During severe nuclear accidents, control rods rapidly liquefy at temperatures above 1250 °C due to eutectic reaction, forming a 304 stainless steel (304SS)-B₄C melt. The melt will relocate and attack surrounding fuel rod claddings made of Zircaloy-4 (Zry-4). To understand to what extent ZrO₂ oxide scale formed on Zry-4 will protect Zry-4 claddings against 304SS-B₄C melt attack, we studied the chemical interactions between pre-oxidized Zry-4 and 304SS-B₄C melt at 1300 °C. Bare Zry-4 was completely dissolved in 304SS-B₄C melt within 60 min. The presence of ZrO₂ oxide scale on Zry-4 significantly delayed the interactions, especially when ZrO₂ oxide scale was dense. Typically, the reaction zone consists of ZrB₂, Zr₆(Fe,Ni,Cr)₂₃ and Fe-Ni-Cr metallic phase at room temperature. Due to the presence of α-Zr and β-Zr in Zry-4 metal matrix, ZrO₂ oxide scale becomes thermodynamically unstable. Dissolution of dense ZrO₂ oxide scale can be described in three stages with different dissolution rates. Dissolution of ZrO₂ oxide scale provides Zr source for the growth of reaction zone. Generally, the thickness of reaction zone linearly increases with time. Compared with the reaction couples of pre-oxidized Zry-4 and solid 316 stainless steel, both ZrO₂ dissolution rate and reaction zone growth rate are much slower in the reaction couples of pre-oxidized Zry-4 and 304SS-B₄C melt. The corresponding reasons were discussed.

在严重的核事故中，由于共晶反应，控制棒在高于1250°C的温度下迅速液化，形成304不锈钢（304SS）-B ₄ C熔体。熔体将重新定位并侵蚀周围由Zircaloy-4（Zry-4）制成的燃料棒包壳。为了了解在Zry-4上形成的ZrO ₂氧化皮能在多大程度上保护Zry-4覆层免受304SS-B ₄ C熔体的侵蚀，我们研究了预氧化的Zry-4和304SS-B ₄ C熔体在1300°C之间的化学相互作用。℃。Bare Zry-4在60分钟内完全溶解在304SS-B ₄ C熔体中。Zry-4上ZrO ₂氧化物水垢的存在显着延迟了相互作用，尤其是当ZrO ₂氧化皮是致密的。通常，反应区在室温下由ZrB ₂，Zr ₆（Fe，Ni，Cr）₂₃和Fe-Ni-Cr金属相组成。由于在Zry-4金属基质中存在α- Zr和β -Zr，ZrO ₂氧化皮在热力学上变得不稳定。浓密的ZrO ₂氧化物水垢的溶解可以用三个阶段来描述，它们具有不同的溶解速率。ZrO ₂氧化物水垢的溶解为反应区的生长提供了Zr源。通常，反应区的厚度随时间线性增加。与预氧化Zry-4和固态316不锈钢的反应对相比，ZrO ₂在预氧化的Zry-4和304SS-B ₄ C熔体的反应对中，溶解速率和反应区生长速率要慢得多。讨论了相应的原因。