阅读说明：本技术 用于将六氟化铀转化为二氧化铀的方法和设备 (Method and apparatus for converting uranium hexafluoride to uranium dioxide ) 是由 安德烈·弗吉耶 布鲁诺·梅索纳 阿兰·雅各比 于 2018-10-09 设计创作，主要内容包括：一种转化方法包括的步骤是通过注入到水解反应器(4)中的气态的UF-6和干燥蒸汽之间的反应而在反应器(4)中将UF-6水解为氟氧化铀(UO-2F-2)；通过UO-2F-2与注入到高温水解炉(6)中的干燥蒸汽和气态二氢(H-2)的反应而在炉(6)中将UO-2F-2高温水解为UO-2；通过包括多个过滤器(52)的捕获装置(50)提取反应器(4)中的过量气体；通过从反应器(4)的外部到内部向过滤器(52)中注入中性气体以使粘附在过滤器(52)上的粉末分离来定期疏通过滤器(52)；以及测量反应器(4)中的相对压力,该转化方法还包括在反应器(4)中的相对压力超过预定的间歇性疏通阈值时实施过滤器(52)的间歇性疏通。(A conversion method comprises the step of passing gaseous UF injected into a hydrolysis reactor (4) 6 And drying steam to UF in reactor (4) 6 Hydrolysis to Uranium Oxyfluoride (UO) 2 F 2 ) (ii) a By UO 2 F 2 With the dry steam and gaseous dihydrogen (H) injected into the pyrohydrolysis furnace (6) 2 ) In a furnace (6) to react UO 2 F 2 Hydrolysis at high temperature to UO 2 (ii) a Extracting excess gas in the reactor (4) by a capture device (50) comprising a plurality of filters (52); through the inner part from the outside of the reactor (4)Partially injecting neutral gas into the filter (52) to separate powder adhered to the filter (52) to periodically unblock the filter (52); and measuring the relative pressure in the reactor (4), the conversion method further comprising effecting intermittent unblocking of the filter (52) when the relative pressure in the reactor (4) exceeds a predetermined intermittent unblocking threshold.)

1. A method for extracting uranium hexafluoride (UF)₆) Conversion to uranium dioxide (UO)₂) The transformation method of (3), which comprises the steps of:

-by gaseous UF injected into the reactor (4) for hydrolysis₆And drying water vapour to obtain UF in said reactor (4)₆Hydrolysis to Uranium Oxyfluoride (UO)₂F₂)；

By UO₂F₂With dry steam and hydrogen (H) injected into the furnace (6) for high-temperature hydrolysis₂) In said furnace (6) to react UO₂F₂Hydrolysis at high temperature to UO₂；

-extracting excess gas in the reactor (4) by means of a capture device (50) comprising a plurality of filters (52);

-periodically unblocking the filter (52) by injecting a neutral gas into the filter (52) from outside to inside the reactor (4) to remove the powder adhering to the filter (52); and

-measuring the relative pressure in the reactor (4),

the conversion process further comprises effecting a scheduled unblocking of the filter (52) when the relative pressure in the reactor (4) exceeds a predetermined scheduled unblocking threshold.

2. The conversion process according to claim 1, comprising injecting a neutral scavenging gas into the reactor (4) to allow UF₆To UO₂F₂The conversion of (2) is carried out under a nitrogen atmosphere.

3. The reforming process according to claim 1 or 2, wherein the water vapor and H are dried₂Is injected into the furnace (6) so as to react with UO in the furnace (6)₂F₂Is circulated in countercurrent to the reactor (4).

4. The conversion process according to any one of the preceding claims, comprising shutting down the conversion plant when the relative pressure in the reactor (4) exceeds a predetermined safety threshold.

5. Conversion method according to claim 4, wherein the safety threshold is between 100mbar and 500mbar, preferably between 200mbar and 450 mbar.

6. Conversion method according to claim 4 or 5, wherein the on-demand unblocking threshold is set, for example, in the range of 100mbar below the safety threshold, and for example 50mbar, preferably 30mbar below the safety threshold.

7. The conversion process according to any one of the preceding claims, comprising vibrating and/or impacting the walls of the reactor (4), preferably periodically or continuously during conversion.

8. Conversion method according to claim 7, wherein the vibration is performed by means of a flow device (56) comprising at least one flow member (58) designed to vibrate and/or impact the wall of the reactor (4) directly or via an intermediate component, such as a removable intermediate component.

9. The transformation method of any preceding claim, comprising introducing UO into the cell₂F₂Conversion to UO₂Of the striking surface (62) of the furnace (6) to remove UO adhering to the inner surface of the furnace (6)₂F₂Or UO₂The powder of (4).

10. Conversion process according to claim 9, wherein the furnace (6) comprises a rotating drum (32) for receiving a UO₂F₂And injecting dry steam and H therein₂Said striking surface (62) being an outer surface of said drum (32).

11. The conversion method according to claim 9 or 10, wherein the step of striking is performed using at least one striking device (60) comprising a striker (64) movable with respect to the striking surface (62) and an intermediate part (66) arranged between the striker (64) and the striking surface (62) such that the striker (64) strikes the striking surface (62) via the intermediate part (66), the intermediate part (66) being movable between a position spaced apart from the striking surface (62) and a striking position in contact with the striking surface (62).

12. A conversion installation designed for carrying out a conversion process according to any one of the preceding claims.

Technical Field

The invention relates to uranium dioxide (UO)₂) Field of production of powders, in particular for manufacturing UO for nuclear fuel rods₂And (3) a core block.

Background

Possibly with uranium hexafluoride (UF)₆) Concentrating the uranium in the form of (1). However, UF then needs to be added₆Conversion to UO₂To make UO₂And (3) a core block.

For this purpose, UF may be used₆Gas and dry steam are injected into the reactor and gaseous UF is hydrolyzed in the reactor₆Conversion to Uranium Oxyfluoride (UO)₂F₂) To obtain UO₂F₂Powder, then by passing UO₂F₂The powder is circulated in a furnace and dry steam and hydrogen (H) are injected into the furnace₂) And UO by high temperature hydrolysis in a furnace₂F₂Conversion of powder to UO₂And (3) powder.

In order to obtain UO of uniform quality₂Powder, can be installed in the furnace to allow vigorous stirring of the UO₂F₂Powdering and promoting UO₂F₂Means for contacting the powder with hydrogen and water vapor.

Successively UF₆→UO₂F₂→UO₂The byproduct of the conversion is Hydrogen Fluoride (HF) gas, which is extremely toxic and corrosive.

The hydrolysis reaction is carried out under an atmosphere of neutral gas (or inert gas), preferably under a nitrogen atmosphere. For this purpose, a neutral gas is injected into the reactor, forming a gas stream which is swept across the reactor.

In the production phase, in order to avoid overpressure in the conversion plant, it is possible to use a device for retaining the particles in suspension (in particular UO)₂F₂And UO₂Particles) filter out neutral gas, excess reaction gas and hydrogen fluoride produced by the conversion.

The filter becomes gradually clogged and can be periodically unclogged by counter-current injection of neutral gas.

In order to prevent the formation of agglomerates of powders on the inner walls of the pyrohydrolysis furnace, the transformation device may be provided with striking members that strike the outer walls of the furnace.

US6136285 discloses such a method for UF₆Conversion to UO₂To a plant for carrying out this transformation process.

In this conversion process, UO is formed in the form of a sinterable powder₂To form UO by sintering₂And (3) a core block.

It is difficult to constantly obtain a good quality UO over time₂Powders, i.e. having satisfactory properties, in particular with respect to apparent density, specific surface area, particle size and chemical composition.

To meet the requirements for use in the nuclear industry, for forming UOs₂UO of pellets₂The powder must be homogeneous. It must have as low a content of impurities as possible (mainly fluorine) and preferably less than 50ppm (50 μ g/g UO)₂) Specific surface area of 1m²G and 4m²Between/g, the oxygen/uranium ratio is between 1.80% and 2.50%, and the relative humidity is less than 1%. It must have good mixing capacity and spontaneous flow capacity (fluidity) so that it can withstand high pellet production rates. Preferably, it also has a uniform particle size distribution (normal law) and reactivity (or sinterability) to natural sintering, so that greater than UO can be obtained on the sintered ceramic pellets₂A density of 96.5% of theoretical density and a hardness of more than 15 daN/m.

In order to obtain a homogeneous UO of constant mass₂Powder ofIt is preferred that the conversion plant is operated continuously and without sudden stops. The accumulation of powder on the filter member can cause the filter to gradually clog, and the resulting increased pressure drop can cause the internal pressure of the conversion apparatus to increase. Such pressure changes may cause the conversion equipment to shut down by exceeding a pressure threshold for cleaning or replacing the filter before the conversion equipment is brought to safety.

US7422626 teaches a method for achieving efficient and uniform unclogging of the filter of a filtering means, which does not interrupt the discharge of gas, thus increasing the efficiency of the plant.

However, the described process is not optimal and may lead to variations in the operating parameters of the conversion plant and the UO produced₂The characteristics of the powder change.

Disclosure of Invention

It is an object of the present invention to provide a method for converting UF₆Conversion to UO₂Can increase the yield of the conversion process and at the same time produce a homogeneous UO of constant quality₂And (3) powder.

To this end, the invention provides a process for the precipitation of uranium hexafluoride (UF)₆) Conversion to uranium dioxide (UO)₂) By gaseous UF injected into the hydrolysis reactor₆And drying the reaction between water vapor to UF in the reactor₆Hydrolysis to Uranium Oxyfluoride (UO)₂F₂) (ii) a By UO₂F₂With dry steam and hydrogen (H) gas injected into the pyrohydrolysis furnace₂) In a furnace to react UO₂F₂Hydrolysis at high temperature to UO₂(ii) a Extracting excess gas in the reactor through a capture device comprising a plurality of filters; periodically cleaning the filter by injecting neutral gas into the filter from the outside to the inside of the reactor to remove powder adhered to the filter; and measuring the relative pressure in the reactor, the conversion method further comprising performing a scheduled unblocking of the filter when the relative pressure in the reactor exceeds a predetermined scheduled unblocking threshold.

According to a particular embodiment, the transformation process comprises the following optional features considered individually or in any technically feasible combination:

it comprises injecting a neutral scavenging gas into the reactor to allow UF₆To UO₂F₂The conversion of (a) is carried out under a nitrogen atmosphere;

drying the steam and H₂Is injected into the furnace so as to be in contact with the UO in the furnace₂F₂Circulating counter-currently towards the reactor;

-it comprises shutting down the conversion device when the relative pressure in the reactor exceeds a predetermined safety threshold;

-a safety threshold value between 100mbar and 500mbar, preferably between 200mbar and 450 mbar;

the on-demand unblocking threshold is set, for example, in a range of 100mbar below the safety threshold, and, for example, 50mbar, preferably 30mbar below the safety threshold;

it comprises vibrating and/or impacting the walls of the reactor, preferably periodically or continuously during the conversion;

-performing the vibration by means of a flow device comprising at least one flow member configured to vibrate and/or impinge on a wall of the reactor directly or via an intermediate component, e.g. a removable intermediate component;

it is included in the UO₂F₂Conversion to UO₂To remove UO adhering to the inner surface of the furnace₂F₂Or UO₂The powder of (4);

the furnace comprises a drum for receiving the UO₂F₂And injecting dry steam and H therein₂The striking surface is the outer surface of the drum;

the step of striking is performed using at least one striking device comprising a striker movable relative to a striking surface and an intermediate part arranged between the striker and the striking surface, such that the striker strikes the striking surface via the intermediate part, the intermediate part being movable between a position spaced apart from the striking surface and a striking position in contact with the striking surface.

The invention also relates to a transformation device designed for implementing the transformation method defined above.

Drawings

The invention and its advantages will be better understood on reading the following description, given by way of example only and made with reference to the accompanying drawings, in which:

FIG. 1 is for UF₆Conversion to UO₂Schematic diagram of the conversion apparatus of (1);

FIG. 2 is a schematic view of a striking device for striking a pyrohydrolysis furnace; and is

FIG. 3 is a continuous supply for discharge UF for hydrolysis reactors₆Schematic of the apparatus for the gas.

Detailed Description

The conversion plant 2 shown in figure 1 comprises a hydrolysis reactor 4 for passing gaseous UF through injection into the reactor 4₆And drying the UF by reaction between water vapor₆Conversion to UO₂F₂And (3) powder.

The reforming apparatus 2 comprises a pyrohydrolysis furnace 6 for passing UO₂F₂Powder with dry steam and H injected into the furnace 6_2yx8xyThe gas reacts to supply UO from the reactor 4₂F₂Conversion of powder to UO₂And (3) powder.

The conversion plant 2 comprises a feeding device 8 designed to introduce a reaction gas (UF)₆Gas, dry steam and H₂Gas) is injected into the reactor 4 and furnace 6.

The supply means 8 are supplied by a source of reactive gas comprising at least one gaseous UF₆Source, at least one source of dry steam and at least one gaseous H₂A source.

The feeding means 8 comprise a reagent injection conduit 10 for injecting reaction gases into the reactor 4 and the furnace 6. The reagent injection line 10 comprises UF which feeds the reactor 4₆Injection line, first dry steam injection line feeding reactor 4, second dry steam injection line feeding furnace 6 and H feeding furnace 6₂And (4) injecting into a pipeline.

The feeding means 8 are also designed for injecting neutral gas into the reactor 4, in particular during the production phase of the conversion plant 2, so that UF₆To UO₂F₂The conversion of (a) is carried out under a neutral gas atmosphere. In this case, the feeding means 8 is preferably designed to allow the neutral gas to be injected into the reactor 4 without injecting the neutral gas into the furnace 6.

Is used for UF₆Conversion to UO₂F₂The neutral gas injected into the reactor 4 in the production stage of (a) is hereinafter referred to as "neutral scavenging gas".

The supply device 8 is preferably designed for neutral scavenging with dry steam (H)₂O) and UF₆Are injected together.

For this purpose, as in the example shown, the feed device 8 comprises, for example, a concentric injector 11 which can inject the drying steam (H) in a concentric manner, i.e. by forming three concentric jets₂O)、UF₆And neutral scavenging.

Preferably, the feeding means 8 are also designed for injecting a neutral gas into the reactor 4 and the furnace 6, so as to be able to maintain a neutral gas atmosphere in the reactor 4 and the furnace 6 when the conversion installation 2 is not in production.

Thus, in the production stage, the feed device 8 injects neutral scavenging gas into the reactor 4 to inject UF under a neutral gas atmosphere without injecting neutral gas into the furnace 6₆Conversion to UO₂F₂And the feeder 8 injects neutral gas into the reactor 4 and the furnace 6 in the shutdown and startup phases to maintain a neutral gas atmosphere.

The feeding means 8 comprise one or more neutral gas injection ducts 12 for injecting neutral gas into the reactor 4 and/or the furnace 6. Each neutral gas injection pipe 12 is fed by a neutral gas source. The neutral gas is preferably nitrogen (N)₂)。

In the example shown, the concentric injector 11 is operated by supplying water vapour (H) to the reactor 4₂O) reagent injection tube 10, andreactor 4 supplies UF₆And a neutral gas injection pipe 12 for injecting a neutral scavenging gas into the reactor 4. Alternatively, the feed device 8 can be designed for supplying water vapor (H) to the reactor 4 when the conversion plant 2 is shut down or started up₂O) reactant injection line 10 and/or supply UF to reactor 4₆And a neutral gas reagent injection line 10.

The supply means 8 comprise a respective supply actuator 14 provided at the inlet of each reactant injection conduit 10 or neutral gas injection conduit 12, the supply actuator 14 being able to control the flow rate of the gas in the injection conduits.

Preferably, the feed actuators 14 are provided in the form of flow regulators adapted to keeping the gas flow through them at a set value.

Preferably and to avoid any UF₆Risk of leakage, the feed actuator 14 of the feed device 8 is resistant to seismic stresses.

The conversion installation 2 comprises an electronic control system 16 for controlling the conversion installation 2 and in particular the feed device 8, in particular the feed actuator 14.

As shown in FIG. 1, reactor 4 defines a reaction chamber 18, and reagent injection line 10 leads to reaction chamber 18 to supply gaseous UF to reactor 4₆And drying the water vapor, and therein hydrolyzing UF₆Conversion to UO₂F₂. UO thus obtained₂F₂In powder form and falls to the bottom of the reaction chamber 18.

The reactor 4 has an outlet pipe 20 extending from the reaction chamber 18 and connected to the furnace 6 for the UO to be injected into₂F₂The powder is transferred from the bottom of the reaction chamber 18 to the furnace 6.

The conversion apparatus 2 comprises a hot chamber 22 surrounding the reactor 4 and a heater 24 for heating the inner volume of the hot chamber 22 and thus the reactor 4.

The furnace 6 has an outlet conduit 20 connected to the reactor 4 for receiving the UO₂F₂Powder inlet 26 and supply UO₂An outlet 28 for the powder.

The conversion plant 2 comprises means for converting UO₂F₂The powder is transferred from the reaction chamber 18 to the transfer means 30 of the furnace 6. The transfer device 30 here comprises an electric worm driven by a motor to transfer the UO₂F₂The powder is pushed from the reaction chamber 18 towards the inlet 26 of the furnace 6.

The furnace 6 comprises a drum 32 having a central axis C, one axial end of which forms the inlet 26 and the opposite axial end of which forms the outlet 28 of the furnace 6.

The drum 32 is arranged for UO₂F₂The powder is circulated from the inlet 26 to the outlet 28 while drying the water vapor and H₂In furnace 6 with UO₂F₂The powder is circulated counter-currently.

The drum 32 is rotatably mounted about its central axis C so as to be inclined relative to a horizontal plane so that the inlet 26 is higher than the outlet 28, rotation of the drum 32 causing the powder to advance from the inlet 26 towards the outlet 28.

The furnace 6 comprises motorized rotary drive means 33 designed to drive the drum 32 in rotation about its central axis C. The rotary drive means 33 comprise, for example, a motor and transmission means, such as a chain or belt, coupling the motor to the drum 32.

Alternatively, the oven 6 may advantageously be provided with a crank that allows the drum 32 to be turned manually in the event of a failure of the rotary drive 33.

The drum 32 is preferably provided with baffles 35 arranged inside the drum 32 for controlling the flow rate of the reaction gas and the passage time of the powders in the furnace 6.

Optionally, the drum 32 is provided with lifting members 37 which protrude from the inner surface of the drum 32 and are designed to lift and drop the powder present in the drum 32 by means of the rotation of the drum 32 about the central axis C, thereby improving the degree of mixing of the powder and promoting uniform contact of the powder particles with the reaction gas circulating in the drum 32. The lifting members 37 are for example in the form of lifting blades or lifting horns distributed on the inner surface of the drum 32.

In an advantageous embodiment, the drum 32 of the furnace 6 and the transfer means 30 of the reaction chamber 18 are designed to operate independently of each other, in particular allowing to stop one of them while keeping the other active.

In the example shown, the drum 32 of the furnace 6 and the transfer device 30 of the reaction chamber 18 are designed for independently rotating, on the one hand, the worm of the transfer device 30 and, on the other hand, the drum 32, in particular for keeping the worm or the drum 32 rotating while stopping the rotation of the other.

In the shutdown phase of the conversion plant 2, this arrangement makes it possible to complete the UO already with the reactor 4, in particular the transfer device 30, stopped₂Removal of the powder from the furnace 6.

In the example shown, a second steam injection line and H₂An injection line feeds drum 32 through outlet 28 to allow dry steam and H from the pyrohydrolysis₂From the outlet 28 to the inlet 26 of the furnace 6.

In the example shown, a neutral gas injection line 12 is connected for connecting H₂A reagent injection line 10 for injecting H into the furnace 6 and/or connected to the means for injecting H₂O is injected into the reagent injection pipe 10 in the furnace 6 to inject neutral gas into the furnace 6 via the reagent injection pipe(s) 10 when the reforming plant 2 is shut down or started up, the injected neutral gas then being circulated from the outlet 28 of the furnace 6 to the inlet 26 of the furnace 6. Alternatively or as a variant, the feeding means 8 comprise a neutral gas injection duct 12 for injecting neutral gas into the furnace 6, which leads directly to the furnace 6 without passing through the reagent injection duct 10.

Supplying a neutral gas through the reactant injection conduit 10 while shutting down the reforming apparatus 2 allows the reagent injection conduit 10 to be cleaned while shutting down at the same time as injecting the neutral gas. The supply of neutral gas through the reagent injection conduit 10 during start-up allows to raise the temperature of the reforming apparatus 2 and to supply reagents to the reforming apparatus 2 when reaction parameters are reached in the reactor 4 or furnace 6.

The furnace 6 includes a heater 34 for heating the drum 32. The heater 34 includes heating elements 36 distributed around the drum 32 and along the drum 32. The furnace 6 includes a hot chamber 38 surrounding the drum 32 and the heating element 36.

The conversion plant 2 comprising a furnace 6A collecting device 40 for collecting the powder at the outlet. The collecting device 40 comprises an inlet duct 42 connected to the outlet 28 of the furnace 6 and leading to a collecting container 44. The collection device 40 includes a hot chamber 46 surrounding the collection container 44. Second steam injection line and H₂The injection line preferably leads to a collection vessel 44.

The conversion plant 2 comprises capture means 50 for capturing and removing the gases returned to the reactor 4, including the excess reaction gas, the Hydrogen Fluoride (HF) produced by the conversion and the neutral gas.

The capture device 50 is arranged in the reactor 4, preferably in the upper region of the reaction chamber 18.

The capture device 50 comprises a plurality of filters 52 for retaining solids, in particular UO, possibly entrained by the gas returned to the reactor 4₂F₂Or is UO₂The particles of (1).

Filter 52 is made of, for example, a porous material to allow excess reactant gas, neutral gas, and UF to pass₆Conversion to UO₂F₂Then converted into UO₂By passage of HF generated by the reaction while maintaining the UO₂F₂Or UO₂The ability of the particles of (a). In a preferred embodiment, the filter 52 is made of ceramic or nickel-base superalloy.

UO₂F₂And UO₂The powder is volatile and is easily carried away by the air flow. In addition, they tend to adhere to the surfaces with which they come into contact.

In operation, powder agglomerates are formed on the filter 52 and on the walls of the reactor 4 and of the furnace 6, which are more or less heterogeneous in composition and more or less dense. These powder agglomerates containing fissile material may be particularly concentrated in retention zones that may be present at various points of the transformation device 2, for example at the junction between the reactor 4 and the furnace 6.

The powder agglomerates may fall off under their own weight and come with the powdery UO₂F₂Powder and UO₂And (4) mixing the powder. The presence of dense agglomerates in the powder can create heterogeneity in the powder treatment in the furnace 6 and may lead to the end of the conversionUO obtained₂Residual UO present in the powder₂F₂Particles, thereby reducing their mass.

In addition, the accumulation of powder on the filter 52 causes the filter 52 to gradually clog, thus causing an increase in the pressure inside the reactor 4. Pressure change versus UO obtained at the end of the hold conversion₂The constant quality of the powder has a significant effect and too high an internal pressure of the reactor 4 may cause a safety alarm of the conversion plant 2.

When the filter 52 is closed by UO₂F₂And/or UO₂When the powder clogs, it is necessary to stop the conversion device 2 and clean or replace the filter 52, which is cumbersome and costly.

Clogging may also occur at the level of the means for injecting reactants into the reactor 4, here the concentric injector 11. In practice, if the injection pressure and temperature of the gas are insufficient, UF₆May crystallize at the outlet of the concentric injector 11, thereby blocking the supply of reactants to the reactor 4. Therefore, it is important to maintain a constant supply pressure, especially at UF₆When the source changes.

The conversion plant 2 advantageously comprises a dredging device 53 designed for dredging the filter 52, for example by injecting a neutral gas through the filter 52 in a countercurrent, i.e. pulsed, towards the inside of the reaction chamber 18 of the reactor 4. The neutral gas is, for example, nitrogen (N)₂)。

Injecting the neutral gas in counter-current tends to disturb the pressure balance inside the reactor 4. It is desirable to unclog in a controlled manner according to certain parameters in order to limit disturbances to the operation of the reactor 4, in particular to the pressure inside the reactor 4.

Advantageously, the unclogging means 53 are designed to unclog the filters 52 in an automatic manner by sequentially passing through the individual combinations of filters 52.

The deoccluding device 53 is therefore designed to inject the neutral gas counter-currently in sequence into different combinations of filters 52. Each set of filters 52 includes a single filter 52 or a plurality of filters 52.

In a preferred embodiment, the filters 52 are divided into two groups, each group containing a corresponding half number of filters 52, and the two groups are alternately unblocked by periodically (e.g., every 30 seconds) injecting neutral gas. It is also possible to carry out a clearing cycle, for example in the order of one third or one quarter, and/or to adjust the injection frequency.

The counter-current neutral gas injection pressure in each filter 52 is selected to limit the turbulence in the reactor 4. The relative pressure applied to each filter 52 (preferably between 2 and 5bar, in particular between 3 and 4.5 bar) makes it possible to satisfactorily unclog the filters 52. Unless the context indicates otherwise, the expression "relative pressure" refers to a pressure difference relative to atmospheric pressure.

In order to ensure that the injection pressure of the neutral gas is constant, the deoccluding device 53 is supplied, for example, by a reservoir 55 which contains the neutral gas and maintains a constant pressure.

The duration of the counter-current neutral gas injection in each filter 52 is chosen to limit the perturbations in the reactor 4, while allowing satisfactory cleaning to be achieved during the injection cycle, in particular over the entire surface of the filter 52. The duration of the counter-current neutral gas injection in each filter 52 is for example less than 1 second.

Preferably, during the counter-current injection of neutral gas into each filter 52, the trapping device 50 is designed to cut off the suction through this filter 52 before counter-current injection of neutral gas, to prevent neutral gas used for unclogging from escaping directly through the trapping device 50.

Preferably, the unclogging means 53 are designed to cyclically perform unclogging, in particular at a period chosen to avoid accumulation of powder on the filter 52 and at the same time limit the impact of such injection on the operation of the conversion device 2. Preferably, the period is between 30 seconds and 1 minute.

Thus, according to a preferred embodiment, the pull through is designed to automatically and cyclically (or periodically) repeat the pull through procedure. The automatic, sequential and periodic opening of the filter 52 ensures that it is inside the reactor 4Operating the conversion device 2 at a relative pressure of, for example, between 10 and 500mbar, preferably between 50 and 400mbar and more preferably between 100 and 350mbar, makes it possible to obtain UO having satisfactory characteristics, in particular a reasonable fluorine content which develops substantially constant over time₂And (3) powder.

The unclogging of the filter 52 causes the powder agglomerates formed on the filter 52 to fall and prevents an excessive rise in pressure in the reaction chamber 18.

Sequential and periodic unclogging can limit the size and compactness of the solid agglomerates formed on the filter 52, avoiding them to separate under their own weight and to drop by gravity too much into the transfer device 30 at the bottom of the reaction chamber 18. In fact, dense agglomerates and powdery UO₂F₂Mixtures of powders may result in UO obtained therefrom₂Heterogeneity of the physical and chemical characteristics of the powder, in particular its fluorine content.

The dredging in the combination of the plurality of filters 52 prevents the powder discharged from one filter 52 from adhering to the other filter 52 as in the case of the single dredging of the filters 52. Unclogging the combination of multiple filters 52 may create a mist, thereby limiting the formation of agglomerates.

As an optional addition to sequential and periodic unblocking, unblocking apparatus 53 may include a manual or automatic controller to allow on-schedule unblocking of filter 52, particularly if filter 52 reaches a useful life and sequential and periodic unblocking becomes insufficient. This on-schedule de-activation may be de-activation of one of the filters 52 or a set of reduced size filters 52.

As shown in fig. 1, the conversion installation 2 preferably also comprises at least one flow device 56 designed to prevent the powder from accumulating on the walls of the reaction chamber 18 and the agglomerates of powder discharged from the filter 52 during the unclogging operation from adhering to the walls of the reaction chamber 18.

The flow means 56 may promote a continuous flow of powder, thus having stability in terms of quantity and quality, in particular over timeThe fluorine content aspect contributes to the supply of UO to the furnace 6₂F₂Stable condition of the powder.

The flow means are designed to vibrate and/or hit at least one wall of the reactor 4, preferably periodically or continuously.

The flow means 56 comprise, for example, one or more beating members, each designed to strike the wall of the reactor 4 to form shock waves in the wall of the reactor 4, and/or one or more vibrating members, for example vibrating cylinders, each arranged on the wall of the reactor 4 and designed to generate a vibration signal (or vibration) and to transmit this vibration to the wall of the reactor 4. In a preferred embodiment, the flow device 56 includes one or more members that create an impact force that lifts the powder from the wall and creates vibrations that assist in its flow.

Hereinafter, the striking member, the vibration member, and the member that transmits these two functions are referred to as "flow member".

Thus, in general, the flow means comprise at least one flow member designed to vibrate and/or impinge on the wall of the reactor 4.

The flow members allow the walls of the reactor 4 to vibrate periodically or continuously.

The flow means 56 here comprise four flow members 58, for example of the electrokinetic impactor type, arranged two by two at two diametrically opposite positions of the outer surface of the wall of the reactor 4.

Advantageously, when the flow device 56 comprises a plurality of flow members 58 and the reactor 4 is operating, the flow members 58 are controlled to act sequentially.

The number, location and sequence of operation of the flow members 58 may be designed according to the geometry of the reactor 4, the quality of the powder and the operating parameters of the deoccluding device 53.

Each flow member 58 may be fixed directly to the wall of the reactor 4 or, for example, via intermediate components. In this case, the intermediate part may be removable, for example, to facilitate maintenance thereof.

The combination of the deoccluding device 53 and the flow device 56 can limit the deposition on the substrateThe size and compactness of the filter 52 and of the powder agglomerates on the walls of the reactor 4, so as to control the fall of the agglomerates towards the bottom of the reactor 4 and thus ensure a UO₂The homogeneity of the powder, especially over time, has a substantially constant fluorine content.

The conversion plant 2 comprises sealing means 54 for ensuring the sealing between the transfer means 30 and the reaction chamber 18, between the reactor 4 and the furnace 6 and between the furnace 6 and the collecting means 40. Sealing means 54 are provided at the junction between the transfer means 30 and the reaction chamber 18, at the junction between the outlet duct 20 of the reactor 4 and the inlet 26 of the furnace 6 and at the junction between the outlet 28 of the furnace 6 and the inlet duct 42 of the collection means 40. The sealing means 54 ensure sealing by allowing the transfer means 30 to rotate with respect to the reactor 4 and the drum 32 of the furnace 6 to rotate with respect to the reactor 4 and the collection means 40.

The sealing device 54 is pressurized with an inert gas, preferably with nitrogen.

To this end, as shown in fig. 1, the conversion apparatus 2 comprises, for example, a pressurized supply device 57 arranged to supply an inert pressurized gas to the sealing device 54.

The pressure of the neutral gas supplied to the sealing means 54 is greater than the pressure present in the conversion device 2, so as to prevent the diffusion of the powder towards the outside of the conversion device 2. In practice, the neutral gas used to pressurize the sealing device 54 may enter the reactor and/or furnace 6, and the design of the operating parameters of the reactor 4 and furnace 6 takes into account this supply of neutral gas.

The conversion installation 2 comprises at least one striking device 60 for striking a striking surface 62 of the oven 6 to cause the UO to strike₂F₂Or UO₂Is removed from the inner surface of the drum 32.

Here, the conversion apparatus 2 comprises a striking device 60 provided at each axial end of the drum 32 for striking a striking surface 62 formed by the outer surface of the axial end of the drum 32 axially remote from the hot chamber 38 of the furnace 6. As a variant, the striking surface 62 may be defined by any other surface of the furnace 6 capable of transmitting vibrations to the peripheral wall of the drum 32 when striking this striking surface 62 of the furnace 6.

The conversion apparatus 2 may advantageously comprise a plurality of beating devices 60 arranged at the same end of the drum 32 and angularly distributed around the drum 32.

In a preferred embodiment, the conversion apparatus 2 comprises two sets of beating devices 60, each set being provided at a respective one of the two ends of the drum 32, and each set of beating devices 60 being angularly distributed around the drum 32.

The striking device 60 is similar. Only one striking device 60 is shown in more detail in fig. 2.

As shown in fig. 2, each of the striking devices 60 includes a striker 64 movable in the striking direction P relative to the striking surface 62, and an intermediate member 66 disposed between the striker 64 and the striking surface 62 so that the striker 64 strikes the striking surface 62 via the intermediate member 66, the intermediate member 66 being movable in the striking direction P between a position spaced apart from the striking surface 62 and a position in contact with the striking surface 62 of the furnace 6.

Here, a plane tangent to the striking surface 62 at the point of contact of the intermediate member 66 and the striking surface 62 is perpendicular to the striking direction P. Here, the striking direction P is substantially in a radial direction with respect to the center axis C of the drum 32.

The striker 64 is carried by a striking actuator 68 adapted to reciprocally translate the striker 64 in a striking direction P. The striking actuator 68 is here a double acting hydraulic or pneumatic cylinder.

The striking device 60 has a support 70 for carrying the actuator 68 and the intermediate part 66 such that the intermediate part 66 is located between the striker 64 and the striking surface 62. The intermediate member 66 is slidably mounted on the support member 70 in the striking direction P.

The intermediate member 66 has a rear surface 66A designed to be struck by the striker 64 and a front surface 66B designed to contact the striking surface 62. In the contact position, the front surface 66B is in contact with the striking surface 62, while in the spaced-apart position the front surface 66B is spaced apart from the striking surface 62.

The striking device 60 includes a resilient return member 72 arranged to return the intermediate part 66 to a spaced apart position. The intermediate part 66 is received in the receptacle 74 of the support 70, with the resilient member 72 interposed between the inner shoulder 74A of the receptacle 74 and the outer shoulder 66C of the intermediate part 66.

The resilient member 72 is here a coil spring surrounding the intermediate part 66 and is compressed when the intermediate part 66 moves from the spaced-apart position to the contact position.

The striking device 60 includes a position sensor 76 that can know the position of the striker 64. The position sensor 76 is, for example, an inductive sensor disposed near the intermediate member 66, and can determine whether the striker 64 is in a position of contact with the intermediate member 66. The impact actuator 68 is controlled in accordance with a position signal provided by a position sensor 76.

In operation, the impact actuator 68 causes the striker 64 to reciprocate in translational movement, thereby moving the striker 64 away from the intermediate member 66 and subsequently moving the striker 64 toward the intermediate member 66 to impact the striking surface 62 through the intermediate member 66. The striker 64 moves the intermediate member 66 from the spaced apart position to a contact position against the resilient member 72.

Repeated impacts of the striker 64 may damage the striker 64 itself and the outer surface of the drum 32. Providing the intermediate part 66 separate from the striker 64 and not permanently connected to the furnace 6 allows the intermediate part 66 to be used as a disposable or consumable part. In the example shown, the intermediate member 66 is mounted for movement relative to the furnace 6.

Obtaining UO with satisfactory characteristics₂Powder, in particular an impurity content of less than 50ppm (essentially fluorine), a uniform particle size distribution, for example in the range of 20 to 100 μm, and less than 4m²The specific surface area/g depends on the operating conditions of the hydrolysis and of the pyrohydrolysis, in particular on the supply rate and temperature of the reactants.

The feed device 8 is designed to supply the reactants and the neutral gas, in particular the neutral scavenging gas, at a determined flow rate.

The heater 24 of the reactor 4 is designed to keep the reactor chamber 4 within a suitable temperature range to obtain the UO₂F₂And subsequently obtaining UO with desired characteristics₂And (3) powder.

Advantageously, during the steady production phase, gaseous UF is supplied to reactor 4₆Is from 75 to 130kg/h, the hourly mass flow rate of the supply of dry steam to the reactor 4 is from 15 to 30kg/h, and the temperature in the reactor 4 is between 150 and 250 ℃.

These numerical ranges may yield UO₂F₂Powder, ultimately a UO having the desired characteristics can be obtained₂And (3) powder. In particular, these numerical ranges can be obtained with 1m²G and 4m²Between/g, preferably 1.9m²G and 2.9m²UO of specific particle surface area between/g₂And (3) powder. In addition, these numerical ranges make it possible to obtain UO having a residual fluorine (F) content of less than 50ppm, preferably less than 35ppm, more preferably less than 20ppm₂And (3) powder.

In an advantageous embodiment, gaseous UF is supplied to reactor 4₆Is between 90 and 120kg/h and the mass flow rate per hour of the supply of dry hydrolysis water vapour to the reactor 4 is between 20 and 25 kg/h.

To prevent UF₆Crystallizing during the injection into the reactor 4, supplying UF to the reactor 4 at a temperature of 75-130 deg.C, preferably 90-120 deg.C₆。

In a particular embodiment, the conversion apparatus 2 comprises a discharge device which can be adjusted by means of the flow rate and UF₆At a temperature of (3) and continuously introducing UF₆Is discharged into the reactor 4.

UF₆In e.g. cylindrical tanks. At room temperature, UF₆In the solid state. The transition from the solid state to the gaseous state is carried out by heating the tank, for example in a heating chamber, in particular in a furnace (not watertight) or in an autoclave (watertight).

As shown in FIG. 3, the reforming apparatus 2 has a means for holding UF₆Reservoir 84 supplies UF to reactor 4₆And a gas discharge device 82. Each reservoir 84 is closed by a sealing valve 85.

Discharge device 82 includes at least two heating chambers 86, each heating chamber 86 configured to receive solid UF₆Is stored inTank 84 and heating it to produce gaseous UF₆Discharge device 82 is designed to feed reactors 4 sequentially through heating chambers 86, preferably without interrupting the supply of UF to reactors 4 when storage tank 84 received in current heating chamber 86 is no longer sufficiently full₆The gas flow is switched from the current heating chamber 86 to the subsequent heating chamber 86. Preferably, each heating chamber 86 is capable of heating and maintaining a respective reservoir 84 at a ratio UF₆At a higher temperature than the triple point temperature of (a), for example a temperature higher than 75 ℃ and preferably a nominal temperature of 95 ℃, for example 95 ℃ ± 10 ℃.

The discharge device 82 therefore comprises a feed circuit 87 designed to selectively discharge UF from one of the heating chambers 86 to the reactor 4₆While another heating chamber 86 is waiting for UF to drain from reservoir 84₆By heating the reservoir 84 or by filling UF₆Is replenished from reservoir 84.

Each heating chamber 86 is connected to the reactor 4, for example by means of a valve 88 for regulating the respective flow rate, the closing of which can isolate the heating chamber 86 from the reactor 4, while the opening thereof can fluidly connect the heating chamber 86 to the reactor 4. Opening valve 85 and then valve 88 of reservoir 84 allows UF due to the pressure differential between reservoir 84 and reactor 4₆From heating chamber 86 to reactor 4. Heating chamber 86 is then in a passive discharge mode.

Optionally, each tank 84 is connected to the reactor 4 by means of a respective pump 90 associated with each heating chamber 86 and arranged in parallel with the valve 88 associated with that heating chamber 86. The pump 90 is preferably a positive displacement pump, more preferably a positive displacement pump with bellows.

When the pressure in the reservoir 84 contained in the heating chamber 86 is insufficient to ensure gaseous UF₆The activation of pump 90 may force such circulation from heating chamber 86 to reactor 4. The heating chamber 86 is then in an active drain mode. When valve 88 is opened, pump 90 is bypassed.

The discharge device 82 comprises, for example, means for opening the valves of the respective tanks 84 from outside each heating chamber 86, and an electronic control unit 92 designed to control the valves 88 and, if necessary, the pumps 90 associated with each heating chamber 86 and to ensure the sequential powering of the heating chambers 86 and, where appropriate, the transition of each heating chamber 86 from the passive mode to the active mode.

The discharge device 82 is designed, for example, to control the transition from one heating chamber 86 to the next and, where appropriate, to control the transition from the passive mode to the active mode based on the pressure in each reservoir 84.

To this end, the discharge device 82 comprises, for example, a pressure sensor 94 associated with each tank 84, an electronic control unit 92 designed to control the valve 88 and, if necessary, the pump 90 associated with each heating chamber 86, according to the measurements provided by the pressure sensor 94.

At the beginning of the production cycle, the reservoir 84 in the first heating chamber 86 is preferably heated under a neutral gas atmosphere to improve the heat exchange between the atmosphere of the heating chamber 86 and the reservoir 84. The neutral gas is, for example, nitrogen. When the desired temperature is reached, i.e. when the solid UF₆UF that has been liquefied and is in storage tank 84₆In the liquid/gas equilibrium stage, UF provided at the outlet of the first heating chamber 86 and the reactor 4 is opened after opening the sealing valve 85 of the reservoir 84₆And starts UF in a passive discharge mode through the first heating chamber 86, into the valve 88 between the injection pipes 10₆And (4) discharging. In parallel, heating of the other reservoir 84 in the second heating chamber 86 begins.

With UF₆The discharge is carried out and the pressure in the reservoir 84 of the first heating chamber 86 drops close to a pressure that may cause UF₆And a value that reverses the flow between the reactor 4 and the reservoir 84 received in the first heating chamber 86. Then still several kilograms of UF in reservoir 84₆. Before this stage is reached, the first heating chamber 86 switches from the passive discharge mode to the active discharge mode with the valve 88 closed and the corresponding pump 90 activated. Thus, UF₆May continue until substantially all UF contained in reservoir 84 exiting first heating chamber 86 is removed₆For example, the absolute pressure in the tank 84 at the end of the discharge is 100 mbar. At this time, is received at the second adderThe reservoir 84 in the hot cell 86 has reached drain UF₆The desired temperature and the sealing valve 85 of the reservoir 84 is opened. The valve 88 associated with the first heating chamber 86 is closed and the valve 88 associated with the second heating chamber 86 is opened so that there is no interruption in the switching from the first heating chamber 86 to the second heating chamber 86 and UF is not significantly altered₆Continues to discharge UF through reservoir 84 of second heating chamber 86 at the flow rate, temperature and pressure of₆. In parallel, the valve 85 of the reservoir 84 received in the first heating chamber 86 is closed, and after cooling the first heating chamber 86 is vented to atmosphere, unlocked and the reservoir 84 is emptied and filled with UF₆Is replaced with a new tank 84.

As a variant and in order to further reduce the supply of UF to the reactor 4₆In this variation, the valve 88 associated with the second heating chamber 86 may be opened before the valve 88 associated with the first heating chamber 86 is closed, thereby continuing to discharge UF through both reservoirs 84₆The first heating chamber 86 operates in an active discharge mode and the second heating chamber 86 operates in a passive discharge mode. The opening of valves 88 associated with second heating chamber 86 may be, for example, when valves 88 of first heating chamber 86 are closed and pump 90 is activated or when UF from reservoir 84 of first heating chamber 86 is stopped₆Any other time before discharge.

Preferably and in order to be able to shut down UF as close as possible to the discharge source in all cases₆Valve 88 is able to resist seismic stresses.

The drain 82 allows for the use of nearly all UF contained in the reservoir 84₆Making the conversion plant 2 continuous, wherein UF₆At the desired pressure and temperature and at the desired flow rate.

Preferably, the reactor 4 is supplied with dry hydrolysis water vapour at a supply temperature of between 175 ℃ and 300 ℃, in particular between 200 ℃ and 270 ℃.

Preferably, the oven 6 is supplied with dry steam from the high-temperature hydrolysis water at a mass supply rate per hour of between 25 and 40kg/h, in particular between 30 and 35 kg/h.

Furthermore, it is preferred that the oven 6 is supplied with dry water vapour from the high temperature hydrolysis water at a supply temperature between 250 ℃ and 450 ℃, preferably between 300 ℃ and 400 ℃.

Preferably for supplying H to the furnace 6₂At a volume flow rate of 10 and 25Nm³H, in particular between 15 and 20Nm³Between/h, ` Nm `³"means standard cubic meters per hour and is a unit of measurement of the amount of gas corresponding to the content of one cubic meter by volume of the gas under standard conditions of temperature and pressure (20 ℃ and 1 atm). H₂Typically at room temperature.

The injection parameters of the neutral purge gas supplied to the reactor 4 influence the reaction taking place in the reactor 4.

Preferably, the supply rate of the neutral purge gas to the reactor 4 is between 1.5 and 5Nm³Between/h, the injection temperature of the neutral scavenging gas is between 80 ℃ and 130 ℃ and the relative supply pressure of this neutral scavenging gas is greater than the relative pressure inside the reactor 4 and preferably less than 1 bar.

In a particular embodiment, the supply rate of neutral scavenging is between 2 and 3Nm³Between/h and the injection temperature of the neutral scavenging gas is between 90 and 105 ℃.

Furthermore, the heating elements 36 of the furnace 6 are controlled to produce a gradually increasing and then decreasing temperature in the furnace 6 from the inlet 26 of the furnace 6 to the outlet 28 of the furnace 6.

The furnace 6 for example comprises a plurality of consecutive sections defined along the furnace 6, in this case six consecutive sections S1 to S6 from the inlet 26 to the outlet 28 of the furnace 6, the sections S1 to S6 being each heated by a heating element 36 dedicated to that section S1 to S6.

The furnace 6 includes a respective temperature sensor 80 associated with each of the sections S1-S6. The temperature of each section of the furnace 6 is considered to be the temperature measured by the temperature sensor 80 associated with that section. Each temperature sensor 80 is, for example, a thermocouple near the heating element 36 associated with the segment.

The heating element 36 dedicated to each of the sections S1-S6 is controlled independently of the heating elements dedicated to the other sections so that the temperature measured by the temperature sensor 80 located in that section is at a determined set point.

In an advantageous embodiment, each of the sections S1 to S6 is provided with a plurality of temperature sensors 80, and the temperature of each of the sections S1 to S6 of the furnace 6 is taken as the average of the temperatures measured by the temperature sensors 80 associated with that section S1 to S6.

In an advantageous embodiment, the heating elements 36 of the oven 6 are controlled to establish the following temperature profile:

first section S1: between 660 and 700 ℃;

second section S2: between 700 and 730 ℃;

-a third section S3: between 720 and 745 ℃;

fourth section S4: between 730 and 745 ℃;

fifth section S5: between 660 and 700 ℃;

sixth section S6: between 635 and 660 ℃.

The temperature curve can control UO₂F₂The development of pyrohydrolysis reactions of powders, which is a complex reaction composed by a variety of elementary reactions that depend inter alia on temperature.

During the production phase, the unclogging device 53 automatically and periodically unclogs. In addition, preferably, the flow means 56 automatically, periodically or continuously vibrate and/or impact the reactor 4 and/or the beating means 60 automatically and periodically impact the furnace 6 to cause the powder adhering to the inner walls to fall before it forms large and/or dense agglomerates.

However, the filter 52 may become excessively clogged during operation of the conversion apparatus 2 and with aging.

An increase in the relative pressure inside the reactor 4 generally indicates that the opening of the filter 52 becomes insufficient.

Monitoring the pressure within the reactor 4 allows monitoring of the cleaning efficiency.

Preferably, during a stable production phase, it is desirable to maintain a relative pressure within reactor 4 of between 10mbar and 500mbar, preferably between 50 and 400mbar, more preferably between 100 and 350 mbar.

The conversion installation 2 comprises a pressure sensor P1 for measuring the pressure inside the reactor 4.

Preferably, the control system 16 is designed to command the shutdown of the conversion installation 2 when the relative pressure inside the reactor 4 exceeds a predetermined safety threshold.

The safety threshold is, for example, between 100 and 500mbar, preferably between 200 and 450mbar, more preferably between 200 and 400mbar, in particular approximately 350 mbar.

Advantageously, the unclogging means 53 are controlled to unclog the filter 52 when the relative pressure inside the reactor 4 exceeds a predetermined unclogging threshold. Such on-schedule dredging can be performed at a dredging injection pressure in the upper limit portion of the injection pressure range for sequential dredging of the neutral gas, or even at an injection pressure greater than this range. Further, the scheduled clearing may be performed specifically for one or more filters 52, such as individually for one or more specific filters 52 that may be individually blocked, or together for a limited number of filters 52.

The clearing threshold is set, for example, in the range of 100mbar below the safety pressure of the device and, for example, 50mbar, preferably 30mbar below the safety threshold of the device.

In fact, in the event of significant clogging of the filter 52, the pressure in the reactor 4 increases rapidly and it is difficult, if not impossible, to avoid UO without stopping the plant or at the outlet₂Unblocking of the filter 52 by manual cleaning or replacement in case of powder heterogeneity, since an uncontrolled amount of agglomerates falling from the filter 52 into the transfer device 30 during the unblocking operation is added to the UO₂F₂In the powder.

Injecting a neutral gas within each filter 52 during de-aeration may trap UO on the outer surface of the filter 52₂F₂The powder particles are discharged while limiting the interference with the reactor 4 operating at a relative pressure between 10mbar and 500 mbar.

It is also possible here to vibrate and/or hit one or more walls of the reactor 4 by means of the flow means 56 provided for the reactor 4UO deposited on the inner wall of the reactor 4₂F₂The particles of the powder break away.

Here, the impact of the striking device 60 against the striking surface 62 of the furnace 6 prevents the formation of powder agglomerates in the furnace 6, which can also affect the UO produced by the conversion device 2₂Mass of the powder.

Controlling the flow rates of the reaction gas and of the neutral scavenging gas and the temperatures in the reactor 4 and in the furnace 6 also allows satisfactory UO to be obtained₂Hydrolysis and high-temperature hydrolysis reactions are established under the condition of powder.

In general, in operation, the injection pressure of all the gases injected into reactor 4 or furnace 6 is greater than the pressure present in reactor 4 or furnace 6, for example at least 20mbar, preferably at least 50mbar higher than the pressure inside reactor 4 or furnace 6.

Regardless of the conversion method and the control of the conversion parameters, it is advantageous to provide striking means on the furnace 6.

Thus, in general, the invention relates to a process for the reduction of uranium hexafluoride (UF)₆) Conversion to uranium dioxide (UO)₂) The apparatus of (1), the conversion apparatus comprising:

hydrolysis reactor for passing gaseous UF₆UF by reaction with dry water vapor₆Conversion to uranium oxyfluoride powder (UO)₂F₂)；

A pyrohydrolysis furnace for passing UO₂F₂Drying the water vapor and hydrogen (H)₂) The reaction between the reactor and the supplied UO₂F₂Conversion of powder to UO₂Powder, the furnace having a striking surface; and

at least one striking device for striking the striking surface, the striking device comprising an impactor movable relative to the striking surface and an intermediate part arranged between the impactor and the striking surface, such that the impactor strikes the striking surface through the intermediate part, the intermediate part being movable between a position spaced apart from the surface of the oven and a striking position of the oven.

The conversion device may also comprise one or more of the following optional features, considered alone or in any technically feasible combination:

the striking device comprises an elastic return member that returns the intermediate part to the spaced-apart position;

the striking device comprises a pneumatic or hydraulic actuator for moving the striker;

the furnace comprises a drum for receiving the UO₂F₂And injecting dry steam and H thereto₂The striking impact surface of the furnace is the outer surface of the drum;

at least one flow device designed to vibrate and/or impinge on at least one wall of the reactor, and preferably comprising at least one flow member provided on the wall of the reactor for vibrating and/or impinging on the wall directly or via an intermediate component, such as a removable intermediate component;

-at least one capture device designed to capture the gases present in the reactor and comprising a filter;

at least one unclogging device designed to unclog the filters, preferably according to individual filter groups (each filter group comprising one or more filters), in particular sequentially according to filter groups and/or cyclically;

for supplying UF to the reactor₆The discharge device of (1), the discharge device comprising: at least one heating chamber, the or each chamber being designed to receive UF in solid state₆And heating it to produce gaseous UF₆(ii) a And a feed loop designed to feed the reactor through the or each heating chamber;

the feed circuit comprises a pump associated with the or each heating chamber to force UF₆From a reservoir received in the heating chamber to the reactor, the or each pump preferably being a positive displacement pump, more preferably a bellows positive displacement pump;

the feed circuit comprises a flow control valve associated with the or each heating chamber and arranged to bypass the pump associated with the heating chamber.