Low temperature cold trapping of uranium hexafluoride containing hydrogen fluoride

Technical Report · Mon Oct 01 00:00:00 EDT 1990

DOI:https://doi.org/10.2172/6291490· OSTI ID:6291490

Hobbs, W E; Barber, E J; Jones, C G

The use of a freezer-sublimer system operating at low desublimation pressures to replace 10-in. nuclearly safe cold traps for low assay (<5% U-235) uranium hexafluoride (UF{sub 6}) would significantly simplify operations and is economically attractive provided the nuclear safety of the system can be assured. A major requirement of such assurance is the availability of conditions guaranteeing that the nuclear safety design criterion, which requires that the H/U atomic ratio in the condensate in the freezer-sublimer always be less than 0.33 for assays up to 5%, will never be violated. A general vapor pressure equation giving the vapor pressure of HF-UF{sub 6} solutions as a function of temperature and mole fraction UF{sub 6} has been developed. The precision of the data at the 95% confidence level is {plus minus}0.1 torr at temperatures between {minus}100{degree}F and {minus}121{degree}F. The calculated vapor pressure of pure HF is 4.6 torr at {minus}100{degree}F and 3.1 torr at {minus}108{degree}F. Theoretical considerations suggest that the true value will be slightly lower. In experimental studies of the cold trapping operation at {minus}108{degree}F and at a trap pressure of 2.2 torr, only 7.3% of the HF entering the trap was retained in the trap. At a trap pressure of 4.6 torr, over 80% of the HF entering the trap was retained. The data obtained in this study confirms that the physical chemistry of the HF-UF{sub 6} system previously developed accurately describes the behavior of the system and that so long as the pressure in the trap is maintained below the vapor pressure of pure HF at the trap temperatures, there is no way that sufficient HF can be trapped to give an H/U ratio of 0.33 regardless of the HF/UF{sub 6} ratio in the feed to the trap. 5 refs., 4 tabs.

• Research Organization: Oak Ridge Gaseous Diffusion Plant (K-25), Oak Ridge, TN (United States)
• Sponsoring Organization: DOE/NE
• DOE Contract Number: AC05-84OT21400
• OSTI ID: 6291490
• Report Number(s): K/ETO-37; ON: DE91005200
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
COLD TRAPS
HYDROFLUORIC ACID
PHASE TRANSFORMATIONS
VAPOR CONDENSATION
URANIUM HEXAFLUORIDE
CHEMICAL REACTION KINETICS
ENRICHMENT
LOW TEMPERATURE
QUANTITATIVE CHEMICAL ANALYSIS
SAFETY
STATISTICAL DATA
STATISTICAL MECHANICS
STATISTICAL MODELS
VAPOR PRESSURE
VAPORIZATION HEAT
ACTINIDE COMPOUNDS
CHEMICAL ANALYSIS
CONDENSERS
DATA
ENTHALPY
FLUORIDES
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
HYDROGEN COMPOUNDS
INFORMATION
INORGANIC ACIDS
KINETICS
MATHEMATICAL MODELS
MECHANICS
NUMERICAL DATA
PHYSICAL PROPERTIES
REACTION KINETICS
THERMODYNAMIC PROPERTIES
TRANSITION HEAT
TRAPS
URANIUM COMPOUNDS
URANIUM FLUORIDES
VAPOR CONDENSERS
050500* - Nuclear Fuels- Uranium Enrichment
050700 - Nuclear Fuels- Fuels Production &amp; Properties