Tooling for working within a tubular element

The frame (9), which is positioned in relation to the tubular element (T), comprises disengagable means (40) for driving the working rod (18) in rotation, and these means can co-operate with at least two regions (26 to 28) of the rod. It is thus possible to work in a plurality of different zones of the tubular element. Application to the sleeve coupling by laser welding of the steam generator tubes of pressurized-water nuclear reactors.

FIELD OF THE INVENTION 
The present invention relates to a tooling for working within a tubular 
element, of the type comprising a rod which comprises at its front end a 
rotary working head equipped with means for centering within the tubular 
element, and a frame traversed by the rod and equipped with means for 
positioning in relation to the tubular element, this frame being equipped 
with means for driving the rod in rotation. It is applicable, in 
particular, to the restoration of the sealing of the steam generator tubes 
of a pressurized-water nuclear reactor. 
BACKGROUND OF THE INVENTION 
The steam generators of pressurized-water nuclear power stations generally 
comprise a bundle consisting of a very large number of tubes of small 
diameter which are curved in a U and fixed at each of their ends by 
crimping in a thick tube plate. That part of the steam generator situated 
below the tube plate constitutes a water reservoir within a first part of 
which the pressurized "primary" water coming from the vessel of the 
reactor is distributed within the tubes of the bundle. In a second part, 
the water which has circulated in the tubes is recovered, in order to be 
sent back, through a conduit of the primary circuit of the reactor, into 
the vessel enclosing the core formed by the fuel assemblies ensuring the 
heating of the pressurised water. The feed water of the steam generator 
comes into contact with the external surface of the tubes of the bundle, 
in that part of the steam generator situated above the tube plate, in 
order to be converted there into steam, and this steam is sent to the 
turbine associated with the nuclear reactor. 
The walls of the tubes of the bundle thus constituted a barrier between the 
pressurised water constituting the primary fluid of the reactor and the 
feed water constituting the secondary fluid. The primary fluid which comes 
into contact with the fuel assemblies and the internal structures of the 
vessel of the reactor contains radioactive products. It is thus 
appropriate to avoid placing of the primary fluid in contact with the 
secondary fluid, the contamination of which might have very undesirable 
consequences. To this end, it is necessary to avoid to the greatest 
possible extent the appearance of leaks through the walls of the tubes of 
the bundle of the steam generator and to repair as quickly as possible and 
in an effective manner any tubes, the wall of which is pierced. 
Such repairs are generally necessary during the normal service life of the 
reactor. In fact, as a result of the stresses of thermal and mechanical 
origin or of the corrosion suffered by the tubes of the bundle, cracks may 
be formed in the walls of the tubes of the bundle, both on the primary 
side and on the secondary side. These repairs are carried out during 
maintenance of the nuclear reactor. 
A process is known for repairing the tubes of the bundle of a steam 
generator by sleeve coupling of these tubes at the location of the defect 
involving a loss of sealing. A sleeve having an external diameter slightly 
less than the internal diameter of the tube to be repaired and having a 
length which is sufficient to cover the defective zone is introduced into 
the tube, by the entrance face of the tube plate on which the ends of the 
tubes are aligned. It is placed thereat, in such a manner as to be aligned 
with the entrance face of the tube plate for the tubes situated in the 
central part of the latter, or at mid-thickness of the tube plate for the 
tubes situated at the periphery of the latter. It is then fixed within the 
tube in such a manner as to effect two sealed joints between itself and 
the tube on either side of the defective zone. 
Numerous methods are known for effecting the fixing of the sleeve on either 
side of the defective zone. In particular, it is known to effect diametric 
expansion of the sleeve in two zones close to its ends situated, in the 
case of one of them, within the thickness of the tube plate and, in the 
case of the other, beyond the exit face of the tube plate, this taking 
place after cleaning of the tube in these two zones. The expansion may be 
obtained either by hydraulic or by mechanical methods, such as rolling in, 
or by expansion by explosion, or by welding or brazing. 
All these operations necessitate the taking of action within the water 
reservoir of the steam generator, i.e., within a part of this generator 
which has been in contact with the primary fluid loaded with radioactive 
products, during the operation of the reactor, and where a human operator 
is subjected to a high degree of radioactivity. 
Automatic and remotely controlled devices have thus been proposed, which 
are capable of effecting at least partially the operations required for 
the sleeve coupling of the tubes. 
There are known, for example, a process and a device permitting the 
installation, within a leaky generator tube, of a sleeve from the exterior 
of the water reservoir. This process and this device have formed the 
subject of the patent application FR 2,598,209. The sleeve is introduced 
into the tube from the exterior of the water is introduced into the tube 
from the exterior of the water reservoir by a flexible tube referred to as 
a boa, on a double hydraulic expander with which the approach within the 
tube is performed: after a sufficient expansion effected in the two zones 
situated at the ends of the sleeve by inflation of the elastic membranes 
of the double expander, the sleeve remains positioned within the tube. 
The membranes are then decompressed and the expander is withdrawn from the 
sleeve. The fixing tools, top tube expander and bottom tube expander, are 
then successively introduced by the same flexible component into the 
sleeve, respectively into the top zone and then into the bottom zone, in 
order to effect the fixing of the sleeve by an operation of rolling in. 
The disadvantage of this method is that it does not permit the production 
of rigorously sealed fixings of the sleeve. 
In order to remedy this disadvantage, it is known to effect the fixing by 
laser welding of the sleeve in the tube at each end of the sleeve. 
Applicant's application FR 2,637,829 proposes a tooling of the type 
indicated above, in which the laser is of the YAG type and its beam is 
conveyed by an optical fiber. 
SUMMARY OF THE INVENTION 
The object of the invention is to permit working in a plurality of zones of 
the tubular element by means of a tooling which is reliable and requires 
little space. 
To this end, the subject of the invention is a tooling of the 
aforementioned type, in which the means for driving in rotation are 
adapted to cooperate selectively with at least two driving regions of the 
rod axially spaced from one another, and are equipped with means for 
engagement-disengagement in relation to this rod, the tooling further 
comprising means for the longitudinal advance of the rod which are 
situated remotely, to the rear in relation to the means for driving in 
rotation.

DESCRIPTION OF PREFERRED EMBODIMENT 
FIGS. 1A and 1B show two types of sleeves used for repairing nuclear 
reactor steam generator tubes; 
FIG. 1A shows a longitudinal cross-section of a sleeve MA used for 
repairing tubes such as TA which are situated within the periphery of a 
tube plate P. A weld seam JA constitutes the lower joint situated towards 
the mid-thickness of the plate P. 
FIG. 1B shows a cross-section, in elevation, of a long sleeve used for 
repairing tubes situated within the central part of the tube plate P: this 
applies in the case of 80% of the tubes. The lower joint J is situated 
near the lower face of the plate. 
The upper joint KA or K is, in both cases, situated beyond the upper face 
of the plate P, near to the upper end of the sleeve. 
The tooling represented in its entirety in FIG. 2 is intended to effect 
automatically the two welds JA, KA or J, K of a sleeving. This tooling 
comprises: 
outside the reactor building 1, a YAG laser 2 and an electrical supply 
cabinet 3; 
in the reactor building outside the water reservoir 4 of the reactor, a 
source of inert gas 5 and a push-pull 6; and 
in the water reservoir, a carrier, the arm 8 of which carries a frame 9 at 
its end, by means of an elevator 10. 
A flexible tube 11 referred to as a boa extends from a lower opening 12 of 
the frame 9 to the push-pull 6, traversing the manhole 14 of the water 
reservoir. Within this boa passes a sheath 13 containing a sheathed 
optical fibre 15 originating from the laser 2, a gas conduit 16 fed by the 
source 5, and electrical cables 17 originating from the cabinet 3, the 
sheath constituting a rear extension of a welding rod 18. 
The rod 18 comprises a flexible rear part 19 of great length and ends 
towards the front in a rigid welding head 20. 
The welding head comprises an optical cell adapted to deflect radially 
through a lateral window 21 (FIG. 3) the laser beam carried by the optical 
fiber, this beam being focused by the optical cell onto the wall to be 
welded. An example of the welding head is described in detail in the 
aforementioned patent application FR 88/13,602. FIG. 2 shows the rod 18 in 
two active positions corresponding to the two welds, top and bottom, to be 
performed, in which the rod traverses an upper opening 22 of the frame 9, 
as well as in a third, retracted position permitting the displacement of 
the arm 8 from one tube to be sleeve-coupled to another. 
FIG. 3 represents the rod 18 in an external view, with its front or upper 
end ogive 23 equipped with a centering brush 24, a centering ring 25 
situated below the window 21 and, below the ring 25, three rigid regions 
for driving in rotation 26 to 28, which are axially spaced from one 
another. 
The two upper regions 26 and 27 are identical. As represented in FIG. 4, 
each of them comprises a circular throat 29 and, below the latter, a 
pinion ring 30 mounted by means of a one way clutch. The lower region 28 
(FIG. 5) comprises the same elements and, in addition, under the pinion, a 
double telescopic sleeve 31 permitting axial movement slightly greater 
than the displacement of the welding head necessary in order to effect a 
plurality of close circular weld seams jointly constituting a welded 
joint. The sheath 32 of the optical fiber is immobilized against rotation, 
the pinion ring 30 of the region 28 and the parts of the rod which are 
situated above being mounted for rotation in relation to this sheath. By 
virtue of the three free wheels, the driving in rotation of pinion 30 
causes the rotation of this pinion and of the entire part of the rod 
situated above, while the part of the rod situated below this pinion 
remains immobile in rotation. As can be seen in FIG. 6, the frame 9 
contains a moveable chassis 33 mounted to slide vertically between a low 
position, defined by an abutment 34 of the frame, and a high position, 
defined by the coming of the chassis into abutment on the upper wall of 
the frame. The upward displacement of this chassis 33 is obtained by means 
of a screw-nut system driven by a motor 36 via a belt 37. 
Within the chassis 33 there is mounted for radial sliding movement (in 
relation to the axis of the rod) a secondary chassis 38 actuated by a 
fluid jack 39. The chassis 38 carries a drive reduction gear set 40 
comprising a drive pinion 41 adapted to engage with a pinion 30 and, above 
the pinion 41, a flat idle roller 42, the peripheral surface of which is 
conjugated with the throats 29. 
The operation is as follows. 
At the outset, the chassis 33 is in the low position and the secondary 
chassis 38 is in the inactive position, i.e., the position displaced 
towards the right in relation to the position illustrated in FIG. 6. The 
pinion 41 and the roller 42 are then completely released from the envelope 
cylinder of the rod. 
The frame 9 is positioned by the arm 8 of the carrier in front of the tube 
T to be repaired, and the elevator 10 applies the frame 9 against the tube 
plate P. The sleeve to be welded M has previously been attached in the 
tube by a known technique, and the corresponding tooling has been 
withdrawn from the boa. 
The rod 18 is introduced into the boa and the push-pull 6 causes it to 
advance as far as into the high position corresponding to the upper weld 
to be performed, this position being determined by a detector 43 provided 
in the frame 9. The region 28 is then situated in the chassis 33. 
The jack 39 is actuated so that the pinion 41 engages with the pinion 30, 
which faces it, and so that the roller 42 simultaneously engages into the 
throat 29, as represented in FIG. 6. The rod, moreover, is supported on 
two cylindrical rollers 44 which turn in the chassis 33, at the height of 
the roller 42 and at 120.degree. from the latter (FIG. 7). 
The motor 36 is actuated; this causes rising of the chassis 3 and, via the 
roller 42, the rod 18, as far as the level corresponding to the first weld 
seam to be performed. The welding laser beam is initiated and the drive 
reduction gear 40 causes the rod to execute a rotation of 360.degree.. 
The motor 36 then causes the chassis 33 and the rod to redescend as far as 
the level of the following seams to be formed, for example of 0.5 mm. The 
laser beam is again initiated, the drive reduction gear 40 causes the rod 
to turn through 360.degree., and so on. 
When the first joint, which comprises, for example, five seams, is 
completed, the chassis 33 is brought back to the low position, the chassis 
38 is brought back to the inactive or disengaged position by displacement 
towards the right in FIG. 6, and the push-pull 6 causes descent of the rod 
over a distance corresponding to the spacing of the two joints to be made. 
The region 27 or the region 26 of the rod is then situated in the chassis 
33, according to the level of the second joint JA or J (FIG. 1A or FIG. 
1B). The weld seams of the second joint are then made as described above. 
It should be noted that the axial movement, of the order of 15 mm, which is 
necessary in order to effect the seams of each joint, is made possible by 
the presence of the double telescopic sleeve 31 in the region 28. In a 
variant, the clearance of the rod in the boa may be sufficient to permit 
this movement. 
The invention can be applied to various types of work to be carried out 
within a tube. Moreover, it is easily possible to choose the number and 
the longitudinal position of the driving region or regions, in dependence 
upon the work to be carried out in the tube.