FR2583205A1 - MACHINE FOR DISASSEMBLING DECLASSED NUCLEAR REACTORS OR COMPONENTS THEREOF - Google Patents

Abstract

MACHINE FOR DISASSEMBLING DECLASSIFIED NUCLEAR REACTORS OR THEIR COMPONENTS. THE MACHINE INCLUDES A STRUCTURE 12 FORMING A SHIELD, ROTATING AT THE OPEN TOP OF THE REACTOR CONTAINER THAT CAN WITHSTAND THE PRESSURE, A MAST 23 MOUNTED ON THE SHIELD 12 TO EXTEND THROUGH AN OPENING 17 IN THE SHIELD, AND A MANIPULATOR 42 CARRYING TOOLS AND MOUNTED ON THE MAST 23. A ROTATING BEAM 25, EQUIPPED WITH A WINCH 36 IS PROVIDED ON THE SHIELD 12 TO HANDLE THE DISASSEMBLED EQUIPMENT. THE OPENING 17 CAN BE CLOSED BY THE SLIDING TRUNKS 20 OF THE SHIELD AND IT 17 CAN BE ENLARGED TO ALLOW TO LIFT THE RETRACTED MANIPULATOR 42, TOWARDS A MODULE 50, 51 PROVIDED FOR TOOL CHANGES.

Description

The present invention relates to operations related to the decommissioning of

  nuclear reactors, or resulting from such decommissioning of reactors which are considered to have

  completed their useful service life and, in particular, the

  The invention concerns machines for performing

  regulated and safe, the disassembly and / or dismantling of the structure

reactor.

  When a nuclear reactor has reached the end of its expected service life; the choice exists, after removal of the nuclear fuel and the cooling fluid of this reactor, between covering the entire structure with a suitable shielding, such as a mound of earth, and taking precautions to ensure that the reactor thus covered is preserved and shielded all the time as a "memorial"

  permanent, and disassemble or dismantle the structure of the reaction

  and to place the disassembled material in small quantities in conventional safe storage facilities and, therefore, return the reactor site to the state it had before reactor construction. This last way of operating is to be preferred, especially because of doubts about the possibility of preserving the shield integrity of the entire reactor structure over the necessary thousands of years before the biologically unsafe amounts radioactivity

decreased enough.

  A conventional nuclear reactor, with cooling

  by gas and moderation by graphite comprises, in a recipe

  able to withstand the pressure, a heart including the moderator and the fuel elements, the latter

  can be loaded and unloaded by a charging machine.

  heat exchangers which remove the heat of the circulating refrigerant circulating through the core and use the heat thus removed to generate electricity, for example by using water vapor and a turbine. When such a reactor has completed its useful life, it may be decided that the reactor is dismantled and the site returned to its previous state. After normal discharge of the elements

  fuel and purge the cooling gas, it is necessary to

  considered safe, from a safety point of view, to use conventional disassembly techniques to remove turbines, heat exchangers, reloading machine and, with adequate temporary shielding, the upper dome of the container capable of supporting the pressure, so as to highlight the heart. To disassemble and remove the pressure-resistant container and to discharge and transfer to a disposal or destruction facility the graphite moderator (which is under

  form of separate blocks and other internal parts of the

  pient, it takes a machine that will perform these operations

  in a safe and fast manner, and the present invention in particular

  purpose of providing such a machine.

  According to the invention, the latter provides a machine for dismantling, unloading and transferring to a storage, evacuation and / or destruction installation a structure

  nuclear reactor and / or components that have been irrationally

  during operation of the reactor, said machine

  comprising a rotating shield for protection against

  the shield installed above the pressure-resistant container in or on a rigid portion of the reactor that has not yet been disassembled, said shield having an offset aperture and at least one movable portion for varying the size of the the opening, a

  driving device for effecting the rotation of the

  a structure mounted on the rotary shield for supporting a mast, generally vertical, which can pass through the shield and extend into the container capable of withstanding the pressure, the mast being retractable to the point where it can fully come above the shield, and a

  manipulator carrying tools, mounted on the mast for

  see being extended or contracted laterally with respect to this mast, the lateral extent of the manipulator, once contracted, being such that it can be withdrawn upward through said opening in the shield when the size of this opening is maximized by proper positioning of the at least one movable portion

shield.

  The machine preferably further comprises a beam, generally horizontal, mounted below said shield to be able to perform angular movement about a generally vertical axis (which may coincide

  with the axis of rotation of the shield), independently of the

  the beam as a track for mounting a winch-type device for lifting the structure and / or components of the disassembled reactor, the beam being movable to at least one angular position in which it is aligned with a or fixed beams forming continuation (s) of said track, so that the winch can be transferred to one or more discharge stations,

to unload the load.

  Devices may be provided for controlling the driving device associated with the shield and the movable beam so that none of these elements can interfere or

  hitting each other at any time.

  A particularity of the invention is that the mast can be fixed offset from the shield and can be obtained by means of the extensible manipulator, simply by rotating the shield to put the mast in a position in which the manipulator can be extended to reach any desired point, access to all points within the container can withstand the pressure. This avoids the need for

  the complication of an assembly intended to allow the mast to

  to make a transverse displacement. In addition, since the

  Since it supports the mast and is itself mounted on the reactor structure, the mast and its supporting and guiding structure can be easily removed from the shield, and the latter can be left in place as a permanent shield. if

we want it.

  An embodiment of the invention will now be

  described by way of example, illustrative and not limita-

  titif, with reference to the accompanying drawings in which Figure 1 is a vertical section along the axis of rotation of a shield forming part of a disassembly machine according to the invention, the drive motors of the shield and the winch support beam being shown offset by 90 from their actual position to facilitate understanding of their operation; Figure 2 is a section in the direction A-A of Figure 1; Figure 3 is a plan view; Figure 4 is a view similar to Figure 1 but showing additional details; Figure 5 is an end view in the direction of the arrow 5 of Figure 4; Figure 6 is a plan view in the direction of the arrow 6 of Figure 5; Figure 7 is a schematic sectional elevation of a gas-cooled nuclear reactor for disassembly by the machine of Figures 1 to 3; and

  Figure 8 is a plan view of the reactor.

  Referring first to FIGS. 7 and 8, it is seen that they show schematically the graphite-moderated gas-cooled nuclear reactor known as the "Windscale Advanced Gas-Cooled Reactor" (WAGR). upgraded Windscale gas-cooled), which has now completed its useful life and needs to be dismantled. The reactor core (not shown), which includes

  the graphite moderator and the fuel element channels

  and other internal parts such as the core support (not shown), the hot box 1 and the vertical pipes

  2 for refueling, are contained in a reci-

  FIGS. 3 being able to withstand the pressure, the figures showing that the upper dome and the upper parts of the vertical tubes 2 have been removed. The volume that the upper dome had occupied is intended to be used to house a machine for

  dismantle, unload and transfer, such as one of the

  which will be described later in this presentation.

  The reactor also comprises four enclosures 4 housing heat exchangers, where heat exchangers

  heat were removed and removed by conventional means.

  with the necessary shielding precautions, since the level of radioactivity of these structures is such that it allows such operations. One of the enclosures 4 serves (when emptied) a temporary warehouse for disassembled equipment, in which classification and designation is carried out for packaging in a building 6 which communicates with the enclosure 5, the small material that can be disposed of in bulk being thrown into a container 7 of

  waste disposed below the temporary warehouse.

  The outer shell 8 of the reactor is conserved and used to

  maintain the overall integrity of the reactor during operations

  disassembly, dismantling and

  rentées. The packing building 6 is outside the building.

  8 and communicates with it by an air lock (not shown).

  sented). The level of the fuel refill floor is designated 9 in FIG. 1, and it is equipped with rails 10 intended to allow the rolling of the machine (already

  removed at the stage of the current description)

reactor fuel.

  Figures 1 to 3 show the reactor in which

  a disassembly machine 11 is in place. The machine 11 com-

  takes a shield 12 of radiation protection, which is rotatably mounted in the floor 9 by means of a fixed annular support structure 13 of the shield (which can be segmented for the convenience of the

  handling), and an annular support arrangement 14.

  The rotating shield 12 is arranged so that its axis

  rotation is generally vertical and essential-

  coaxial with the axis of the container 3 can withstand pressure. A drive motor 15 serves to rotate the shield 12 by means of a rack and pinion drive 16, the rack being bent and

  extending the entire perimeter of the shield.

  clier 12 comprises an opening 17 arranged eccentrically and a number of sliding sections 18, 19, 20 shield,

  mounted on wheels 21 and rails 22 provided for a movement

  sliding position between the solid lines and the phantom positions shown in FIG. 3. In the latter position, the shield sections release the opening 17 while in the first position they limit the opening to cross-sectional area corresponding to that of a vertical mast 23 by providing

  intervals 24 allowing the passage of a series of cables.

  A rotating beam 25 is mounted below the

  shield 12 and it is supported so as to be able to

  around a vertical axis (which may coincide with the axis

  rotation of the shield 12) by means of a

  slope comprising an annular beam 26 and posts 27 mounted in turn, via an annular support arrangement 28, on an annular support 29 installed in the biological shield 30. The rotation of the beam

  turn 25 is performed using a drive motor 31.

  a vertical transmission 32 extending through the fixed shield 13 and a rack and pinion gear 33, the rack extending over the entire circumference of the annular beam 26. As can be seen in FIG. As can be seen in FIG. 1, the rotating beam can be rotated to reach a position in which it is aligned with one or more fixed beams 34, 35 which can extend to respective enclosures 4 of heat exchangers the role of warehouses for the

  disassembled material. A motorized winch 36 for lifting

  the disassembled material and components is suspended from the lower flanges of the rotating beam 25 so as to execute a movement along the beam 25, and this winch

  can be transferred from the beam 25 to a beam 34, 35 selected

  (when aligning) to transport the disas-

  seemed to the desired warehouse. Cables 37 for the function

  the winch (eg power supply and control signal transmission cables) pass from a cable feed coil 38 disposed on the rotating shield 12 through a through hole.

  39 equipped with a pad, an arrangement 40 pulley available

central section and a guide 41.

  The mast 23 consists of sections bolted or otherwise attached together end to end and is a guide for the platform 43 of a manipulator 42 that can be moved along the mat from a lower position (see FIG. 1) and a top position (see FIGS. 1 and 4) using winches 44 mounted on a platform

  45 fixed on pillars 46 above the opening 17.

  The platform also serves to mount a number of winding drums 47 to unwind and take up various service cables 48 for the operation of the manipulator 42 and tools carried by it. Guides, such as groups of rollers 49, serve to position and guide the mat 23 as it is lowered section by section using

  a crane arranged at the head (not shown).

  The manipulator comprises an arm having multiple degrees of freedom and, as shown in FIG. 4, it can be folded into a compact structure to allow it to be withdrawn through the opening 17 when the sections 18, 19 and 20 of the shield are removed. When not in use, the manipulator is raised to the position shown in Figures 1 to 4 to minimize contamination. It is also raised in this position, then undergoes a complete extension as shown in phantom in Figure 1, when changes of tools are necessary. The area under the platform 45, and the area in which the manipulator protrudes for tool changes, are surrounded within enclosures

  , 51 removable with access doors 52, 53.

  A chamber 54, housing a glove box and having a

  part 55 of access, is provided above the platform 45.

  As previously mentioned, the mast 23 includes

  a number of sections (see 56, 57 in Figure 4).

  The mast is constructed one section at a time by lowering each section, using the crane head, until an opening in this section aligns with a unit 58 for introducing a locking pin , the peg 59 then being inserted to retain the section while the next section is assembled above it; the peg 59 is removed, the assembly is lowered,

  the next section is held by ankle and so on.

  In practice, the mast 23 will be built in stages over a period of time so that as the mast descends, the structure and the internal parts of the reactor can

  be disassembled using the manipulator 42 and the winch 36.

  The mast will then be raised, which involves removing the sections one by one. After disassembly of the mast 23, the opening 17 can be completely plugged and the shield 12 can be

left in place.

  It goes without saying that, without departing from the scope of the invention,

  tion, many modifications can be made to the machine described and shown to disassemble, unload

  and transfer a structure and / or components of a reaction

  nuclear reactor, which have been irradiated during the

of this reactor.

Claims (3)

  1. Machine for dismantling, unloading and transferring to a storage or disposal facility and,   destruction, a nuclear reactor structure   area and, where appropriate, components of such a reactor that have been irradiated during the operation of the reactor,   characterized in that it comprises a rotatable shield   tif (12) protection against radiation, shield   above the container (3) able to withstand the pressure   in, or on a rigid part of the reactor that does not have   has been dismounted, said shield (12) including an opening   an eccentric head (17) and at least one movable section (18, 19, 20) for varying the size of the opening (17), driving members (15, 16) for rotating the shield (12). a structure (44, 45, 46) mounted on the rotary shield (12) for supporting a generally vertical mat (23) which can pass through the shield (12) and extend into the container (3) being pressure-responsive, said mast (23) being retractable to be fully fed over the shield (12), and a tool-carrying manipulator (42) mounted on the mat (23) to be extended and being contracted laterally with respect to the mat, the lateral span of the manipulator (42), when contracted, being such that it can be withdrawn upwardly through said opening (17) in the shield (12) when the dimension of this opening (17) is maximized by proper positioning   one or more movable sections (18, 19, 20) of the shield.   2. Machine according to claim 1, characterized in that it comprises a beam (25) generally   horizontal, mounted below said shield (12) for   see executing an angular movement about an axis, generally vertical, independently of the shield (12), the beam (25) serving as a track for mounting winch members (36, 44) for lifting the disassembled structure of the reactor or its components or, where appropriate, this structure and its components, the beam being movable to reach at least one angular position in which it is aligned with one or more fixed beams (34, 35) forming the extensions of said track, which allows the winch to be transferred to one or more storage stations for evacuation, in order to unload the winch of its load.   3. Machine according to claim 1 or 2, characterized   in that it comprises means for controlling the driving members (15, 16; 21, 22; 31, 32, 33) associated with the shield (12) and the movable beam (25) so that none of these elements or organs can interfere or strike another at any time.