Large scale molten fuel coolant interaction experiment: explosion initiation and propagation

1347992 Sonder This grant supports development of an experimental capability to control influencing parameters and study the behavior of phreatomagmatic events. Specifically, the PIs will develop a significantly and, as of yet unexplored, up-scaled device for controlling and observing the behavior of triggered explosive phreatomagmatic volcanism by: 1) assembling and developing a tiltable furnace for melting natural igneous rock; 2) developing a 25-50 L insulated crucible into which the melt would be poured and through the base of which water can be injected at various isolated points throughout the melt to create a phreatomagmatic ?premix? in which a quasi-stable water vapor phase separates the liquid water from the melt; 3) developing a trigger system (e.g., an air gun directed into the crucible containing the premix or a hammer device) to induce breakdown of separating water vapor phase such that direct interaction of hot magma and liquid water causes rapid cooling and leads to explosive volcanism; and 4) instrumenting the crucible with observation methodologies to study the mechanical and dynamical behavior of the system (e.g., high-speed force transducers mounted on the bottom of the crucible to measure the vertical forces of explosion, thermocouples within the crucible to measure melt temperatures, high speed cameras to observe ejecta). The development of the device will involve consultation with scientists at Wurzburg University in Germany and engage a Ph.D. student in instrument system engineering and experimentation. Initial experiments will varying the pre-mix parameters (injected water geometry and volumes and preloading of water down the crucible supply ramp ? dynamic premix), testing differing triggering mechanisms and subsequent study of ejecta (e.g., grain size analysis, spatial distribution, textural and mineralogical study of ash minerals). Melt composition will be maintained as a constant for experiments. The explosive experiments will be carried out at an extant outdoor facility (the GeoHazards Field Station leased by SUNY-Buffalo that is already permitted for explosives. The proposed scale of the device represents the potential for a two order of magnitude increase in the volume of magma premix that has hitherto been experimentally controlled to study phreatomagmatism and presents an interesting mid-scale parameter space to study of phreatomagmatic behavior and the conditions that favor hazardous ash clouds and pyroclastic density current formation. This scale of experiment is far from the scale of natural systems, but should offer new insights into questions surrounding the nature of phreatomagmatism including: 1) what is the influence of many water domains entrapped in the melt on explosion intensity when they are homogeneously and inhomogeneously distributed? and 2) is there a minimum trigger energy necessary to start the explosion, or can a premix effectively explode by itself? Experimental results will feed into models that attempt to scale laboratory observations to natural system behavior. ***