THE VOLATILITY OF UO$sub 1$ $sub 2$+-x AND PHASE RELATIONS IN THE URANIUM- OXYGEN SYSTEM

Technical Report · Wed Apr 01 04:00:00 EST 1964

DOI:https://doi.org/10.2172/4033972· OSTI ID:4033972

Chapman, A. T.; Meadows, R. E.

The volatility of UO/sub 2 plus or minus x/ and the phase relations in the uranium-oxygen system were studied using thermogravimetric techniques. Chemical reactions describing the loss of uranium from UO/sub 2 plus or minus x/ at temperatures between 1100 and 2200 deg C in oxygen pressures between approximately 10 and 10/sup -6/ torr are proposed. The uranium-bearing vapor species above UO/sub 2 plus or minus x/ appears to be UO/sub 4/(g). Evidence supporting the existence of UO/sub 4/(g) included the volatilization of material with an oxygen-to-uranium ratio of 4 during the decomposition of UO/sub 2 plus or minus x/ (0.2 > x > 0) to near-stoichiometric UO/sub 2/ in vacuum above 1500 deg C and the dependence of the evaporation rate of the uranium dioxide on the oxygen pressure between 1200 and 1500 deg C. The equilibrium oxygen pressures over compositions between UO/sub 2.02/ and UO/sub 2.63/ in the UO/sub 2+x/ and U/ sub 3/O/sub 8/- regions and over the boundary between these phases were measured between 1000 and 1600 deg C. The equilibrium oxygen-to-uranium ratio of UO/sub 2 plus or minus x/ was less than 2 above 1700 deg C in vacuum. (auth)

• Research Organization: Oak Ridge National Lab., Tenn.
• DOE Contract Number: W-7405-ENG-26
• NSA Number: NSA-18-018352
• OSTI ID: 4033972
• Report Number(s): ORNL-3587
• Country of Publication: United States
• Language: English

Related Subjects

CHEMICAL REACTIONS
DECOMPOSITION
EVAPORATION
GRAIN BOUNDARIES
HIGH TEMPERATURE
MEASURED VALUES
METALS, CERAMICS, AND OTHER MATERIALS
OXYGEN
PHASE DIAGRAMS
PRESSURE
REACTION KINETICS
THERMAL ANALYSIS
THERMODYNAMICS
THERMOGRAVIMETRY
URANIUM DIOXIDE
URANIUM OXIDES
VACUUM
VAPORS
VOLATILITY
WEIGHT