Fuel-Cladding Interaction Between U-Pu-Zr Fuel and Fe

Abstract

This work investigates fuel-cladding chemical interaction (FCCI) between U-25Pu-14Zr (in wt pct) fuel and pure Fe at elevated temperatures, understanding of which is critical for evaluation of the fuel performance. Phases and microstructure formed in the quaternary uranium-plutonium-zirconium-iron (U-Pu-Zr-Fe) system were characterized using the transmission electron microscopy technique. Phases formed within the FCCI layer were identified using selective area electron diffraction (SAED) analysis as Fe 2 U (Fd-m), Fe 2 Zr (Fd-3m), a-U (Cmcm), Fe 2 Pu (Fd-3m), b-Pu (C12/m1), and b-Zr (Im-3m).

TEM examination of phases formed between U–Pu–Zr fuel and Fe

“…showed that even though chemical compositions of high-Zr inclusions are consistent with previous reports, the crystal structure of precipitates is face-centered cubic [16]. Previous work on U-25Pu-14Zr (wt%) fuel showed formation of β-Zr precipitates as well [18]. Formation of fcc Zr inclusion has been reported in nanocrystals and thin films but not in larger crystals [19][20].…”

“…Figure 10 shows bright-field transmission electron micrograph of the Zr precipitate observed in the third lift-out and its corresponding experimental and simulated electron diffraction patterns. Formation of high-Zr inclusions has been previously reported in a variety of transmutation fuels [11][12][13][14][15][16][17][18]. These precipitates were assumed to be α-Zr stabilized by dissolved impurities such as N, O, C, Cl, C, and Si.…”

Ab-initio molecular dynamics study of lanthanides in liquid sodium

“…As the fuel swells during burnup, the lanthanide (Ln) fission products with particularly abundant cumulative yield can migrate to the fuel periphery and form low-melting point intermetallic compounds with cladding constituents such as Fe and Ni [2]. This chemical interaction between the fission products and the cladding can not only reduce cladding thickness, but also degrade its load-bearing capability [3]. The FCCI phenomenon is deemed as one of the limiting factors of operation of this particular fuel.…”