Exploring Uranium Hexafluoride Material Distributions in 30B Cylinders with Center of Gravity Measurements

The nuclear industry commonly uses uranium hexafluoride (UF6) in uranium conversion plants, uranium enrichment plants, and fuel fabrication plants. This chemical form of uranium is typically stored in 48Y and 30B cylinders while awaiting processing and in transit between facilities. The behavior of nuclear material inside 48Y and 30B cylinders while they are stored outside for long periods of time is an open question in the nuclear community. This is a difficult thing to measure because of the hazards associated with handling UF6, particularly its violent reaction with water. This work uses a force measurement to explore the behavior of UF6 inside a 30B cylinder over time. A platform scale system with four individually instrumented load cells was used to measure the force applied by the cylinder at each load cell. This information was then used to calculate the center of gravity in two dimensions. The validity of this approach was demonstrated in a laboratory setting, and corrections for sources of uncertainty (e.g., cylinder positioning and rotation) were developed to improve the ability to compare measured values. The experimental measurements collected by the platform scale system showed that UF6 does move over time inside a 30B cylinder sitting outside in a storage yard. The data also demonstrated that material movement appears to occur as a result of temperature, providing evidence that sublimation and desublimation occur in a cylinder while it is sitting outside.