Out-of-Pile Performances of Zr-Sn-Nb-Fe Alloys for PWR Fuel Cladding

Abstract

The safety and reliability of Pressure Water Reactors (PWRs) is closely related to the performances of zirconium (Zr) alloy as fuel rod cladding material. Zr-Sn-Nb-Fe series alloys are one of the important directions for continuous improvement of zirconium alloys for high burn-up fuel element claddings. Two new zirconium alloys, N1(Zr-0.5Sn-0.15Nb-0.5Fe-0.25V) and N2(Zr-0.2Sn-1.3Nb-0.1Fe-0.05V) have been developed to use as advanced PWR fuel rod cladding materials through the studies of the corrosion behavior of Zr-Sn-Nb-Fe Alloys, the composition optimization, the preparation of claddings and the out-of-pile performances and in-pile tests of new zirconium alloys. The results are obtained by out-of-pile performance tests of two Zr alloy claddings. Transmission Electron Microscopy (TEM) results shown that fine and uniform distribution of β-Nb and/or ZrFeV(Nb) particles could lead to excellent out-of-pile corrosion resistance. Autoclave testing in 360 °C/18.6 MPa pure water, 60 °C/18.6 MPa/70 ppm Li+ aqueous solution and 360 °C/18.6 MPa/1000 ppm B3+/3.5 ppm Li+ aqueous solution indicated that both of N1 and N2 alloys possessed better corrosion resistance than Zr-4 alloy. The hydrogen uptake results of two kinds of alloys from corrosion reactions under various corrosion conditions showed hydrogen uptake increased with the exposure time or oxide thickness, and hydrogen uptake rate of the new alloys after long-term corrosion are lower than Zr-4. Moreover, the new alloys have demonstrated superior or similar out-of-pile tensile, burst and creep properties relative to Zr-4.