Empirical Cover Gas Correction, Sample Freezing Time, and Air Buoyancy Adjustment for the Analysis of Uranium in Uranium Hexafluoride. Revision 1

摘要

The gravimetric analysis of uranium (U) in uranium hexafluoride (UF sub 6 ) necessitates subsampling UF sub 6 by transferring an aliquot of liquid UF sub 6 through a vacuum manifold to a polytrifluorochloroethylene (TFCE) vial by cooling with liquid nitrogen. Once frozen, a cover gas is admitted to the vacuum manifold and the vial. The vial is then removed in the cover gas atmosphere and sealed with a nut-plug-gasket assembly. The cover gas is admitted to prevent exposure of the frozen UF sub 6 to moisture in the atmosphere, and the weight of the cover gas then must be considered as part of the gross weight, but not of the net weight of the UF sub 6 within the vial. An air bouyancy correction is also applied to correct for the air displacement of the brass weight equivalents used in obtaining the UF sub 6 new weight. This empirical study concerns (1) the time required to sufficiently cool the UF sub 6 in the sample vial to obtain not only the UF sub 6 but also any residual gases present in the sample, (2) the air buoyancy correction required for determining the net weight of UF sub 6 contained in the sample vial, and (3) the correction for the quantity of cover gas remaining in the sample vial after sealing 4 refs., 7 tabs., 7 figs. (ERA citation 12:006910)