Radiation Resistance of the U(Al, Si)₃ Alloy: Ion-Induced Disordering.

Louisa Meshi,Gennady Rafailov,Gili Yaniv,Arik Kiv,Jiri Vacik,Pavel Horak,Itzchak Dahan,Natalia Mykytenko,David Fuks

doi:10.3390/ma11020228

Abstract

During the exploitation of nuclear reactors, various U-Al based ternary intermetallides are formed in the fuel-cladding interaction layer. Structure and physical properties of these intermetallides determine the radiation resistance of cladding and, ultimately, the reliability and lifetime of the nuclear reactor. In current research, U(Al, Si)3 composition was studied as a potential constituent of an interaction layer. Phase content of the alloy of an interest was ordered U(Al, Si)3, structure of which was reported earlier, and pure Al (constituting less than 20 vol % of the alloy). This alloy was investigated prior and after the irradiation performed by Ar ions at 30 keV. The irradiation was performed on the transmission electron microscopy (TEM, JEOL, Japan) samples, characterized before and after the irradiation process. Irradiation induced disorder accompanied by stress relief. Furthermore, it was found that there is a dose threshold for disordering of the crystalline matter in the irradiated region. Irradiation at doses equal or higher than this threshold resulted in almost solely disordered phase. Using the program “Stopping and Range of Ions in Matter” (SRIM), the parameters of penetration of Ar ions into the irradiated samples were estimated. Based on these estimations, the dose threshold for ion-induced disordering of the studied material was assessed.

Highlights

In nuclear reactors, where U is used as a fuel, cladding is usually made of Al alloys
The alloys were examined by powder X-ray diffraction (XRD), scanning electron microscopy (SEM, JEOL, Tokyo, Japan) and transmission electron microscopy (TEM)
Final thinning was done by a Gatan precision ion polishing system (PIPS) at 5 keV

Summary

Introduction

In nuclear reactors, where U is used as a fuel, cladding is usually made of Al alloys (with Si as major alloying element). The fuel-cladding chemical interactions (both radiation driven or/and thermally assisted) are considered to be the life-limiting events of the fuel system. Study of the U-Al-Si system, which is the main component of cladding-fuel interaction layer, is of crucial importance. The changes in the interaction layer under irradiation can lead to significant radiation effects in the fuel and to break the balance in the nuclear reactor as a whole. This layer can acquire a thermal conductivity that affects fuel performance [1,2], or it can become brittle such that, in the case of monolithic fuel, fuel/cladding separation could result [3]. Regarding the crystal structure of the U-alloys, it was reported that irradiation can cause partial or full amorphization of the U-Si and

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Conclusion