Conversion of depleted uranium hexafluoride to a solid...

Chemistry of inorganic compounds – Radioactive – Uranium compound

Reexamination Certificate

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Details

C423S010000, C423S011000, C423S261000

Reexamination Certificate

active

06303090

ABSTRACT:

BACKGROUND OF THE INVENTION
There are large worldwide stored inventories of the depleted uranium hexafluoride (UF
6
) tailings from past gaseous-diffusion-enrichment plants for nuclear fuel-cycle operations. In the U.S. alone, there are currently ≈700,000 metric tons of that material stored in U.S DOE facilities at Paducah, Ky., Portsmouth, Ohio and Oak Ridge, Tenn. One conversion process considered in the past by the DOE would use steam for high-temperature hydrolysis of the hexafluoride, to convert it to (a) UO
2
for use in other nuclear programs or for disposal, and (b) anhydrous HF for industrial use. The present invention relates to a low-temperature aqueous process to convert the hexafluoride to UO
2
for use in other nuclear programs, and high-purity calcium fluoride for sale.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a process for converting UF
6
to a solid uranium compound, comprising: contacting UF
6
vapor with an aqueous solution of NH
4
OH at a pH greater than 7 to precipitate at least some solid uranium values as a solid leaving an aqueous solution containing NH
4
OH and NH
4
F and remaining uranium values, separating the solid uranium values from the aqueous solution of NH
4
OH and NH
4
F and remaining uranium values, diluting the aqueous solution of NH
4
OH and NH
4
F and remaining uranium values with additional water precipitating more uranium values as a solid, leaving trace quantities of uranium in a dilute aqueous solution.
Another object of the present invention is to provide a process for converting UF
6
to a solid uranium compound and CaF
2
, comprising: contacting UF
6
vapor with an aqueous solution of NH
4
OH at a pH greater than 7 to precipitate at least some solid uranium values as a solid leaving an aqueous solution containing NH
4
OH and NH
4
F and remaining uranium values, separating the solid uranium values from the aqueous solution of NH
4
OH and NH
4
F and remaining uranium values, diluting the aqueous solution of NH
4
OH and NH
4
F and remaining uranium values with additional water precipitating more uranium values as a solid leaving trace quantities of uranium in a dilute aqueous solution, contacting the dilute aqueous solution with an ion-exchange resin to remove substantially all the uranium values from the dilute aqueous solution, and contacting the dilute aqueous solution having substantially all uranium values removed with Ca(OH)
2
to precipitate CaF
2
leaving dilute NH
4
OH.
The invention consists of certain novel features and a combination of parts hereinafter fully described, illustrated in the accompanying drawings, and particularly pointed out in the appended claims, it being understood that various changes in the details may be made without departing from the spirit, or sacrificing any of the advantages of the present invention.


REFERENCES:
patent: 3806579 (1974-04-01), Carles et al.
patent: 3961027 (1976-06-01), Crossley
patent: 72-011340 (1972-04-01), None

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