Process to produce commercial grade anhydrous hydrogen fluoride (AHF) and uranium oxide from the delfuorination of uranium hexafluoride (UF6)

The present invention relates generally to a method for recovering products from the defluorination of uranium hexafluoride. More particularly, the present invention relates to the recovery of commercial grade liquid anhydrous hydrogen fluoride and water insoluble stable triuranium octoxide.

BACKGROUND OF THE INVENTION

Commercially useful uranium isotopes such as U

235

have been produced in well known processes for over 40 years. The feed material for these processes have been produced from a uranium hexafluoride (UF6) enrichment process which takes natural uranium, which contains 0.7% U

235

, to suitable levels for nuclear fuel. The enrichment process leaves behind a UF

6

material that contains mostly U

238

and 0.1-0.3% U

235

. The material is referred to as depleted UF

6

(DUF

6

) and as of yet has little commercial value although there is hope in the future that new enrichment technologies will allow for more of the U

235

to be removed from the DUF

6

essentially turning it into a resource.

The DUF

6

that has been produced for the last 40 years is stored in carbon steel cylinders and amounts to around 50,000 cylinders or over 1 billion pounds of material. Storage of these cylinders is not considered a long term solution because of the potential for corrosion to the cylinders which could cause a release of the material into the environment. UF

6

reacts readily with the moisture in the air to form hydrofluoric acid and water soluble uranyl fluoride (UO

2

F

2

). It is looked upon as a potential safety and environmental hazard. It is therefore desirable to have a cost effective process which can convert the DUF

6

into its most stable insoluble form uranium oxide (U

3

O

8

). In addition, the process will create virtually no waste while recovering the hydrogen fluoride (HF) values of the DUF

6

.

While others have practiced the chemical equations mentioned in the present invention, (U.S. Pat. No. 5,346,648) no one has succeeded in putting together a complete process, or achieved the objectives of the present invention in the manner in which those objectives are achieved by the present invention. The present invention has fulfilled a long felt need for recovering commercially useful anhydrous hydrogen fluoride (AHF) from uranium hexafluoride (UF

6

). Furthermore the method of the present invention produces a stable insoluble uranium oxide, U

3

O

8

, that is less toxic than UF

6

and can be stored for future use, disposed of in a low radiation level burial site at minimal cost, or used in current shielding applications.

While the method in U.S. Pat. No. 5,346,648 appears similar to the present invention, the present invention uses a liquid phase first reactor. Because of this it has numerous advantages over its predecessor. The present invention can be run at low temperatures and pressures. It can therefore use less expensive materials of construction than the super alloys required to withstand the high temperatures described in U.S. Pat. No. 5,346,648. The present invention is easier to control than its predecessor by nature of maintaining water in excess. The only feeds to the process are UF

6

vapor and a small water makeup stream in the form of aqueous HF that is mixed into the internal recycle stream. It is safer to run than the method of U.S. Pat. No. 5,346,648 because it is run at low temperatures and pressures. Still another improvement is the intermediate uranyl fluoride hydrate that is made in present invention's liquid phase reactor which is different than the uranyl fluoride intermediate made in its predecessor. Many other improvements exist and are realized.

SUMMARY OF THE INVENTION

The present invention is a method for recovering two distinct and separable products from the defluorination of uranium hexafluoride. The first product is a commercial grade liquid anhydrous hydrogen fluoride (AHF). The second is water insoluble uranium oxide such as uranium dioxide (UO

2

), uranium trioxide (UO

3

) and preferably, stable triuranium octoxide (U

3

O

8

) which can be stored safely for future use or disposed of in a conventional manner. A liquid recycle stream consisting of the azeotrope of water and hydrogen fluoride also exists and is used as a feed stock to the primary and or secondary reactor. The present method produces a commercially valuable material while reducing the amount of hazardous material that needs to be stored or disposed of in addition to making it less of a safety and environmental concern.

The method includes a primary reactor which is a reservoir, pump tank/settler/vaporizer around which a stream of an aqueous hydrogen fluoride solution circulates. A gaseous stream of uranium hexafluoride (UF

6

) is introduced into the circulating solution. The UF

6

reacts with some of the excess water in the circulating stream producing a uranyl fluoride intermediate (UO

2

F

2

.H

2

O) and HF which dissolve in the solution. When the resulting solution has been saturated with UO

2

F

2

.H

2

O solid, the uranyl fluoride intermediate begins to precipitate out of solution and settles out at the bottom of the pump tank (settler). As water is reacted away and HF is evolved the resulting solution becomes more and more concentrated in HF and the resulting vapor is high in HF concentration. By controlling the temperature of the solution in the pump tank, HF rich vapor and water vapor essentially free of uranium can be condensed and fed into a conventional distillation column.

The solid uranyl fluoride intermediate produced is fed to a secondary reactor and reacted with water vapor to produce a uranium oxide product such as triuranium octoxide product and a gaseous mixture of water, hydrogen fluoride, and oxygen. This gaseous mixture is combined with the gaseous mixture of water and hydrogen fluoride from the primary reactor, condensed and subsequently fed into the conventional distillation column. The components are separated in a distillation column to obtain a commercial grade anhydrous hydrogen fluoride product stream overhead and an aqueous azeotropic recycle stream containing water and hydrogen fluoride. The azeotrope composition recycle stream is returned in part or in its entirety to the primary reactor as a water makeup to the system. The recycle stream can also be vaporized and combined with a small amount of makeup steam and used as a water feed source to the second reactor.

Hydrogen gas may be used in place of water as a feed to the secondary reactor with the resulting stream of HF and hydrogen

UO

2

F

2

.H

2

O+H

2

→U

3

O

8

+HF+H

2

gas (small amount) being combined with the HF rich vapor from the primary reactor, condensed and fed into the conventional distillation column. In this case makeup water will need to be fed to the primary reactor.

A third reactor may be added that would act as a fluoride stripper for soluble fluorine in the triuranium octoxide product. Solid triuranium octoxide material is fed to the reactor and contacted with steam. If the third reactor is added any makeup water that is needed for the entire system is fed to it. The resulting mixture of steam with a very slight amount of HF is fed directly into the second reactor or should a hydrogen feed be selected as a reactant in the second reactor the steam and HF mixture would be condensed and fed to the primary reactor as makeup water.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1

is a schematic flowchart of the method of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to

FIG. 1

, the units of operation include a first reactor

1

, a circulation pump

2

, a pump/settling tank/vaporizer

3

, a second reactor

4

, a fluorine stripper

5

, a separation unit

6

, two condensers

7

a

and

7

b

, two vaporizers

8

a

and

8

b

, and a transfer pump

9

. The material streams defined by the method are designated

10

-

25

and are further described with reference thereto. The pump/settling tank

3

is initially charged with a liquid hydrogen fluoride (HF) and water solution in the range of 37% to 65% HF. The solution is circulated around a closed loop (stream

10

) through the first reactor

1

. The solution is initially heated by an external source in pump/settling tank

3

close to its boiling point. The actual temperature depends on the concentration of HF in the solution, but in the range of 78-115° C. Feed stream

11

, comprised of gaseous uranium hexafluoride (UF

6

), is fed into the first reactor

1

and contacts stream

10

. The UF

6

reacts with some of the excess water in circulating stream

10

to produce a uranyl fluoride hydrate (UO

2

F

2

.H

2

O) intermediate and HF which initially dissolve in the solution by the following reaction equation (1):

UF

6

+2H

2

O→UO

2

F

2

. H

2

O

(s)

+4HF

As the UF

6

feed process continues the HF content of the solution increases and the solubility limit of UO

2

F

2

.H

2

O is reached and solid UO

2

F

2

.H

2

O precipitates out of solution and settles to the bottom of pump/settling tank

3

. As water is reacted away and HF is evolved the concentration of HF in the solution increases and the solution will begin to boil producing a HF rich vapor stream

12

comprised of between a ratio of 37.7/62.3% HF/water and make up stream

14

up to >98/<2% HF/water depending on the vapor/liquid equilibrium of the HF solution at its boiling point.

First reactor

1

and pump/settling tank

3

are kept at a pressure of 1-5 psig and a temperature dependent on the boiling point of the HF solution contained therein. The temperature is set thereby controlling the composition of vapor stream

12

. The solubility of UO

2

F

2

.H

2

O is dependent upon the concentration of HF in the solution. 6.6 weight % UO

2

F

2

.H

2

O was the observed solubility in a solution containing 38.22% HF at ambient temperature and 4.34 weight % UO

2

F

2

.H

2

O was found to be soluble in a 52.4% HF solution at ambient temperature.

Two outlet streams

12

and

13

are recovered separately from the pump/settling tank

3

. Stream

13

is comprised of a slurry of solid UO

2

F

2

.H

2

O and HF/water/ UO

2

F

2

.H

2

O solution that is fed into second reactor

4

. The HF and water in the stream are boiled off as it enters the hot second reactor essentially drying the solids. Some reaction does occur between the water and UO

2

F

2

, but it is incomplete so steam (stream

20

) is also fed to second reactor

4

in a stoichiometric excess to the amount of UO

2

F

2

.H

2

O in stream

13

and preferably at an excess of from about 200 to 500%. The steam finishes the reaction of the UO

2

F

2

.H

2

O in second reactor

4

which is maintained at a temperature of 427-704° C. and preferably between 538 and 649° C. Second reactor

4

is maintained at a pressure between about 0-5 psig and preferably between about 2-4 psig.

The reaction products of water and uranyl fluoride leave second reactor

4

separately as stream

24

and

25

which are characterized by the following generalized reaction equation (2):

3UO

2

F

2

+3H

2

O→U

3

O

8(s)

+6HF+0.5O

2

(2)

As indicated by equation (2), outlet stream

25

comprises solid triuranium octoxide (U

3

O

8

) product with a less than 200 ppm soluble (unreacted) fluoride content and outlet stream

24

comprises a gaseous mixture of water, HF, and oxygen. The U

3

O

8

of stream

25

is fed to a fluorine stripper

5

if it does not meet the specification for concentration of soluble fluorides. Water fed into vaporizer

8

a

is turned into steam (stream

23

) and is fed into fluorine stripper

5

in a large stoichiometric excess from about 200 to 500% of the amount of UO

2

F

2

.H

2

O in stream

25

. Two separate outlet streams,

20

and

22

, leave fluoride stripper

5

. Product stream

22

comprises triuranium octoxide product with a less than 25 ppm soluble fluoride concentration and is isolated from the process for storage or disposal. Stream

20

, comprised of essentially steam, becomes a feed stream to second reactor

4

. If fluorine stripper

5

is not necessary stream

23

and stream

20

are the same, as are stream

25

and

22

.

As a variation, stream

13

is reacted with hydrogen gas instead of steam or HF/water azeotrope as a water source in second reactor

4

. Stream

20

becomes hydrogen. In that case the outlet streams

24

and

25

are characterized by the generalized equations (3) and (4).

2UO

2

F

2

+2H

2(excess)

→2UO

2

+4HF+2H

2

O+H

2(excess)

(3)

3UO

2

+O

2

→U

3

O

8

(4)

Outlet stream

25

, comprised of UO

2

is unstable at elevated temperatures and reacts to the triuranium octoxide when exposed to air after second reactor

4

. If hydrogen is used as the feed and the fluorine stripper

5

is necessary then the stream outlet of fluorine stripper

5

goes to pump/settling tank

3

as the water makeup for the system.

First reactor

1

and second reactor

4

outlet streams

12

and

24

respectively are combined before condenser

7

a

to form stream

19

comprised of a gaseous mixture of HF/water/oxygen and in some cases H

2

. Stream

19

is cooled as it passes through condenser

7

a

and depending on the temperature and pressure conditions of stream

19

it may be entirely in a liquid state, but more than likely it will be in two states, a gaseous state comprised mainly of oxygen and a liquid state comprised of HF and water. Stream

19

becomes a feed to separation unit

6

. It is further understood that streams

12

and

24

may not be combined before separation unit

6

, but may be mixed inside separation unit

6

internally without the use of condenser

7

a.

Regardless, separation unit

6

is a distillation column wherein stream

19

is separated into two separate streams

15

and

16

. Stream

16

is a gaseous mixture of HF and oxygen essentially free of water and uranium. Outlet stream

16

is subsequently fed to condenser

7

b

from which a gaseous stream

17

comprised essentially of oxygen, which will be vented to a scrubber and a liquid stream

18

composed of commercial grade anhydrous hydrogen fluoride with less than 1 ppm uranium and less than 500 ppm water which is packaged for transfer to customer end use. Outlet stream

15

is a liquid stream comprised of about 37% HF and about 63% water which is the azeotrope composition of HF/water and is used in its entirety or in part as recycle feed to first reactor

1

and second reactor

4

. Transfer pump

9

moves stream

15

after which stream

15

is split into recycle streams

14

and

21

. Stream

14

is recycled as a liquid to first reactor

1

to keep a constant level and desired HF concentration in first reactor

1

. Stream

21

is vaporized and recycled back and used as a substitute or supplement to feed stream

20

into second reactor

4

. After the recycle streams

14

and

21

are going the amount of water makeup to the entire system in the form of stream

23

is adjusted to keep the system at steady-state operation or in other words the stoichiometric amount needed to react with the UF

6

feed from stream

11

.

The following examples demonstrate the practice and utility of the present invention, but are not to be construed as limiting the scope thereof.

EXAMPLES

Example 1

Example 1 is an example of the first reactor starting with a 38.92% HF solution. 3038.8 grams of an 38.92% HF/water solution were originally charged to a 3.7 liter vessel used as the pump/settling tank. A small diaphragm pump circulated the solution around a closed loop system and past a nozzle located inside a mixing tee which acted as the reactor. A UF

6

feed cylinder was prepared and placed on a scale. An inert gas, nitrogen (N

2

), purge was flowing through the UF

6

feed line, out the nozzle and into the circulating HF solution to keep the nozzle free of moisture. The UF

6

feed was turned on and co-fed with the nitrogen. The nitrogen purge was decreased over time until it was completely turned off. A solution 38.92% HF, was added during the experiment totaling 621.2 grams. A total of 853.6 grams of UF

6

was fed to the reactor system. UO

2

F

2

/HF/water slurry material were drained out of the pump/settling tank periodically during the experiment. The reactor was kept at atmospheric pressure during the run by venting the vessel through a brine condenser. Any vapors that passed from the brine condenser were captured in an absorber filled with potassium hydroxide (KOH) solution of strength 27.30% KOH. After the run the resulting material in the reactor system, the caustic absorber, and the UO

2

F

2

/HF/water slurry collected during the run were analyzed and a detailed mass balance on HF, water, and UO

2

F

2

was performed. Results indicated that 99.06% of the theoretical amount of HF was collected, 98.58% of the UO

2

F

2

was accounted for and 91.71% of the water was accounted for. The UO

2

F

2

was analyzed for purity by testing it for % soluble fluorides. Since UO

2

F

2

is soluble in water the analysis for soluble fluorides is a good test to check its purity. An unexpected discovery was made using this analysis. The amount of soluble fluoride in the sample was found to be 11.50% and the amount of soluble fluoride in pure UO

2

F

2

is 12.34%. The amount of soluble fluoride in a UO

2

F

2

hydrate however is 11.62%. It was discovered that a hydrated UO

2

F

2

.H

2

O material is made when UF

6

reacts with water in the liquid form. See Table 1 for results.

Example 2

Example 2 is a demonstration of the second reactor starting with some of the slurry material collected from Example 1. Four experiments numbered 26-29 were conducted using a 2″ diameter MONEL muffle reactor with an external electric heating source. For each experiment a monel container was filled with about 9-10 grams of the UO

2

F

2

.H

2

O/HF/water slurry material. The composition of the slurry was 28.83% UO

2

F

2

.H

2

O, 32.83% HF, and 38.34% water. The boats were placed in the muffle reactor and heated to 649° C. for 15-30 minutes. The reactor was kept at atmospheric pressure by venting the reactor to a caustic absorber. A slight 20 cc/min nitrogen purge was put on the reactor. The % conversion is found by analyzing the material for soluble fluorides since UO

2

F

2

dissolves in water and the triuranyl octoxide product does not. The results found in Table 2 show that the conversion of UO

2

F

2

to U

3

O

8

was from about 58.8 to about 64% indicating that the HF and water had boiled off before the reaction was complete as the material left behind was dry. An additional source of water in the form of steam or HF/water azeotrope was fed to the second reactor to complete the reaction. See Table 2 for results.

Example 3

Example 3 is a demonstration of the second reactor using pre-dried UO

2

F

2

.H

2

O obtained from the experiment in example 1 and reacted to completion with a steam feed. Pre-dried UO

2

F

2

.H

2

O was obtained from the slurry material from Example 1 by putting a sample of the slurry in a platinum dish and drying it under a UV lamp. 43.6727 grams of slurry were placed in a platinum dish and dried over night. 12.5293 grams or 28.69% of the original material was left in the dish. It was analyzed for soluble fluorine and had 11.50% which is the amount found in a UO

2

F

2

hydrate, namely UO

2

F

2

.H

2

O. Eight experiments numbered 16-S-23S were run using the same reactor setup as above. Temperatures of 538 and 649° C. were used at different residence times and excess water amounts. All the experiments ran at 649° C. showed greater than 99.9% conversion of UO

2

F

2

to U

3

O

8

with only about 20.6 ppm to 87.6 ppm soluble fluoride left in the product. The experiments using 538° C. temperatures ranged from about 57 to about 90% conversion. See Table 3 for results.

Example 4

Example 4 is a demonstration of the second reactor using HF/water azeotrope as a water source instead of steam with pre-dried UO

2

F

2

.H

2

O obtained from the experiment in Example 1. One experiment numbered

33

-A was run using the same reactor setup as Example 3. A temperature of 649° C. was chosen. The experiment showed greater than 99.9% conversion of UO

2

F

2

to U

3

O

8

with about 2.23% soluble fluoride left in the product. See Table 4 for results.

Example 5

Example 5 is a demonstration of the second reactor using hydrogen to reduce the UO

2

F

2

to U

3

O

8

with pre-dried UO

2

F

2

.H

2

O obtained from the experiment in example 1 and reacted to completion. One experiment numbered

25

-H was run using the same reactor setup as above. A temperature of 649° C. was chosen and a 100 cc/min hydrogen feed with a 100 cc/min nitrogen (inert gas) co-feed was used. The experiment showed greater than 99.9% conversion of UO

2

F

2

to U

3

O

8

with less than 100 ppm soluble fluoride left in the product. See Table 5 for results.

Example 6

Example 6 is an example of the first reactor starting with a 64.73% HF solution. It demonstrates the first reactor with a high concentration of HF and the composition of the vapor that can be expected when the UF

6

feed is on. It is also an excellent demonstration of a flash distillation of the pump/settling tank contents. 3202.9 grams of an 64.73% HF/water solution were originally charged to a vessel used as the pump/settling tank. The solution was heated to its boiling point of about 78° C. A brine condenser was attached to the vapor port on the top of the vessel. The noncondensibles were vented from the vessel through the brine condenser until the vessel vapors comprised of HF/water were condensing and refluxing back into the tank. A small diaphragm pump circulated the solution around a closed loop system and past a nozzle located inside a mixing tee which acted as the reactor. A UF

6

feed cylinder was prepared and placed on a scale. An inert gas, N

2

, was flowing through the UF

6

feed line, out the nozzle and into the circulating HF solution to keep the nozzle free of moisture. The UF

6

feed was turned on and co-fed with the nitrogen. The nitrogen purge was decreased over time until it was completely turned off. Initially enough UF

6

was fed to saturate the HF solution with UO

2

F

2

. The UF

6

feed was stopped and a flash distillation was done on the saturated solution. A total of four reflux samples were taken and analyzed for %HF and concentration of uranium. They showed greater than 98% HF and between about 0.33 and 2.15 ppm uranium after reaching steady state.

The UF

6

feed was resumed using a slight, 0-130 cc/min, co-feed of nitrogen. During the time that UF

6

was being fed a total of four vapor reflux samples and analyzed for %HF and concentration of uranium. The feed rate of UF

6

was varied for each sample. The %HF ranged from about 93% to about 99%. The uranium concentration ranged from about 0.58 ppm to about 240 ppm.

A total of 392.9 grams of UF

6

was fed to the reactor system. The reactor was kept at atmospheric pressure during the run by venting the vessel through a brine condenser. Any vapors that escaped from the brine condenser were captured in a startup absorber filled with potassium hydroxide (KOH) solution of strength 20.53% KOH or a parallel run absorber filled with Distilled and Deionized water. After the run the resulting material in the reactor system, each absorber, and all samples collected during the run were analyzed and a detailed mass balance on HF, water, and UO

2

F

2

was done. Results indicated that 98.24% of the theoretical amount of HF was collected, 95.16% of the UO

2

F

2

was accounted for and 96.64% of the water was accounted for. Results of these experiments are summarized in Table 6.

Example 7

Example 7 demonstrated that a distillation column could make anhydrous hydrogen fluoride that was within existing commercial grade specifications for uranium. A distillation column was constructed consisting of a vessel with external electric heating source for a reboiler, a column packed with Kynar mesh packing, and a tube in tube condenser. The theoretical plates were calculated to be 10.6.

The results of vapor reflux samples taken from Example 7 were used to synthesize a representative reboiler charge. The charge consisted of 0.0958 grams of UO

2

F

2

added to 1481.6 grams of 64.73% HF solution to make up a reboiler charge with a 50 ppm uranium concentration.

The reboiler was heated to 79-80° C. until the reboiler contents boiled. The noncondensibles were vented off the top of the condenser through the brine condenser until a liquid reflux was established. The column pressure was kept at atmospheric pressure. After 1.25 hours a sample of the reflux liquid was taken and analyzed for HF concentration (by titration) and uranium content (by ICP-MS). The sample was high in uranium concentration as the column had not come to equilibrium yet. It was already seen that the distillation would work because of the results of the flash distillation experiment done earlier with a saturated (4.34% UO

2

F

2

) 65% HF solution in example 6. Samples were taken periodically and analyzed for both HF concentration and U until the 1 ppm U spec was satisfied. Sample 4 had a 0.76 ppm U concentration. All samples taken were greater than 99% HF. Results of these experiments are summarized in Table 7.

TABLE 1

1st Reactor Mass Balance

IN

3670 total gms 38.92% HF solution

1428.4 grams of HF from starting and make-up solutions

2241.6 grams of H

2

O from starting and make-up solutions

853.5 total grams of UF

6

fed

Theoretical amount of UO

2

F

2

and HF produced

UF

6

+

2H

2

O

−>

UO

2

F

2

+

4HF

Moles

2.4

4.8

2.4

9.7

Grams

853.5

97.0

746.8

194.0

1622.3 total grams of HF IN

2144.6 total grams of water IN

OUT

Total Out

1607.1 grams HF

736.2 grams UO

2

F

2

1966.8 grams H

2

O

Mass Balance Calculation

HF

1607.1/1622.3*100 =

99.06%

UO

2

F

2

736.2/746.8*100 =

98.58%

H

2

O

1966.9/2144.6*100 =

91.71%

Analysis of UO

2

F

2

product shows a soluble fluoride

content of 11.50% F

−

. This is a UO

2

F

2

hydrate because

pure UO

2

F

2

has 12.34% soluble F

−

and UO

2

F

2

.H2O has 11.62%

soluble F

−

.

TABLE 2

2nd Reactor Pyrohydrolysis of UO

2

F

2

.H

2

O/HF/H

2

O Slurry

Purpose is to see if the slurry from the liquid phase reactor

will react to completion without additional water feed.

3UO

2

F

2

+ 3H

2

O −> U

3

O

8

+ 6HF + 1/2O

2

Residence

Temp. ° C.

* Soluble F

−

% Conv.

Act. slurry

Time

Actual

in product

of

EXP #

wt. (gm)

(min)

(Ave.)

%

UO

2

F

2

26

8.9524

30

645

4.42%

64.2

27

9.5387

30

654

5.08%

58.8

28

9.2622

30

653

4.40%

64.3

29

9.2891

30

653

4.68%

62.1

The starting material was from the 1st reactor with a starting HF solution of 38.92% strength from Example 1. The uranium compound, by soluble F

−

analysis, appears to be a UO

2

F

2

.H

2

O hydrate.

* Note:

Starting UO

2

F

2

.H

2

O hydrate had 11.50% soluble F

−

by the same analytical method. Pure UO

2

F

2

.H

2

O has 11.65% soluble F

−

.

TABLE 3

Design of Experiments for 2nd Reactor Pyrohydrolysis

Steam Feed

Amount of

DESIGN

Amount

Residence

Feed rate

Steam

% Excess

EXP #

UO

2

F

2

(gms)

Temp (° C.)

Time (min)

(g/min)

feed (gms)

H

2

O

16-S

4.0

649

15

0.33

5

2038.9

17-S

4.0

649

15

1.00

15

6316.7

18-S

4.0

649

30

0.17

5

2038.9

19-S

4.0

649

30

0.50

15

6316.7

20-S

4.0

538

15

0.33

5

2038.9

21-S

4.0

538

15

1.00

15

6316.7

22-S

4.0

538

30

0.17

5

2038.9

23-S

4.0

538

30

0.50

15

6316.7

3UO

2

F

2

+ 3H

2

O → U

3

O

8

+ 6HF + ½O

2

H

2

O needed

U

3

O

8

U

3

O

8

U

3

O

8

% Conv.

H

2

O Feed

Temp. ° C.

*Soluble F

ACTUAL

Act. UO

2

F

2

UO

2

F

2

wt. (gm)

moles

wt. (gm)

wt. (gm)

of

wt. (gm)

% excess

Actual

in product

EXP #

wt. (gm)

moles

Theory

Theory

Theory

Actual

UO

2

F

2

Actual

H

2

O

(Ave.)

ppm or %

16-S

3.9998

0.0130

0.2338

0.0043

3.6448

3.6774

99.99

5

2039

645

<75

17-S

4.0002

0.0130

0.2338

0.0043

3.6452

3.6569

99.99

15

6316

654

<25

18-S

4.0002

0.0130

0.2338

0.0043

3.6452

3.6812

99.99

5

2039

653

<90

19-S

4.0000

0.0130

0.2338

0.0043

3.6450

3.6642

99.99

15

6317

653

<25

20-S

4.0002

0.0130

0.2338

0.0043

3.6452

3.8676

53.79

5

2039

543

5.31%

21-S

3.9999

0.0130

0.2338

0.0043

3.6449

3.8177

65.54

15

6317

534

3.96%

22-S

3.9999

0.0130

0.2338

0.0043

3.6449

3.8539

53.70

5

2039

541

5.32%

23-S

4.0002

0.0130

0.2338

0.0043

3.6452

3.7163

89.08

15

6316

539

1.26%

The starting material was from the 1st reactor with a starting HF solution of 38.92% strength from Example 1.

The uranium compound, by soluble F

−

analysis, appears to be a UO

2

F

2

.H

2

O hydrate.

*Note:

Starting UO

2

F

2

.H

2

O hydrate had 11.50% soluble F

−

by the same analytical method. Pure UO

2

F

2

.H

2

O has 11.65% soluble F

−

.

TABLE 4

1st Reactor Material Pyrohydrolysis using HF/water Azeotrope as a Water Source

HF/water azeo feed

Amount of

DESIGN

Amount

Residence

Feed rate

Steam

% Excess

EXP #

UO

2

F

2

Temp (° C.)

Time (min)

(g/min)

feed (gms)

H

2

O

33-A

4.0

649

60

0.50

30

12733.3

3UO

2

F

2

+ 3H

2

O → U

3

O

8

+ 6HF + ½O

2

H

2

O needed

U

3

O

8

U

3

O

8

U

3

O

8

% Conv.

H

2

O Feed

Temp. ° C.

*Soluble F

ACTUAL

Act. UO

2

F

2

UO

2

F

2

wt. (gm)

moles

wt. (gm)

wt. (gm)

of

wt. (gm)

% excess

Actual

in product

EXP #

wt. (gm)

moles

Theory

Theory

Theory

Actual

UO

2

F

2

Actual

H

2

O

(Ave.)

ppm or %

33-A

4.1530

0.0135

0.2427

0.0045

3.7844

3.9601

81.93

35

14321

649

2.23%

The starting material was from the 1st reactor with a starting HF solution of 38.92% strength from Example 1.

The uranium compound, by soluble F

−

analysis, appears to be a UO

2

F

2

.H

2

O hydrate.

*Note:

Starting UO

2

F

2

.H

2

O hydrate had 11.50% soluble F

−

by the same analytical method. Pure UO

2

F

2

.H

2

O has 11.65% soluble F

−

.

TABLE 5

2nd Reactor Pyrohydrolysis Reactions of UO

2

F

2

H

2

feed

2UO

2

F

2

.H

2

O + 2H

2

→ 2UO

2

+ 4HF + 2H

2

O

3UO

2

+ O

2

→ U

3

O

8

Nitrogen

Hydrogen

DESIGN

Amount

Residence

Feed rate

Feed rate

EXP #

UO

2

F

2

Temp (° C.)

Time (min)

(cc min)

(cc/min)

25-H

4.0

649

30

100

100

Actual

H

2

needed

U

3

O

8

U

3

O

8

1

U

3

O

8

% Conv.

H

2

feed

Temp. ° C.

*Soluble F

ACTUAL

UO

2

F

2

.H

2

O

UO

2

F

2

wt. (gm)

moles

wt. (gm)

wt. (gm)

of

amount (g)

% excess

Actual

in product

EXP #

wt. (gm)

moles

Theory

Theory

Theory

Actual

UO

2

F

2

Actual

H

2

feed

(Ave.)

ppm

25-H

4.0009

0.0126

0.0252

0.0042

3.5312

3.5581

99.99

4.65

18384

649

<100

The starting material was from the 1st reactor with a starting HF solution of 38.92% strength from Example 1.

The uranium compound, by soluble F

−

analysis, appears to be a UO

2

F

2

.H

2

O hydrate.

*Note:

Starting UO

2

F

2

.H

2

O hydrate had 11.50% soluble F

−

by the same analytical method. Pure UO

2

F

2

.H

2

O has 11.65% soluble F

−

.

1

The color of the product was a uniform deep olive green.

TABLE 6

1st Reactor Mass Balance

1st reactor was run with a starting HF solution concentration of

64.73% HF.

IN

3202.9 grams of 64.73% HF solution

1129.7 grams of H

2

O from starting solution

2073.2 grams of HF from starting solution

392.9 total grams of UF

6

fed

Theoretical amount of UO

2

F

2

and HF produced

UF

6

+

2H

2

O

−>

UO

2

F

2

+

4HF

Moles

1.12

2.23

1.12

4.46

Grams

392.9

44.6

343.8

89.3

2162.5 total grams of HF IN

1085.0 total grams of H

2

O IN

OUT

Total Out

2124.38 grams HF

327.15 grams UO

2

F

2

1048.51 grams H

2

O

Mass Balance Calculation

HF

2124.38/2162.5*100 =

98.24%

UO

2

F

2

327.15/343.8*100 =

95.16%

H

2

O

1048.51/1085.0*100 =

96.64%

The results of the flash distillation of a 65% HF solution saturated

with UO

2

F

2

are as follows:

Elapsed

Sample

Sample

Time (min)

Size (gm)

% HF

U conc.

1

60

11.76

66.22

<1.40 ppm

2

75

18.86

99.50

<0.36 ppm

3

120

24.52

99.74

<0.35 ppm

4

135

12.96

98.79

<2.16 ppm

The results of the analysis of pump tank vapor samples when UF6

feed was on are as follows:

Sample

UF

6

Rate

Sample

Size (gm)

(g/min)

% HF

U conc.

1

10.39

NA

99.29

<0.58 ppm

2

12.77

3.5

98.71

<0.14 ppm

3

3.90

1.4

93.07

<240 ppm

4

13.32

4.8

99.15

<11 ppm

TABLE 7

Distillation Results/Data

A distillation column was constructed consisting of a reboiler, 16″ L × 1″ OD column packed with

Kynar mesh packing, and a tube in tube condenser. The theoretical plates were calculated to be 10.6.

0.0958 grams of UO

2

F

2

were added to 1481.6 grams of 64.73% HF solution to make a 50 ppm uranium

concentration reboiler charge.

Samples were taken periodically and analysed for both HF and uranium concentration until the 1 ppm

uranium spec (set as an experimental goal) was satisfied. Results/data are as follows:

Elapsed

Sample

Sample

Time (min)

Size (gm)

% HF

U conc.

1

75 min

35.05

99.10

<54 ppm

2

174 min

32.43

99.25

<8 ppm

3

206 min

32.24

99.70

<1.6 ppm

4

248 min

32.1

99.00

<0.8 ppm

Splitter

Top

System

Cooling

Set Time

Elapsed

Reboiler

Column

Reflux

Pressure

in Temp

seconds

Time (min)

Temp ° C.

Temp ° C.

Temp ° C.

psig

° C.

closed/open

Comments

0

79.1

44

35

0

−16.5

reflux visible

9

81.3

44

40

0

−16.4

44

84.1

23

23

0

−11.5

77

82.9

21

22

0

−18.8

6/2

start sample 1

166

86

19

20

0

−16.4

6/1

start sample 2

176

84.6

17

18

0

−16.7

6/1

end sample 1

196

90

21

22

0

−17.7

8/1

start sample 3

215

90.5

21

22

0

−17.1

8/1

end sample 3

240

94.5

23

24

0

−16.7

15/1

start sample 4

From the Examples, it is apparent that the method of the invention provides a complete process that can run at low temperatures and pressures so that less expensive materials can be used to produce the apparatus.

While the particular process for recovery of anhydrous hydrogen fluoride and uranium oxide products from depleted, natural or enriched uranium hexafluoride as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of operation herein shown other than as described in the appended claims.

Number	Name	Date	Kind
3333930	Grant et al.	Aug 1967	A
3765844	Rode	Oct 1973	A
3906081	Welty	Sep 1975	A
3978194	Knudsen et al.	Aug 1976	A
4053559	Hart et al.	Oct 1977	A
4397824	Butler et al.	Aug 1983	A
4830841	Urza	May 1989	A
5066429	Larson et al.	Nov 1991	A
5346684	Mestepey	Sep 1994	A

Process to produce commercial grade anhydrous hydrogen fluoride (AHF) and uranium oxide from the delfuorination of uranium hexafluoride (UF6)

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

CPC

US Classifications

Field of Search

US

International Classifications

Term Extension

Abstract

Description

Claims

US Referenced Citations (9)