FR2684481A1 - Device for support and positioning of a means for intervention on the baffle assembly of the core of a pressurised water nuclear reactor - Google Patents

Abstract

The device comprises a carriage (30) mounted movably on a vertical mast (21) in the vertical direction, a first turntable (36) mounted movably in rotation on the carriage (30) about a vertical axis, a second turntable (45) mounted movably in rotation about a vertical axis on the first turntable (36) and a support (28) for the intervention means, carried by the second turntable (45). The first turntable (36) comprises rotational drive means consisting of a toothed ring (37), a motor means (38) and a drive gear (40) integral with the output shaft of the motor means (38). The second turntable (45) is integral with a toothed circular sector (46) whose pitch-circle diameter is identical to the pitch-circle diameter of the toothed ring (37). The drive gear (40) makes it possible to turn the first turntable (36) and the second turntable (45) in opposite directions and at the same speed. The support (28) and the intervention means (50) thus remain continuously oriented in the same direction during the rotation of the first turntable (36).

Description

 The invention relates to a device for supporting and positioning a means of intervention on the partitioning of the core of a pressurized water nuclear reactor, placed underwater, so as to allow intervention on the irradiated partitioning, after a certain time. of the reactor.

 Pressurized water nuclear reactors generally comprise a core constituted by combustible assemblies of prismatic shape arranged vertically and juxtaposed. The core is placed inside the nuclear reactor vessel through which the reactor cooling water circulates. The heart is surrounded by a partition which closely follows the shape of its peripheral surface and ensures its maintenance inside a heart envelope of cylindrical shape with vertical axis. The core envelope is integral, at its lower part, with a core support plate crossed by cooling water passage openings at the level of each of the zones in which a fuel assembly comes to rest. Generally, fuel assemblies have a square section and four water passage holes are located at each of the assemblies.

 The core envelope integral with the lower plate for supporting the assemblies constitutes, with the partitioning which is fixed in its internal part, above the lower core plate, the lower internal equipment of the reactor.

 These lower internal equipments are placed inside the reactor vessel, the core shell resting by means of a flange on a part of the vessel adjacent to the joint plane of the closure cover of this vessel.

 During periods of nuclear reactor shutdown, for example to reload the core, the lower internal equipment of the reactor can be taken out of the tank and placed on an intervention stand, inside the fuel pool. These operations are carried out after depressurization and cooling of the tank, opening of the cover and unloading of the core assemblies. It is possible to carry out, on the internal equipment placed on their intervention stand, various control and repair operations which may relate in particular to the partitioning of the heart.

 The partitioning of the core comprises vertical partitioning plates placed at right angles to one another so that their internal surface constitutes the bearing surface of the peripheral assemblies of the core as well as horizontal reinforcing plates arranged in a spaced manner according to the height of the heart, in an annular space formed between the periphery of the heart and the interior surface of the envelope of the heart.

 The generally annular reinforcements have an internal peripheral edge along which the vertical partition plates are fixed, this peripheral edge having a complex polygonal shape corresponding to the peripheral contour of the core delimited by the vertical partition plates.

 The various elements constituting the partitioning are generally assembled by screws made of a material capable of having good mechanical resistance and good resistance to corrosion in the operating nuclear reactor, these screws undergoing high thermal and mechanical stresses and being moreover subject intense radiation flows insofar as they are located near the reactor core.

 It can therefore occur damage, cracks or even ruptures of some of the assembly screws of the partition.

 During the periods of shutdown and reloading and maintenance of the nuclear reactor, it may be necessary to carry out a check and possibly a sampling and replacement of some of the partition assembly screws.

 More generally, it may be necessary to carry out various control, repair or machining operations at any level depending on the height of the partitioning, the internal equipment being placed on their storage stand in the reactor pool.

 These operations can be carried out on any of the partition plates and at a variable level depending on the height of the partition. These interventions are generally carried out from inside the partition, the internal space delimited by the vertical partition plates being accessible from the upper level of the reactor pool.

 It has already been proposed, to carry out such interventions, to use a device having one or more masts whose height is greater than the height of the lower internal equipment and which can be placed inside or outside the partitioning. The position of the mast (s) can be adjusted using a handling device, to ensure their positioning in the vicinity of an area in which an intervention is carried out.

 In the case where a single mast is used, such a mast generally comprises hooking means at its upper part making it possible to connect it to a lifting device, means for connecting to the upper part of the internal equipment or the partitioning also located in the vicinity of its upper part and a base plate comprising centering pins in the water passage openings passing through the lower core plate.

 The mast constitutes a support and positioning device for intervention means which can be placed in a desired arrangement depending on the height of the mast.

 The mast provided with its intervention means placed in a determined position is introduced into the lower internal equipment so that the pins constituting the lower extension of its base plate engage in holes in the lower core plate chosen from so as to place the mast in a desired position to perform the intervention on the internal equipment and for example to replace one or more screws of the partition.

 The upper part of the mast is connected by the corresponding connecting means to the upper part of the partition or internal equipment to ensure its fixing.

 In most cases, interventions on the partitioning of the heart must be carried out in specific areas with very high precision; for example, tools must intervene in a direction corresponding perfectly to the axial direction of a partition assembly screw, so that the device for supporting and positioning the intervention means constituted by the mast must have a very large rigidity and must be set up and adjusted inside the internal equipment of the reactor with great precision.

 It has therefore been proposed in FR-A-89-17143, a device for supporting and positioning a means of intervention in a determined zone of the partitioning of the core of a pressurized water nuclear reactor which comprises a set of fixing and pressing the mast against the internal wall of the partition at an angle formed by two successive partition plates.

 In the case where numerous interventions must be carried out on the partitioning, in different zones, it is necessary to disassemble the mast, its handling, its installation and its plating in a new working position, between two successive interventions , in different areas of the partitioning.

 These pre-intervention operations can be long and require certain precautions.

As a result, the total duration of interventions on the partitioning can be long, which adds to the period of time during which the nuclear reactor is not available for the production of electricity.

 The object of the invention is therefore to propose a device for supporting and positioning a means of intervention under water, on the partitioning of the core of a pressurized water nuclear reactor, constituted by flat partitioning plates placed vertically above a substantially circular, horizontal core bottom plate pierced with through openings and assembled to each other at right angles to form a prismatic wall whose cross section through a horizontal plane is of polygonal shape, comprising a vertical mast for supporting and guiding the intervention means provided with means for positioning in openings of the lower core plate at its lower end and fixing means at its upper end, this device making it possible to carry out successive interventions in different areas of the partitioning, in a very short time and without requiring disassembly and repackaging lace of the device between two interventions in different zones of the partitioning.

 For this purpose, the device according to the invention further comprises - a carriage mounted movable on the vertical mast in the vertical direction, - a first turntable mounted movable in rotation on the carriage around a vertical axis constituting the longitudinal axis of the mast, - means for driving the first rotary table in rotation constituted by a toothed ring carried by the carriage and coaxial with the vertical mast, a motor means carried by the first rotary table and a drive pinion secured to a shaft vertical outlet of the drive means in engagement with the ring gear, - a second turntable mounted mobile in rotation about a vertical axis on the first turntable and secured to a circular toothed sector whose pitch diameter is identical to the pitch diameter of the ring gear, having for axis the axis of rotation of the second plate and in engagement with the drive pinion in a diametrically opposite arrangement with respect wearing the ring gear, - and a support for the intervention means carried by the second plate and allowing movement of the intervention means in a vertical plane.

 In order to clearly understand the invention, we will now describe, by way of nonlimiting example, with reference to the attached figures, an embodiment of a device according to the invention.

 FIG. 1 is a general view of the swimming pool of a pressurized water nuclear reactor, during a shutdown phase for recharging and repairing the reactor.

 Figure 2 is an exploded perspective view of the lower internal equipment of a pressurized water nuclear reactor.

 Figure 3 is an elevational view in section through a vertical plane of the device according to the invention in the intervention position in the internal equipment of a pressurized water nuclear reactor, during a reactor shutdown phase.

 FIG. 4 is a view in elevation and in section through a vertical plane, of the lower part of the intervention device shown in FIG. 3.

 FIG. 5 is a top view and in section along 5-5 of FIG. 4.

 Figure 6 is a top view of the device in the working position on the lower core plate of a nuclear reactor showing the possibilities of use of the device, in the case of various types of partitioning.

 In Figure 1, we see the concrete structure 1 of the pool 2 of a pressurized water nuclear reactor, comprising a tank 3 disposed in a tank well forming part of the structure 1 of the pool.

 The nuclear reactor is stopped, the tank is open and the pool 2 is filled with water to its upper level. Above the swimming pool, rails 4 are arranged on which the loading machine 5 of the reactor is capable of moving.

 This machine 5 comprises a loading mast 5a making it possible to remove or replace the fuel assemblies from the core. The fuel assemblies constituting the core are placed inside the lower internal equipment 6 which are themselves arranged inside the tank 3.

 In Figure 1, there is shown a structure 7 suspended from the bridge 8 of the nuclear power plant during engagement inside the internal equipment 6 disposed in the tank 3. The structure 7 allows the lower internal equipment to be removed from the tank 3 after removal of the fuel assemblies from the core to place these internal equipment in their position 6 'on a storage and intervention stand 10 placed in the pool.

 When the internal equipment 6 is in their position 6 ′, it is possible to carry out interventions such as checks, machining or repairs, using specially adapted tools which can be used by operators using the machine. loading 5 or auxiliary lifting means of this machine. The biological protection of the operators is ensured by the layer of water in the reactor pool located above the internal equipment 6.

 In FIG. 2, part of the internal equipment 6 of a pressurized water nuclear reactor is shown, which conventionally comprises a core casing 11 secured, at its lower part, to a lower core plate 12 and a partition 13 fixed on the casing 11 so that its lower part is situated above the upper face of the lower core plate 12.

 The partitioning 13 comprises vertical partitioning plates 14 along the entire height of the partitioning corresponding substantially to the height of the core and horizontal reinforcing plates 15 on which are fixed the vertical plates 14, in a joined manner, any two successive plates 14 being placed perpendicular to each other.

 In addition, the horizontal reinforcing plates 15 of generally annular shape and distributed at regular intervals along the height of the partitioning comprise an internal peripheral edge cut out according to a polygon of complex shape along which the plates 14 are attached, as is visible in particular on FIG. 6. The outer peripheral edge of the horizontal reinforcing plates 15 has a circular shape corresponding to the circular inner section of the core envelope 11.

 FIG. 6 shows a part of the cross section of the partitioning of a pressurized water nuclear reactor corresponding substantially to a quarter of this section and according to three different embodiments 13, 13 ', 13 ". The other three quarters of the section of partitions 13, 13 ′, 13 "are identical to the sections shown in FIG. 6.

 The partitioning which is constituted by vertical partitioning plates 14 assembled at right angles along a polygonal contour has the form of a prismatic wall whose vertical axis coincides with the axis of the lower core plate 12 of circular shape constituting part of the lower internal equipment 6 of the reactor.

 In FIG. 3, we see the assembly of the intervention device 20 according to the invention which mainly comprises a vertical mast 21 integral, at its lower part, with a positioning plate 22 on the lower core plate 12 of the equipment internal 6 and, at its upper part, a star structure 23 allowing the fixing of the intervention device 20 on the upper part of the internal equipment 6 constituted by an upper flange of the core casing 11.

 The device 20 can be installed inside the internal equipment 6 in position on their storage stand 10, using the bridge 8 of the power station shown in FIG.

 An operator 24 can carry out, from a gateway 27 disposed above the reactor pool, various operations at the level of the tool support 28 of the device 20, using a pole 25 on which a lift 25a is movably mounted.

 A means 26 carried by a support fixed on the partition allows the intervention area to be lit, so as to facilitate the work of the operator 24.

 Operator interventions may consist of mounting or dismounting tools or control means on the support 28 of the device 20, recovering damaged screw fragments extracted from the partitioning or machining shavings or even supplying a tool fixed on the support 28 in new assembly screws.

 As can be seen in FIGS. 4 and 5, the vertical mast 21 of the intervention device 20 produced in tubular form with circular section comprises on a substantial part of its height corresponding substantially to the height of the partition 13 of the reactor, four slides 29 arranged at 90C from each other around the mast 21 and in the vertical direction, over a substantial height of the mast 21 corresponding substantially to the height of the partition 13.

 A trolley 30 of tubular shape is mounted movable in the vertical direction on the mast 21, the tubular trolley 30 being engaged around the mast 21 and comprising sets of rollers 31 in engagement with the slides 29.

 The positioning means 22 of the lower part of the device 21 on the lower core plate 12 consist of a simple plate 32 fixed by ribs 33 to the lower end of the mast 21 in a horizontal position and carrying positioning pins 34 which are introduced, during the installation of the mast 21 in the internal equipment, in the water passage holes 16 of the lower core plate 12.

 As shown in FIG. 3, the vertical mast 21 is then placed along the vertical axis ZZ 'common to the lower core plate 12 and to the partitioning 13 and held at its upper part by the star support 23 resting on the upper part of the heart envelope 11.

 The carriage 30 carries at its lower part an orientation ring 35 which is constituted by a large ball bearing fixed around the carriage 30, in an arrangement coaxial with the carriage and the vertical mast 21.

 A turntable 36 is fixed on the outer ring of the slewing ring 35, so as to be movable in rotation about the vertical axis of the mast 21, relative to the carriage 30.

 A toothed crown 37 is fixed to the lower part of the carriage 30, in an arrangement coaxial with the orientation crown 35 and the mast 21.

 The turntable 36 carries a motor 38, the output axis 39 of which has a vertical arrangement carries a drive pinion 40 which meshes with the fixed toothed crown 37.

 The rotation of the motor (or geared motor) 38 makes it possible to rotate the turntable 36 around the vertical axis of the mast 21, the pinion 40 having an orbital path around the ring gear 37.

 In addition, the turntable 36 carries two lower arms constituting a yoke 42 which itself carries a vertical axis 43.

 A second turntable 45 is rotatably mounted on the first turntable 36, by means of the vertical axis 43 and of a semi-circular toothed sector 46 integral with the second turntable 45.

 The semi-circular toothed sector 46 has a pitch diameter identical to the pitch diameter of the fixed gear ring 37.

 The drive pinion 40 meshes with the ring gear 37 and with the toothed sector 46, at two diametrically opposite points.

 During the rotation of the drive pinion 40, the first turntable 36 and the toothed ring 46 integral with the second turntable 45 rotate in opposite directions and at the same speed, due to their identical pitch diameter and the common drive by the pinion 40.

 The second turntable 45 carries the support 28 of the tool 50 via cross-motion tables 49, 51 making it possible to move the support 52 of the tool 50 in two perpendicular directions X and Y of the vertical plane.

 The tool support 52 comprises three slides in the form of a dovetail on three perpendicular faces two by two directed outwards. The tool 50 comprises a dovetail-shaped tenon which can be engaged in a slide of the support 52 in order to ensure its fixing in one of three positions corresponding to one of the three slides of the support 52.

 Depending on the nature of the intervention carried out, the tool 50 may be placed in one of the three positions ensuring its orientation in a direction perpendicular to one of the partitioning plates 14 in order to perform an operation such as the extraction of a damaged screw, machining or inspection.

 The device 20 shown in FIGS. 4 and 5 also includes the play take-up member 55 associated with the drive pinion 40 meshing with the ring gear 37 and with the toothed sector 46 as well as a braking device 54 interposed between the first turntable 36 and the second turntable 46.

 In Figure 6, there is shown, in a view similar to the view of Figure 5, the lower part of the intervention device 20, after a certain rotation of the first turntable 36, around the vertical axis of the mast 21 .

 The rotation of an angle a of the turntable 36 from its position shown in Figure 5 was obtained by rotating the drive pinion 40 which has moved by an angle a around the fixed ring gear 37, from its position 40a corresponding to the position of the turntable 36 shown in FIG. 5 up to position 40b corresponding to the position of the turntable 36 shown in FIG. 6.

 The rotation of the pinion 40 to obtain its displacement by an angle a between the positions 40a and 40b has also resulted in an identical rotation of the toothed sector 46 and of the second rotary plate 45, in the opposite direction to the rotation of the plate 36, because the pitch diameter of the toothed sector 46 is identical to the pitch diameter of the fixed crown 37.

 As a result, the axis 60 along which the tool support 28 is fixed to the second plate 45 remains constantly directed in the same direction which corresponds to the horizontal direction in FIG. 6.

 In the case where the tool 50 is fixed on the support 52 as shown, the interventions can be carried out in directions perpendicular to the partition plates 14 having a first direction corresponding to the vertical direction in FIG. 6, at different locations corresponding for example at screw positions which are extracted, machined, checked or replaced.

 By placing the tool 50 on the front face of the support 52, as shown in FIG. 5, interventions can be carried out in a direction perpendicular to the partitioning plates 14 directed in a second direction which corresponds to the horizontal direction in FIG. 6 .

 As can be seen in FIG. 6, the support and positioning device 20 according to the invention makes it possible to carry out interventions on various types of partitioning such as the partitions 13, 13 ′, 13 ".

 Indeed, the tool support 52 can be moved in two directions of the vertical plane and in particular along the horizontal direction corresponding to the axis 60 (direction X). These complementary movements, after the tool has been put in place by rotation of the plates 45 and 46, make it possible to carry out an intervention on partitions whose dimensions may be variable.

 In all cases, the device according to the invention allows very simple positioning of a tool at any point in a partitioning of the core of a prismatic nuclear reactor. In all cases, the axis of the tool can be kept perfectly perpendicular to the partition plates on which the intervention is carried out, during the rotational movement of the first turntable around the axis of the vertical mast corresponding to the axis of the partitioning and of the lower heart plate 12.

 It is therefore possible to carry out successive interventions at each of the partitioning plates without having to dismantle and move the device 20 whose vertical mast remains fixed in the central position on the lower core plate 12.

 However, in the case of the device shown in Figures 4, 5 and 6, the maximum angle of rotation a of the first turntable 36 in one direction or the other must be limited to a value slightly greater than 45, the made of the structure of the device and possible debates ments of the second turntable 45 relative to the first tray.

 It is therefore possible to scan an area of the partitioning whose amplitude is greater than 90.

 To carry out a complete scanning of the partitioning, it is necessary to successively place the device 20 in four positions which are deduced from one another by a rotation of the vertical mast 21 by 90 "around its axis.

 A complete scan of the partitioning is thus obtained with a certain overlap.

 It is quite obvious that it would be possible to envisage a support and positioning device which would make it possible to carry out a complete scanning of the entire internal surface of the partitioning by a continuous rotation of 360, using a circular toothed plate instead of '' a toothed sector such as sector 46.

 It is also obvious that the displacements in the vertical direction of the carriage 30 make it possible to carry out a complete scanning of the partitioning over its entire height corresponding to the height of the core.

 In the case of a pressurized water nuclear reactor, this height has a value close to four meters.

 The device according to the invention therefore makes it possible to carry out successive interventions in different zones of the partitioning very quickly and without having to dismantle and replace a support mast in different successive positions.

 The invention is not limited to the embodiment which has been described.

 This is how we can imagine a different mounting and structure for the carriage, the first and the second turntables.

 The carriage can be guided on the vertical mast by a set of slides different from four 90 "slides. However, at least three slides must be used which, in this case, are placed 1200 from one another, to ensure a efficient carriage guidance.

 In general, the device according to the invention can be adapted to the interventions to be carried out on the partitioning.

 Finally, the device according to the invention can be used in the case of any nuclear pressurized water nuclear reactor comprising a partitioning of prismatic shape constituted by vertical plates assembled at right angles.

Claims (8)

 1.- Support and positioning device for a means of intervention under water on the partitioning (13) of the core of a pressurized water nuclear reactor constituted by flat partitioning plates (14) placed vertically above a bottom circular plate (12) substantially circular and horizontal and pierced with openings (16) passing through and assembled to each other at right angles to form a prismatic wall whose cross section through a horizontal plane is of polygonal shape, comprising a vertical mast (21) for supporting and guiding the intervention means provided with positioning means (22, 34) in openings (16) of the lower core plate (12) at its lower end and means for fixing (23) at its upper end, characterized in that it further comprises - a carriage (30) mounted movably on the vertical mast (21) in the vertical direction, - a first turntable (36) mounted mob island in rotation on the carriage (30) around a vertical axis constituting the longitudinal axis of the mast (21), - means for driving in rotation the first rotary plate (36) constituted by a toothed ring (37) carried by the carriage (30) and coaxial with the vertical mast (21), a drive means carried by the first turntable (38) and a drive pinion (40) integral with a vertical output shaft of the drive means (38) in engagement with the ring gear (37), - a second turntable (45) mounted movable in rotation about a vertical axis on the first turntable (36) and secured to a circular toothed sector (46) whose diameter pitch is identical to the pitch diameter of the ring gear (37), having as its axis the axis of rotation (43) of the second plate (45) and in engagement with the drive pinion (40) in an arrangement diametrically opposite with respect to to the ring gear (37), - and a support (28) of the intervention means (50) carried by the second plate (45) and allowing movement of the intervention means in a vertical plane,  2.- Device according to claim 1, characterized in that the vertical mast (21) comprises at least three vertical slides (29) arranged in positions regularly distributed angularly at its periphery and that the carriage (30) of tubular shape is placed coaxially around the mast (21) and comprises rollers (31) engaged with the slides (29) to ensure its guidance when moving in the vertical direction.  3.- Device according to any one of claims 1 and 2, characterized in that the first turntable (36) is rotatably mounted on the carriage (30), by means of an orientation ring (35 ) consisting of a ball bearing coaxial with the carriage (30) and the vertical mast (21).  4.- Device according to any one of claims 1, 2 and 3, characterized in that the first turntable (36) comprises arms constituting a yoke (42) carrying an axis (43) on which the second turntable (45) is rotatably mounted.  5.- Device according to claim 4, characterized in that the second turntable is rotatably mounted on the axis (43) via the toothed sector (46) of substantially semi-circular shape.  6.- Device according to any one of claims 1 to 5, characterized in that the support (28) of the intervention means (50) comprises tables with crossed movements in two perpendicular directions (49, 51) and a base (52) for the intervention means integral with the second cross-motion table (51).  7.- Device according to claim 6, characterized in that the base (52) of the intervention means (50) comprises slides in the form of a dovetail for the engagement of a stud of corresponding corresponding shape the intervention means (50).  8.- Device according to claim 7, characterized in that the base (52) of the intervention means comprises three slides arranged on faces of the base perpendicular two by two.