How is uranium hexafluoride stored?
Depleted UF6 is typically stored in large steel cylinders. Although there are different sized cylinders in use, most of the cylinders contain 14 tons (12-metric tons) of UF6. For storage, the depleted UF6 cylinders are typically stacked two cylinders high in large areas called yards.
Cylinders are initially filled to 95% capacity with liquid depleted UF6, which is allowed to cool over several days. As the liquid UF6 cools, it contracts, forming a solid that fills approximately 60% of the internal cylinder volume. During storage, a cylinder contains solid UF6 in the bottom and UF6 gas at less than atmospheric pressure in the top. The UF6 inside the cylinder combines with the iron on the inner surfaces to form a surface layer of iron fluoride that inhibits internal corrosion.
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