High-temperature ex-vessel corium spreading. Part 2: scaling principles for gravity-viscous spreading with slip at the melt–substrate interface
High-temperature ex-vessel corium spreading. Part 2: scaling principles for gravity-viscous spreading with slip at the melt–substrate interface
复制标题
高温容器外真皮铺展。第 2 部分：熔体-基材界面滑移的重力粘性铺展的缩放原理。
DOI：
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发表时间：
2021
影响因子：
1.2
通讯作者：
C. Journeau
中科院分区：
文献类型：
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作者：
Michael Johnson;Thomas Schiano;A. Denoix;V. Bouyer;C. Journeau
摘要在严重核事故后，促进熔融的真皮扩散是消散衰变热和保持安全壳完整性的关键策略。在高温熔体铺展实验中，很难实现精确的重复性，因此需要比例因子来校正对比实验之间的流量、粘度和密度的差异。最近在陶瓷和牺牲混凝土衬底上进行的千克级VE-U9实验中，为在二维展开几何中展开而推导的重力-粘性动量平衡建立了无滑移展开长度与质量流率的平方根的比例。降低的质量流率和增加的粘度的比例表明，熔体在牺牲混凝土上的扩散比在惰性陶瓷基板上的扩散远37%。通过在熔融-基材界面施加与剪切成正比的滑移速度，研究了熔融混凝土和烧蚀气体的润滑膜在下边界减少摩擦的可能性。对一定范围的Navier滑移长度的模拟表明，铺展长度随滑移长度与熔体厚度的比率而变化，在几乎无摩擦的界面上，铺展长度可以增加多达68%。
ABSTRACT Promoting the spreading of molten corium represents a key strategy in the dissipation of decay heat and in the maintainence of containment integrity in the aftermath of a severe nuclear accident. Precise repeatability is difficult to achieve during high-temperature melt spreading experiments, and so scaling factors are necessary to correct for differences in flow rate, viscosity, and density between comparative experiments. A gravity-viscous momentum balance derived for spreading in the two-dimensional spreading geometry employed during recent kg-scale VE-U9 experiments on ceramic and sacrificial concrete substrates establishes that no-slip spreading length scales with the square root of the mass flow rate. Scaling for the reduced mass flow rate and enhanced viscosity implied that the melt spread 37% further on the sacrificial concrete than on the inert ceramic substrate. The possibility of a lubricating film of molten concrete and ablation gases reducing friction at the lower boundary is investigated through the imposition of a slip velocity proportional to the shear at the melt–substrate interface. Simulations over a range of Navier slip lengths implied that spreading length scales with the ratio of slip length to the melt thickness and that spreading length can be augmented by as much as 68% in the case of a virtually frictionless interface.