ABSTRACT

In-vessel retention (IVR) is a viable method of preserving reactor pressure vessel integrity in severe reactor accidents. Accurate knowledge of the bubble lift-off diameter for a downward-facing inclined heating surface is vital for successfully implementing IVR following the critical heat flux (CHF). A research facility was designed to visualize bubble lift-off for different heating surface orientations from downward-facing horizontal to vertical in IVR and experimentally determined the bubble lift-off diameter. A significant effect of inclination angle on lift-off diameter was found. The maximum lift-off diameter was achieved in the downward-facing horizontal position of the heating surface, whereas the minimum one was with vertical orientation. The existing lift-off models of Sugrue et al. and Situ et al. follow the experimental data parametrically, but with significant average errors of 51.99% and 102.08%, respectively. These models either ignore bubble sliding velocity or assume it is constant with respect to the local liquid velocity. An improved mechanistic model is proposed considering the bubble velocity as a dynamic variable for the lift-off diameter including the inclination effect of the heating surface, and it predicts the experimental data with a mean relative error of 9.89%.

摘要

容器内保留（IVR）是在严重反应堆事故中保持反应堆压力容器完整性的一种可行方法。准确了解朝下倾斜加热表面的气泡升起直径对于在临界热通量 (CHF) 后成功实施 IVR 至关重要。设计了一个研究设施来可视化 IVR 中从水平向下到垂直的不同加热表面方向的气泡升起，并通过实验确定气泡升起直径。发现倾斜角对提离直径有显着影响。在加热面朝下的水平位置实现了最大的提升直径，而在垂直方向的最小提升直径。Sugrue 等人现有的升空模型。和 Situ 等人。参数化地遵循实验数据，但平均误差分别为 51.99% 和 102.08%。这些模型要么忽略气泡滑动速度，要么假设它相对于局部液体速度是恒定的。提出了一种改进的力学模型，将气泡速度作为包括加热面倾斜效应在内的提升直径的动态变量，预测实验数据的平均相对误差为9.89%。