How DUF6 is Stored
Depleted UF6 is stored in steel cylinders that hold
9 - 12 metric tons of depleted UF6.
Depleted UF6 Cylinders
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.
Cylinder Capacities, Dimensions, and Components
Several different cylinder types are in use, although the vast majority of cylinders are designed to contain 14-tons (12-metric tons) of depleted UF6. The 14-ton-capacity cylinders are 12 ft (3.7 m) long by 4 ft (1.2 m) in diameter, with most having an initial wall thickness of 5/16 in. (0.79 cm) of steel. The cylinders have external stiffening rings that provide support. Lifting lugs for handling are attached to the stiffening rings. A small percentage of the cylinders have skirted ends (extensions of the cylinder walls past the rounded ends of the cylinder). Each cylinder has a single valve for filling and emptying located on one end at the 12 o'clock position. Similar, but slightly smaller, cylinders designed to contain 10 tons (9 metric tons) of depleted UF6 are also in use. Cylinders are manufactured in accordance with an American National Standards Institute standard (ANSI N14.1, American National Standard for Nuclear Materials - Uranium Hexafluoride - Packaging for Transport) as specified in 49 CFR 173.420, the federal regulations governing transport of depleted UF6.
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.
A New Depleted UF6 Cylinder
Cylinders that exhibit external corrosion from outdoor storage.