Zr-Sn-Nb合金1000~1250℃蒸汽氧化行为

Oxidation Behaviors of a Zr-Sn-Nb Alloy in 1000~1250℃ Steam

摘要:

核反应堆包壳管在失水事故中会因剧烈的高温蒸汽氧化而破裂,从而引起核燃料泄露的严重后果。为此,本文研究了Zr-Sn-Nb核包壳合金1000~1250℃蒸汽氧化行为。采用增重法计算了蒸汽氧化试样单位面积的质量变化,通过扫描电子显微镜观察了蒸汽氧化试样截面形貌并测量了氧稳定α相层(α-Zr(O))和氧化锆层(ZrO₂)厚度,得到Zr-Sn-Nb合金氧化增重和α-Zr(O)、ZrO₂层生长动力学曲线。结果表明：1000℃蒸汽氧化时,α-Zr(O) 层生长动力学曲线始终服从抛物线规律；氧化1500s后,氧化增重和ZrO₂层生长动力学曲线由抛物线转变为直线规律,ZrO₂层内产生大量裂纹。1100~1250℃蒸汽氧化时,氧化增重和α-Zr(O)、ZrO₂层生长动力学曲线均服从抛物线规律, ZrO₂层结构始终保持完整。Zr-Sn-Nb合金的抗氧化性能优于Zr-4合金,其ZrO₂层和α-Zr(O)层生长速度慢于Zr-4合金。

关键词:Zr-Sn-Nb合金;蒸汽氧化;α-Zr(O);ZrO₂

Abstract:

During loss of coolant accident, the oxidation can cause burst of the cladding tube in high temperature steam, which lead to the leakage of the nuclear fuel. At present work, the oxidation behaviors of a Zr-Sn-Nb alloy were investigated in 1000~1250℃ steam. The weight gains per area were calculated by the weight gain method. The microscopic morphology, thickness of the alloy were measured by a scanning electron microscope. The oxidation kinetics of the alloy was characterized by weight gain and the thickness increase of α-Zr (O) and ZrO₂ layers. The results show that the parabolic weight gain curves and ZrO₂ layer growth kinetics curves become to be linear in 1000℃ steam for about 1500s, while α-Zr (O) growth kinetics always follow the parabolic law. Meanwhile, a large number of cracks are formed in the ZrO₂ layers. The weight gain kinetics curves and α-Zr (O) and ZrO₂ layers growth kinetics curves all follow the parabolic law in 1100~1250℃ steam,and the ZrO₂ layer is almost intact. The oxidation resistance of Zr-Sn-Nb alloy is higher than that of Zr-4 alloy. The growth rate of ZrO₂ layer and α-Zr (O) layer is slower than that of Zr-4 alloy.

Key words:Zr-Sn-Nb;alloy, steam;oxidation, α-Zr(O), ZrO₂