EP2946160B1 - Melting installation to consolidate contaminated waste - Google Patents

Description

This invention relates to a fusing apparatus for consolidating contaminated scrap and a consolidation method that can be carried out using the fusing apparatus.

When dismantling nuclear facilities, such. As nuclear power plants, research centers, uranium enrichment plants and reprocessing plants are contaminated scraps fall, for example, in the category "low-level radioactive waste". If necessary, these can be decontaminated by the remelting process and returned to the normal material cycle. It may also be medium-contaminated scrap and equally high-level radioactive waste. These scraps can no longer be returned to the normal material cycle and must be disposed of in a repository. In order to keep the disposal costs as low as possible, it is necessary to consolidate the volume of the resulting scrap by melting into a solid block. The present invention describes a melting device specifically designed for this task and the associated method.

When dismantling the nuclear facilities, process equipment, such. As containers, pipelines, fittings, measuring equipment, storage racks, linings but also metallic structural elements, such as stages, scaffolding, stairs, etc., which are located in contaminated areas, or have come into contact with radioactive media, disposed of in a repository. These components are cut during dismantling with appropriate measures and fall as a mixture of lumpy scrap and chips. The material is not always sorted, but is a mixture of different qualities, such as carbon steel, stainless steel, copper, brass, aluminum, magnesium, cadmium and others. The storage of unconsolidated material would leave many voids that would massively increase the repository volume and therefore the cost. Furthermore, such scraps provide a very large surface from which radionuclides could be removed or released.

• Die Abgase aus den Anlagen werden in den Raum abgegeben und müssen über eine aufwändige Abgasreinigungsanlage entsorgt werden.
• Die Schmelztiegel dieser Anlagen sind aus Feuerfestkeramik hergestellt, unterliegen aufgrund thermischer sowie mechanischer Belastung einem Verschleiß und müssen nach einer Schmelzkampagne ausgebrochen werden. Bei diesem Vorgang werden die keramischen Tiegel zerstört und in definierte Reststücke zerkleinert. Dabei fallen zusätzlich große Mengen an kontaminiertem Abfall und Staub als Sekundärabfall an.
• Der nukleare Kontrollbereich dieser Anlagen ist relativ groß.
• Bei den bekannten Anlagen handelt es sich um ortsfeste Anlagen, zu denen der radioaktiv kontaminierte Schrott transportiert werden muss.
• Schrotte, die reaktive Metalle enthalten, wie z.B. Magnesium, können nicht eingeschmolzen werden.
• Schrottbestandteile, die gesundheitsgefährdende Dämpfe entwickeln, wie z.B. Cadmium, können nur eingeschränkt eingeschmolzen werden.
• Leichtflüchtige radioaktive Isotope können nicht zurückgehalten werden.
• Der Rückbau solcher Anlagen ist sehr aufwändig.

At present, for melting the scrap from nuclear plants melting devices are known, which are designed as air-open induction furnaces, in which the liquid melt is poured into molds. The inventors of the melting device according to the invention have identified in the solutions of the prior art inter alia the following restrictions:

• The exhaust gases from the plants are released into the room and have to be disposed of via a complex emission control system.
• The crucibles of these plants are made of refractory ceramics, are subject to wear due to thermal and mechanical stress and must be broken after a smelting campaign. In this process, the ceramic crucible are destroyed and crushed into defined remnants. In addition, large amounts of contaminated waste and dust accumulate as secondary waste.
• The nuclear control area of these plants is relatively large.
• The known systems are fixed installations to which the radioactively contaminated scrap must be transported.
• Scrap containing reactive metals, such as magnesium, can not be melted down.
• Scrap components that develop harmful vapors, such as cadmium, can only be melted to a limited extent.
• Volatile radioactive isotopes can not be retained.
• The dismantling of such systems is very expensive.

The previously known melting plants are all affiliated to central disposal centers, where large control areas are set up. As a result, contaminated material has to be transported from the decommissioning site to the disposal centers, resulting in increased costs for a large transport volume of nuclear material.

DE 34 04 106 A1 describes a process for the recovery of metallic components of nuclear power plants. A crucible is described which is introduced into the smelting furnace. The furnace comprises a furnace chamber with furnace chamber bottom. The oven is not hermetically sealed. Rather, a part of the resulting exhaust gas is sucked by means of a suction hood. This melting furnace can therefore only be operated in a large security area, which has facilities that prevent the contamination of the environment. Thus, the system described there can not be used as a mobile system.

DE 33 31 383 A1 describes a plant for the recovery of metallic components of nuclear power plants. The system must be operated in a low-pressure hall. The system is therefore neither hermetically sealed nor transportable.

FR2447592 discloses a fusing apparatus and method for filling a storable container with solid radioactive material. Thus, numerous melting devices are known from the prior art. All have in common that the melting devices are not or only with great effort transportable. Therefore, the scrap to be processed always had to be transported to the melting device. Transports of radioactive material are risky, however, and regularly encounter opposition from the population.

It is the object of this invention to provide a melting device for reducing the volume of radioactively contaminated material, which makes it possible to significantly reduce the transport of radioactive material.

The object is solved by the subject matters of claims 1-12. The present invention provides an improved method by providing a novel mobile fusing device and method as defined in the claims. The invention provides a plant and a method suitable for achieving a volume reduction of such radioactively contaminated material as obtained in the deconstruction of nuclear installations (hereinafter "material to be melted"). The system can be operated cost-effectively and does not pose any risks to people and the environment during operation.

The melting device according to the invention is a mobile melting device with a crucible base and a crucible chamber, which is suitable for receiving the crucible. The crucible base comprises a chamber bottom and the crucible chamber comprises a Shell. The melting device has a transport device which is suitable for moving the crucible base with the crucible from a first position outside the crucible chamber to a second position within the crucible chamber (also: melting position). The chamber bottom and the shell are designed so that they together form a gas-tight furnace housing in the second position.

The crucible can thus be moved from a location outside the crucible chamber to a location within the crucible chamber and vice versa. The transport device is preferably arranged below the crucible chamber during operation so that the crucible can be lifted upwards by means of the transport device into the crucible chamber. The transport device may be a scissor lift. Alternatively, a lifting table can be used, which works with tension spindles or hydraulic cylinders and a web guide.

The crucible is preferably arranged on the crucible base. The crucible is preferably made of a heat-resistant material, in particular of ceramic, graphite, Tongraphit or mixtures thereof. The crucible preferably has a cylindrical shape, wherein the lateral surface of the cylinder is delimited by a crucible wall and the base surface by a crucible bottom. The crucible can be moved from the second position to the first position using the transport device. As a result, the crucible and the crucible base are accessible on the one hand for maintenance purposes and on the other hand facilitate the removal of the crucible with its contents. The crucible can then be removed from the crucible chamber and another crucible can be inserted into the crucible chamber. Thus, a high utilization of the system is possible without long cooling times must be waited. The crucible is thus preferably a replaceable crucible. Due to the relatively thin crucible walls and the relatively thin crucible bottom, which are preferably reinforced in operation by support elements or a bottom plate, the crucible is relatively easy to handle. In the case of a broken pot, it can be disposed of without large amounts of additional waste.

One component of the crucible base is preferably a bottom plate on which the crucible can be arranged. The bottom plate reinforces the crucible. This supports the crucible bottom without making the crucible heavier. The bottom plate is preferably thicker than the crucible bottom to ensure sufficient stability. In preferred embodiments, the bottom plate is more than twice as thick as the crucible bottom. The bottom plate is preferably made of a heat-resistant material, in particular of ceramic.

The crucible base preferably comprises a collecting trough. The drip pan serves to catch escaping melt, should the crucible be damaged. At the outlet of the melt due to a pot damage, the melt is in the drip pan in the portable crucible base and is moved out by means of the transport device. Thus, the melting device can be operated without maintenance. Only the crucible base has to be processed. The drip tray is preferably made of refractory material.

The shell preferably represents the outer shell of the crucible chamber. The shell contributes to the fact that the furnace housing is gas-tight. For this purpose, the shell is a closed shell. However, it comprises at least one opening to introduce the crucible, and preferably at least one chamber opening to be able to reload the material to be melted. Furthermore, it may comprise one or more openings for the passage of leads for the heating device. In addition, it may comprise an opening which allows the connection of a suction device. The shell is preferably made of metal, in particular steel.

The chamber bottom is designed so that it forms together with the shell a gas-tight oven housing. It is preferably made of the same material as the shell. The bottom of the chamber preferably closes the crucible base downwards. The remaining components of the crucible base, in particular bottom plate and drip pan, are located inside the chamber bottom, ie on the side which faces in the melting position of the crucible chamber. Where chamber bottom and shell meet, preferably at least one sealing element is arranged. The sealing element seals the furnace housing. It is preferably a lip seal made of a rubber-elastic material.

The crucible chamber is shaped so that it can receive the crucible. The crucible is then preferably arranged in the crucible chamber during the melt Support elements stabilized. The support members are configured to relieve the crucible wall from the hydrostatic pressure of the melt when the crucible is within the crucible chamber. The support elements are in the melting position between the crucible and the shell. The support elements preferably form a common contact surface with the bottom plate. The support elements are particularly resistant to withstand the high loads during the melting process. The support elements are preferably designed so that they can be withdrawn if the crucible is to be removed from the melting position. The shape of the support elements is thus adapted to the shape of the crucible wall.

The melting device furthermore has a heating device which is suitable for heating the material in the crucible. The heating device is in particular a component of the crucible chamber. The heating device is preferably an induction heater and / or a resistance heater. The heating device is preferably a component of the crucible chamber. The heating device is preferably arranged with a minimum distance from the crucible, so that no contact between the heating device and the melt is to be feared even in cases of escaping melt. In one embodiment, the heater is an induction heater. This has the advantage that the material to be consolidated can be heated very quickly because the heat is generated directly in the crucible. In another embodiment, the heater is a resistance heater. This has the advantage that no cooling water must be used in the vicinity of the melt. This minimizes the risk of water vapor explosion. The heater is preferably located substantially within the envelope, except for the leads to the heater.

Furthermore, the melting device according to the invention preferably has a charging device which is suitable for filling the scrap to be consolidated into the crucible. The charging device is preferably arranged above the crucible chamber during operation, so that the material to be melted can be discharged from above into the crucible chamber and thus into the crucible. This process can be done remotely, so that contamination risks are avoided. So that the crucible can be filled in the melting position, the shell of the crucible chamber preferably has a chamber opening. The chamber opening is preferably in the upper area the shell arranged. The chamber opening can be closed with any closing element, such as a lid. Preferably, a lock is arranged on the chamber opening, which is also part of the crucible chamber.

The lock is preferably hermetically sealed. Thus, the material to be consolidated can be discharged into the crucible without dusts and vapors escaping into the room. The lock is part of the crucible chamber. The filling of the crucible through the lock takes place when the crucible is in the melting position, the shell and the chamber bottom thus together form a gas-tight furnace housing. Thereby, and through the hermetically sealed lock, material to be melted can be discharged into the crucible without contaminating the environment. The lock is then arranged between the gas-tight oven housing and charging device.

For example, the charging device may include a crane that can pivot a charging basket to an area above the chamber opening. There, the charging basket can be lowered, so that the material to be melted passes through the chamber opening in the crucible. But there are also other Chargiereinrichtungen conceivable. In particular, a movable charging trolley is conceivable, which can preferably be moved on rails from a position above the chamber opening to a receiving position. The charging trolley may have a pulley system such that a charging basket at the picking position, e.g. can be pulled up from a place at ground level next to the transport device, and at a position above the chamber opening, the filling of the crucible can be made. Charging trolleys, rails and cable system are then part of the charging facility.

The charging trolley is preferably provided with a housing into which the charging basket can be guided. Thus, the charging trolley can be hermetically sealed. The housing of the charging trolley may be designed so that it closes with the upper end of the lock, that when the material to be melted into the lock no dusts or vapors can escape.

The melting device according to the invention preferably comprises an exhaust gas purification system. It can be connected via a connecting element, e.g. a tube to be connected to the crucible chamber. The exhaust gas purification system may be part of the chamber module or else of the optionally present feed module. But it can also be arranged separately.

Preferably, the melting device comprises a vacuum pump, which is suitable for evacuating the gas-tight oven housing. The vacuum pump can be connected via a connecting element, e.g. a tube to be connected to the crucible chamber. In one embodiment, located behind the vacuum pump, an emission control system. From the exhaust gas purification system, the exhaust gas can be passed into an exhaust gas disposal system, which is usually already present in nuclear facilities.

An inventively preferred melting device is a fixed furnace system, in which the crucible are retracted and locked on the crucible base from below. In addition, preferably a charging device is provided which operates with a hermetically sealed lock. As a result, a complete remote control of the melting device is made possible in conjunction with a camera monitoring of the melting chamber.

The melting device according to the invention is designed as a mobile system which can be used at the location where e.g. a nuclear facility is built back, can be temporarily built in an existing building with a nuclear control area. Auxiliary systems for operating the melting device may be located in containers which may be set up outside the control area. Such auxiliary systems are, for example, the melt power supply, the cooling water distribution, the process gas supply and the electrical switchgear with the control panel.

After completion of the work, this melting device according to the invention can be degraded again and be moved to another point of use, because it is preferably modular.

"Modular design" means that the melting device can be easily disassembled into parts or assemblies that can each be easily transported individually. The construction of the melting device contributes to the need for a transportable Plant also account for the fact that it can be brought into a state in which the parts of the melting device, which can come into contact with radioactive material, are encapsulated. In this case, needed auxiliary systems are already in suitable transport containers and the modules of the melting device can be easily introduced into a transport container. This reliably prevents stress on people and the environment during transport. Melting devices of the prior art can not be disassembled with reasonable effort. In addition, their decomposition would pose a high risk of contamination for the workers involved in the dismantling.

The melting device according to the invention therefore preferably has a plurality of modules. These are preferably at least one chamber module, a charging module and a transport module. Each module in the modules is grouped in such a way that each module is easy to transport per se.

The melting device therefore preferably has at least one chamber module. The chamber module is the most important module because it is where the actual melting process takes place. The chamber module comprises the crucible chamber. The charging module comprises at least the charging device. The transport module comprises at least the transport device.

The crucible base is not part of the mentioned modules, but is transported separately. The melting device according to the invention can be operated with several different crucible bases. Thus, after a melting process, a crucible base with the crucible thereon can be removed from the crucible chamber, and immediately thereafter another crucible base can be introduced into the crucible chamber with another crucible. This allows a particularly economical process management.

The transport module can also be designed to optimize the process flow so that the transport device can be moved on a rail system. Such an embodiment is preferably such that a crucible base can be loaded with a crucible at a loading position, then moved to the first position below the crucible chamber, then lifted to the melt position, lowered back to the first position after the melt, and finally to one Unloading position is spent. This has the advantage that the loading of a second crucible in the loading position can already take place during the melt in a first crucible. Once the contents of the first crucible have melted and the first crucible base has been moved to the unloading position with the first crucible, the second crucible base may be brought to the melt position with the second crucible. Thus, two crucible bases can be used simultaneously.

After the transport of the melting device, the modules can be easily reconnected to build up the melting device. In this case, the transport module is preferably arranged below the chamber module. The charging module is preferably arranged above the chamber module. So that the modules can be transported well, they are preferably provided with support elements. The support elements reinforce the modules and secure the individual components within a module against damage during transport. The support elements may e.g. Be steel beam.

The size of the individual modules is preferably chosen so that they can be easily transported. Before transport, for example, the chamber module is separated from the transport module and possibly the charging module and loaded individually. Preferably, the modules are designed so that they can be loaded well on trucks or railroad cars. Advantageous embodiments relate to modules sized to be loaded into 20-foot standard containers or 40-foot standard containers. This means that the modules are preferably each no longer than 5.71 m long, not more than 2.352 m wide and not more than 2.385 m high. The mass of the modules should preferably not exceed a value of 20,000 kg each, preferably 10,000 kg and more preferably 5,000 kg.

1. a. Befüllen des Tiegels mit dem zu schmelzenden Material,
2. b. Aufheizen des zu schmelzenden Materials innerhalb des Tiegels,
3. c. optional Nachchargieren einer weiteren Portion zu schmelzenden Materials in den Tiegel,
4. d. Erstarrenlassen des geschmolzenen Materials im Tiegel zu einem Block.

The method according to the invention provides the following steps:

1. a. Filling the crucible with the material to be melted,
2. b. Heating the material to be melted inside the crucible,
3. c. optionally recharging a further portion of material to be melted into the crucible,
4. d. Solidifying the molten material in the crucible to a block.

The filling of the crucible can take place with the aid of a charging device, which is preferably arranged above the crucible chamber. Alternatively, the crucible can also be filled at least partially outside the crucible chamber. The crucible is then placed in the crucible chamber with the material to be melted. After this first portion has been melted down, one or more further portions can be recharged using the charging device. Thus, the crucible volume can be optimally utilized. If necessary, the melting device is built up before filling the crucible. The first filling can therefore take place outside the melting position (ie outside the crucible chamber), e.g. in a loading position in a scrap warehouse. Here, the filling of the crucible with a sheet metal drum is conceivable in which the material to be melted. Thus, damage to the crucible can be avoided. At the end, the tin drum is melted together with the material to be melted.

When filling using the charging device, the material to be melted is thus filled through a chamber opening in the crucible located in the gastight furnace housing, e.g. by means of a charging basket. For this purpose, the charging basket can be lowered and its contents are then introduced into the crucible. The crucible may already contain molten material at the moment. The chamber opening can be designed as a lock.

Depending on the process, the crucible may already contain scrap to be consolidated when it is introduced into the crucible chamber. The charging device can then be used to reload additional material to be melted in order to achieve a higher degree of filling of the crucible. The method according to the invention preferably provides the step of recharging material to be melted after a first portion of material to be melted has already been melted in the crucible. Melting reduces the volume of the material, leaving the crucible room for another portion of consolidating material.

The material to be melted is preferably heated to temperatures of at least 1000 ° C, more preferably at least 1350 ° C, and most preferably at least 1500 ° C. Of course, the chosen temperature depends on the material to be melted. After heating, the material to be melted is held for a certain time at the high temperature, so that the material melts as completely as possible. The melting process, which begins with heating and ends immediately before solidification, preferably lasts at least 4 hours, more preferably at least 6 hours. If too short a period is selected, the melt may not be complete. In addition, overheating should be avoided too quickly, as it may cause local overheating in or on the crucible that would stress the crucible too much. Furthermore, this can cause excessive convection, which would also increase the erosion of the pot. Thus, the life of the crucible would decrease.

However, it has been found that a melting time of 16 hours, especially 10 hours must not be exceeded, because the melt is then usually complete and a shorter melting time due to the lower cost is always beneficial. Even if there are refractory fractions in the material to be melted, which do not melt at the stated temperatures, it would nevertheless lead to a filling of the cavities in the material by lower melting material.

The melting of the material to be melted takes place within the crucible, if it is at the melting position, ie inside the gas-tight furnace housing. In this position, the melting device is constructed so that the crucible chamber and the crucible base through the shell and the chamber bottom form a gas-tight furnace housing. Thereby, the melting can be carried out under vacuum or inert gas atmosphere, wherein an oxidation of the material to be melted is avoided. As a result even reactive metal scrap, e.g. Magnesium or cadmium contained, be consolidated. In addition, less volatile products are formed.

Before the crucible is removed, preferably the protective gas and any by-products of the melt contained therein are preferably removed by suction and preferably an exhaust gas purification subjected. The exhaust gas purification can be carried out with the aid of an exhaust gas purification system, which can be a condensation trap. Other cleaning methods are also conceivable, eg filtering, in particular using HEPA filters.

Impurities of the material to be melted can be removed by means of vacuum-thermal pretreatment in the crucible. These are e.g. moisture, solvents, paints, oils, greases and / or plastics.

The process is preferably carried out depending on the material-specific requirements in vacuum or under protective gas. This ensures that reactive constituents of the material to be melted do not form explosions or volatile oxides, which can not be ruled out when working under air atmosphere.

The chamber opening is preferably closed with a closing element during the melting process. The closure member may be part of a lock which allows the material to be melted to be filled into the crucible without the crucible contents being able to contaminate the environment. This measure helps ensure that the safety area around the melting device can be kept very small. Furthermore, material to be melted during operation can be recharged if a volume contraction has occurred due to the consolidation of a first scrap portion. Thus, vacuum or a protective gas atmosphere is maintained in the furnace housing even during recharging.

The solidification of the molten material is preferably carried out while the crucible is within the furnace housing. The material already cools down at least partially and forms a block. It is not necessary for the block to cool to ambient temperature in this position. It is enough that it cools down so far that it can be removed safely. Cooling to room temperature then preferably takes place at another location, e.g. at the unloading position mentioned above. Meanwhile, another crucible, possibly on another crucible base, can be introduced into the crucible chamber.

The block can be removed from the crucible or disposed of together with the crucible. Before removing the block from the crucible, the crucible with the aid of Transport device moves from the second position to the first position outside the crucible chamber. It is preferred that the crucible is lowered from the second position to the first position. This means that the crucible is removed in a downward movement from the crucible chamber. The crucible can then be removed from the area below the crucible chamber. This can be done by the transport device mediated or using a separate further transport device. In a particular embodiment, the transport device with crucible base and crucible arranged thereon can preferably be moved on rails. By removing the crucible from the area below the crucible chamber, another crucible can be inserted into the crucible chamber. This makes it possible to use the residual heat in the crucible chamber and to use the melting device well. During the cooling on the unloading position, the block removal and the reloading in the loading position, a new melting process can already be carried out with another crucible.

Furthermore, the melting device has the advantage that in a crucible failure, the melt can flow into a collecting trough located in the crucible base. There, the melt can solidify. The crucible base with the defective crucible can then be removed from the crucible chamber and the consolidation process can be continued with another crucible on a further crucible base.

During the melting process, there is an atmosphere within the crucible chamber which is substantially free of oxygen. This means that the oxygen partial pressure there is less than 10 kPa, more preferably less than 1 kPa. This can be achieved either by a vacuum or a protective gas atmosphere in the crucible. A preferred shielding gas is nitrogen because it effectively suppresses the formation of volatile oxides and is inexpensive.

The fact that a high utilization is possible because of the use of replaceable seals, the melting device at the same throughput in their dimensions may be smaller than is the case with other systems. This in turn facilitates the transport. In addition, the crucible and thus the entire melting device can be designed more easily because a check of the crucible is possible after each melting cycle. In conventional melting devices, the crucibles became extremely robust because they were partly used in continuous operation, which does not allow for checks in the process.

After completion of the melting process, the molten material in the crucible can solidify, so that forms a block, which has no voids and thus a much higher density compared to the starting material.

After cooling the block, preferably within the crucible, the block may be removed from the crucible and transferred, for example, to a standardized waste package (e.g., a tin drum). The crucible is thus preferably designed so that a block is obtained which fits into a standardized waste container. The block is preferably a cylindrical body having a diameter of about 400 to 600 mm and a height of about 800 to 1000 mm.

Crucibles that have reached the end of their life can be provided together with the solidified block in a likewise standardized larger waste packages for final disposal, without destroying the crucible thereby.

The tightness of the furnace housing and the charging device can be verified at each start of a new consolidation melt, so preferably before heating, by a short pressure rise test and thus ensured. The oven housing is preferably hermetically sealed. This means that the pressure increase at a vacuum of 20 mbar for 1 hour is less than 20 mbar. The same applies preferably also for the lock and in particular also for the charging device.

The method according to the invention is furthermore preferably characterized in that the steps of filling, heating, melting, possibly recharging and solidification to a block for batch of material to be melted take place in a single exchangeable crucible, preferably under a vacuum and / or controlled atmosphere. The preferably metallic block can be used at a later time, if necessary, after further modification for disposal or storage. An inventive feature is that the melt is not poured from the crucible.

• Unbehandelte nukleare Schrotte müssen nicht über öffentliche Verkehrswege transportiert werden, weil die mobile Schmelzeinrichtung zum zu konsolidierenden Material transportiert werden kann.
• Der erstarrte Block an konsolidiertem Material kann direkt in ein Endlagergebinde eingebracht werden und es werden keine zusätzlichen Kokillen benötigt.
• Das Einschmelzen, Nachchargieren und Erstarren des Blockes erfolgt in einem hermetisch abgeschlossenen Ofengehäuse unter weitgehendem Sauerstoffausschluss, wodurch eine Freisetzung von Dämpfen und Stäuben in den Kontrollbereich verhindert wird.
• Die Dämpfe und Stäube können in einem Abgasreinigungssystem zurückgehalten werden.
• Die Schmelzeinrichtung ist vorzugsweise so ausgeführt, dass im Falle eines Tiegelversagens die austretende Schmelze sicher in eine vorzugsweise ungekühlte Auffangwanne abgeführt wird, ohne dabei eine Wasserdampfexplosion oder Belastung der Umgebung zu riskieren.
• Das Feuerfestmaterial des Tiegels muss nicht ausgebrochen werden, daher entsteht kein Sekundärabfall und der Kontrollbereich ist entsprechend reduziert.
• Die Anlage benutzt einen bereits bauseits vorhandenen Kontrollbereich, somit fallen keine zusätzlichen Rückbaukosten an.

The melting device according to the invention offers a number of advantages over conventional melting devices:

• Untreated nuclear scrap does not have to be transported by public transport because the mobile melting equipment can be transported to the material to be consolidated.
• The solidified block of consolidated material can be placed directly into a repository container and no additional molds are needed.
• The smelting, recharging and solidification of the block takes place in a hermetically sealed oven housing with extensive exclusion of oxygen, whereby a release of vapors and dusts in the control area is prevented.
• The vapors and dusts can be retained in an exhaust gas purification system.
• The melting device is preferably designed so that in the event of a crucible failure, the exiting melt is safely removed into a preferably uncooled drip pan, without risking a water vapor explosion or environmental stress.
• The refractory of the crucible does not have to be broken, so there is no secondary waste and the control area is correspondingly reduced.
• The system uses an on-site control area, so there are no additional costs for dismantling.

figure description

• Figur 1 zeigt eine Schnittansicht der Tiegelkammer (3) und des Tiegels (2) mit der Tiegelbasis (9) in der ersten Position, d.h. der Tiegel (2) befindet sich außerhalb der Tiegelkammer (3). Die Tiegelbasis (9) ist unterhalb des Tiegels (2) angeordnet und umfasst eine Auffangwanne (6), die geeignet ist, geschmolzenes Material aufzunehmen, wenn der Tiegel (2) undicht werden sollte. In der gezeigten Position kann der Tiegel (2), die Tiegelkammer (3) und die Tiegelbasis (9) gewartet werden.
  Der Tiegel (2) weist eine Tiegelwand (11) und einen Tiegelboden (12) auf, die aus einem feuerfesten Material, insbesondere aus Graphit, Tongraphit oder Keramik, bestehen. Die Tiegelwand (11) und der Tiegelboden (12) sind vergleichsweise dünn ausgestaltet. Dies hat den Vorteil, dass die Masse des Tiegels (2) geringer ist als bei üblichen Tiegeln. Das erleichtert die Handhabung des Tiegels (2). Die notwendige Stabilität, um den hohen Belastungen während des Betriebes standzuhalten, erhält der Tiegel insbesondere durch eine Bodenplatte (13), die unterhalb des Tiegelbodens (12) angeordnet ist, und durch Unterstützungselemente (14), die Bestandteil der Tiegelkammer (3) sind. Die Unterstützungselemente (14) können nach der Schmelze zurückgezogen werden, um den Tiegel (2) absenken zu können.
  Die Tiegelkammer (3) weist ferner eine Hülle (15) auf, welche vorzugsweise die äußere Begrenzung der Tiegelkammer (3) darstellt.
  Die Tiegelbasis (9) umfasst einen Kammerboden (16), der so ausgestaltet ist, dass er zusammen mit der Hülle (15) der Tiegelkammer (3) einen hermetisch abgedichteten Raum darstellt, wenn sich die Tiegelbasis (9) in der zweiten Position befindet.
  Damit die erforderliche hermetische Abdichtung erzielt werden kann, sind am unteren Rand der Hülle (15) und am oberen Rand des Kammerbodens (16) Dichtungselemente (17) angeordnet, die dazu dienen, ein gasdichtes Ofengehäuse zu bilden, wenn der Kammerboden (16) die Tiegelkammer (3) schließt.
  Im oberen Bereich der Tiegelkammer (3) befindet sich eine Kammeröffnung (18), die geeignet ist, zu schmelzendes Material in den Tiegel (2) zu füllen. Die Kammeröffnung (18) kann mit einem Schließelement (19) verschlossen werden, welches Teil einer Schleuse sein kann.
• Figur 2 ist ebenfalls eine Schnittansicht und zeigt wie der Kammerboden (16) zusammen mit der Hülle (15) ein gasdichtes Ofengehäuse (10) ausbildet, wenn der Tiegel (2) unter Verwendung der Transporteinrichtung (nicht gezeigt) in die zweite Position (Schmelzposition) gebracht wurde. Die Dichtungselemente (17) sorgen für eine hermetische Abdichtung des gasdichten Ofengehäuses (10). Auch das Schließelement (19) ist vorzugsweise gasdicht ausgestaltet.
  Es ist zu erkennen, dass die Bodenplatte (13) mit den Unterstützungselementen (14) gemeinsame Kontaktflächen (20) ausgebildet hat. Dadurch wird der Tiegel (2) während des Konsolidierungsverfahrens stabilisiert. Sollte es dennoch zu einer Beschädigung des Tiegels (2) kommen, die ein Austreten der Schmelze zur Folge hat, so würde die Auffangwanne (6) die Schmelze auffangen. Die Schmelze wäre dann sicher in der gasdichten Zelle (10) eingeschlossen, weil weder die Hülle (15) noch der Kammerboden (16) dadurch beeinträchtigt werden können. In einem solchen Fall könnte abgewartet werden, bis die ausgetretene Schmelze in der Auffangwanne (6) erstarrt ist und sicher entnommen werden kann. Während die ausgetretene Schmelze in der Auffangwanne (6) weiter abkühlt, kann bereits ein weiterer Tiegel auf einer weiteren Tiegelbasis in die Tiegelkammer (3) eingeführt und der Konsolidierungsvorgang fortgesetzt werden.
• Figur 3 ist eine Schnittansicht, die eine erfindungsgemäße mobile Schmelzeinrichtung (1) zeigt. Es ist ersichtlich, dass die Schmelzeinrichtung einen modularen Aufbau aufweist. Das Kammermodul (21) ist oberhalb eines Transportmoduls (22) angeordnet. Über dem Kammermodul (21) ist ein Chargiermodul (23) gezeigt. Die Module sind so ausgebildet, dass sie bei einer Demontage der Anlage leicht voneinander getrennt und einzeln verladen werden können.
  Es ist erkennbar, dass das Kammermodul (21) unter anderem die Tiegelkammer (3) mit ihren Bestandteilen umfasst. Auf dieser Abbildung ist auch ein Verbindungselement (24) gezeigt, das die Tiegelkammer (3) einerseits und eine Schleuse (25) mit einer Abgasreinigungsanlage und/oder einer Vakuumpumpe (nicht gezeigt) verbindet.
  Das Basismodul (22) umfasst hingegen die Transporteinrichtung (7), die hier ein Scherenhubtisch ist.
  Es ist gut erkennbar, dass die einzelnen Module durch Stützelemente (26) stabilisiert werden, die hier als Stahlträger ausgeführt sind. Dadurch wird den Modulen eine Form und Stabilität verliehen, die den Transport vereinfacht und auch die Komplexität des Zusammenbaus der Schmelzeinrichtung reduziert.
  Es ist auch ein Chargiermodul (23) gezeigt, welches über eine Schleuse (25) mit der Tiegelkammer (3) verbunden ist. Das Chargiermodul (23) umfasst die Chargiereinrichtung, die einen auf Schienen verfahrbaren Chargierwagen mit einem Gehäuse umfasst.
• Figur 4 zeigt die mobile Schmelzeinrichtung in transportfertigem Zustand.
• Figur 5 zeigt zwei Ansichten einer aufgebauten mobilen Schmelzeinrichtung mit Hilfssystemen.

The following description relates to a preferred embodiment of the melting device and its components.

• FIG. 1 shows a sectional view of the crucible chamber (3) and the crucible (2) with the crucible base (9) in the first position, ie the crucible (2) is located outside the Crucible chamber (3). The crucible base (9) is located below the crucible (2) and comprises a sump (6) suitable for receiving molten material when the crucible (2) should be leaking. In the position shown, the crucible (2), the crucible chamber (3) and the crucible base (9) can be maintained.
  The crucible (2) has a crucible wall (11) and a crucible bottom (12), which consist of a refractory material, in particular of graphite, Tongraphite or ceramic. The crucible wall (11) and the crucible bottom (12) are made comparatively thin. This has the advantage that the mass of the crucible (2) is lower than in conventional crucibles. This facilitates the handling of the crucible (2). The necessary stability to withstand the high loads during operation, the crucible receives in particular by a bottom plate (13), which is arranged below the crucible bottom (12), and by support elements (14) which are part of the crucible chamber (3). The support elements (14) can be withdrawn after the melt in order to lower the crucible (2) can.
  The crucible chamber (3) further comprises a sheath (15), which preferably represents the outer boundary of the crucible chamber (3).
  The crucible base (9) comprises a chamber bottom (16) adapted to constitute, together with the shell (15) of the crucible chamber (3), a hermetically sealed space when the crucible base (9) is in the second position.
  So that the required hermetic seal can be achieved, sealing elements (17) are arranged at the lower edge of the shell (15) and at the upper edge of the chamber bottom (16), which serve to form a gas-tight furnace housing when the chamber bottom (16) Crucible chamber (3) closes.
  In the upper region of the crucible chamber (3) there is a chamber opening (18) which is suitable for filling material to be melted into the crucible (2). The chamber opening (18) can be closed with a closing element (19), which may be part of a lock.
• FIG. 2 is also a sectional view and shows how the chamber bottom (16) together with the sheath (15) forms a gas-tight oven housing (10) when the crucible (2) was brought to the second position (melting position) using the transport device (not shown). The sealing elements (17) ensure a hermetic seal of the gas-tight furnace housing (10). Also, the closing element (19) is preferably designed gas-tight.
  It can be seen that the bottom plate (13) has formed with the support elements (14) common contact surfaces (20). This stabilizes the crucible (2) during the consolidation process. Should it nevertheless come to a damage of the crucible (2), which has a leakage of the melt result, the drip pan (6) would catch the melt. The melt would then be safely enclosed in the gas-tight cell (10), because neither the shell (15) nor the chamber bottom (16) can be affected thereby. In such a case, it could be waited until the leaked melt in the drip pan (6) is solidified and can be safely removed. While the leaked melt in the sump (6) continues to cool, another crucible on another crucible base can already be introduced into the crucible chamber (3) and the consolidation process can be continued.
• FIG. 3 is a sectional view showing a mobile melting device (1) according to the invention. It can be seen that the melting device has a modular construction. The chamber module (21) is arranged above a transport module (22). Above the chamber module (21) is shown a charging module (23). The modules are designed so that they can easily be separated from each other and disassembled individually when disassembling the system.
  It can be seen that the chamber module (21) comprises inter alia the crucible chamber (3) with its components. In this figure, a connecting element (24) is shown, which connects the crucible chamber (3) on the one hand and a lock (25) with an exhaust gas purification system and / or a vacuum pump (not shown).
  By contrast, the base module (22) comprises the transport device (7), which here is a scissor lift table.
  It can easily be seen that the individual modules are stabilized by supporting elements (26), which are designed here as steel beams. This will give the modules a shape and stability that simplifies transportation and also reduces the complexity of assembling the fuser.
  There is also shown a charging module (23), which is connected via a lock (25) with the crucible chamber (3). The charging module (23) comprises the charging device, which comprises a rail-mounted charging trolley with a housing.
• FIG. 4 shows the mobile melting device in transport ready state.
• FIG. 5 shows two views of a constructed mobile melting device with auxiliary systems.

LIST OF REFERENCE NUMBERS

(1)

mobile melting device

(2)

crucible

(3)

pot chamber

(4)

charging device

(5)

heater

(6)

drip tray

(7)

transport means

(8th)

block

(9)

crucible base

(10)

gas-tight oven housing

(11)

crucible wall

(12)

crucible bottom

(13)

baseplate

(14)

support element

(15)

shell

(16)

chamber floor

(17)

sealing element

(18)

chamber opening

(19)

closing element

(20)

contact area

(21)

chamber module

(22)

transport module

(23)

Chargiermodul

(24)

connecting element

(25)

lock

(26)

support element

Claims (12)

1. A mobile melting installation (1) having a crucible basis (9) and a crucible chamber (3) which is suitable for taking-up a crucible (2),
   characterized in that the
   crucible basis (9) comprises a chamber bottom (16) and the crucible chamber (3) comprises a casing (15),
   wherein the installation further comprises a transport installation (7) which is suitable for moving the crucible basis (9) together with the crucible (2) from a first position to a second position, wherein the crucible (2) is in the first position outside the crucible chamber (3) and in the second position inside the crucible chamber (3),
   and wherein the chamber bottom (16) and the casing (15) are designed such that they form in the second position a gastight oven housing (10),
   wherein the transport installation (7) together with the crucible basis (9) and crucible (2) arranged on it is portable so that the crucible (2) can be removed from the area below the crucible chamber (3) and a further crucible (2) can be introduced into the crucible chamber (3),
   wherein the melting installation (1) comprises a charging installation (4) which is arranged above the crucible chamber (3),
   and wherein in the crucible chamber (3) support elements (14) are arranged which stabilize the crucible (2) during the melting.
2. The melting installation (1) according to claim 1, wherein the charging installation (4) is gastight.
3. The melting installation (1) according to one of claims 1 or 2, wherein the crucible chamber (3) comprises a heating installation which makes it possible to heat the crucible (2).
4. The melting installation (1) according to claim 3, wherein the heating installation is an induction heater.
5. The melting installation (1) according to one of claims 1 to 4 having a collecting tray (6) which is arranged below the crucible (2) in the crucible basis (9).
6. The melting installation (1) according to one of claims 1 to 5, wherein the melting installation is characterized by a modular design.
7. A method for consolidating a material in a melting installation according to one of claims 1 to 6, comprising the steps

   a. filling of a crucible (2) with a material to be consolidated,

   b. heating of the material to be melted in the crucible (2) so that at least a part of the material to be melted melts,

   c. recharging of material to be melted,

   d. solidifying of the molten material in the crucible (2) to a block (8).
8. The method according to claim 7, wherein in the crucible chamber (3) during the heating a non-oxidizing atmosphere is present.
9. The method according to claim 7, wherein the crucible (2) during the method steps heating, melting, recharging and solidifying is arranged in the crucible chamber (3).
10. The method according to one of claims 7 to 9, wherein the crucible (2) after solidifying is removed from the crucible chamber (3) and is cooled and during said cooling a further crucible is introduced into the crucible chamber (3).
11. The method according to one of claims 7 to 10, wherein the partial pressure of oxygen in the crucible chamber (3) during said melting is lower than 10 kPa.
12. The method according to one of claims 7 to 11, wherein the steps filling, heating, melting and optionally recharging are conducted in one single crucible under vacuum and/or controlled atmosphere.

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