FR2863098A1 - Dismantling of damaged industrial plant, such as nuclear facility, comprises confining and sealing off damaged section and decontaminating via access from undamaged section - Google Patents

Abstract

The process comprises confining the damaged section (10) of the plant with a structure (30) that covers and seals it, and then decontaminating the damaged section using access from the undamaged section (28) in order to process dangerous materials removed from the damaged section. The decontamination process is carried out with a pressure below atmospheric inside the sealed confinement structure, which can be built at a distance from the damaged section and then moved into place on tracks (32, 34) to cover it.

Description

2863098 1

  The present invention relates to a method of dismantling hazardous industrial accidents, as well as a containment device useful for implementing this method, and a method of manufacturing such a containment device.

  The dismantling method according to the invention applies only in the case where the damaged installation part to be dismantled adjoins a non-accident industrial installation part.

  In the following description of the invention, the term "dismantling" is understood to mean an operation which necessarily comprises a decontamination, but which may furthermore comprise the destruction of the structure of the decontaminated part.

  Although the invention can be applied to various situations, the invention is described in its application to the dismantling of the rugged part of the Chernobyl nuclear power plant comprising reactor No. 4.

  The Chernobyl nuclear power plant is known to have four adjacent reactors in pairs. Thus, the reactors No. 3 and 4 share a common intermediate structure including a chimney. When, in 1986, the No. 4 reactor was damaged, the reactor part relating to the No. 3 reactor and the intermediate common structure were not damaged and continued to operate and supply electric power until 2000. .

  Given the dangers presented by the installation of reactor No. 4, the international community has mobilized to find a solution against the risks presented by this situation. In the current state of the projects, it is envisaged to build a gigantic containment enclosure intended to cover the protection set up urgently around the reactor n 4, called the "sarcophagus". This enclosure must be very large, since it is planned to install decontamination and waste storage facilities, when, after the containment has been put in place, the dismantling of the facility will be undertaken since outside the sarcophagus, especially from the roof.

  In the current state of the projects, no timetable is known for the execution of these dismantling operations, and it is therefore envisaged to build a chamber capable of withstanding for a century.

  The invention relates to a method for dismantling the accident site of reactor No. 4 at the Chernobyl power station, which can be executed in a few years only. More precisely, according to the invention, the dismantling, including the decontamination and the conditioning of the extracted waste, is carried out from the part of the installation used for the reactor n 3 which is no longer used and is being dismantled. This part of the installation has all the necessary properties of protection against radioactivity and against other risks, and it has a considerable volume, much higher than the volume necessary for the housing of a dismantling installation and temporary storage of waste.

  Access to the uneven installation part of the reactor n 4 from the installation part used for the reactor n 3 is carried out through the intermediate structure common to the reactors 3 and 4, by drilling openings in the existing robust parts. of this intermediate structure.

  A major advantage of this process is the increased safety of the populations, up to considerable distances from the Chernobyl power station. First, since it is not necessary to access the interior of the damaged reactor through the sarcophagus, but only from a resistant structure that has already been proven, the risk of collapse of the sarcophagus when dismantling is reduced. Then, as the duration of the dismantling is considerably shortened, the time during which the risk exists is also considerably reduced.

  Another important advantage is that the cost of dismantling is considerably reduced, on the one hand because it is not necessary to build a specific installation, and on the other hand since this dismantling can be done very quickly, given that that the installation already exists.

  More specifically, the invention relates to a method of dismantling a portion of industrial plant accidentally dangerous to humans, which adjoins a non-uneven industrial plant part that has protection characteristics against hazardous materials; according to the invention, this method comprises the confinement of the damaged part by a confinement device which covers it in a substantially watertight manner, and the decontamination of the damaged part by access to it from the non-damaged part, with use of the protection characteristics the non-accidental part for the treatment of hazardous materials removed from the damaged part. For example, hazardous materials are radioactive.

  Preferably, the confinement is carried out with a confinement device which covers the rugged part 20 in close proximity to the latter.

  It is advantageous that the containment device is substantially sealed, and that the decontamination operation is performed while the confinement device is kept in depression.

  Preferably, access to the rugged portion from the non-rugged portion is achieved by drilling a structure separating the rugged portion of the non-rugged portion.

  It is advantageous for the confinement step to comprise the construction of a remote confinement device of the installation, and the displacement of the confinement device so that it covers the rugged part, for example by rolling on rollers.

  Preferably, the method comprises, after the displacement of the confinement device, the creation of a seal between the lower part of the confinement device and the ground, for example by pouring concrete at ground level.

  Preferably, the method comprises, after the displacement of the confinement device, the creation of a seal between the structure of the damaged part and the edge of an opening of a face of the confinement device, for example by guillotine devices.

  According to an improvement, the method further comprises, after the decontamination of the damaged part, the destruction of the structure of this part at least.

  According to another improvement, the method further comprises a step of confining the water table at least around the rugged part.

  The invention also relates to a hazardous accidental industrial installation containment device, particularly useful for the implementation of the aforementioned dismantling process.

  This device, very useful in the case of the Chernobyl plant, however, has much wider applications. In fact, after an accident on an industrial installation containing dangerous materials for humans, in particular radioactive materials, it can happen that the damaged part which is weakened releases into the atmosphere, in an unpredictable way, a large quantity of residues. dangerous for humans, at a very high concentration, in a more or less extensive area around the hilly site. The residues can spread in the atmosphere very quickly under certain climatic conditions. The problem of the occurrence of such a discharge is even more important during the phase of dismantling and decontamination of industrial sites with dangerous residues hazardous to humans, because it is then necessary to perform interventions on the site itself.

  When it is too dangerous or too difficult to start decontaminating the hilly site quickly to eliminate the danger it poses to the environment, for example in the case of the installation of the Chernobyl accidental nuclear power station, which may emit a very strong radiation, it may be necessary to temporarily 2863098 confine the installation. The containment system shall prevent accidental release of residues hazardous to humans and the environment, and must be sufficiently sealed for a period of time sufficient to complete the decommissioning of the accident site. In a general way, it must be able to be built and installed in the best safety conditions, while allowing a dismantling of the accidental installation in the best safety conditions.

  During the construction of such a containment device, there is the problem of the safety of the workers. On the one hand, it is necessary that the workers work in an atmosphere protected against possible dangerous emissions, which is very difficult to obtain completely in the framework of a building site, and on the other hand that they have quick access shelters that protect them completely against these emissions.

  It is essential that the time elapsed between the time when the workers are warned by a system of vigilance of an accidental release from the accidental installation and the moment when they access the shelters is as short as possible so that the risks exposure to a hazardous substance are limited. For the same reasons, it is essential that the time elapsing between the time when the responders are warned and the moment when the dangerous substances reach the construction site is as long as possible. In some cases, especially in case of explosion of the accident facility, this period can be very short.

  It is also important that the duration of the project is as short as possible, for a constant number of stakeholders, so that the risks of exposure of the personnel are limited. Finally, it is important, for the same safety reasons, that the duration of the containment work be as short as possible so that the risks that the accidental installation presents for its environment only exist during the shortest possible period. .

  Pre-fabricated containment devices have been proposed far away from the hilly site, of very large size and intended to cover all of the hilly installations, these devices being subsequently moved on raceways to the hilly site. Such a device is envisaged to confine the rugged part of the Chernobyl nuclear site. However, because of the considerable size of this containment system, it is necessary to plan a lot of work at height, and there is no guarantee that, in the event of release of hazardous materials, the workers can reach a protective shelter before residues do not reach the construction site.

  A method of manufacturing such a containment enclosure on the site of the accident site, based exclusively on robotic means, is already known. However, these means do not make it possible to progress quickly, they are very expensive, and especially they do not make it possible to construct a sufficiently watertight enclosure of confinement.

  The invention therefore also relates to a device for confining a damaged industrial installation part, which can be prefabricated at a distance from this part of a damaged installation, of very large size, sufficient to cover the entire part of the uneven installation, which can be moved on rolling tracks to the hilly site.

  More specifically, the invention relates to a device for confining a damaged industrial plant containing residues dangerous to humans, intended to be moved between a place of construction and a place of use above the accident industrial facility ; according to the invention, the device comprises a frame and at least one coating, and the frame consists of metal modules arranged in horizontal layers.

  Preferably, the metal modules are formed of a light alloy, preferably aluminum.

  In an advantageous embodiment, the confinement device has a parallelepipedal shape intended to surround the accidental installation, and it has at least one aperture of a shape adapted to the shape of the rugged part to be covered.

  Preferably, the coating substantially seals the containment device.

  In one embodiment, the upper portion of the containment device forms an inclined roof.

  Preferably, the device comprises a device for putting the inside of the confinement device under overpressure during the construction of the confinement device.

  Preferably, the device comprises a device for putting the inside of the confinement device in depression during use.

  In an advantageous embodiment, the device comprises lifting means integrated into a base layer of the framework and working in the vertical direction so that they allow the height of the confinement device to be moved upwards by at least a layer, for example cylinders.

  Preferably, the coating comprises at least two coating layers, one inside and one outside the enclosure. The coating layers advantageously comprise at least one cladding carried by the modules, for example also formed of light alloy. The coating layers each advantageously comprise at least one fabric unrolled from top to bottom.

  Preferably, the device comprises bracing cables.

  Preferably, the device comprises at least one internal lifting device.

  Preferably, the device comprises buttresses arranged at least at the inner corners of the face having an opening.

  Preferably, the device comprises at least one access lock inside the containment device.

  The invention also relates to a method of manufacturing a containment device of an accidental industrial installation, the confinement device being formed of horizontal layers; according to the invention, the method comprises the construction of a seat provided with lifting means and an upper part of the confinement device, the lifting of the upper part of the confinement device with the lifting means of a height substantially equal to the height of at least one layer for the formation of a space above the seat, the construction of a layer of the framework in this space, with the joining of this layer and the structure overcoming it, then repeating the steps of lifting and building a layer for the construction of at least one additional layer, until the construction of all layers of the framework.

  Preferably, the construction of the seat and an upper part of the confinement device comprises the construction of a first building having a height corresponding to at least four layers of the frame, this building having a length at least equal to the width of the containment device to be constructed and a width much less than the length of this device, and the progressive construction of the seat and the upper part of the confinement device from a short side by association of modules, some of which at least have cylinders.

  In one embodiment, the method further comprises, after the construction of the upper part, the construction, around this upper part, of a protection gallery having a height at least equal to the height of two layers.

  In another advantageous embodiment, the method is carried out at a distance from the industrial facility it is intended for, and it also comprises the construction of a construction site protection wall having a height at least equal to the height of two layers of framing on the side facing the uneven installation.

  Preferably, the method comprises, throughout the entire construction, the application to the coating modules 2863098 9 ensuring a certain tightness to the entire device under construction, and the slight overpressure of the inside of the device under construction.

  In an embodiment in which the confinement device has, in at least one lateral face, an opening opening towards the bottom, the method advantageously comprises the construction, in the part intended to form the opening, of a removable device ensuring sealing.

  Other features and advantages of the invention will be better understood on reading the following description of embodiments, with reference to the accompanying drawings, in which: FIG. 1 is a diagrammatic perspective view of a containment device currently being considered for the Chernobyl No. 4 reactor site; FIG. 2 is a corresponding perspective view of a containment device according to the invention and of all the parts of the Chernobyl power plant containing the reactors 3 and 4, allowing the implementation of the dismantling process according to FIG. the invention; FIG. 3 is a plan view showing how the containment device according to the invention can be put into place, in the general context of the dismantling process of reactor No. 4 at the Chernobyl power plant; Figure 4 is a schematic side elevation and partial sectional view of a portion of the installation shown in Figure 3; and FIGS. 5 to 9 illustrate successive steps in the construction of the containment device that can be used for reactor No. 4 of the Chernobyl nuclear power plant.

  Figure 1 is a schematic perspective view of the provision currently officially recommended for the treatment of the problem posed by the reactor No. 4 of the Chernobyl nuclear power plant. In FIG. 1, the arrow generally designates the heteroclite structure (sarcophagus) constructed just after the explosion of the No. 4 reactor to provide immediate protection. This sarcophagus is still the only barrier existing around the reactor No. 4. This reactor No. 4 is adjacent to an intermediate structure 12 which comprises a solid built structure 14 which carries a discharge stack 16 intended not only to the reactor No. 4 , but also to reactor No. 3, which does not appear in FIG. 1, which reproduces an official drawing.

  Note also in Figure 1 the presence of a long building 18 which is placed along the reactors No. 3 and 4, but also the reactors 1 and 2 and which is therefore of great length. This building 18 is seriously contaminated only at the reactor n 4.

  The officially recommended solution includes, for the dismantling of the damaged part, the construction of a containment device 20 in the form of a large double-walled arch, intended to be built at a distance from the damaged part and to be moved to come cover the sarcophagus. This arch has a very large width and must also have a great length, because it is expected that it can cover not only the sarcophagus 10 of the reactor No. 4, but also a dismantling installation 24 and a device 26 for storing radio materials - active. These two installations 24, 26 are intended to be built inside the arch 20. Of course, on both sides in half-ellipse, the arch must be closed, on the one hand around the sarcophagus and on the other share to the ground.

  It is expected that the arch 20 must have a lifetime of the order of a century, its dimensions are gigantic because it must cover a considerable volume, and its cost is very high.

  FIG. 2 is a diagrammatic perspective view illustrating the implementation of the method according to the invention applied to the dismantling of reactor No. 4 of the Chernobyl power station. With respect to FIG. 1, the buildings constituting the structure of the reactor 3, as indicated by the reference 28, have been added. These are very large buildings in which the reactor 3 operated until the year 2000. and is currently unloading.

  2863098 11 This structure 28 is substantially symmetrical to that which contained the reactor n 4 before its accident, compared to the central structure 14 which contains the services shared by the two reactors. The structure 28 provides a very good protection against radioactivity and currently the interior of this structure is the safest part against the radioactivity of the whole neighborhood of the rugged part.

  According to the invention, the structure 28 which housed the reactor No. 3 is reused as a dismantling and storage facility for the radioactive materials contained in the sarcophagus 10. For this purpose, in addition to the existing accesses, accesses can be created in the structure intermediate 14 so that the inside of the sarcophagus is reached. This process therefore allows the extraction of radioactive materials, and in particular fuel from reactor No. 4, via structure 14.

  An advantageous characteristic in this process is that the structure which contained the reactor No. 4 is symmetrical with the structure 28 containing the reactor No. 3. In this way, once access paths formed in the intermediate structure 14, it is easy to refer to the arrangement of the interior of the structure 28 to know that of the interior of the sarcophagus.

  Of course, the dismantling must begin, for reasons of public safety, by the establishment of a containment structure, as indicated by reference 30, above the sarcophagus. This containment device 30 can be remotely constructed, as described below, and moved along a first raceway 32, then a second raceway 34 in the perpendicular direction. In the intermediate position, the confinement device 30 takes the position 36 at which the opening corresponding to the sarcophagus is disengaged.

  During the dismantling, a first operation includes mounting extraction devices by pumping dust contained in the atmosphere of the sarcophagus. The dust is then packaged as 2863098 12 waste that can be easier to treat. Then, the dismantling comprises the evacuation of the pulverulent materials, then larger materials which undergo for example a crushing and grinding. The materials are sorted and packaged before being stored. This storage is an intermediate storage and the waste is evacuated. All these operations extraction, crushing and grinding, sorting and packaging of waste are performed inside the structure 28.

  An essential feature of the method according to the invention is that the sarcophagus is kept as it is, inside the confinement device, so it is unlikely to collapse and pose additional problems of contamination. Not only is the sarcophagus not destroyed, but it can also be covered, from inside the containment device 30, with a tight and light coating intended to constitute an additional barrier reducing the potential emission of dust.

  The dismantling process may further comprise the dismantling of the structures, once the radioactivity is sufficiently reduced by the removal of the radioactive materials.

  In addition, it is advantageous that an underground containment is also formed around the installation, and even around the entire plant, for the protection of the water table. Mold wall forming techniques forming an enclosure up to the water table are well known in the art and are not described in more detail.

  We now consider, with reference to Figures 5 to 9, a method of construction of a containment device according to the invention.

  The construction begins at a location located at a significant distance from the rugged part, for example of the order of 2 km. In this way, the intensity of the radiation is much smaller than near the rugged part. For example, at 2 km, the radioactivity is 100 times lower than 200 m from the accident site.

  The structure 38 is a mobile building having a height equal to about five framework layers, that is to say that of five modules used for the construction of the confinement device. This building 38 has a form of gantry which can be closed and in which is built another building 40 having also an elongate gantry shape open on one side, but which can be sealed by a removable device.

  Using the first building 38, the second building 40, the height of which corresponds to about four modules, is constructed over a length corresponding to a little more than the width that the completed confinement device must have, as shown in FIG. 5.

  Figure 6 indicates that when the second mobile building 40 has been completed, the construction of the containment device itself begins. This construction is carried out by progressive displacement of the building 40 on the tracks 42. The constructed structure 44 is progressively made and comprises the upper part 46 of the confinement device 30 and a base comprising lifting means, such as cylinders 50 (FIG. Figure 8). The seat preferably comprises, in addition to cylinders, modules similar to those used for the rest of the confinement device.

  When the structure 44 has been constructed, the building 40 is remote and is no longer used. Protection galleries 50 forming shelters around the bottom of the structure are constructed. The structure is then made in layers, above the seat which has the thickness of a module and which contains the cylinders. The shelter gallery 50 therefore has a height slightly greater than the height of two modules. The construction is done in layers, with preparation of the opening 48 which must be on the side of the sarcophagus.

  The cylinders 50, during the construction operation, are intended to lift the upper part of the confinement device to form a space of a height at least equal to that of a module so that an additional layer 2863098 14 can be constructed by inserting modules. Construction is progressing from the bottom.

  All construction work is done outside at shelters 50, and inside. The 5 speakers are therefore always sheltered.

  The construction includes the layout of a cladding inside and outside, and the arrangement of canvases inside and outside, in the form of two coatings. In this way, the entire constructed structure is still relatively watertight. An overpressure device is connected and maintains the containment device under construction at a slight overpressure so that, in the event of an incident causing the release of dust and radioactive gases, the personnel working in the enclosure as in the galleries do not can not be quickly contaminated.

  According to an essential characteristic of the invention, the personnel always work near the ground level. Shelters are present on the ground around the interior of the structure, so that as soon as an alert is given, the staff can be quickly put under cover.

  When the containment device 30 has been made, it must be moved. For this purpose, it is sufficient to construct concrete raceways 32 from the construction site to the vicinity of the sarcophagus, as shown in FIG. 3. On the latter, it can be seen that the raceway 32 brings the confinement device near the sarcophagus, that is to say at the position 36 indicated in FIG. 2. At this moment, the opening which had remained closed from the place of construction is disengaged, and the confinement is brought to the sarcophagus. The seal between the opening and the sarcophagus is obtained by guillotine sealing devices as described for example in French Patent No. 2,746,130.

  The displacement of the confinement device on the raceways can be effected in various ways. An advantageous method, similar to the technique used for moving the bridge arches, includes the use of stationary devices 54 arranged either on a raceway 32, 34, or on resilient supports 52 and having rollers. 56 mounted on a beam and protruding at the top. These rollers preferably cooperate with a rail 58 formed in the lower part of the confinement device, that is to say below the first layer. This rail is incorporated in the construction from the construction of the seat that includes the cylinders. Such a displacement makes it possible to take account of the possible unevenness of the ground by arrangement of shims under the supports 54 of rollers.

  A first advantage of the invention is that the entire dismantling can be performed very soon and in a reduced time through the reuse of the structure of the reactor No. 3.

  A second advantage that stems from the first is the considerable cost reduction since it is not necessary to build a specific structure for dismantling. This cost reduction is increased because the containment device can be smaller and therefore less expensive.

  A third advantage, much more important than the previous ones, is the increase in the safety of both populations (containment and dismantling achieved more quickly) than those involved (reduction of exposure to radiation, constant proximity to shelters). This increase in security in turn allows, by a synergy effect, a further reduction in the time required for the operation (reduction of rotation frequencies of the parties involved, increased mobility) and therefore Costs.

  Of course, various modifications can be made by those skilled in the art to the methods and devices which have just been described by way of non-limiting example without departing from the scope of the invention.

Claims (10)

  A method of dismantling a portion of a damaged industrial plant (10) dangerous to man, adjacent to a non-uneven industrial plant part (28) which has protective features against hazardous materials, characterized in that it includes: the containment of the damaged part (10) by a containment device (30) which covers it in a substantially watertight manner, and the decontamination of the damaged part (10) by access to it from the non damaged (28), with use of the protection characteristics of the non-damaged part (28) for the treatment of dangerous substances removed from the damaged part (10).   2. Method according to claim 1, characterized in that the confinement device (30) is substantially sealed, and the decontamination operation is performed while the confinement device (30) is kept in depression.   3. Method according to one of claims 1 and 2, characterized in that the access to the rugged part (10) from the non-rough part (28) is achieved by drilling a structure (14) separating the damaged part of the non-rugged part.   4. Method according to any one of claims 1 to 3, characterized in that the confinement step comprises the construction of a confinement device (30) remote from the damaged portion (10), and the movement of the device containment (30) to cover the damaged portion (10).   5. Containment device of a damaged industrial installation containing residues dangerous to humans, intended to be moved between a place of construction and a place of use above the industrial accident site (10), characterized in that it comprises a frame and at least one coating, and in that the frame consists of metal modules arranged in horizontal layers.   2863098 17 6. Device according to claim 5, characterized in that it comprises a device for putting the inside of the confinement device (30) in depression during use.   7. Device according to one of claims 5 and 6, characterized in that it comprises lifting means (50) integrated with a seat layer of the frame and working in the vertical direction so that they allow the displacement in height of the confinement device (30) the height of at least one layer.   8. Device according to any one of claims 5 to 7, characterized in that the coating comprises at least two coating layers, one inside and one outside the enclosure.   9. A method of manufacturing a device for confinement-ment of a crashed industrial facility (10), the containment device (30) being formed of horizontal layers, characterized in that it comprises the construction of a seat provided lifting means (50) and an upper portion (44) of the containment device (30), lifting the upper portion (44) of the containment device with the lifting means (50) by a height substantially equal to the height of at least one layer for the formation of a space above the seat, the construction of a layer of the framework in this space, with the attachment of this layer and the structure which forms it overcomes and then repeats the steps of lifting and building a layer for the construction of at least one additional layer, until the construction of all layers of the framework.   10. The method of claim 9, characterized in that it comprises, throughout the construction, the application to the coating modules ensuring a good seal to the entire device (30) under construction, and the slight overpressure of the interior of the device (30) under construction.