Apparatus for rebuilding nuclear fuel assemblies

The apparatus is intended for rebuilding an assembly comprising a skeleton formed by two end members connected by tie rods attached to the end members and grids distributed between the end members along the tie rods and adapted to retain a cluster of fuel rods trapped between the end members. The apparatus comprises a first chamber (AI) for receiving a fuel assembly, a second chamber (AS) for receiving a new skeleton, a repair station comprising a lift adapted to receive the two vertically disposed aligned chambers and to bring the chambers to a level such that there subsists a layer of protective water above the rods, a transfer tool (106) to draw one fuel rod at a time into the skeleton from the assembly contained in the first chamber, and means for mounting the end members on the skeleton.

BACKGROUND AND SUMMARY OF THE INVENTION 
The invention relates to the rebuilding of nuclear fuel assemblies of the 
kind which comprises a skeleton formed by two end members connected by tie 
rods attached to the end members and grids distributed between the end 
members along the tie rods and adapted to maintain a cluster of fuel rods 
trapped between the end members. 
Assemblies of the kind specified are used almost universally in natural 
water cooled and moderated reactors, more particularly in pressurized 
water reactors. In some cases an assembly has to be removed and some or 
all the rods which it contains removed. This situation arises more 
particularly when the elements of the skeleton of an assembly have become 
so damaged that an assembly must be rebuilt by removing the rods and 
replacing them in a new skeleton. Another situation is one in which some 
or all the rods of an assembly are to be transferred to a new assembly in 
a different arrangement, or associating the rods with new or different 
rods (for example, to associate rods containing uranium oxide with rods 
containing a neutron absorbent, an inert material or a plutonium-enriched 
fuel). Yet another situation is that in which an assembly modifying the 
moderating rate is to be constructed. 
Different methods of connecting the elements forming the skeleton have been 
proposed. In the majority of the assemblies at present in operation the 
tie rods are non-releasably attached to the upper end member and are 
attached to the lower end member via means enabling the latter to be 
removed. Some of the assemblies belonging to this group use attachment by 
a screwthreaded socket which is locked in place by a pin; others use 
attachment by a screwthreaded socket having a skirt which is subsequently 
deformed to prevent the socket from rotating. Reference can be made, for 
example, to French patent application No. 2 521 763 for a description of 
an assembly of this kind. 
In contrast, another group of assemblies, described in French patent 
application No. 2,536,261, comprises a removable upper end member; this 
method has the advantage of eliminating the need for tilting the assembly 
through 180.degree. between its stored position and the position in which 
the rods are removed. 
It is more particularly an object of the invention to provide a method and 
apparatus which enable a nuclear fuel assembly to be rebuilt by 
transferring fuel rods taken from an existing, generally heavily 
irradiated and often damaged assembly to a new skeleton, while using only 
simple means and limiting the risk of error or breakdown. Another object 
of the invention is to provide a method and apparatus which is very 
flexible to use and can more particularly be adapted to the various groups 
of fuel assemblies mentioned hereinbefore. 
To this end the invention provides more particularly a method for 
rebuilding an assembly of the type hereinbefore defined, wherein the 
assembly whose fuel rods are to be extracted is disposed in a first 
vertical chamber, the detachable end member of such assembly being 
directed upwards; the detachable end member is removed; a second chamber 
containing and retaining a new assembly skeleton is moved above the end 
chamber in the same orientation as the assembly of the first chamber and 
in alignment therewith; the rods to be extracted from the assembly are 
drawn into the skeleton; and the skeleton is completed by putting the end 
members in place. 
If only the lower end member of the assembly is detachable, the assembly is 
first placed in the normal position in the first chamber and is blocked in 
position therein; the chamber is turned over; the new skeleton is moved 
into an inverted position in its chamber to enable the rods to be 
extracted from the assembly contained in the first chamber to be drawn 
upwards towards the skeleton. 
As a general rule the two chambers rest on one another via a retaining and 
centring mask. 
It is found that this method of procedure simplifies the handling of the 
rods and moreover almost completely eliminates the risk of introducing a 
rod into unaligned passages in the grids of the new skeleton, since the 
grab which must be lowered through the grids of the new assembly to seize 
the rods to be drawn upwards ensures guidance. 
The new skeleton can have new rods of fissile, fertile, inert or absorbent 
material which will contribute towards guiding the fuel rods as they rise. 
In an advantageous embodiment of the invention the method allows the 
rebuilding, from a fuel assembly of the kind only the lower end member of 
which can be removed, of an assembly provided to enable the rods to be 
extracted after the removal of the upper end member--i.e., an assembly 
which can be repaired by the use of the apparatus disclosed in French 
patent application No. 2,536,261. 
This procedure begins with a sequence of operations which remains the same, 
whatever the nature of the assembly of the new skeleton may be. The 
damaged assembly is deposited in a lower chamber placed in a pool of water 
and is immobilised in such chamber; the chamber is turned over through 
180.degree.; the chamber is lifted in the pool, while remaining submerged, 
to a level such that a lower plug of the chamber can be removed and a 
guide mask put in place; the means for attaching the lower end member of 
the damaged assembly are eliminated, for instance, by cutting off the pin 
and then removing screws in the case of a usual kind of assembly; the 
lower chamber containing the assembly without its lower end member is 
lowered into the bottom position in the pool; an upper chamber, into which 
a new skeleton without its end members and disposed in the inverted 
position has already been placed and immobilised, is moved above the lower 
chamber and aligned therewith; a tool for transferring the rods is 
positioned above the chamber, and a grab with which it is equipped is 
lowered through the skeleton to the level of the rod to be extracted and 
then actuated to seize the rod and lifted into the skeleton, where the rod 
is released the; operations are repeated until all the rods have been 
transferred; the lower end member of the new skeleton is fixed; the upper 
chamber can then be withdrawn and turned over, before its upper end member 
is put in place. 
Once the skeleton of the damaged assembly has been emptied, the operation 
can be completed by the replacement of the lower end member before 
removal. 
The invention also relates to an apparatus for enabling the process defined 
hereinbefore to be put into effect, such apparatus advantageously also 
including means for repairing an assembly in which certain rods are to be 
replaced, so as to widen the field of use of the apparatus. 
The invention will be more clearly understood from the following 
description of an example of an apparatus forming a particular embodiment 
of the invention and of the method put into effect in such apparatus. The 
description refers to the accompanying drawings.

DESCRIPTION OF A PREFERRED EMBODIMENT 
The assembly 10 shown in FIG. 1 comprises a cluster of fuel rods 11 
retained by spacer grids 12 distributed along the cluster. The grids 12 
define passages through the majority of which fuel rods 11 extend while 
extending through the others are tie rods 15 attached to a lower end 
member 13 and an upper end member 14 whose upper part has a shape enabling 
it to be seized by a handling tool. In a conventional fuel assembly the 
tie rods 15, formed by guide tubes enabling elements outside the assembly 
to slide therein, are permanently attached to the upper end member. They 
are attached to the lower end member by screwthreaded sockets 16 
immobilised by transverse pins 17. Only the lower plug of the rods 11 is 
formed with a gripping circumferential groove 18 in such a conventional 
assembly. 
In contrast, in recent assemblies the tie rods 15 are attached to the upper 
end member 14 by removable means formed by sockets having a screwthreaded 
lower portion adapted to be screwed into the lower portion of a tie rod 
and a head bearing against the end member 14. 
The apparatus which will now be described more particularly enables a fuel 
assembly to be rebuilt by extracting fuel rods contained in a damaged 
assembly and introducing them into a new skeleton, while the elements 
having high radioactivity remain submerged in the water at an adequate 
depth to ensure the biological protection of the operators. 
In practice the apparatus will in general be mounted on the evacuation pool 
of the exhausted fuel unloaded from a nuclear reactor. It can be 
considered to be formed by the following main assemblies, which will be 
described in succession: 
a repair station, the general makeup of which is shown in FIG. 2, having a 
fixed frame placed at the bottom of the deactivation pool and having a 
lift for moving assembly-receiving chambers between a high level and a low 
level, and also control mechanisms, 
a device for turning assemblies over, whose general makeup is shown in FIG. 
3, the rotating mechanism being shown on an enlarged scale in FIG. 4, 
handling tools for handling the rotatable chambers, 
tools for removing the lower end member of the assembly; in accordance with 
the particular case, these can be limited to tools limited to a 
conventional assembly, or they can be distributed in a number of sets 
adapted to assemblies of a different nature, 
a device for transferring rods from an assembly contained in a chamber to a 
skeleton contained in another chamber, 
tools for putting the end member in place on the new skeleton; some of 
these, adapted to an assembly with removable end members, can be of the 
same kind as those already disclosed in French patent application No. 
2,536,261. 
The repair station (2) enables at one and the same time the rebuilding of 
assemblies and the replacement of the rods by the method disclosed and 
claimed in French patent application No. 2,536,261, by the use of suitable 
tools. This station comprises a parallelepipedic lattice work frame 20 
placed on the bottom of the irradiated fuel evacuation compartment in a 
deactivation pool 22. To facilitate its handling, the frame can be made up 
of a number of assembled sections. In the embodiment illustrated in FIG. 1 
the frame comprises a lower section 23 having adjustable feet 24 whose 
height and position can be controlled. Rigidly disposed in that section is 
a rod storage chamber 26 adapted to receive a rack (not shown) in which 
the rods are distributed in the same arrangement as in an assembly. 
An intermediation section 25 connected to the lower section by mechanical 
indexing and locking means, is open on one of its side faces to enable 
assemblies to be introduced into the repair station. The intermediation 
section 25 is connected by mechanical means to an upper section 28 which 
is also open on one of its side faces. Disposed in the upper part of the 
section 28 is a support 29 for the attachment of tools for taking action 
on the assemblies. The upper section 28 also bears rails 30 on which a set 
of carriages 31 for positioning tools can run. 
The three sections each accommodate a portion of the path of travel of a 
lift 32 adapted to move a fuel chamber between a low level, to enable an 
assembly to be introduced into and removed from the chamber, and a high 
level, where access may be had to the fuel assembly top end member. The 
lift 32 comprises two holders 34 disposed one above the other for the 
attachment of chambers. The lift 32 illustrated has an upwardly directed 
manoeuvring rod 35, enabling the lift to be displaced by means of an 
outside member, such as the tackle of a travelling crane. The rod 35 also 
enables the lift to be locked in the top and bottom positions. 
The frame 20 also comprises in its intermediate portion 25 vertical rails 
for the movement of a carriage bearing a stand 36 for receiving 
tool-guiding masks; these masks will be described hereinafter. For this 
purpose the stand 36 has upwardly projecting pins 37. The stand will 
generally be of adequate dimensions to form a location for receiving a box 
(not shown) for evacuated irradiated elements, for example, screwthreaded 
sockets for attaching end members. The carriage of the stand can have a 
disconnectable rod 38 enabling the carriage to be moved by the tackle of a 
travelling crane and immobilised. 
The set of carriages 31 borne by the upper section 28 enables movements to 
be performed in directions X, Y and Z at right angles. The set of 
carriages accurately positions the tools during phases of operation on the 
rods, when the lift is in the bottom position, or on the end members, when 
the lift is in the top position. The set of carriages can also be used 
during assembly reconstituting operations by the method according to the 
present invention and also for a rod replacing operation of the kind 
disclosed in French patent application No. 2,536,261. 
The lower carriage 40 can be moved in the direction Y on the rails 30 
attached to the upper section 35. It has a floor giving access to 
personnel to enable them to work with tools. The carriage 40 carries a 
guide 42 adapted to receive columns 117 of the rod-transferring tool (FIG. 
8) which will be described hereinafter. 
The carriage 40 bears the elements for entraining and guiding carriage 44 
which can be moved along the direction of X. Finally, a third carriage 46 
is provided which can be moved over a short distance in the direction Z 
with respect to carriage 44. This carriage can move over short shafts 
provided on the carriage X. It comprises a supporting plate 48 adapted to 
receive the tool to be positioned. Due to the availability of a vertical 
travel the supporting plate can be inserted over guide elements on the 
tool used and on the element handled by the tool. For example, the 
vertical travel can enable bottom pins with which an extracting tool is 
equipped (for example, the tools shown in FIGS. 26 to 28 of French patent 
application No. 2,536,261) to be brought up to the guide strips of the 
assembly-retaining chamber, without the need to use a travelling crane 
supporting the tool. 
The lift 32 is adapted to receive two superimposed chambers as shown in 
FIG. 5. The upper chamber AS initially contains a new skeleton without its 
end members. The lower chamber AI receives the assembly, without its lower 
end member, whose rods are to be extracted. 
The two chambers are generally made up in the same way, enabling them to be 
attached to the lift 32 and tilted through 180.degree. by means of the 
turning-over device shown in FIGS. 3 and 4. 
Each chamber has a mechanically welded structure with four angle irons 
strutted by belts. Attached to the centre of each chamber are two 
strengthening members 54 each having a half-pivot or trunnion 56. Two 
plates are attached by bolts to the ends of the structure of each chamber. 
In FIG. 5 these plates are denoted by ASS and ASI for the upper chamber (a 
plate is to be considered a lower plate if it is disposed on the same side 
as the lower end member of the assembly which is contained in the chamber, 
and conversely). Similarly, the plates of the lower chamber are denoted by 
the references AII and AIS. The plates enable the chamber to be handled, 
put in place and closed by plugs, such as plugs BIS and BSI which are 
shown in FIGS. 5, 7 and 7A. The plates also are adapted to index an 
assembly or skeleton and the tools to be used on the assembly. 
In practice the plate AII disposed on the lower chamber AI on the side of 
the lower assembly end member (FIG. 6) has two grooved columns 58 enabling 
the chamber to be handled by a tool which will be described hereinafter. 
The columns 58 are also used for locating the corresponding end plug (not 
shown in the drawings). Three other columns 60 enable the tools for taking 
action on the assembly contained in the chamber AI to be centred. Four 
shoes 62, which can be moved together or apart by a wheel and endless 
screw mechanism from a square shaped head 64, which can be manoeuvred by a 
rod, provided for centring the assembly in the chamber and releasing it. 
Two centring rings 66 which are borne by plate AII enable the chamber AI 
to be attached in the repair station shown in FIG. 2. Flat bars 68 welded 
to the edge of the plate and formed with aligned holes enable the plate to 
be handled for operations other than those of repair or rebuilding. 
The plate AIS (FIG. 7A) adjacent to the upper end member of the assembly 
contained in the chamber AI has the same accessorires as the plate AII and 
they have like references, although the plate AIS has no shoes for 
centring the assembly. 
The plates of the lower chamber are adapted to receive plugs BIS and BII. 
These plugs retain the irradiated assembly when the chamber AI containing 
it is rotated into inverted position. The plug BII adjacent to the lower 
end member has at its centre a non-adjustable shoe which axially abuts the 
fuel assembly. It has two columns formed with circumferential grooves for 
handling purposes and it is formed with two indexing holes for engagement 
onto the columns of plate AII. 
As in the case of the preceding one, the plug BIS disposed on the side of 
the upper end member has two handling columns, two attaching screws 67 and 
two positioning holes. Its shoe 69 is mounted at the end of a screw which 
can be manoeuvred by remote control under water by means of a rod, so that 
the assembly can be blocked axially and accidental axial displacements can 
be avoided. 
The upper chamber AS comprises end plates which are slightly different from 
those of the lower chamber AI. The plate ASI (FIG. 7) differs from the 
plate AII in that the former has two strips 70 disposed on either side of 
its square opening; these strips are adapted to position the columns of 
the lower carriage of the tool for extracting and replacing rods, shown in 
FIGS. 26 to 28 of French patent application No. 2,536,261. The plate ASI 
also comprises two grooved columns 71 and three pins 72 for positioning 
the rod-transferring tool. The corresponding plug BSI is identical with 
the plug BII, except that its central shoe 74 can be adjusted 
longitudinally (FIG. 7). 
Lastly, the plate ASS disposed on the side of the upper end member (FIG. 6) 
is similar to the plate ASI. However, it has no strips; it has an 
adjustable abutment ring 76 on each of the three columns 77 for 
positioning the upper chamber AS on the lower chamber AI. The rings enable 
the relative position of the chamber to be adjusted when they are in the 
repair station. 
No plug need be provided at the upper end (i.e., on the upper side of the 
assembly) for the chamber AS. On the other hand, however, the chamber is 
designed to have a retaining mask MR (FIGS. 5 and 6). The functions of the 
mask are as follows: 
to form an axial abutment for the assembly skeleton contained in the 
chamber AS when the latter is turned over, 
to transmit the weight of the skeleton and the rods introduced into the 
skeleton when the assembly is rebuilt, while allowing the rebuilding grab 
to have free access to all the rods contained in the lower chamber AI, 
to precisely align the upper part of the skeleton contained in the upper 
chamber AS with the skeleton of the assembly contained in the lower 
chamber AI. 
The mask or template MR (FIG. 6) comprises a small plate 78 formed with two 
lugs having holes 79 enabling the mask to be centred on the two handling 
columns 82 of the chamber AS. The small plate is attached to the main 
plate by two screws 80. Attached to the small plate 78 are two grooved 
handling columns 83, with the same spacing as the plug-handling columns. 
The square aperture in the centre of the small plate 78 gives access to 
the rods disposed at the centre of the assembly contained in the lower 
chamber AI. Around the square central aperture 84 there are rectangular 
apertures separated by ligaments 86 provided to act as supports for the 
ends of the tie rods of the assembly skeleton contained in the chamber AS. 
Pins 88 attached to the small plate stand out from it on either side. They 
are adapted to engage in the peripheral tie rods, formed by guide tubes of 
the two assemblies during the rebuilding operations. Two holes 90 with 
which the small plate is formed give access to the squares 64 for 
manoeuvering the clamping shoes 62 of the plate AII. 
The assembly turning-over device shown in FIGS. 3 and 4 is adapted to 
receive chambers of the kind disclosed hereinbefore. For reasons of 
simplicity, the device given by way of example is manually controlled. The 
device must enable: 
a chamber containing an irradiated assembly to be retained under a height 
of water compatible with protecting the operators, 
the chamber to be tilted through 180.degree. around a horizontal axis, 
while ensuring that the chamber is vertical in the initial and final 
positions. 
The device shown in FIG. 3 is in two assembled parts, thus facilitating 
storage and enabling it to be adapted to different depths. Moreover, it 
forms a detachable assembly which can be inserted into the passage giving 
access to the fuel evacuation pit. 
The lower part of the device mainly comprises a mechanically welded frame 
92 resting on the bottom of the passage via shoes 94 which can be adjusted 
to make the frame vertical. The shoes 94 can be manoeuvred from an 
operating floor diposed above the pool, using a rod acting on manoeuvering 
squares with which the shoes are equipped. The frame comprises two lateral 
supports 95 receiving the pivot of the chamber to be tilted. Each support 
95 has two rollers 96 (FIG. 4) enabling a ready-tilting of the pivot, 
which is driven by a shaft 97 to which a wheel 98 driven by a screw 99 is 
pinned. A rod enables a manoeuvering square with which the screw 99 is 
equipped to be rotated from the operating floor. 
The frame 92 also comprises two upwardly extending vertically tubular 
guides 100 adapted to receive the uprights 101 of a gallows-shaped member 
102. 
The gallows-shaped member 102, which is adapted to enable the turning-over 
device to be handled, comprises uprights 101 which can be attached to 
guides 100 in a number of positions by means of pins 103, and a cross 
member 104 welded to the uprights. The pins can be formed with a number of 
holes, to enable the overall height of the turning-over device to be 
shortened during handling outside the pool. Attached to the cross member 
104 are two forks each having two clamping shoes 105 adapted to bear on 
either side of the wall 106 bounding the neck. The shoes form a safety 
device which completely prevent the device from being upset during the 
assembly turning-over operations. 
The upper section of the frame of the station (FIG. 2) is adapted to 
receive more particularly a rod-transferring tool 106 shown 
diagrammatically in FIGS. 8 and 9. The tool is adapted to be moved above 
the chambers when they are disposed in the repair station, to pull the 
sound rods out of the damaged skeleton, and to re-introduce them into the 
new skeleton disposed above. 
The tool 106 comprises a mechanical portion partially submerged in the pool 
and an electronic and pneumatic assembly (not shown) disposed outside the 
pool and adapted to actuate the moving elements of the tool. 
The mechanical portion can be regarded as being formed by a supporting 
frame a vertically movable coupling having at its lower end a grab for 
seizing the rods, and a cage for guiding the movable coupling during its 
vertical displacement. 
FIG. 8 shows that the supporting frame comprises a framework formed by two 
vertical tubular uprights 108 connected from place to place by spurs 110. 
The two uprights 108 are attached at their ends to the base of an upper 
cross motion table 112 and the base of a lower cross motion table 114. The 
framework can rest on the chamber AS via hollow supporting columns 116 
which engage on the positioning pins 72 rigidly connected to the base ASI, 
so as to properly determine the horizontal and vertical position of the 
supporting frame in the repair station. Two retaining pins 117 rigidly 
connected to the columns 108 index the tool on the upper section of the 
station. 
A bowed member 118 attached to the base of the upper table 112 and to a 
strut of the uprights 108 enables the tool to be handled with a tackle. 
The upper cross motion table is adapted to adjust the horizontal position 
of the guide cage 111. The table is disposed above the level of the water 
in the pool when the tool is used. It carries two variable speed d.c. 
motors 120 adapted to actuate the plates which can be moved in the 
direction X and the direction Y respectively. 
The plate which can be moved in the direction X comprises two arcades 122 
sliding on rails and each bearing one end of the rails 126 for guiding the 
plate which can move in the direction Y. The axes of the two rails 124 and 
of the screw 128 for entraining the plate are in the same vertical plane. 
The plate which can be moved in the direction Y is formed with grooves for 
retaining the guide cage 111 which will be described hereinafter. The 
plane can be moved in the direction Y by any transmission mechanism. In 
the embodiment illustrated in FIG. 8, the transmission mechanism comprises 
a square rod for rotating a screw with balls 130, which slides in its 
drive pinion (not shown in the drawing) which is rigidly connected for 
translation to the plate which can be moved in the direction X. 
The lower cross motion table 114 must reproduce the movements of the upper 
table and therefore has the same general configuration. The movements of 
its plates in the directions X and Y are controlled from motors 120 via 
shaft 124 and 134 for the directions X and Y respectively. The plate 136 
which can be moved in the direction X is mounted to slide on two guide 
rails disposed in the same horizontal plane and attached to a base 138 
rigidly connected to the two uprights 108 of the framework. The three 
hollow rods 116 for supporting the framework on the upper chamber are 
attached to such base. The plate 136 is moved in the direction X by a 
bevel gear and a ball circulation screw-and-nut connection 140. 
The plate 142 movable in the direction Y is mounted to slide on rails 
belonging to the carriage X. It supports the cage 111 for guiding the 
movable coupling and comprises a grab guide. 
The cage 111, which acts as a vertical guide for the movable coupling and 
the rod-handling grab, is attached to the plate 142 movable in the 
direction Y of the lower cross motion table 114 and is guided in the 
corresponding plate of the upper table 112. The cage is made up of three 
rails 144 regularly distributed at an angle of 120.degree. from one 
another around an axis and connected by circular struts. The upper end of 
the rails 144 bears a plate 146 which receives the motorization mechanism 
of the movable coupling. The mechanism is not shown in FIG. 8, but 
appears, with the upper part of the movable coupling 148, on FIG. 9. The 
motorization mechanism comprises a variable speed, reversible d.c. 
electric motor 150 which drives a shaft 152 via a step-down gear and a 
torque limiter. The shaft 152 bears toothed wheels 153 which drive chains 
155 to displace the movable coupling 148 in the vertical direction 
(direction Z), and also grooved wheels for guiding electric cables and 
pneumatic flexible tubes 154 connected to the moving coupling. The cables 
and flexible tubes also pass over grooved wheels 156 mounted on the front 
part of the plate 146 forming a return to length-compensating systems 
conventionally comprising pulleys mounted on a movable support. 
The movable coupling 148 is adapted to confer the different necessary 
movements on the grab 149 for seizing the rods and its interal components. 
It supports the members for monitoring such movements and forces applied 
to the rod. 
The grab 149 forms the lower part of the moving coupling. The grab is so 
designed that it can pass through the new skeleton and comprises (FIG. 9A) 
a traction tube connected to the frame of the moving coupling, bearing the 
member for seizing the rods, which is formed by four resilient plates 
whose profile fits snugly around the shape of the plug of the rods 11 to 
be transferred. The plates can be locked in the groove by the descent of 
an outer sheath 151. Disposed in the axis of the grab is a feeler 160, 
which allows a check that the rod plug is correctly engaged in the end of 
the grab before locking. 
The frame of the moving coupling 148 (FIGS. 8, 9 and 9A) comprises a frame 
whose two end plates each have three guide rollers 157 on the rails 144. 
The frame is suspended from two chains 155 via means for maintaining them 
under a substantially constant tractive force (not shown). 
Referring to FIG. 9A, the lower stage I of the coupling 148 bears the means 
for locking the grab 149 which seizes the rods 11. The sheath 151 closing 
the grab is connected to cylinder 158 of a double-acting jack whose piston 
159 is rigidly connected to the frame. Progressive springs are interposed 
between the columns and a plate connected to the sheath, to allow the 
necessary clearances for monitoring the forces. 
Stage II of the moving coupling is adapted to monitoring the movements of 
the grab and the forces. It comprises a shaft 160a which is rigidly 
connected to the cylinder 158 and extends through flanges 161 of the 
coupling frame. The end of the shaft 160a actuates end-of-travel contacts, 
only one 162a of which is shown, for controlling the locking and unlocking 
movements of the grab. the contacts are disposed in the circuits of the 
control logic. 
Bellows 162 enable the forces exerted on the rods 11 to be transferred to 
be controlled. These variations in length are followed by a, for example, 
inductive displacement pickup 163 attached on the one hand to the traction 
tube of the grab and on the other to the coupling frame. 
Stage III is adapted to ensure the forced opening of the grab after 
unlocking, in order to release the rod, if anything goes wrong when the 
rod is at the top level, where it is to be released. To this end the stage 
III comprises a double-acting jack 164 driving a rotary nut 165 formed 
with a vertical groove. A finger 166 rigidly attached to the feeler 
extends to the groove. The actuation of the jack 164 makes the feeler 160 
rotate, whose lower end has four projections (not shown) which in the 
normal position are received between the resilient blades of the grab. 
Stage IV is adapted to monitor the position of the grab and the relative 
position of the rod. It comprises a pickup 167 controlling the position of 
the rod 169 of the feeler, such rod resting on the end of the fuel rod 
during the transfer. The pickup 167 is attached to the upper plate of the 
frame of the coupling 148. 
The handling tools adapted to take action on the chambers comprise a 
chamber-handling tool OMA, a tool OMB for handling the masks and plugs, 
and control and manoeuvering rods. 
The tools OMA and OMB are similarly constructed. The tool OMA, an overall 
view of which is given in FIG. 10, is used for handling the chamber AI and 
AS which can be turned over from a travelling crane. It is formed by two 
sections: 
a lower section 170, which is locked on the two grooved columns 58 or 82 
with which each of the end plates of the chambers is provided: 
an upper section 172, which is a lengthening piece interposed between the 
upper section and the crane hook, to prevent a loaded chamber from being 
possibly brought out of the water, since its length is such that when the 
crane hook abuts at the top, a layer of protective water subsists above 
the assembly. 
The section 170 is similar to the tool illustrated in FIG. 7 of application 
No. 2,536,261, to which reference can be made. It is made up of two 
coaxial tubes which can rotate in relation to one another between a 
position allowing the engagement of the tool with the columns (the 
position shown in FIG. 10) and a locking position. Attached to the lower 
end of the external tube, for instance, by welding, is a plate 176 having 
two vertical cylindrical guides 178 adapted to fit over the columns 58 or 
82. Each guide 178 is formed with a horizontal aperture over almost 
three-quarters of the angular extent of the guide, in line with the 
horizontal groove in the handling column to be seized. 
Attached to the lower end of the inner tube, for example, by welding, is a 
blade 180. 
When the inner tube is in the locking position, two notches 182 with which 
the blade 180 is formed engage, via the apertures in the guides 178, in 
the horizontal grooves in the columns, thus interlocking the tool OMA of 
the chamber to be handled. When, on the other hand, the inner tube is in 
the position shown in FIG. 10, the blade 180 releases the path of the 
handling columns and enables the tool to be engaged or disengaged. 
In the case illustrated in FIG. 10, the tubes can be orientated in relation 
to one another by means of a set of two handles 184. 
The upper section 172 is formed by a tubular rod having a handling ring 
(not shown) at its top end. At its bottom end the rod comprises a square 
hole adapted to receive a terminal square portion 187 of the section 170 
to provide interlocking during rotation. The bottom end of the upper 
section also comprises a tapped ring for the connection of the lower 
section. 
The tool OMB for handling the masks and plugs has the same construction as 
the tool OMA, except that the guides 178 are at a smaller distance apart, 
since the distance apart of the axes of the grooved columns as 83 of the 
masks is smaller than on the chambers. 
The tool OMB (not shown in the drawings) is used for the underwater 
handling of the chamber end plugs and various accessories used in the 
repair or rebuilding operations. 
The tool OMB can be limited to its lower section, the upper section being 
shared with the tool OMA. 
The control and manoeuvering rods are used to act under water on the 
various manoeuvering squares, for example, 
the squares of the shoes 94 of the turning-over device 
the actuating square for the chamber turning-over mechanism on the 
turning-over device, 
the manoeuvering squares of the wheel and endless screw systems for 
centring and assembly in the chambers, 
the squares for tightening and loosening the screws 67 for attaching the 
chamber end plugs to their plates. 
As a rule a number of rods of different lengths will be provided. FIG. 11 
shows by way of example the lower portion of such a rod, forming an 
adjustment tool OR. The tool is a simple socket wrench having a shape 
corresponding to that of a manoeuvering square. The rod can be in a number 
of sections connected by tapped rings, as in the case of the tool OMA. 
The tools for removing the lower end members will depend on the nature of 
the means for connecting the lower end member of the damaged assembly and 
the tie rods. We shall now describe the tools to be used in the case of a 
lower end member of fuel assemblies considered to be standard ones, whose 
lower end member is, as shown in FIG. 1, attached by slot-headed screws 16 
rendered unreleasable by the addition in their slot of pins 17 welded to 
the end member. 
The dismantling tools comprise tools for exerting an action--i.e., active 
elements--and masks adapted to guide such tools and each adapted to a 
corresponding tool. To take action on a standard assembly of the kind 
shown in FIG. 1, the dismantling tools comprise: 
a tool OF for milling pins 17 for immobilizing screws 16 for attaching the 
end member 13 to the tie rods of the skeleton, 
a mask MF for guiding the milling tool on the lower end member to be 
removed, 
a screwdriver tool TIS for unscrewing the screws for attaching the end 
member, 
a mask MIS for guiding the screwdriver tool TIS on the end member, such 
mask also serving for the evacuation of the screws, 
a pusher tool OP for disengaging the screws from the guide mask. 
In FIGS. 12 and 13 the milling tool is shown attached to its manoeurvering 
tackle and in place on a lower chamber having a mask MF. FIGS. 14 and 15 
show more clearly the structure of the lower part of the tool and of the 
mask MF. Lastly, FIG. 16 shows the way in which the milling cutter of the 
tool acts on a pin 17. 
The guide mask MF (FIGS. 14 and 15) performs two functions. It guides the 
lower end of the milling tool OF so that it is coaxial with the connecting 
screws between the tie rods 15 and the lower end member 13. It forms an 
axial abutment for the body of the tool when the milling cutter is 
advanced as machining progresses. 
The mask MF is made up of a plate 188 attached, for example, by bolts, to a 
baseplate 190 adapted to rest on the feet of the end member 13. Extending 
through the plate-and-base assembly are two split bushes 192 which can be 
expanded by means of conical nuts 194, to enable to mask MF to be locked 
in the assembly positioning holes with which the feet of the standard end 
members are formed. The nuts can be actuated by manoeuvering squares 196 
by means of the manoeuvering tool OR, shown in chain-lines in FIG. 14. 
The plate 188 has bushes 196 adapted to engage over the three columns 60 of 
the lower plate AII, these being shown in chain-line in FIG. 14. The plate 
188 has two grooved columns 198 enabling it to be seized by the handling 
tool OMB. 
The plate-and-base assembly is formed with 24 bores 197 for guiding the 
tool OF. Two bayonet passages open into each bore in the plate, to allow 
the introduction of stubs 199 with which the milling tool OF is formed, in 
order to produce an axial abutment for the attachment of the milling tool 
OF. 
The general construction of the tool OF is shown in FIG. 12. It should be 
pointed out incidentally that the way in which the tool OF is attached 
(FIG. 12) is also adopted for the other dismantling and reassembling 
tools. The tool OF, which is typically a tubular assembly about 4 m in 
height, can be regarded as comrising a sleeve 201 having a handle 202 for 
suspension from the winch of the travelling crane, a sheath 200 which can 
slide in the sleeve 201, a step-down gearing 204 borne by the sheath 200, 
and a rotary unit driven by the motor and guided in the sheath 200 by ball 
bearings (not shown in the drawings). The rotary unit comprises a pin 
connected to the output shaft of the step-down gearing 204 via a toothed 
coupling (not shown) and a rod with an end milling cutter 206 guided in 
the sheath by bronze rings 208 (FIG. 14). A lever 210 enables the sheath 
to be moved longitudinally in the sleeve 201 over a length corresponding 
to the required advance of the milling cutter to cut off a blocking pin. 
The milling tool OF is completed in the embodiment illustrated in FIGS. 12 
and 13, by a filtration assembly 212 comprising a removal tube 214 
connected to a chip-removing duct 215 on the sheath, so as to suck up the 
swarf, and a return conduit 216. The pipe 214 is rigid and attached along 
the sheath 200. It has a flap valve 217 which prevents the chips entering 
the pool if the pumping system stops accidentially. In its upper part it 
has a bend terminating in a connection to a flexible pipe for connection 
to the filtration assembly. Incidentally, the milling tool, like the other 
tools, is operated manually, the only electrical accessories being the 
drive motor of the pump of the water filtration system and the motor of 
the milling tool. 
FIG. 17 shows the dismantling screwdriver tool in place on a screw to be 
removed, its guide mask MIS being shown only in part. The mask will not be 
described again, since it can be very similar to the mask MF, except that 
it is adapted to enable the screws to be evacuated after they have been 
removed. 
The screwdriver tool OT comprises an outer tube 218 having an operating 
handle 220 and a rod 222 guided in the tube 218. The top end of the rod 
has a shoulder for retaining it on the tube and terminates in a 
manoeuvering square enabling the loosening torque to be applied by a 
dynamic wrench. The end of the rod is adapted to receive profiled end 
members 224 acting as a screwdriver blade. 
FIG. 17 shows how the holes for guiding the screwdriver tool in the mask 
MIS, unlike the mask MF do not have bayonet grooves, but they have rings 
226 receiving elastomeric sleeves 227 which trap the screw heads on 
completion of unscrewing and enable them to be evacuated with the mask. 
Lastly, the screw-pushing tool, adapted to disengage simultaneously all the 
screws trapped in the elastomeric sleeves of the mask MIS after the 
evacuation thereof, can be limited to a tubular rod having a handle which 
has in its lower part 24 pins forming pushers: to drive out the screws it 
is enough to insert the 24 pins simultaneously by lowering the rod. 
Like the end member removing tools, the end member replacing tools must be 
adapted to the method of attachment adopted. In what follows it will be 
supposed that the end member to be remounted is attached by means of 
screws having expandable ferrule for immobilizing the screw once it has 
been completely introduced. 
The screwdriver tool TIA can be identical with the tool TIS shown in FIG. 
17, except that its lower end member is adapted to the profile of the slot 
in the screw to be tightened. 
During its use, the screwdriver tool TIA must be carried by a mask MIA. The 
mask, a fraction of which is shown in FIG. 18, can be identical with the 
mask MIS, except that it has no elastomeric sleeves, which would interfere 
with the passing of the expansion tool OEI, and it is formed with grooves 
terminating in the guide holes to form axial abutments for the stubs of 
the expansion tool. 
The expansion tool (FIG. 19) is adapted to lock the screws unloosenable and 
unloosenable by the deformation of their cups into recesses of the lower 
end member. To this end the tool comprises an outer tube 226 having an 
operating handle 228. The lower portion of the outer tube has stubs 238 
adapted to act as an axial and circumferential abutment by engaging in the 
grooves in the mask MIA. A rod in two parts is mounted in the tube 226. 
The lower portion 232 of the rod bears a mandrel 234 for crimping the 
screws to change their skirts 236 from the shape shown in FIG. 20A to the 
shape shown in FIG. 20B. The rod is so connected for corotation to the 
outer tube 226 as to ensure the orientation of the mandrel in relation to 
the stubs 230, but it can make a translational movement over a limited 
length, a spring (not shown) returning the rod to the top position. The 
upper portion of the rod bears axially against the lower portion. It is 
connected to the outer tube via a screw-and-nut connection which can be 
controlled by means of a square 237. The application of a torque to the 
square 237 by means of a dynamometric wrench causes an axial force, 
transmitted by a plane/sphere contact, for deforming the skirts of 
ferrules 236. 
A description will now be given, by way of example and referring to FIGS. 
22A-22C, of the operations which are taken with a view to rebuilding an 
assembly by the transfer to a new skeleton of the rods of a damaged 
assembly 10 of standard type. 
It will be remembered that the term "lower chamber plug" BSS or BIS refers 
to the plug disposed on the side of the lower end member of the assembly 
contained in the chamber, and conversely. 
In the initial condition of the apparatus, the lower chamber AI is 
deposited in upstanding position on the lift (at the lower level of 
attachment, the upper plug being removed). The upper chamber AS is in the 
meantime stored in the inverted position, with the retaining mask MR in 
place. The upper chamber contains a new assembly skeleton, without end 
members, clamped by means of the pad 74. The damaged assembly 10 is taken 
by a travelling crane and deposited in the lower chamber AI. The latter is 
raised to the higher level by the lift. Upper plug BIS is inserted and 
locked. The assembly 10 is blocked axially and clamped radially by acting 
on the pad 74. 
The chamber AI is attached to the handling tool OMA, transferred by the 
crane to the turning-over device and tilted. After being turned over, the 
chamber is seized by the handling tool OMA again and then placed at the 
lower attachment level on the lift while the latter is in top position 
(arrows f.sub.1, f.sub.2, f.sub.3 in the FIG. 22A). 
The lower plug BII of the lower chamber AI is then withdrawn to enable the 
lower end member 13 to be removed. Such removal requires the following 
operations: 
bringing in the mask MF by means of the handling tool OMB and depositing 
the mask on the lower end member 13 of the damaged fuel assembly, 
the immobilization of the mask, by the expansion of its two split bushes 
192 in the end member positioning holes, 
bringing the tool OF for milling the pins into one of the guide holes, and 
locking the bayonets by the engagement of the stubs 199 (FIG. 22B), 
hydraulic connection to the pumping set 212, starting up and controlling 
the water flow, 
successive milling of all the pins 17, for example 24, 
stopping and evacuating the tool and the pumping assembly, 
disconnection and evacuation of the mask MF, 
bringing in the mask MIS for indexing on the lower end member, and 
immobilization thereof by the expansion of the split bushes of the mask, 
unscrewing the screws 16 with the screwdriver TIS, and simultaneous 
engagement in the sleeves of the mask, 
withdrawal of the mask MIS, rigidly connected to the end member 13 and 
containing the screws 16, using the handling tool OMB; depositing the 
assembly on a container for evacuating the screws, disconnection of the 
mask MIS from the end member 13, 
ejection of the screws 16 using the pusher tool OP, 
taking up the mask MIS again with the handling tool OMB and depositing it 
on its storage stand. 
The lift carrying the lower chamber AI is then descended to its bottom 
position. The upper chamber AS is placed on the lift at the top attaching 
level, then aligned with the lower chamber AI. The rod-transferring tool 
106 is positioned above the chambers and its supporting columns 116 are 
engaged with the columns of the plate ASI. The grab is lowered through the 
upper skeleton as far as the level of the plug of the rod 11 to be 
extracted. The grab is locked and then lifted to transfer the rod to the 
upper skeleton (FIG. 22C). The rod is released, then operations are 
resumed until all the rods (for example, 264) have been transferred. 
Once the rods have been transferred, the skeleton must be given new end 
members to reconstruct a complete assembly. The mounting of the end 
members calls for the following operations: 
Introduction and positioning of the lower end member: 
The mask MIS, already rigidly connected to the lower end member in proper 
position and containing the 24 new screws for attachment to the skeleton 
is brought in by the handling tool OMB and put in position on the 
skeleton, 
The level of the mask can be checked, for example, using a measuring tool 
OT of the kind illustrated in FIG. 21, 
Each of the 24 screws is tightened with a suitable torque, using the 
screwdriver tool TIA, 
The skirts of the 24 screw are successively deformed by bringing in and 
lowering the expansion tool OEI to make the screws unloosenable, 
The mask MIS is removed and deposited on its storage stand, 
The lower plug BSI of the upper chamber AS is screwed on to its plate ASI, 
then the upper chamber AS is taken again by the handling tool OMA, 
deposited on the turning-over device, then tilted through 180.degree.. 
After removing the upper chamber from the lift, the used assembly, emptied 
of its rods, can be completed by an end member and evacuated; for this 
purpose, the lift of the repair stationis returned to the top position. 
The lower end member of the damaged skeleton, still attached to the mask 
MIS, is replaced on the skeleton by means of the handling tool OMB and 
four screws are screwed back on to their guide tubes to allow the 
evacuation of the skeleton. The lift is lowered into the bottom position 
and the damaged skeleton is removed to a storage area. The lift is taken 
up again, then the lower plug BII of the chamber AI is attached. The lower 
chamber is withdrawn from the station and placed in a stand-by position. 
Introduction and positioning of the upper end member: 
The upper chamber AS is put on the lift at the bottom attaching point, 
Using the handling tool, the mask MIS, already rigidly connected to the 
upper end member 14 and containing 24 new screws for attachment to the 
skeleton of the rebuilt assembly, is brought up and placed on the tie 
rods, 
The level of the mask is checked with the measuring tool OT, 
The 24 screwthreaded bushes are screwed individually, using the screwdriver 
tool TIA, into the guide tubes, 
The skirts of the screwthreaded bushes are deformed to make them unlosable 
and unloosenable, using an expansion tool similar to the tool OEI, 
The lift is lowered into its bottom position. 
The rebuilt assembly is then removed to storage by means of the travelling 
crane associated with the power station fuel handling tool. The lift is 
taken up again and the upper plug BSS is attached to the upper chamber AS, 
which is then removed to a storage position. The lower chamber AI is 
attached to the lift at the lower attachment level, its plug is removed, 
then the lift is brought down again to return to the initial situation.