are identified within the fuel kernel, that can be attributed to the high-temperature post safety-testing, (3) fission products Zr, Nb, Mo, Ru, Tc and Rh were found to segregate preferentially into UC phase or to form metallic precipitates while the lanthanide fission products tend to stay in the solution of UO phase, and (4) Pd was detected in the rod-shaped precipitates. (C) 2019 Elsevier B.V. All rights reserved.

【 授权许可】

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