EP0631089A1 - Apparatus for removing deposits from the tubesheet of a steam generator - Google Patents

Abstract

A support structure (12) is adapted to be mounted at an access port of a steam generator. A lance tube (14) extends from the support structure into the generator. A spool (16) attached to a high pressure water pipe is received in the lance tube (14). A system of drive rolls (42, 44), mounted on the support structure (12) is used to drive the reel (16) through the lance tube (14). High pressure water flows through the drilled slots in the coil and out of the holes (30) in the lance tube against the tubes and the tube sheet. A rocking motor (70) rotates or rocks the lance tube back and forth to create a sweeping action. The lance tube (14) can also be adjusted axially to ensure that the water jets are directed towards the passages of the tubes.

Description

The present invention relates, in general, to an installation for cleaning steam generators and, in particular, to a high pressure fluid lance for removing sludge from the tubular plate and from the tubes connected to this plate, by an opening of it.

In nuclear power reactors, steam generators are used, in particular such as recycling steam generators (GVR) for the formation of steam for driving turbines. A first fluid, heated by the nuclear reactor core, is led through a series or a bundle of tubes in the GVR. A second fluid, usually water, brought into the space surrounding the tubes, receives heat from these tubes, to produce a continuous cycle of vapor formation. Due to the constantly high temperature and the difficult operating environment, a sludge, consisting mainly of iron oxide such as magnetite, accumulates on the outer and lower part of the tubes and on the tubular plates which support the bundle of these tubes.

Because the sludge deposited on the tube bundle and on the tube sheets reduces the efficiency of heat transfer and can cause corrosion, it it is desirable and even necessary that the tubes and the tubular plates be cleaned periodically to eliminate this mud.

The elimination of sludge with a lance for conventional GVRs consists in using segmented lances, usually screwed together, which are moved in and out of the tube bundle by an arm mounted outside. The implementation of these lances requires that the sections be removed or added when these lances are moved back or advanced.

The addition or removal of these sections requires that the sludge removal operation be stopped, which requires the presence of personnel in a radioactive area. Depending on the work and the number of passages required with the lance, at least half the time required for the operation corresponds to the addition and removal of the sections. This results in increased exposure of personnel to radiation and a loss of time in the production of steam by the nuclear reactor.

The known patents, relating to the disposal with the lance of sludge from the tubular plate and tubes of a generator for nuclear reactor, are the following.

US Patent No. 4,079,701 describes a system for removing sludge from a steam generator in which manifold pipes are arranged vertically from the sludge to be removed and in which a fluid lance is moved along a line between these manifolds.

U.S. Patent No. 4,424,769 describes an apparatus for removing mud deposits from the tube plate of a steam generator, in which a lance system is moved into and through the generator by a motor mechanism. The cleaning is carried out in successive sequences, with different lances which direct the cleaning fluid towards the tube plate in the different zones, more and more distant from the lances.

U.S. Patent No. 4,515,747 describes a wheeled conveyor, pulled by cables along the tubular plate, between the bundle of tubes and the enclosure of the steam generator. A monitoring installation and a tube plate cleaning nozzle can be attached to the conveyor.

U.S. Patent No. 4,566,406 describes a steam generator having a manifold having a plurality of nozzles for cleaning sludge from the tube plate. The manifold is rigidly attached to the tube plate and remains in place during normal generator operation.

U.S. Patent No. 4,700,662 describes a mud lance rod for cleaning single-pass forced steam generators. A curved tube for supplying fluid under high pressure, has a plurality of extensions, fixed at a first end and having nozzles arranged at a second end for directing the fluid towards the tubular plate when the rod is moved through the generator steam.

US Patent No. 4,757,785 describes a device for eliminating sludge from a steam generator, in which a rail is fixed between the outer enclosure of the steam generator with a single forced passage and a circular protective envelope around the bundle of tubes. A motorized carriage, rolling on the rail, directs the fluid under high pressure to the tube bundle through windows in the circular protective envelope.

The present invention relates to the equipment necessary for cleaning steam generators in a direct manner and relates to a device for removing mud deposits from the tubes and the tube plate of a steam generator.

A tubular support structure has a flange extending radially from one end, for mounting at an access port to a steam generator.

A tube, received in the support structure, extends beyond the flange in the steam generator. The tube has a plurality of holes spaced along its length, beyond the support structure.

A coil, tightly incorporated into the tube, has an axial hole closed at one end, the central part of the coil being drilled to make slots therein. A high pressure water hose is attached to one end of the coil so as to be in fluid communication with the axial hole thereof.

A motorized mechanism, mounted on the support structure at the opposite end of the flange, grasps the pressurized water hose to cause movement of this hose and the coil through the tube. Pressurized water flows through the pipe to the coil and exits through the slots drilled in it. This pressurized water in the tube exits through the holes spaced along its length and removes the mud on the tubes and the tube plate.

A second motorized mechanism, mounted on the support structure, can be used to produce a reciprocating rotation of the tube, in order to orient the water jets so that they come into contact with larger area and create a sweeping action along the tube plate, towards the outer sides of the tube bundle.

• La Figure 1 est une vue latérale en partie éclatée de l'appareil de l'invention.
• La Figure 2 est une vue d'extrémité de l'appareil.

For a better understanding of the nature and objects of the present invention, reference is made to the description which follows, in relation to the accompanying drawings in which similar parts have the same reference numbers, and in which:

• Figure 1 is a partially exploded side view of the apparatus of the invention.
• Figure 2 is an end view of the apparatus.

Referring to the drawings, it can be seen in FIG. 1 that the apparatus is generally designated by the number 10.

The sludge removal device 10 generally consists of a tubular support structure 12, a lance tube 14, a coil 16, a high pressure water hose 18, a means 20 for driving the reel 16 and the pipe 18 moving axially in the lance tube 14, with means 21 for axially adjusting the position of the tube 14 in the structure 12, and with means 22 for causing a rotational movement or of rocker from front to back of the tube 14 in this structure 12.

As shown in FIG. 1, the support structure 12 is elongated and includes first and second ends 24, 26. The flange 28 extends radially from the first end 24 and is provided with holes 30 passing through it, which are spaced apart to allow the structure 12 to be fixed by bolts to an access orifice of a steam generator, such as a gallery or a cleaning hole. This allows the part of the tube 14, which extends beyond the first end 24, to be positioned between the rows of tubes, in the steam generator.

The lance tube 14 is received so as to be moved in the support structure 12 to allow an axial adjustment of the position of this tube 14 relative to the structure 12 and to the tubes of the steam generator inside thereof. ci and to allow a rotational or rocking movement back and forth of the lance tube 14 during the sludge removal operations.

The part of the lance tube 14 housed inside the support structure 12, comprises an elongated collar 34, which is fixed to it and which cooperates with the axial adjustment means 21 and the rotation means 22, to cause the movement of tube 14.

The part of the lance tube 14 which extends beyond the first end 24 of the support structure 12 is provided with a plurality of holes 32, spaced approximately 180 ° around the circumference of the tube 14.

The spacing of the holes 32 along the length of the lance tube 14 corresponds to the pitch of the spacing of the tubes in the steam generator to be cleaned. A cotter pin 33 is provided through the end of the tube 14 to prevent the coil 16 from coming out of this tube.

The coil 16 has its ends sized to provide a close tolerance fit, within the tube 14, approximately 0.075mm, while still allowing movement through it. The central part of the coil 16 has a reduced diameter, drilled to make three slots 36 spaced 120 ° apart. The coil 16 has an axial hole, closed at one end.

The open end 38 is adapted to receive a fitting 40 on a high pressure water pipe 18.

This places the axial hole and the holes 36 in the cylinder 16 in fluid communication with the high pressure water pipe 18.

Pipe 18 is any high pressure water pipe capable of delivering pressurized liquid to cylinder 16 and is connected at one end to a source of liquid (not shown).

A means 20, intended to cause axial movement of the coil 16 and of the pipe 18 in the lance tube 14, generally consists of a system of driving rollers controlled by a double gear motor 42, 44. As best seen in Figure 2, the systems 42, 44 are each formed by a frame 46, a drive motor 48, a drive roller 50, a position encoder 52, a drive belt for the roller 54 , and a position encoder control belt 56.

The systems 42, 44 are placed at a distance of 180 ° around the support structure 12, so that the driving rollers are in opposite positions.

The two drive roller systems 42, 44 are articulated on the support structure 12, as indicated at 58. This allows the roller assemblies 42, 44 to pivot away from the support structure 12 to allow the insertion or removal of the coil 16 and the hose 18.

A blocking device 60 is used to hold the first driving roller system 42 in its operating position, adjacent to the second system 44, in order to provide pressure from the rollers 50 on the pipe 18, during the cleaning operations. Any way Adequate locking can be used to ensure that the correct pressure is maintained on pipe 18.

A means 21 for axially adjusting the position of the lance tube 14 is provided, in the form of an in-line drive motor 62, a gear pinion 64, and an adjustment ring 66. The rotation of the pinion 64 causes a corresponding rotation of the adjustment ring 66. This adjustment ring 66 cooperates by threading with a threaded surface 68 of an elongated collar 34. The rotation of the adjustment ring 66 thus causes axial movement of the collar and of the lance tube 14.

A means 22, for causing a reciprocating or rocking movement of the lance tube 14, consists of a rocking motor 70, a gear pinion 72, a toothed sector 74 and a position encoder 76, according to the tilting created.

The rocker motor 70 is mounted on the support structure 12 and drives the gear pinion 72, which engages and controls the toothed sector 74. This toothed sector 74 has its base fixed to the collar 34 to cause a corresponding movement of the tube. spear 14.

The tilt position encoder 76 is mounted on the support structure 12 and is driven by the gear pinion 72, to indicate the relative radial position of the holes 32 in the lance tube 14.

In operation, the lance tube 14 is formed from one or more sections screwed together to form a tube which exceeds either the radius or the total diameter of the steam generator. The lance tube 14 is inserted into the access hole and the support structure 12 is fixed, by bolts, to the steam generator. The drive roller systems 42, 44 are separated and the coil 16 is inserted into the lance tube 14.

The pipe 18 is used to push the reel 16 by hand, approximately towards the first set of holes 32 in the pipe 14.

The drive roller systems 42, 44 are closed and blocked on the pipe 18.

A flow of water under high pressure in the pipe 18 is then initiated and the axial adjustment means 21 is used to move the lance tube 14 so that the holes 32 are in line with the passages between the tubes in the generator. steam.

The rocker position encoder 76 is used to verify the correct rocking action. The coil 16 is controlled at the end of the lance tube 14 by the drive roller systems 42, 44, the function of the position encoders 52 is checked, and the counter is set to zero.

Lance disposal can now begin without the need for personnel to return to the steam generator every six passes of the coil 16 from top to bottom of the lance tube 14. The rocking action scans the point impact of water along the tube plate in the annular space and towards the sections at the outer edge of the bundle.

At the end of each pass, the coil 16 is aligned with the wash holes of the annular space 78 in the lance tube 14. This pours the entire water flow in both directions to provide direct flow for cleaning annular space.

Because many diverse and varied embodiments can be realized in the field of the invention envisaged and because many modifications can be made in the illustrated embodiment, it should be understood that the details of the description should be interpreted as illustrative only and not in a limiting sense.

Claims (7)

1 - Device for eliminating mud deposits from the tubes and the tube plate of a steam generator, characterized in that it comprises: at. a tubular support structure (12) having first and second ends (24, 26) having a flange (28) extending radially from its first end; b. a lance tube (14) received so as to be displaced in said support structure and extending beyond the first end of the latter, said tube having a plurality of holes (30) spaced along said tube, which extends beyond said support structure; vs. a coil (16) received tightly in said tube (14) for axial movement therein, said coil having an axial hole closed at one end, the central portion of said coil being pierced; d. a high pressure water hose (18) attached to one end of said coil so as to be in fluid communication with the hole thereof, said hose extending through the second end of the support structure; and e. means (20) attached to said support structure for causing axial movement of said coil and said pipe in said lance tube. 2 - Device according to claim 1, wherein said means (20) for driving an axial movement of said coil and said pipe comprises a system of driving rollers (42, 44) mounted on said support structure (12). 3 - Device according to claim 1, further comprising means (22) for causing a back-and-forth rotation movement of said lance tube (14) inside said support structure (12). 4 - Device according to claim 1, further comprising means (21) for axially adjusting the position of said lance tube (14) in said support structure (12). 5 - Device for eliminating sludge deposits from the tubes and the tube plate of a steam generator, characterized in that it comprises: at. a tubular support structure (12) comprising first and second ends (24, 26) having a flange (28) extending radially from its first end; b. a lance tube (14) received so as to be displaced in said support structure and extending beyond the first end of the latter, said tube having a plurality of holes (30) spaced along said tube, which extends beyond said support structure; vs. a coil (16) tightly received in said tube (14) for axial movement therein, said coil having an axial hole closed at one end, the central portion of said coil being pierced; d. a high pressure water pipe (18) attached to one end of said coil so as to be in fluid communication with the hole thereof, said pipe extending through the second end of the support structure; e. means (20) attached to said support structure for causing axial movement of said coil and said pipe in said lance tube (14) comprising a system of driving rollers (42, 44), mounted on said support structure (12); and f. means (22) for causing a back-and-forth rotational movement of said lance tube inside said support structure. 6 - Device according to claim 5, further comprising means (21) for axially adjusting the position of said lance tube (14) in said support structure (12). 7 - Device according to claim 5, further comprising means (52) for determining the axial position of said coil in said lance tube.

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