EP1138045A1 - Method and installation for treating a nuclear fuel powder - Google Patents
Method and installation for treating a nuclear fuel powderInfo
- Publication number
- EP1138045A1 EP1138045A1 EP99956080A EP99956080A EP1138045A1 EP 1138045 A1 EP1138045 A1 EP 1138045A1 EP 99956080 A EP99956080 A EP 99956080A EP 99956080 A EP99956080 A EP 99956080A EP 1138045 A1 EP1138045 A1 EP 1138045A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- particles
- size
- powder
- reduction
- reduced
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
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- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C19/00—Arrangements for treating, for handling, or for facilitating the handling of, fuel or other materials which are used within the reactor, e.g. within its pressure vessel
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
- B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
- B02C18/00—Disintegrating by knives or other cutting or tearing members which chop material into fragments
- B02C18/06—Disintegrating by knives or other cutting or tearing members which chop material into fragments with rotating knives
- B02C18/062—Disintegrating by knives or other cutting or tearing members which chop material into fragments with rotating knives with rotor elements extending axially in close radial proximity of a concentrically arranged slotted or perforated ring
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B60/00—Obtaining metals of atomic number 87 or higher, i.e. radioactive metals
- C22B60/02—Obtaining thorium, uranium, or other actinides
- C22B60/0204—Obtaining thorium, uranium, or other actinides obtaining uranium
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- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C3/00—Reactor fuel elements and their assemblies; Selection of substances for use as reactor fuel elements
- G21C3/42—Selection of substances for use as reactor fuel
- G21C3/58—Solid reactor fuel Pellets made of fissile material
- G21C3/62—Ceramic fuel
- G21C3/623—Oxide fuels
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Definitions
- the present invention relates to a method and an installation for treating a nuclear fuel powder.
- the invention relates more particularly to the treatment of such a powder, of the oxide type, such as U0 2 , obtained downstream of the step aimed at transforming into this oxide a compound, such as UFg.
- the powder having undergone this conversion step is then subjected to a phase of reduction of the average size of the particles which constitute it.
- U0 2 can be obtained in different ways.
- a first mode leads to the production of coarse aggregates, the average diameter of which is around 1 mm.
- the step of reducing the average size of the particles consists in shifting the particle size spectrum as a whole, without modifying the general appearance of this spectrum. This is obtained, in the usual way, by grinding by means of mechanical installations, such as for example ball, hammer or air jet mills. All of the particles forming the combustible powder are subjected to the action of these mechanical mills.
- the average size of the particles flowing through this sieve is therefore less than that of the particles admitted upstream of the latter. Contrary to the techniques aiming to shift the granulometric spectrum as a whole, one proceeds here to a clipping, which contributes to modify the general shape of this spectrum.
- the particles of large size, retained by the mesh of the sieve, must be subjected to operations aimed at recycling and defluorinating them with a view to their subsequent mixing with finer particles.
- Damaged screens can be repaired to keep costs down, but these repairs reduce the filtering surface.
- the use of sieves induces a clogging problem, due to the fact that the powder agglomerates and clogs the sieve. It is then necessary to implement unclogging, for example by ultrasound, or even by percussion, which then causes mechanical degradation of the screen.
- the present invention proposes to implement a method for treating nuclear fuel powder making it possible to overcome all of the drawbacks inherent in the various methods of the prior art mentioned above.
- the invention also relates to an installation for treating a powder of a nuclear combustible material, of the type containing an oxide, such as U0 2 , said installation being arranged in particular downstream of a unit for converting said oxide into a compound, such as UF s , said installation comprising a unit for reducing the average size of the particles forming the powder, inducing a modification in the general appearance of the spectrum of particles, said unit comprising so-called particle retaining means coarse, larger than a predetermined size, or critical size, said retaining means being capable of allowing free flow of so-called fine particles, of size smaller than the critical size, characterized in that said reduction unit also comprises means for continuously reducing coarse particles, so as to form particles, called reduced, of size smaller than the critical size, as well as means for distributing the reduced particles in the free flow of fine particles.
- the invention makes it possible to achieve the objectives mentioned above. Indeed, the fact of reducing the particles whose size is greater than a critical size, in order to disperse them among the particles flowing freely allows, while not allowing the passage of a precise fraction of the powder, to get rid of the operation of evacuation of this fraction considered, as was the case in the prior art using sieves.
- the process according to the invention therefore proves to be significantly less contaminating than those using such sieves.
- the process according to the invention is also capable of operating continuously, without appreciable flow break and possibly by means of successive powders of different natures. It also allows the treatment of powders whose flow rates are able to vary significantly.
- the process according to the invention has remarkable efficiency, in so far as all the particles flowing downstream of the reduction means actually have a size less than the predetermined critical size.
- the process according to the invention guarantees, to a large extent, an absence of pollution, since it does not involve either re-treatment of products which may have been eliminated, or reprocessing of any fluids used to reduce the particle size.
- the nuclear fuel powder processing installation according to the invention is very flexible. Indeed, it is likely to treat products whose enrichment, even the nature, are different. Since the installation according to the invention is devoid of zone of retention of powder, it is not necessary to carry out any cleaning when switching from one product to another.
- the installation according to the invention makes it possible to reach high flow rates, which can for example be five to ten times greater than those authorized by means of a treatment installation using screens.
- the installation of the invention generates reduced operating costs compared to the prior art. It also guarantees a very satisfactory integrity of the treated powder, since it makes it possible to avoid, to a large extent, all overheating and therefore does not induce any oxidation phenomenon. Since this installation does not use any lubricant, the powder, during its passage through the installation, is not subject to contamination due to its contact with such an external product.
- the installation according to the invention overcomes clogging problems, thanks to the drive effect of the turbine which equips it and which causes a suction of the powder during its passage through the unit. particle reduction.
- the installation according to the invention is also very flexible in terms of adjustments since the critical size, above which particles are reduced, can be modulated very simply by modifying one of the parameters of the installation involved in determining this critical size. In addition, once this critical size has been determined, no further adjustment is necessary.
- FIG. 1 is a schematic view of a nuclear fuel powder processing installation according to the invention
- - Figure 2 is an exploded perspective view, with parts broken away, of the various constituent elements of the particle reduction unit of the installation of Figure 1
- - Figure 3 is a partial diametral sectional view of the reduction unit of Figure 2;
- FIG. 4 is a cross section from above, showing a turbine and cutting blades belonging to the particle reduction unit illustrated in FIGS. 2 and 3.
- FIG. 1 shows, schematically, a nuclear fuel powder processing installation.
- This installation is provided, at its upper end, or upstream, with a flange or crown 2 allowing the docking of a container 4 whose bottom is provided with a valve not shown, for example of the guillotine type.
- This container is loaded with a nuclear fuel powder obtained by conversion, for example in a dry process, intended to transform an initial compound such as UF 6 into an oxide, such as U0 2 .
- the crown 2 surmounts a pipe 6 extending, at its lower end, by a conical hopper 8 with a double envelope.
- Line 6 is provided, at its upper end, with a detection probe 12 suitable for detecting the presence of powder and being in relation to an automatic valve 14 intended to close the line in the absence of powder.
- a flow regulator not shown, is provided at the downstream end of the pipe 6, at the connection with the hopper 8.
- This hopper 8 is connected, at its downstream end, to a metal particle detector of known type, designated in as a whole by the reference 18.
- This detector which is provided with a bypass line 20 capable of collecting metallic impurities, is connected, via an intermediate tube 22, to a unit 24 for reducing powder particles.
- This reduction unit 24 which will be described in more detail below, is connected, at its downstream end, to an outlet conduit 26 of the installation, in which the treated nuclear fuel powder circulates, which is directed towards a storage unit 27.
- This outlet duct 26 is provided with a valve 28 intended to selectively block the flow thereof.
- a double pipe 29 (or recirculation) makes it possible to balance the pressure between upstream and downstream of the unit 24 for reducing powder particles.
- Figures 2 and 3 illustrate the particle reduction unit 24, shown on a larger scale than in Figure 1.
- This unit 24 comprises a hopper 30 for admitting powder to be treated, placed in communication with the downstream end of the tube 22 shown in FIG. 1.
- This hopper 30 is provided, at its lower end, with a collar 32 which is flush, as shown in particular in Figure 3, the upstream end of a chamber 34, in which are housed all the elements arranged downstream of the flange 32.
- the latter is supported, by means of a annular flange 36, against the upper end of a micro-cutting head designated as a whole by the reference 38.
- this micro-cutting head 38 comprises two annular flanges respectively upper 40 and lower 42, between which blades are arranged 44.
- the upper flange 40 bears against the underside of the flange 32 and against a shoulder 46 which is provided with an upper edge 48 of the chamber 34.
- the lower flange 42 is secured, for example by screwing, to a support 50, the lower end of which rests on a non-chassis depicted of the installation.
- the annular head 38 receives, in its internal volume, a circular turbine 52, comprising two flanges respectively upper 54 and lower 56, between which fins 58 are fixed, which will be shown more precisely in FIG. 4.
- the upper flange 54 has a frustoconical upper end 60 defining an upstream orifice 62 of the turbine 52, placed in communication with the downstream end of the inlet funnel 30.
- the lower flange 56 has a bottom 64 extended by an upper flange 66.
- This bottom 64 is pierced with a central orifice intended for the passage of a stud 68, cooperating with a washer 70 and a nut 72 for the purpose of fixing the turbine 52 to a shaft 74 for driving the turbine, which is connected to a motor not shown and is free to rotate inside the support 50.
- a connecting piece 75 surrounded by an O-ring 75A, is interposed between the bottom 64 and the shaft 74. This part 75 is fixed to the bottom by pins 75B.
- a lower retaining ring 76, or wear ring, to which a flange 78 of corresponding profile is attached, with the interposition of a seal of rectangular section 80, is disposed between the walls opposite the lower flange 42 of the head 38 and from the bottom 64 of the lower flange 56 of the turbine 52.
- FIG. 4 illustrates, on a larger scale than FIGS. 2 and 3, part of the blades 44 equipping the micro-cutting head 38, as well as one of the fins 58 equipping the turbine 52.
- the blades 44 are for example provided at number of 180, at the periphery of the micro-cutting head 38.
- Each blade 44 has, in top view, a generally rectangular profile and has two faces 82, 84 in relief, extending symmetrically with respect to the main axis A of this blade.
- the cross section of the blade increases towards the inside of the cutting head.
- These faces 82, 84 have draft angles a, a ', with respect to the axis A, which are between 0 and 10 °. These angles. and ⁇ 'can be the same or different.
- the distance d separating two adjacent blades 44, at their flared inner end, is for example between 0.03 and 3 mm and, preferably, between 0.1 and 0.4 mm.
- the axis A of each blade is inclined, relative to the diameter D of the cutting head, at an angle ⁇ between 0 and 10 °, preferably between 1 and 5 °. This inclination can be adjusted in a known manner.
- the fin 58 which extends over the outer periphery of the turbine 52, has a curved shape and comprises a body 58A made for example of stainless steel and terminated by an end plate 58B made of tungsten carbide.
- the opposite faces of the inner end of the blades 44 and of the plate 58B of the fin 58 are separated from a distance of between 0.3 and 0.6 mm, depending on the wear of the blades and the turbine.
- each fin 58 is rotated, according to arrow F, at a speed of between 6,000 and 12,000 revolutions per minute.
- the container 4 is approached on the crown 2.
- the container 4 valve, the valve 28 and a valve (not shown) controlling the supply of the nozzle 25 with nitrogen are successively opened.
- the particle detector 18 is started up and the upper automatic valve 14 is opened, so that the powder flows from the container 4 towards the reduction unit 24.
- the powder is admitted into the reduction unit 24 via the hopper 30, then flows towards the upstream orifice 62 of the turbine. It then pours onto the upper surface of the lower flange 56 of the turbine, and is driven centrifugally due to the high speed rotation to which this turbine is subjected. These particles are therefore directed towards the blades 44 with which the micro-cutting head 38 is provided.
- Two neighboring blades define, by their opposite lateral faces, a path 86 along which a particle larger than a particle which cannot be progressed cannot be advanced, which is also known as critical size.
- Each pair of adjacent blades 44 therefore constitutes a means for retaining coarse particles.
- the critical size is a function of the distance d separating the facing faces of two adjacent blades, the angles of inclination ⁇ and ′ of these faces, the angle of inclination ⁇ of each blade with respect to the diametrical axis D of the head 38, as well as of the speed of rotation of the turbine 52. Only the powder particles whose size is less than this critical size flow freely through the path 86 defined by the assembly of the blades 44.
- free flow means a flow in which the particles are not affected by the action of the blades 44.
- particles whose size is greater than this critical size are subjected to reduction by grinding. The latter is generated by the action of the end plates 58B of the fins 58, which, during their rotational movement, continuously shear the coarse particles against the active faces of the blades 44.
- the particles reduced to a size less than the critical size then flow along the paths provided by each pair of adjacent blades and are dispersed in the flow of particles of size below the critical size, which are not subjected to the 'action of the blades 44.
- the set of paths 86 the width of which increases towards the outside of the head 38, due to the clearance of the blades 44, forms a common path for the fine particles and the reduced particles.
- the particles initially admitted inside the turbine 52 flow, possibly after being reduced, towards the outside of the cutting head 38 and are admitted into the chamber 34.
- the average particle size, downstream of the blades 44, is less than that of the particles upstream of these blades, due to the grinding operation to which some of these particles are subjected.
- the reduction unit 24 therefore constitutes a unit for lowering the average size of the particles, inducing a modification of the general allule of the spectrum of these particles.
- the flow of the particles is directed by gravity towards the outlet conduit 26, so as to be stored in a container, not shown.
- the upper valve 14 is closed and an additional container, similar to that shown in FIG. 1, can be docked at the level of the upper crown 2.
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- Plasma & Fusion (AREA)
- General Engineering & Computer Science (AREA)
- High Energy & Nuclear Physics (AREA)
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- Geology (AREA)
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- Food Science & Technology (AREA)
- Organic Chemistry (AREA)
- Crushing And Pulverization Processes (AREA)
- Inorganic Compounds Of Heavy Metals (AREA)
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- Disintegrating Or Milling (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
The invention concerns a method comprising a step which consists in passing the powder through a unit for reducing (24) the average size of the powder particles, bringing about a modification in the general appearance of the spectrum of the particles, step whereby are retained in the reduction unit so-called coarse particles whereof the size is greater than a predetermined size, or critical size, while so-called fine particles whereof the size is less than said critical size are allowed to pass through. The size of the coarse particles is continuously reduced (in 44) in the reduction unit so as to form particles with a size less than the critical size, or reduced particles, and the reduced particles are distributed in the free flow of fine particles. The method eliminates the problems of clogging, contamination and recycling.
Description
PROCEDE ET INSTALLATION DE TRAITEMENT D'UNE POUDRE COMBUSTIBLE NUCLEAIRE PROCESS AND PLANT FOR THE TREATMENT OF NUCLEAR FUEL POWDER
La présente invention concerne un procédé et une installation de traitement d'une poudre combustible nucléaire.The present invention relates to a method and an installation for treating a nuclear fuel powder.
L'invention vise plus particulièrement le traitement d'une telle poudre, du type oxyde, tel qu'U02, obtenue en aval de l'étape visant à transformer en cet oxyde un composé, tel qu'UFg. La poudre ayant subi cette étape de conversion est alors soumise à une phase de réduction de la taille moyenne des particules qui la constituent.The invention relates more particularly to the treatment of such a powder, of the oxide type, such as U0 2 , obtained downstream of the step aimed at transforming into this oxide a compound, such as UFg. The powder having undergone this conversion step is then subjected to a phase of reduction of the average size of the particles which constitute it.
L'obtention d'U02 peut être opérée de différentes façons. Un premier mode, dit par voie humide, conduit à l'obtention d'agrégats grossiers, dont le diamètre moyen est d'environ 1 mm. Dans ce cas, l'étape de réduction de la taille moyenne des particules consiste à décaler le spectre granulométrique dans son ensemble, sans modifier l'allure générale de ce spectre. Ceci est obtenu, de manière habituelle, par broyage au moyen d'installations mécaniques, telles que par exemple des broyeurs à boulets, à marteaux ou à jet d'air. L'ensemble des particules formant la poudre combustible est soumis à l'action de ces broyeurs mécaniques.U0 2 can be obtained in different ways. A first mode, called wet, leads to the production of coarse aggregates, the average diameter of which is around 1 mm. In this case, the step of reducing the average size of the particles consists in shifting the particle size spectrum as a whole, without modifying the general appearance of this spectrum. This is obtained, in the usual way, by grinding by means of mechanical installations, such as for example ball, hammer or air jet mills. All of the particles forming the combustible powder are subjected to the action of these mechanical mills.
Cette solution connue présente cependant certains inconvé- nients . Ainsi, les broyeurs à boulets ne permettent pas un débit important et induisent des problèmes de contamination liés à leur déchargement. Ils sont de surcroît bruyants et ne permettent pas de résoudre le problème de ré-agglomération de la poudre. Les broyeurs à marteaux, outre leur caractère bruyant, ne garantissent pas l'obtention de poudre d'une homogénéité satisfaisante.This known solution has certain drawbacks, however. Thus, ball mills do not allow a significant flow and induce contamination problems related to their unloading. They are also noisy and do not solve the problem of re-agglomeration of the powder. Hammer mills, apart from their noisy nature, do not guarantee obtaining powder of satisfactory homogeneity.
Enfin, les broyeurs à jet d'air sont à l'origine de problèmes de colmatage et induisent des échauffements importants, ce qui implique de travailler avec un débit peu élevé. II est également nécessaire d'adjoindre une installation de retraitement des gaz à de tels broyeurs.Finally, air jet mills cause clogging problems and induce significant overheating, which means working with a low flow rate. It is also necessary to add a gas reprocessing installation to such mills.
Il existe également des procédés de conversion d'UF6 en U02 utilisant une voie dite sèche et conduisant à l'obtention d'une
poudre plus fine que celle correspondant à la voie humide, formée de particules agrégées dont la taille moyenne est d'environ 100 micromètres. Cette poudre contient cependant des particules fluorées du type U02F2, qui possèdent une taille plus importante que les particules constitutives du reste de la poudre. Lorsque ces particules fluorées dépassent une taille critique, d'environ 300 micromètres, elles sont à l'origine de problèmes notamment liés au frittage, de sorte qu'il est nécessaire de les éliminer. A cette fin, il est connu de mettre en oeuvre un tamisage destiné à retenir les particules dont la taille est supérieure à la taille critique précédemment évoquée. La taille moyenne des particules s 'écoulant au travers de ce tamis est donc inférieure à celle des particules admises en amont de ce dernier. Contrairement aux techniques visant à décaler le spectre granulométrique dans son ensemble, on procède ici à un écrêta- ge, qui contribue à modifier l'allure générale de ce spectre.There are also processes for converting UF 6 into U0 2 using a so-called dry route and leading to the production of a finer powder than that corresponding to the wet process, formed of aggregated particles whose average size is approximately 100 micrometers. This powder, however, contains fluorinated particles of the U0 2 F 2 type , which have a larger size than the constituent particles of the rest of the powder. When these fluorinated particles exceed a critical size, of around 300 micrometers, they are the cause of problems in particular related to sintering, so that it is necessary to eliminate them. To this end, it is known to implement a sieving intended to retain the particles whose size is greater than the critical size previously mentioned. The average size of the particles flowing through this sieve is therefore less than that of the particles admitted upstream of the latter. Contrary to the techniques aiming to shift the granulometric spectrum as a whole, one proceeds here to a clipping, which contributes to modify the general shape of this spectrum.
Les particules de taille élevée, retenues par les mailles du tamis, doivent être soumises à des opérations visant à les recycler et à les défluorer en vue de leur mélange ultérieur avec des particules plus fines.The particles of large size, retained by the mesh of the sieve, must be subjected to operations aimed at recycling and defluorinating them with a view to their subsequent mixing with finer particles.
Cette solution mettant en oeuvre le tamisage présente également certains inconvénients. En effet, les particules ne s 'écoulant pas au travers du tamis, forment ce que l'on appelle le "refus tamis" et doivent être régulièrement évacuées, ce qui provoque des arrêts fréquents dans la fabrication. Ces opérations d'évacuation sont, la plupart du temps, mises en oeuvre de façon manuelle et se révèlent donc particulièrement contaminantes . Du fait de leur structure mécanique, les tamis possèdent une résistance limitée et sont sujets à des ruptures. Ceci implique alors de retraiter l'ensemble de la poudre s 'étant écoulée au travers du tamis considéré. Cette fragilité implique également qu' il est nécessaire de procéder à un changement fréquent de ces tamis.This solution using sieving also has certain drawbacks. Indeed, the particles not flowing through the sieve, form what is called "sieve rejection" and must be regularly removed, which causes frequent stops in manufacturing. These evacuation operations are, most of the time, carried out manually and therefore prove to be particularly contaminating. Due to their mechanical structure, the screens have limited strength and are subject to breakage. This then involves reprocessing all of the powder that has flowed through the screen in question. This fragility also means that it is necessary to change these screens frequently.
Les tamis endommagés peuvent être réparés afin de limiter les coûts mais ces réparations ont pour conséquence de réduire la surface filtrante.
Dans le cas de poudres possédant une mauvaise coulabilité, l'utilisation de tamis induit un problème de colmatage, dû au fait que la poudre s'agglomère et obstrue le tamis. Il est alors nécessaire de mettre en oeuvre un décolmatage, par exemple par ultra-sons, ou bien encore par percussion, ce qui provoque alors une dégradation mécanique du tamis.Damaged screens can be repaired to keep costs down, but these repairs reduce the filtering surface. In the case of powders having poor flowability, the use of sieves induces a clogging problem, due to the fact that the powder agglomerates and clogs the sieve. It is then necessary to implement unclogging, for example by ultrasound, or even by percussion, which then causes mechanical degradation of the screen.
La présente invention se propose de mettre en oeuvre un procédé de traitement de poudre combustible nucléaire permettant de pallier l'ensemble des inconvénients inhérents aux différents procédés de l'art antérieur évoqués ci-dessus.The present invention proposes to implement a method for treating nuclear fuel powder making it possible to overcome all of the drawbacks inherent in the various methods of the prior art mentioned above.
A cet effet, elle a pour objet un procédé de traitement d'une poudre combustible nucléaire, du type oxyde, tel qu'U02, ledit procédé étant réalisé notamment après une phase de conversion en ledit oxyde d'un composé, tel qu'UFs, ledit procédé comprenant une étape de passage de la poudre à travers une unité de réduction de la taille moyenne des particules de la poudre, induisant une modification de l'allure générale du spectre des particules, étape dans laquelle on retient, dans l'unité de réduction, des particules, dites grossières, dont la taille est supérieure à une taille prédéterminée, ou taille critique, alors qu'on laisse s'écouler librement des particules, dites fines, dont la taille est inférieure à ladite taille critique, caractérisé en ce qu'on réduit en continu dans l'unité de réduction, la taille des particules grossières, de manière à former des particules de taille inférieure à la taille critique, ou particules réduites, et on distribue les particules réduites dans l'écoulement libre des particules fines .To this end, it relates to a process for treating a nuclear combustible powder, of the oxide type, such as U0 2 , said process being carried out in particular after a phase of conversion into said oxide of a compound, such as UF s , said method comprising a step of passing the powder through a unit for reducing the average size of the particles of the powder, inducing a modification of the general appearance of the spectrum of particles, step in which we retain, in the reduction unit, so-called coarse particles, the size of which is greater than a predetermined size, or critical size, while particles, called fine particles, whose size is less than said critical size, are allowed to flow freely, characterized in that the size of the coarse particles is continuously reduced in the reduction unit so as to form particles of size less than the critical size, or reduced particles, and d distributes the reduced particles in the free flow of fine particles.
L'invention a également pour objet une installation de traitement d'une poudre en un matériau combustible nucléaire, du type renfermant un oxyde, tel qu'U02, ladite installation étant disposée notamment en aval d'une unité de conversion en ledit oxyde d'un composé, tel qu'UFs, ladite installation comprenant une unité de réduction de la taille moyenne des particules formant la poudre, induisant une modification de l'allure générale du spectre des particules, ladite unité comportant des moyens de retenue de particules dites grossières, dont la taille est supérieure à une taille prédéterminée,
ou taille critique, lesdits moyens de retenue étant propres à laisser s'écouler librement des particules dites fines, de taille inférieure à la taille critique, caractérisée en ce que ladite unité de réduction comprend également des moyens de réduction en continu des particules grossières, de manière à former des particules, dites réduites, de taille inférieure à la taille critique, ainsi que des moyens de distribution des particules réduites dans l'écoulement libre des particules fines . L'invention permet de réaliser les objectifs précédemment mentionnés. En effet, le fait de réduire les particules dont la taille est supérieure à une taille critique, afin de les disperser parmi les particules s 'écoulant librement permet, tout en n'autorisant pas le passage d'une fraction précise de la poudre, de s'affranchir de l'opération d'évacuation de cette fraction considérée, comme cela était le cas dans l'art antérieur faisant appel à des tamis. Le procédé conforme à l'invention s'avère donc nettement moins contaminant que ceux utilisant de tels tamis. Le procédé conforme à l'invention est également susceptible de fonctionner en continu, sans rupture sensible de flux et éventuellement au moyen de poudres successives de natures différentes. Il permet également le traitement de poudres dont les débits sont à même de varier de façon importante . Le procédé conforme à l'invention possède une efficacité remarquable, dans la mesure où toutes les particules s 'écoulant en aval des moyens de réduction possèdent effectivement une taille inférieure à la taille critique prédéterminée.The invention also relates to an installation for treating a powder of a nuclear combustible material, of the type containing an oxide, such as U0 2 , said installation being arranged in particular downstream of a unit for converting said oxide into a compound, such as UF s , said installation comprising a unit for reducing the average size of the particles forming the powder, inducing a modification in the general appearance of the spectrum of particles, said unit comprising so-called particle retaining means coarse, larger than a predetermined size, or critical size, said retaining means being capable of allowing free flow of so-called fine particles, of size smaller than the critical size, characterized in that said reduction unit also comprises means for continuously reducing coarse particles, so as to form particles, called reduced, of size smaller than the critical size, as well as means for distributing the reduced particles in the free flow of fine particles. The invention makes it possible to achieve the objectives mentioned above. Indeed, the fact of reducing the particles whose size is greater than a critical size, in order to disperse them among the particles flowing freely allows, while not allowing the passage of a precise fraction of the powder, to get rid of the operation of evacuation of this fraction considered, as was the case in the prior art using sieves. The process according to the invention therefore proves to be significantly less contaminating than those using such sieves. The process according to the invention is also capable of operating continuously, without appreciable flow break and possibly by means of successive powders of different natures. It also allows the treatment of powders whose flow rates are able to vary significantly. The process according to the invention has remarkable efficiency, in so far as all the particles flowing downstream of the reduction means actually have a size less than the predetermined critical size.
Le procédé conforme à l'invention garantit, dans une large mesure, une absence de pollution, étant donné qu'il n'implique ni re-traitement de produits éventuellement éliminés, ni retraitement d'éventuels fluides mis en oeuvre pour la réduction de la taille des particules.The process according to the invention guarantees, to a large extent, an absence of pollution, since it does not involve either re-treatment of products which may have been eliminated, or reprocessing of any fluids used to reduce the particle size.
L' installation de traitement de poudre combustible nucléaire conforme à l'invention est très flexible. En effet, elle est susceptible de traiter des produits dont l'enrichissement, voire la nature, sont différents. Etant donné que l'installation conforme à l'invention est dépourvue de zone de
rétention de poudre, il n'est pas nécessaire de procéder à un quelconque nettoyage lors du passage d'un produit à un autre. L'installation conforme à l'invention permet d'atteindre des débits élevés, qui peuvent par exemple être de cinq à dix fois plus importants que ceux autorisés par le biais d'une installation de traitement faisant appel à des tamis. L'installation de l'invention engendre des coûts de fonctionnement réduits par rapport à l'art antérieur. Elle garantit également une intégrité très satisfaisante de la poudre traitée, étant donné qu'elle permet d'éviter, dans une large mesure, tous les échauffements et n'induit donc aucun phénomène d'oxydation. Etant donné que cette installation ne fait appel à aucun lubrifiant, la poudre, lors de son passage dans l'installation, n'est pas soumise à une contamination du fait de sa mise en contact avec un tel produit extérieur.The nuclear fuel powder processing installation according to the invention is very flexible. Indeed, it is likely to treat products whose enrichment, even the nature, are different. Since the installation according to the invention is devoid of zone of retention of powder, it is not necessary to carry out any cleaning when switching from one product to another. The installation according to the invention makes it possible to reach high flow rates, which can for example be five to ten times greater than those authorized by means of a treatment installation using screens. The installation of the invention generates reduced operating costs compared to the prior art. It also guarantees a very satisfactory integrity of the treated powder, since it makes it possible to avoid, to a large extent, all overheating and therefore does not induce any oxidation phenomenon. Since this installation does not use any lubricant, the powder, during its passage through the installation, is not subject to contamination due to its contact with such an external product.
L'installation conforme à l'invention permet de s'affranchir des problèmes de colmatage, grâce à l'effet d'entraînement de la turbine qui l'équipe et qui provoque une aspiration de la poudre lors de son passage dans l'unité de réduction des particules.The installation according to the invention overcomes clogging problems, thanks to the drive effect of the turbine which equips it and which causes a suction of the powder during its passage through the unit. particle reduction.
L'installation conforme à l'invention est également d'une grande flexibilité en termes de réglages puisque la taille critique, au-dessus de laquelle des particules sont réduites, peut être modulée de façon très simple en modifiant l'un des paramètres de l'installation intervenant dans la détermination de cette taille critique. De plus, une fois cette taille critique déterminée, aucun réglage supplémentaire n'est nécessaire .The installation according to the invention is also very flexible in terms of adjustments since the critical size, above which particles are reduced, can be modulated very simply by modifying one of the parameters of the installation involved in determining this critical size. In addition, once this critical size has been determined, no further adjustment is necessary.
L'invention va être décrite ci-dessous, en référence aux dessins annexés, donnés uniquement à titre d'exemples non limitatifs et dans lesquels :The invention will be described below, with reference to the accompanying drawings, given only by way of nonlimiting examples and in which:
- la figure 1 est une vue schématique d'une installation de traitement de poudre combustible nucléaire conforme à l'invention ; - la figure 2 est une vue en perspective éclatée, avec arrachements, des différents éléments constitutifs de l'unité de réduction des particules de l'installation de la figure 1 ;
- la figure 3 est une vue en coupe partielle diamétrale de l'unité de réduction de la figure 2 ; et- Figure 1 is a schematic view of a nuclear fuel powder processing installation according to the invention; - Figure 2 is an exploded perspective view, with parts broken away, of the various constituent elements of the particle reduction unit of the installation of Figure 1; - Figure 3 is a partial diametral sectional view of the reduction unit of Figure 2; and
- la figure 4 est une coupe transversale du dessus, montrant une turbine et des lames de coupe appartenant à l'unité de réduction des particules illustrée aux figures 2 et 3.FIG. 4 is a cross section from above, showing a turbine and cutting blades belonging to the particle reduction unit illustrated in FIGS. 2 and 3.
La figure 1 représente, de manière schématique, une installation de traitement de poudre combustible nucléaire. Cette installation est pourvue, à son extrémité supérieure, ou amont, d'une bride ou couronne 2 permettant l'accostage d'un conteneur 4 dont le fond est pourvu d'une vanne non représentée, par exemple du type guillotine. Ce conteneur est chargé d'une poudre combustible nucléaire obtenu par conversion, par exemple en voie sèche, destinée à transformer un composé initial tel qu'UF6 en un oxyde, tel qu'U02.Figure 1 shows, schematically, a nuclear fuel powder processing installation. This installation is provided, at its upper end, or upstream, with a flange or crown 2 allowing the docking of a container 4 whose bottom is provided with a valve not shown, for example of the guillotine type. This container is loaded with a nuclear fuel powder obtained by conversion, for example in a dry process, intended to transform an initial compound such as UF 6 into an oxide, such as U0 2 .
La couronne 2 surmonte une canalisation 6 se prolongeant, à son extrémité inférieure, par une trémie conique 8 à double enveloppe. La canalisation 6 est pourvue, à son extrémité supérieure, d'une sonde de détection 12 propre à déceler la présence de poudre et se trouvant en relation avec une vanne automatique 14 destinée à obturer la canalisation en l'absence de poudre . Un régulateur de débit non représenté est prévu à l'extrémité aval de la canalisation 6, au niveau du raccordement avec la trémie 8. Cette trémie 8 est reliée, à son extrémité aval, à un détecteur de particules métalliques de type connu, désigné dans son ensemble par la référence 18. Ce détecteur, qui est muni d'une ligne de dérivation 20 propre à recueillir les impuretés métalliques est raccordé, via une tubulure intermédiaire 22, à une unité 24 de réduction des particules de poudre. Un piquageThe crown 2 surmounts a pipe 6 extending, at its lower end, by a conical hopper 8 with a double envelope. Line 6 is provided, at its upper end, with a detection probe 12 suitable for detecting the presence of powder and being in relation to an automatic valve 14 intended to close the line in the absence of powder. A flow regulator, not shown, is provided at the downstream end of the pipe 6, at the connection with the hopper 8. This hopper 8 is connected, at its downstream end, to a metal particle detector of known type, designated in as a whole by the reference 18. This detector, which is provided with a bypass line 20 capable of collecting metallic impurities, is connected, via an intermediate tube 22, to a unit 24 for reducing powder particles. A stitching
25 d'alimentation en azote débouche à l'intérieur de l'unité de réduction 24, à l'extrémité aval de cette dernière.25 supplying nitrogen opens into the reduction unit 24, at the downstream end thereof.
Cette unité de réduction 24, qui sera décrite plus en détail dans ce qui suit, est reliée, à son extrémité aval, à un conduit de sortie 26 de l'installation, dans lequel circule la poudre combustible nucléaire traitée, qui est dirigée vers une unité de stockage 27. Ce conduit de sortie 26 est pourvu d'une vanne 28 destinée à en obturer sélectivement l'écoulement. Une
double canalisation 29 (ou recirculation) permet d'équilibrer la pression entre l'amont et l'aval de l'unité 24 de réduction des particules de poudre.This reduction unit 24, which will be described in more detail below, is connected, at its downstream end, to an outlet conduit 26 of the installation, in which the treated nuclear fuel powder circulates, which is directed towards a storage unit 27. This outlet duct 26 is provided with a valve 28 intended to selectively block the flow thereof. A double pipe 29 (or recirculation) makes it possible to balance the pressure between upstream and downstream of the unit 24 for reducing powder particles.
Les figures 2 et 3 illustrent l'unité de réduction 24 des particules, représentée à plus grande échelle que sur la figure 1.Figures 2 and 3 illustrate the particle reduction unit 24, shown on a larger scale than in Figure 1.
Cette unité 24 comprend une trémie 30 d'admission de poudre à traiter, mise en communication avec l'extrémité aval de la tubulure 22 représentée à la figure 1. Cette trémie 30 est pourvue, à son extrémité inférieure, d'une collerette 32 qui affleure, comme le montre en particulier la figure 3, l'extrémité amont d'une chambre 34, dans laquelle sont logés l'ensemble des éléments disposés en aval de la collerette 32. Cette dernière prend appui, par l'intermédiaire d'une bride annulaire 36, contre l'extrémité supérieure d'une tête de micro-coupe désignée dans son ensemble par la référence 38.This unit 24 comprises a hopper 30 for admitting powder to be treated, placed in communication with the downstream end of the tube 22 shown in FIG. 1. This hopper 30 is provided, at its lower end, with a collar 32 which is flush, as shown in particular in Figure 3, the upstream end of a chamber 34, in which are housed all the elements arranged downstream of the flange 32. The latter is supported, by means of a annular flange 36, against the upper end of a micro-cutting head designated as a whole by the reference 38.
Comme cela sera décrit de manière plus précise en référence à la figure 4, cette tête de micro-coupe 38 comporte deux flasques annulaires respectivement supérieur 40 et inférieur 42, entre lesquels sont disposées des lames 44. Le flasque supérieur 40 est en appui contre la face inférieure de la collerette 32 et contre un épaulement 46 dont est pourvu un rebord supérieur 48 de la chambre 34. Le flasque inférieur 42 est assujetti, par exemple par vissage, à un support 50, dont l'extrémité inférieure repose sur un châssis non représenté de 1' installation.As will be described more precisely with reference to FIG. 4, this micro-cutting head 38 comprises two annular flanges respectively upper 40 and lower 42, between which blades are arranged 44. The upper flange 40 bears against the underside of the flange 32 and against a shoulder 46 which is provided with an upper edge 48 of the chamber 34. The lower flange 42 is secured, for example by screwing, to a support 50, the lower end of which rests on a non-chassis depicted of the installation.
La tête annulaire 38 reçoit, dans son volume intérieur, une turbine circulaire 52, comprenant deux flasques respectivement supérieur 54 et inférieur 56, entre lesquels sont fixées des ailettes 58, qui seront représentées de manière plus précise à la figure 4. Le flasque supérieur 54 possède une extrémité supérieure tronconique 60 définissant un orifice amont 62 de la turbine 52, mis en communication avec l'extrémité aval de l'entonnoir d'admission 30. Le flasque inférieur 56 comporte un fond 64 prolongé par une collerette supérieure 66. Ce fond 64 est percé d'un orifice central destiné au passage d'un goujon 68, coopérant avec une rondelle 70 et un écrou 72 en vue de la fixation de la turbine
52 à un arbre 74 d'entraînement de la turbine, qui est relié à un moteur non représenté et est libre de tourner à l'intérieur du support 50. Une pièce de liaison 75, entourée d'un joint torique 75A, est intercalée entre le fond 64 et l'arbre 74. Cette pièce 75 est fixée au fond par des pions 75B.The annular head 38 receives, in its internal volume, a circular turbine 52, comprising two flanges respectively upper 54 and lower 56, between which fins 58 are fixed, which will be shown more precisely in FIG. 4. The upper flange 54 has a frustoconical upper end 60 defining an upstream orifice 62 of the turbine 52, placed in communication with the downstream end of the inlet funnel 30. The lower flange 56 has a bottom 64 extended by an upper flange 66. This bottom 64 is pierced with a central orifice intended for the passage of a stud 68, cooperating with a washer 70 and a nut 72 for the purpose of fixing the turbine 52 to a shaft 74 for driving the turbine, which is connected to a motor not shown and is free to rotate inside the support 50. A connecting piece 75, surrounded by an O-ring 75A, is interposed between the bottom 64 and the shaft 74. This part 75 is fixed to the bottom by pins 75B.
Un anneau inférieur de retenue 76, ou anneau d'usure, sur lequel est rapportée une bride 78 de profil correspondant, avec interposition d'un joint de section rectangulaire 80, est disposé entre les parois en regard du flasque inférieur 42 de la tête 38 et du fond 64 du flasque inférieur 56 de la turbine 52. Un tel agencement permet de maintenir l'anneau et d'éviter le passage de poudre non broyée.A lower retaining ring 76, or wear ring, to which a flange 78 of corresponding profile is attached, with the interposition of a seal of rectangular section 80, is disposed between the walls opposite the lower flange 42 of the head 38 and from the bottom 64 of the lower flange 56 of the turbine 52. Such an arrangement makes it possible to maintain the ring and to avoid the passage of unground powder.
La figure 4 illustre, à plus grande échelle que les figures 2 et 3 , une partie des lames 44 équipant la tête de micro-coupe 38, ainsi qu'une des ailettes 58 équipant la turbine 52. Les lames 44 sont par exemple prévues au nombre de 180, à la périphérie de la tête de micro-coupe 38.FIG. 4 illustrates, on a larger scale than FIGS. 2 and 3, part of the blades 44 equipping the micro-cutting head 38, as well as one of the fins 58 equipping the turbine 52. The blades 44 are for example provided at number of 180, at the periphery of the micro-cutting head 38.
Chaque lame 44 présente, en vue de dessus, un profil globalement rectangulaire et possède deux faces 82, 84 en dépouille, s' étendant de manière symétrique par rapport à l'axe principal A de cette lame. La section transversale de la lame augmente vers l'intérieur de la tête de coupe. Ces faces 82, 84 présentent des angles de dépouille a , a ' , par rapport à l'axe A, qui sont compris entre 0 et 10°. Ces angles . et α' peuvent être identiques ou différents.Each blade 44 has, in top view, a generally rectangular profile and has two faces 82, 84 in relief, extending symmetrically with respect to the main axis A of this blade. The cross section of the blade increases towards the inside of the cutting head. These faces 82, 84 have draft angles a, a ', with respect to the axis A, which are between 0 and 10 °. These angles. and α 'can be the same or different.
La distance d séparant deux lames 44 adjacentes, au niveau de leur extrémité intérieure évasée, est par exemple comprise entre 0,03 et 3 mm et, de préférence, entre 0,1 et 0,4 mm. L'axe A de chaque lame est incliné, par rapport au diamètre D de la tête de coupe, selon un angle β compris entre 0 et 10°, de préférence entre 1 et 5° . Cette inclinaison peut être réglée de manière connue.The distance d separating two adjacent blades 44, at their flared inner end, is for example between 0.03 and 3 mm and, preferably, between 0.1 and 0.4 mm. The axis A of each blade is inclined, relative to the diameter D of the cutting head, at an angle β between 0 and 10 °, preferably between 1 and 5 °. This inclination can be adjusted in a known manner.
L'ailette 58, qui s'étend sur la périphérie extérieure de la turbine 52 , présente une forme recourbée et comprend un corps 58A réalisé par exemple en acier inoxydable et terminé par une plaquette d'extrémité 58B réalisée en carbure de tungstène. Les faces en regard de l'extrémité intérieure des lames 44 et de la plaquette 58B de l'ailette 58 sont séparées
d'une distance d' comprise entre 0,3 et 0,6 mm, en fonction de l'usure des lames et de la turbine. En service, chaque ailette 58 est mise en rotation, selon la flèche F, à une vitesse comprise entre 6 000 et 12 000 tours par minute. On va maintenant décrire la mise en oeuvre du procédé de traitement de poudre combustible nucléaire conforme à l'invention, en faisant référence à l'ensemble des figures 1 à 4.The fin 58, which extends over the outer periphery of the turbine 52, has a curved shape and comprises a body 58A made for example of stainless steel and terminated by an end plate 58B made of tungsten carbide. The opposite faces of the inner end of the blades 44 and of the plate 58B of the fin 58 are separated from a distance of between 0.3 and 0.6 mm, depending on the wear of the blades and the turbine. In service, each fin 58 is rotated, according to arrow F, at a speed of between 6,000 and 12,000 revolutions per minute. We will now describe the implementation of the nuclear fuel powder treatment process according to the invention, with reference to all of FIGS. 1 to 4.
On accoste tout d'abord le conteneur 4 sur la couronne 2. On procède ensuite aux ouvertures successives de la vanne du conteneur 4, de la vanne 28, et d'une vanne non représentée commandant l'alimentation du piquage 25 en azote. Puis, on initie la mise en marche du détecteur de particules 18 et on commande l'ouverture de la vanne automatique supérieure 14, de sorte que la poudre s'écoule depuis le conteneur 4 en direction de l'unité de réduction 24.First of all, the container 4 is approached on the crown 2. Next, the container 4 valve, the valve 28 and a valve (not shown) controlling the supply of the nozzle 25 with nitrogen are successively opened. Then, the particle detector 18 is started up and the upper automatic valve 14 is opened, so that the powder flows from the container 4 towards the reduction unit 24.
La poudre est admise dans l'unité de réduction 24 par l'intermédiaire de la trémie 30, puis s'écoule en direction de l'orifice amont 62 de la turbine. Elle se déverse ensuite sur la surface supérieure du flasque inférieur 56 de la turbine, et se trouve chassée de manière centrifuge du fait de la rotation à grande vitesse à laquelle est soumise cette turbine. Ces particules sont donc dirigée vers les lames 44 dont est munie la tête de micro-coupe 38.The powder is admitted into the reduction unit 24 via the hopper 30, then flows towards the upstream orifice 62 of the turbine. It then pours onto the upper surface of the lower flange 56 of the turbine, and is driven centrifugally due to the high speed rotation to which this turbine is subjected. These particles are therefore directed towards the blades 44 with which the micro-cutting head 38 is provided.
Deux lames voisines définissent, par leurs faces latérales en regard, un chemin 86 le long duquel ne peut pas progresser une particule supérieure à une taille qu'il est possible de déterminer au préalable, encore dénommée taille critique. Chaque couple de lames adjacentes 44 constitue donc un moyen de retenue des particules grossières. La taille critique est fonction de la distance d séparant les faces en regard de deux lames adjacentes, des angles d'inclinaison α et ' de ces faces, de l'angle d'inclinaison β de chaque lame par rapport à l'axe diamétral D de la tête 38, ainsi que de la vitesse de rotation de la turbine 52. Seules les particules de poudre dont la taille est inférieure à cette taille critique s'écoulent librement au travers du chemin 86 défini par l'ensemble des lames 44. Par écoulement libre, on entend un écoulement dans lequel les
particules ne sont pas affectées par l'action des lames 44. En revanche les particules dont la taille est supérieure à cette taille critique sont soumises à une réduction par broyage. Ce dernier est généré par l'action des plaquettes terminales 58B des ailettes 58, qui, lors de leur mouvement de rotation, cisaillent en continu les particules grossières contre les faces actives des lames 44.Two neighboring blades define, by their opposite lateral faces, a path 86 along which a particle larger than a particle which cannot be progressed cannot be advanced, which is also known as critical size. Each pair of adjacent blades 44 therefore constitutes a means for retaining coarse particles. The critical size is a function of the distance d separating the facing faces of two adjacent blades, the angles of inclination α and ′ of these faces, the angle of inclination β of each blade with respect to the diametrical axis D of the head 38, as well as of the speed of rotation of the turbine 52. Only the powder particles whose size is less than this critical size flow freely through the path 86 defined by the assembly of the blades 44. By free flow means a flow in which the particles are not affected by the action of the blades 44. On the other hand, particles whose size is greater than this critical size are subjected to reduction by grinding. The latter is generated by the action of the end plates 58B of the fins 58, which, during their rotational movement, continuously shear the coarse particles against the active faces of the blades 44.
Les particules réduites à une taille inférieure à la taille critique s'écoulent alors le long des chemins ménagés par chaque couple de lames adjacentes et sont dispersées dans l'écoulement des particules de taille inférieure à la taille critique, qui ne sont pas soumises à l'action des lames 44. L'ensemble des chemins 86, dont la largeur augmente vers l'extérieur de la tête 38, du fait de la dépouille des lames 44, forme un trajet commun pour les particules fines et les particules réduites.The particles reduced to a size less than the critical size then flow along the paths provided by each pair of adjacent blades and are dispersed in the flow of particles of size below the critical size, which are not subjected to the 'action of the blades 44. The set of paths 86, the width of which increases towards the outside of the head 38, due to the clearance of the blades 44, forms a common path for the fine particles and the reduced particles.
Les particules initialement admises à l'intérieur de la turbine 52 s'écoulent, éventuellement après avoir été réduites, vers l'extérieur de la tête de coupe 38 et sont admises dans la chambre 34. La taille moyenne des particules, en aval des lames 44, est inférieure à celle des particules en amont de ces lames, du fait de l'opération de broyage à laquelle sont soumises certaines de ces particules. L'unité de réduction 24 constitue donc une unité d'abaissement de la taille moyenne des particules, induisant une modification de l'allule générale du spectre de ces particules. L'écoulement des particules est dirigé par gravité vers le conduit de sortie 26, de manière à être stockée dans un conteneur non représenté. Lorsque la sonde 12 détecte l'absence de poudre, la vanne supérieure 14 est fermée et un conteneur supplémentaire, analogue à celui 4 représenté à la figure 1, peut être accosté au niveau de la couronne supérieure 2.The particles initially admitted inside the turbine 52 flow, possibly after being reduced, towards the outside of the cutting head 38 and are admitted into the chamber 34. The average particle size, downstream of the blades 44, is less than that of the particles upstream of these blades, due to the grinding operation to which some of these particles are subjected. The reduction unit 24 therefore constitutes a unit for lowering the average size of the particles, inducing a modification of the general allule of the spectrum of these particles. The flow of the particles is directed by gravity towards the outlet conduit 26, so as to be stored in a container, not shown. When the probe 12 detects the absence of powder, the upper valve 14 is closed and an additional container, similar to that shown in FIG. 1, can be docked at the level of the upper crown 2.
Dans les exemples décrits et représentés, il a uniquement été fait mention d'une installation de traitement globalement verticale, dans laquelle les particules progressent par gravité. Il est également possible de convoyer ces particules par d'autres voies, notamment grâce à des moyens pneumatiques.
In the examples described and shown, only a generally vertical treatment installation has been mentioned, in which the particles progress by gravity. It is also possible to convey these particles by other routes, in particular by pneumatic means.
Claims
1. Procédé de traitement d'une poudre combustible nucléai- re , du type oxyde, tel qu'U02, ledit procédé étant réalisé notamment après une phase de conversion en ledit oxyde d'un composé, tel qu'UF5, ledit procédé comprenant une étape de passage de la poudre à travers une unité de réduction de la taille moyenne des particules de la poudre induisant une modification de l'allure générale du spectre des particules, étape dans laquelle on retient, dans l'unité de réduction, des particules, dites grossières, dont la taille est supérieure à une taille prédéterminée, ou taille critique, alors qu'on laisse s'écouler librement (en 86) des particules, dites fines, dont la taille est inférieure à ladite taille critique, caractérisé en ce qu'on réduit en continu (en 44) dans l'unité de réduction (24), la taille des particules grossières, de manière à former des particules de taille inférieure à la taille critique, ou particules réduites, et on distribue les particules réduites dans l'écoulement libre (en 86) des particules fines.1. Method for treating a nuclear combustible powder, of the oxide type, such as U0 2 , said method being carried out in particular after a phase of conversion into said oxide of a compound, such as UF 5 , said method comprising a step of passing the powder through a unit for reducing the average size of the particles of the powder inducing a modification of the general appearance of the spectrum of the particles, step in which we retain, in the reduction unit, particles, called coarse, whose size is greater than a predetermined size, or critical size, while particles (called 86) are allowed to flow freely (fine), whose size is less than said critical size, characterized in what is continuously reduced (at 44) in the reduction unit (24), the size of the coarse particles, so as to form particles of size smaller than the critical size, or reduced particles, and one distributes particles reduced in the free flow (at 86) of fine particles.
2. Procédé de traitement suivant la revendication 1, caractérisé en ce qu'on réduit (en 44) la taille des particules grossières en même temps qu'on empêche le passage de ces particules grossières.2. Treatment method according to claim 1, characterized in that the size of the coarse particles is reduced (at 44) while the passage of these coarse particles is prevented.
3. Procédé de traitement suivant la revendication 1 ou 2 , caractérisé en ce qu'on dirige le long d'un trajet commun (86) , les particules fines et les particules réduites.3. Treatment method according to claim 1 or 2, characterized in that directs along a common path (86), the fine particles and the reduced particles.
4. Procédé de traitement suivant la revendication 3, caractérisé en ce que le trajet commun comprend au moins un chemin (86) défini par des faces en regard d'éléments de réduction (44) des particules grossières, le ou chaque chemin (86) possédant des dimensions adaptées pour que les particules fines puissent s'y écouler librement et pour que les particules grossières ne soient pas admises dans ce chemin (86) .4. Treatment method according to claim 3, characterized in that the common path comprises at least one path (86) defined by opposite faces of reduction elements (44) of coarse particles, the or each path (86) having dimensions adapted so that fine particles can flow there freely and so that coarse particles are not admitted in this path (86).
5. Procédé de traitement suivant la revendication 4, caractérisé en ce qu'on cisaille (par 58B) lesdites particules grossières contre au moins une face des éléments de réduction (44) définissant le ou chaque chemin (86) .5. Treatment method according to claim 4, characterized in that said coarse particles are sheared (by 58B) against at least one face of the reduction elements (44) defining the or each path (86).
6. Installation de traitement d'une poudre combustible nucléaire, du type oxyde, tel qu'U02, ladite installation étant disposée notamment en aval d'une unité de conversion en ledit oxyde d'un composé, tel qu'UF6, ladite installation comprenant une unité (24) de réduction de la taille moyenne des particules formant la poudre, induisant une modification de l'allure générale du spectre des particules, ladite unité comportant des moyens de retenue (44) de particules dites grossières, dont la taille est supérieure à une taille prédéterminée, ou taille critique, lesdits moyens de retenue (44) étant propres à laisser s'écouler librement des particules dites fines, de taille inférieure à la taille critique, caractérisée en ce que ladite unité de réduction (24) comprend également des moyens de réduction (44) en continu des particules grossières, de manière à former des particules, dites réduites, de taille inférieure à la taille critique, ainsi que des moyens de distribution des particules réduites dans l'écoulement libre des particules fines . 6. Installation for processing a nuclear combustible powder, of the oxide type, such as U0 2 , said installation being arranged in particular downstream of a unit for converting a compound into said oxide, such as UF 6 , said installation comprising a unit (24) for reducing the average size of the particles forming the powder, inducing a modification of the general appearance of the spectrum of the particles, said unit comprising means (44) for retaining so-called coarse particles, the size of which is greater than a predetermined size, or critical size, said retaining means (44) being adapted to allow free flow of so-called fine particles, of size less than the critical size, characterized in that said reduction unit (24) also comprises means for continuously reducing (44) coarse particles, so as to form so-called reduced particles, of size smaller than the critical size, as well as means s distribution of reduced particles in the free flow of fine particles.
7. Installation de traitement suivant la revendication 6, caractérisée en ce que les moyens de retenue (44) des particules grossières et les moyens de réduction des particules grossières sont confondus.7. Treatment installation according to claim 6, characterized in that the means for retaining (44) coarse particles and the means for reducing coarse particles are combined.
8. Installation de traitement suivant la revendication 7, caractérisée en ce que les moyens de retenue et de réduction comprennent au moins un couple d'éléments de réduction (44), dont des faces en regard définissent un chemin (86) , lesdits éléments de réduction étant disposés pour laisser s'écouler librement les particules fines le long du chemin (86) et pour réduire la taille des particules grossières.8. Treatment installation according to claim 7, characterized in that the retaining and reduction means comprise at least a pair of reduction elements (44), of which opposite faces define a path (86), said elements of reduction being arranged to allow fine particles to flow freely along the path (86) and to reduce the size of coarse particles.
9. Installation de traitement suivant la revendication 8, caractérisée en ce que les éléments de réduction (44) sont disposés sur un organe de réduction (38) annulaire recevant, dans son volume intérieur, un moyen de convoyage (52) rotatif propre à diriger la poudre, par effet centrifuge, vers les éléments de réduction (44) .9. Treatment installation according to claim 8, characterized in that the reduction elements (44) are arranged on an annular reduction member (38) receiving, in its internal volume, a conveying means (52) suitable for direct rotation the powder, by centrifugal effect, towards the reduction elements (44).
10. Installation de traitement suivant la revendication 9, caractérisée en ce que ledit moyen de convoyage (52) rotatif est pourvu de moyens de cisaillement (58B) des particules grossières contre les éléments de réduction (44) .10. Treatment installation according to claim 9, characterized in that said rotary conveying means (52) is provided with means for shearing (58B) the coarse particles against the reduction elements (44).
11. Installation de traitement suivant l'une des revendications 8 à 10, caractérisée en ce que les éléments de réduc- tion sont des lames de broyage (44) .11. Treatment installation according to one of claims 8 to 10, characterized in that the reduction elements are grinding blades (44).
12. Installation de traitement suivant la revendication12. Treatment installation according to claim
11, caractérisée en ce que chaque lame (44) possède une ou deux faces latérales en dépouille par rapport à un axe longitidinal (A) de la lame, selon un angle compris entre 0 et 10°. 11, characterized in that each blade (44) has one or two side faces in clearance with respect to a longitudinal axis (A) of the blade, at an angle between 0 and 10 °.
13. Installation de traitement suivant la revendication13. Treatment installation according to claim
12, caractérisée en ce que l'axe longitudinal (A) de chaque lame (44) est incliné, par rapport à un axe diamétral (D) de l'organe de réduction (38) annulaire, selon un angle compris entre 0 et 10 ° . 12, characterized in that the longitudinal axis (A) of each blade (44) is inclined, relative to a diametral axis (D) of the annular reduction member (38), at an angle between 0 and 10 °.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR9814733 | 1998-11-19 | ||
FR9814733A FR2786116B1 (en) | 1998-11-19 | 1998-11-19 | PROCESS AND PLANT FOR THE TREATMENT OF NUCLEAR FUEL POWDER |
PCT/FR1999/002834 WO2000031747A1 (en) | 1998-11-19 | 1999-11-18 | Method and installation for treating a nuclear fuel powder |
Publications (1)
Publication Number | Publication Date |
---|---|
EP1138045A1 true EP1138045A1 (en) | 2001-10-04 |
Family
ID=9533077
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP99956080A Withdrawn EP1138045A1 (en) | 1998-11-19 | 1999-11-18 | Method and installation for treating a nuclear fuel powder |
Country Status (9)
Country | Link |
---|---|
EP (1) | EP1138045A1 (en) |
JP (1) | JP2002538413A (en) |
KR (1) | KR20010086039A (en) |
CN (1) | CN1331829A (en) |
AR (1) | AR021280A1 (en) |
AU (1) | AU1277000A (en) |
FR (1) | FR2786116B1 (en) |
TW (1) | TW436809B (en) |
WO (1) | WO2000031747A1 (en) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
KR100969942B1 (en) * | 2008-12-26 | 2010-07-14 | 한전원자력연료 주식회사 | Crusher of raw materials |
Family Cites Families (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3819804A (en) * | 1971-06-16 | 1974-06-25 | Gen Electric | Conversion of uranium hexafluoride to uranium dioxide structures of controlled density and grain size |
DE2344618A1 (en) * | 1973-09-05 | 1975-03-27 | Kernforschungsanlage Juelich | PROCESS AND DEVICE FOR CRUSHING REFUELED COMBUSTION AND / OR INCUBATOR ELEMENTS FOR NUCLEAR REACTORS |
US4167081A (en) * | 1977-07-07 | 1979-09-11 | Westinghouse Electric Corp. | Centerless grinder |
DE3010547A1 (en) * | 1980-03-19 | 1981-10-01 | Alkem Gmbh, 6450 Hanau | METHOD FOR PRODUCING NITROGEN-MIXED NUCLEAR FUEL TABLETS |
SE434128B (en) * | 1980-10-16 | 1984-07-09 | Jan Abom | HIGH SPEED MILL FOR FINMING OF BIOMASS AND CLEAR MATERIAL |
JPS5924738B2 (en) * | 1980-12-16 | 1984-06-12 | 株式会社東芝 | Nuclear fuel conversion device |
DE3230039C2 (en) * | 1982-08-12 | 1984-11-08 | Alkem Gmbh, 6450 Hanau | Apparatus for treating a granular substance, in particular nuclear reactor fuel in powder form, and a method for operating the apparatus |
EP0150737B1 (en) * | 1984-01-26 | 1989-10-04 | Westinghouse Electric Corporation | Process for treating nuclear fuel scrap |
FR2622343B1 (en) * | 1987-10-26 | 1990-01-19 | Commissariat Energie Atomique | PROCESS FOR PRODUCING NUCLEAR FUEL PELLETS BASED ON MIXED OXIDE (U, PU) O2 |
US5405094A (en) * | 1994-01-31 | 1995-04-11 | Poser; Kimberly | Multi-staged size reduction machine |
FR2720540B3 (en) * | 1995-06-15 | 1996-04-12 | Siemens Ag | Process for the production of mixed oxide tablets of (U, Pu) O2. |
US5607062A (en) * | 1995-08-18 | 1997-03-04 | Quadro Engineering Inc. | Screen module for preparing cosmetics nested screens of different mesh sizes |
-
1998
- 1998-11-19 FR FR9814733A patent/FR2786116B1/en not_active Expired - Fee Related
-
1999
- 1999-11-16 AR ARP990105808 patent/AR021280A1/en unknown
- 1999-11-18 JP JP2000584486A patent/JP2002538413A/en active Pending
- 1999-11-18 EP EP99956080A patent/EP1138045A1/en not_active Withdrawn
- 1999-11-18 KR KR1020017006208A patent/KR20010086039A/en not_active Application Discontinuation
- 1999-11-18 AU AU12770/00A patent/AU1277000A/en not_active Abandoned
- 1999-11-18 CN CN99814752A patent/CN1331829A/en active Pending
- 1999-11-18 WO PCT/FR1999/002834 patent/WO2000031747A1/en not_active Application Discontinuation
- 1999-11-19 TW TW88120210A patent/TW436809B/en not_active IP Right Cessation
Non-Patent Citations (1)
Title |
---|
See references of WO0031747A1 * |
Also Published As
Publication number | Publication date |
---|---|
FR2786116A1 (en) | 2000-05-26 |
KR20010086039A (en) | 2001-09-07 |
CN1331829A (en) | 2002-01-16 |
FR2786116B1 (en) | 2001-01-12 |
TW436809B (en) | 2001-05-28 |
JP2002538413A (en) | 2002-11-12 |
AU1277000A (en) | 2000-06-13 |
AR021280A1 (en) | 2002-07-03 |
WO2000031747A1 (en) | 2000-06-02 |
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