Multi-Camera Based Setup for Geometrical Measurement of Free-Falling Molten Glass Gob

High temperatures complicate the direct measurements needed for continuous characterization of the properties of molten materials such as glass. However, the assumption that geometrical changes when the molten material is in free-fall can be correlated with material characteristics such as viscosity opens the door to a highly accurate contactless method characterizing small dynamic changes. This paper proposes multi-camera setup to achieve accuracy close to the segmentation error associated with the resolution of the images. The experimental setup presented shows that the geometrical parameters can be characterized dynamically through the whole free-fall process at a frame rate of 600 frames per second. The results achieved show the proposed multi-camera setup is suitable for estimating the length of free-falling molten objects.

Analysis of Transient Corium Pool Structure in the Lower Plenum of Reactor Vessel

The transient stratification of the corium in the lower plenum and its impact on the heat flux distribution on the outside of reactor vessel is analyzed in this work. A method for predicting the kinetic corium pool structure is proposed, which takes into account both thermo-chemical equilibrium and density evaluation of the corium. The transient stratification of the corium pool formed after a large loss of coolant accident (LLOCA) and a station blackout (SBO) accident of ACP1000 nuclear power plant in China was analyzed by this method. The transient structure of the corium pool was calculated at the moment when the amount of molten materials in the corium pool increased obviously. The results shown that the formation of a three-layer pool is highly possible when a two-layer pool is formed in the previous moment with a heavy metal layer on the bottom and the density of the heavy metal layer at the bottom is greater than the density of the newly added molten material at the next moment. The heat flux on the outside of the vessel wall faced the thin top metal layer and the vessel failure probability of the vessel here are high if a three-layer pool occurred.

Modeling of Materials Heating on Solar Furnace and Cooling of Melt

The possibilities of calculating the rate of heating and cooling of molten materials on the example of pyroxene rocks under the influence of concentrated solar radiation in the Big Solar Furnace are shown. The dependences of the microstructure of the material obtained from the cooled melt on the cooling rate of the melt are analyzed. It is shown that a different method of cooling the melt can achieve different cooling rates: 102 ; 103 and 104 deg/s.

Experimental Research on Energy Release and Fragments Characteristics Under Molten Materials Discharged Into Liquid Sodium

Hypothetical Core Disruptive Accidents (HCDA) are dominantly concerned during safety assessment and evaluation in Sodium-cooled Fast Reactor (SFR). With molten core materials discharged into liquid sodium, positive reactivity is potentially introduced due to sodium boiling and molten core compaction, which can cause terrible recriticality. The possibility of recriticality and efficient cooling on the relocated debris bed are significantly affected by the fragmentation behavior of molten core in liquid sodium. With few available mechanism models and benchmarks, many investigations have been conducted on the fragmentation characteristics during molten fuel-coolant interaction (MFCI). In the present study, molten copper is used for molten simulant to be discharged into the liquid sodium pool through guiding tube based on a multifunctional experimental facility (COSA). The simulants are heated by electromagnetic induction system in customized ceramic crucible and the molten materials are controlled by magnetic lifting system to be drained through the guiding tube into the bottom liquid sodium pool. Temperature variation and pressure change in the liquid sodium pool are acquired against the energy release during MFCI. Furthermore, the fragments cleaned by water medium are measured and recorded for distribution and morphology analysis. Significant pressure pulses and temperature gradient almost not occur during MFCI and the molten copper is finely fragmented possibly due to hydrodynamic and thermodynamic effects. And the experimental results are helpful to confirm the prediction of fragmentation mechanism and to validate physical model, which can be applied to the development and validation of analysis code.

Textural equilibrium melt geometries around tetrakaidecahedral grains

In textural equilibrium, partially molten materials minimize the total surface energy bound up in grain boundaries and grain–melt interfaces. Here, numerical calculations of such textural equilibrium geometries are presented for a space-filling tessellation of grains with a tetrakaidecahedral (truncated octahedral) unit cell. Two parameters determine the nature of the geometries: the porosity and the dihedral angle. A variety of distinct melt topologies occur for different combinations of these two parameters, and the boundaries between different topologies have been determined. For small dihedral angles, wetting of grain boundaries occurs once the porosity has exceeded 11%. An exhaustive account is given of the main properties of the geometries: their energy, pressure, mean curvature, contiguity and areas on cross sections and faces. Their effective permeabilities have been calculated, and demonstrate a transition between a quadratic variation with porosity at low porosities to a cubic variation at high porosities.

Research on IVR-Relevant Phenomena of Material Thermodynamic Interaction and Corium Pool Configuration

In-Vessel Retention (IVR), which arrests relocated molten core materials in the vessel during severe accident, has been singled out as an appealing accident management approach to many reactors. The heat transfer imposed by in-vessel corium is a vital part for IVR success considering the difficulty of significantly altering ex-vessel CHF. For a given decay power, corium pool configuration determines the heat flux profile along the vessel wall, which may produce uncertainties associated with IVR strategy. In this paper, a thermodynamic tool is employed to study the corium pool configurations by analyzing the possible interaction among relocated corium, zircalloy cladding and core internals. The results reveal the immiscibility gap phenomena under high temperature which separates molten materials into oxidic and metal phase in the lower head. The oxidic phase is quite stable and its density is only slightly changed by various accident scenarios. The metal phase is relatively unstable and its density is susceptible to the condition of cladding oxidation degree and crust integrity. The corium pool configurations in the lower head are determined based on the results of thermodynamic analysis and phase density comparison. Both two-layer and three-layer corium pools are likely to be formed under different accident scenarios. CAP1400 has intentionally increased the mass of lower core support plate, which is a beneficial design change to prevent possible focusing effect if material infiltration through crust is assumed to be impossible.