JPH0144646B2 - - Google Patents

Description

[Detailed description of the invention] Activity 2 under quantitative utilization of hydrogen fluoride or fluorine
The present invention relates to a method for reacting uranium dioxide and hydrogen fluoride to produce uranium tetrafluoride, and reacting uranium tetrafluoride and fluorine to produce uranium hexafluoride, without producing waste.

To produce uranium hexafluoride (UF ₆ ), uranium tetrafluoride (UF ₄ ) is first produced and reacted with elemental fluorine in a second reaction to form UF ₆ .
The production of UF ₄ is carried out industrially by reacting uranium dioxide (UO ₂ ) with anhydrous hydrogen fluoride (HF) at 500-600 °C during a drying process according to the following reaction formula: UO ₂ +4HFUF ₄ +H ₂ O At this time, since this reaction is an equilibrium reaction, it returns to the hydrolysis reaction at the same temperature, so drying
In the production of UF ₄ , the stoichiometrically required amount of hydrogen fluoride cannot be used quantitatively: approximately 7% of the amount theoretically required for the reaction is discarded as a dilute aqueous hydrofluoric acid solution during the process. Occurs in gas.

In the known production process for UF ₄ , a dilute aqueous hydrofluoric acid solution together with CaO forms insoluble calcium fluoride (CaF ₂ ), which is slightly radioactive and must be stored as active waste. Besides the fact that hydrogen fluoride is an important cost factor when producing UF ₄ , the storage of active CaF ₂ -waste also causes high costs and environmental problems.

The production of UF ₆ from UF ₄ +F ₂ =UF ₆ in a so-called reverberatory furnace is carried out almost quantitatively. However, the elemental fluorine required for this by electrolytic production still contains hydrogen fluoride, and since fluorine reacts with traces of water or moisture with the formation of HF, considerable quantities are also used in the production of UF ₆ . of HF is produced which likewise has to be converted together with CaO to CaF ₂ , further aggravating the waste problem already described.

Therefore, the problem of the present invention is to produce uranium tetrafluoride by reacting uranium dioxide and hydrofluoric acid, and to produce uranium hexafluoride by reacting uranium tetrafluoride with fluorine, which has an activity of 2. The next step was to find a way to quantitatively and completely use the hydrofluoric acid or fluorine required for the reaction without producing waste products.

This problem has been solved according to the present invention by converting hydrogen fluoride-containing and fluorine-containing waste gases generated during the reaction into uranium()-
Uranium tetrafluoride (UF ₄ 2.5H ₂ O) containing poorly soluble water of crystallization is absorbed into an ion-containing aqueous solution.
This is achieved by further processing. It is advantageous to use an aqueous solution of uranium sulphate () for the absorption.

According to the present invention, quantitative return of hydrogen fluoride and fluorine to the process, and therefore quantitative utilization thereof, can be easily achieved by fluorination from the reaction of UF ₄ - or UF ₆ -conversion. The hydrogen-containing and fluorine-containing waste gas is preferably passed through an aqueous solution of uranium sulfate (), in which the hydrogen fluoride and fluorine are converted to uranium ().
- In excess of ions, they combine quantitatively to form poorly soluble UF ₄ 2.5H ₂ O according to the following reaction formula: U(SO ₄ ) ₂ +2.5H ₂ O+4HF=UF ₄ 2.5H ₂ SO ₄ 6U (SO ₄ ) ₂ +4F ₂ +13H ₂ O=2UF ₄・2.5H ₂ O+4UO
SO ₄ +8H ₂ SO ₄ The sparingly soluble uranium tetrafluoride formed is filtered off and used directly or after drying for the production of UF ₄ or as water-free product for the production of UF ₆ . thus,
It has been achieved that during the process for the production of UF ₄ and UF ₆ hydrogen fluoride and fluorine remain quantitatively and do not give rise to active secondary waste which must be reliably stored.

The required uranium sulfate () solution is advantageously obtained by dissolving uranium trioxide (UO ₃ ) in sulfuric acid and subsequently adding U()
- ions by partial electrolytic reduction to U()- ions. A U()-compound ( _UO2 .
SO ₄ ) is similarly reduced to U(), which can be further used to absorb HF or F ₂ . However, it is not necessary to completely reduce U() to UF(), as long as U() is in sufficient excess relative to the HF- or _F2- concentration in the waste gas.

Advantageously, the U() concentration in the absorption solution is between 10 and 200 gU/U(), additional U() being present. However, it is important that U() is present in excess relative to the HF or _F2 for absorption.

It is also advantageous to circulate the uranium() solution or the uranium()/uranium() solution, in which case the filtered-off UF ₄ 2.5H ₂ O is replenished by addition of UO ₃ and subsequent reduction to uranium(). Ru.

The invention will now be explained in detail with reference to examples.

Example 1 A uranium sulfate solution containing 100 g of uranium per unit and free sulfuric acid at a concentration of 1.5N was prepared by dissolving uranium trioxide in sulfuric acid, and was electrolyzed to produce a uranium () concentration of 40 g/and a uranium () concentration of 60
It was reduced to g/g/g. The solution at 40° C. is passed through a spray washer having a sieve plate at the bottom, a filtration device placed on the side and a heat exchanger following it, first through a nozzle into the washer, then through a filter and The flow was pumped through the heat exchanger and back through the nozzle.

During this washing machine, UF ₄ - 1 kg of water vapor produced as waste gas in the equipment is passed through the descending pipes in the floor of the washing machine.
and 0.162 Kg of HF and 10 of N ₂ are introduced per minute. The resulting _UF4.2.5H2O is suction filtered from the uranium()/uranium() solution through a filter, and the solution is cooled to 40° _C in a heat exchanger.
Pump into the washer again.

The nitrogen carrier supplied in this example (little nitrogen is produced in the technical process) was continuously removed and introduced into a 10-potassium hydroxide solution vessel, if necessary to absorb any fluorine still present. Next, fluorine was measured in this potassium hydroxide solution using an electrode sensitive to fluorine ions. The amount of total fluoride in potassium hydroxide solution is small after 30 minutes.
It was HF0.317. This is for using HF162g
Corresponds to a degree of separation of 99.8%.

Example 2 1 Kg of UF ₄ .2.5H ₂ O obtained according to Example 1 was washed with water, dried at 90° C. and then mixed with 9 Kg of UO ₂ . This mixture was dried in an Inconel furnace at 550°C.
Hydrofluorination was carried out using HF. The obtained anhydrous UF ₄ was of satisfactory quality.

Example 3 UF ₄・2.5H ₂ O0.2 obtained in Example 1 and washed
Kg was carefully dehydrated in vacuo at a temperature range of 100-300°C. The anhydrous UF ₄ thus obtained was reacted with elemental fluorine to form UF ₆ in a cylindrical furnace made of finely ground Monel alloy. A very small amount of unreacted solid residue, 2.1 g, remained. Therefore, the materials used
98.95% became UF ₆ .

In this way, the _UF4 .
2.5H ₂ O can be fed into the hydrofluorination step to produce UF ₄ according to example 2 or during the fluorination step to produce UF ₆ according to example 3. Thus, the fluorination yield targeted in Example 1 was achieved in the entire process.
Make 99.98% possible.

Claims (1)

[Claims] 1. To produce tetrafluoride by reacting uranium dioxide and hydrogen fluoride without producing active secondary waste, with quantitative utilization of hydrogen fluoride or fluorine necessary for the reaction. In a method for producing uranium oxide and reacting uranium tetrafluoride and fluorine to produce uranium hexafluoride, hydrogen fluoride and fluorine-containing waste gas generated in the reaction are absorbed into an aqueous solution containing uranium ()-ions. A method for producing uranium tetrafluoride and uranium hexafluoride, characterized in that uranium tetrafluoride (UF ₄ .2.5H ₂ O) containing poorly soluble water of crystallization is further treated. 2. The method according to claim 1, wherein the uranium ()-aqueous solution contains uranium sulfate (). 3. The method according to claim 1 or 2, wherein the uranium () solution contains 10 to 200 gU/. 4. Claim 1 of manufacturing a uranium () solution by dissolving UO ₃ in sulfuric acid and subsequently reducing uranium () to uranium ().
The method according to any one of Items 1 to 3. 5. The method according to any one of claims 1 to 4, wherein the uranium ()-absorbing solution is circulated.