Mechanical engineering note - safety analysis of molten uranium/water interaction in the uranium foundry furnace Page: 10 of 84
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This analysis investigates the following possible hazards associated with molten metal
and water interaction in the vacuum vessel.
" Steam generation leading to over pressure
" Hydrogen deflagration
" Damaging steam explosion pressures
" Thermal melt through of vacuum vessel floor
The safety philosophy in the furnace design is to limit the amount of water available to
participate in a molten uranium/water interaction by isolating the coolant flow when an
accident condition is detected. The safety analysis (see Appendix A) concluded that
hydrogen deflagration and damaging shock pressures resulting from the interaction
between molten uranium (- 1500 C) and water can be ruled out due to lack of sufficient
premixing between the molten metal and water. The maximum pressure in the vessel
from a worst case accident scenario has been calculated to be less than 15 psig over
pressure with proper venting capability. This is a conservative estimate because the
condensing capability of the vessel wall has been ignored. The vessel is designed to
withstand a 15 psig over pressure. Hence, even in the worst case accident condition, the
vacuum vessel will not fail.
The primary system response to a water leak inside the vacuum vessel is that the
roughing pump isolation valve opens when the vessel pressure rises above the setpoint,
pumping steam and hydrogen out of the vessel. The roughing pump remains on during a
run and quickly provides a pumping capacity of 3200 cfm to vent the vessel into the
negative air duct.
Even if the primary system response fails, the vessel will not pressurize because of the
two pressure relief valves and the rupture disc. These two backup systems preserve the
structure integrity of the vessel and allow the steam and hydrogen to vent into the
negative air duct in a safe manner.
The potential of thermal melt-through due to the accumulation of the molten uranium
(-100 kg) on the vessel floor can be ruled out. The calculation shows that the vessel floor
temperature will rise to ~ 230 C, it is well below the eutectic temperature for the uranium
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Gourdin, W H & Sze, J. Mechanical engineering note - safety analysis of molten uranium/water interaction in the uranium foundry furnace, report, August 19, 1999; California. (https://digital.library.unt.edu/ark:/67531/metadc622935/m1/10/: accessed March 26, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.