Materials Development, Inc, 3090 Daniels Court, Arlington Heights, IL, 60004, USA.
X-ray Science Division, Argonne National Laboratory, Argonne, IL, 60439, USA.
Sci Rep. 2018 Feb 5;8(1):2434. doi: 10.1038/s41598-018-20817-z.
In the exceedingly rare event of nuclear reactor core meltdown, uranium dioxide fuel reacts with Zircaloy cladding to produce eutectic melts which can subsequently be oxidized by coolant/moderator water. Oxidized corium liquids in the xUO·(100 - x)ZrO system were produced via laser melting of UO-ZrO mixtures to temperatures in excess of 3000 K. Contamination was avoided by floating the droplets on a gas stream within an aerodynamic levitator and in-situ high-energy x-ray diffraction experiments allowed structural details to be elucidated. Molecular dynamics simulations well reproduced diffraction and density data, and show less compositional variation in thermal expansion and viscosity than suggested by existing measurements. As such, corium liquids maintain their highly penetrating nature irrespective of the amount of oxidized cladding dissolved in the molten fuel. Metal-oxygen coordination numbers vary with both composition and temperature. The former is due to mismatch in native values, n(x = 100) ≈ 7 and n(x = 0) ≈ 6, and the requirement for oxygen site stabilization. The latter provides a thermal expansion mechanism.
在极为罕见的核反应堆堆芯熔毁事件中，二氧化铀燃料与锆合金包壳发生反应，生成共晶熔体，随后可被冷却剂/慢化剂水氧化。通过激光熔融 UO-ZrO 混合物，将 xUO·(100 - x)ZrO 体系中的氧化包壳液体加热到 3000 K 以上。通过在气动升力器内的气流上漂浮液滴来避免污染，并进行原位高能 X 射线衍射实验以阐明结构细节。分子动力学模拟很好地再现了衍射和密度数据，并且显示出热膨胀和粘度的组成变化小于现有测量结果所表明的。因此，无论溶解在熔融燃料中的氧化包壳数量如何，共晶液体都保持其高穿透性。金属-氧配位数随组成和温度而变化。前者是由于固有值的不匹配，n(x = 100) ≈ 7 和 n(x = 0) ≈ 6，以及需要稳定氧位。后者提供了热膨胀机制。
