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Laboratory experiments were performed in the temperature range 1800 to 2000°C in inert gas to study the chemical interaction between solid uranium dioxide (UO2) and liquid Zircaloy-4, and the wettability of UO2 by molten Zircaloy as functions of time and Zircaloy oxygen concentration. The experiments were interrupted after various reaction times to determine the extent of the chemical interaction and of the UO2 dissolution. The results show that the dissolution of UO2 by molten Zircaloy is primarily a chemical process, and that the extent of the interaction depends on the wettability of UO2 by molten Zircaloy. The wettability, however, depends strongly on the oxygen content of the Zircaloy and therefore on the time of UO2/Zircaloy contact. The wettability improves with increasing oxygen content. Zircaloy reduces UO2 to form a homogeneous [uranium, zirconium, oxygen (U,Zr,O)] melt at low oxygen concentrations or a heterogeneous (U,Zr,O) melt which contains (U,Zr)O2 particles at high oxygen concentrations. During cooling, the (U,Zr,O) melt decomposes into a (U,Zr) alloy with high uranium content and oxygen-stabilized α-Zr(O). The amount of fuel which can be liquefied by molten cladding depends on the initial oxygen content of the melt. Oxygen-free liquid Zircaloy can dissolve considerably more UO2 than Zircaloy rich in oxygen. The significance of these experiments is that UO2 fuel can be “liquefied” by molten Zircaloy far below the melting point of UO2.

Little quantitative experimental data are available describing the behavior of immiscible contaminants in unsaturated heterogeneous porous media. Such data are, however, essential to the fundamental understanding of the processes governing nonaqueous phase liquid behavior and for the validation of modeling tools. The effect of macro-heterogeneity on light nonaqueous phase liquid (LNAPL) fl ow and distribution in the unsaturated zone was investigated experimentally by simulating LNAPL spills in layered soil systems consisting of sands with various textures. Two multiphase fl ow experiments were conducted in a twodimensional fl ume (180 × 120 × 8 cm). The vertical distribution of water and LNAPL pressure were measured using hydrophilic and hydrophobic tensiometers. An image analysis technique was used to estimate the saturation distribution of the fl uids in a two-dimensional vertical plane. The experiments show that LNAPL entrapment, which contributes to long-term soil and water contamination, depends strongly on the initial water saturation and water pressure at the layer interfaces and on the texture contrasts between the soil layers, which lead to permeability and capillary barrier effects. Thus, the knowledge of the initial water pressure and saturation distribution in unsaturated layered soil formations is critical to the correct prediction of LNAPL infi ltration and drainage.

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Three sets of equations provide upper and lower values bound ing the experimentally obtained electrical and thermal conduc tivities as well as the magnetic permeabilities (=“field properties”) of porous ceramics. These equations are as I‐order upper bound: φp=φM(1‐P) (φ=effective field property of the porous material, φM=field property of the nonporous material, P=porosity), and as I‐order lower bound: φr=φM (1‐P)7. Closer bounds corresponding to isotropic porous materials are the II‐order upper bound: φPII,=φM,[2(1‐P)/ (2+P)], and the II‐order lower bound: φPIII=φM(1‐P)3. Even closer bounds, referring to isotropic porous materials containing closed, unconnected pores are the III‐order upper bound: φPIII=φM(1‐P)3/2, and the III‐order lower bound: φPIII=φM(1‐p)3.