Patent Number: 043280714
Section: description

In FIG. 1, there is shown the main vessel of an integrated-type fast nuclear reactor 2 suspended from a shield roof 4, said roof being in turn supported by a massive concrete structure 6. Within the interior of the main reactor vessel 2 are placed the primary vessel 8 and the diagrid 10 which supports the reactor core 12 and serves to supply this latter with liquid metal coolant. Since reference is made to a reactor of the integrated type in the example under consideration, there is also shown a primary heat exchanger 14 suspended from the shield roof 4 and a primary pump 16 which is also suspended from said roof. Provision is made within the top shield roof 4 for the small rotating shield plug 18 which is rotatable about the axis X--X' and is in turn mounted within the large rotating shield plug 20. Said large plug is capable of rotating about its axis Y--Y' which coincides with the axis of the main reactor vessel 2. It is thus apparent that any point located in fixed relation to the small rotating shield plug 18 is endowed with planetary motion with respect to the stationary shield roof 4 by a combination of movements of rotation of the small shield plug 18 and of the large shield plug 20. Various devices 22 such as the handling grab and a number of other installations have also been shown diagrammatically on the small rotating shield plug 18. There are also shown the top containment casing 24 which surrounds the space above the shield roof 4. The whole of the foregoing description can relate to any fast reactor of the integrated type such as the French Superphenix reactor, for example. In this general figure, there is also shown very diagrammatically the device 30 for guiding tubes and cables which are intended to penetrate through the small rotating shield plug to the reactor core lid according to a first embodiment. Said mechanism 30 comprises a hanger 32 constituted by a vertical portion of column 32a and by a horizontal portion or arm 32b, said hanger 32 being fixed on the periphery of the small rotating shield plug. The hanger 32 is constructed in such a manner that the extremity of the horizontal arm 32b of the hanger 32 is disposed on the axis X--X' of rotation of the small shield plug 18. From the extremity of the horizontal portion 32b of the hanger 32, there extends upwards a vertical central portion forming a bundle-type assembly 34 which is so arranged that its vertical axis coincides with the axis of rotation X--X' of the small shield plug. The device 30 further comprises the following components disposed substantially in the same horizontal plane: a first lever-arm 36 pivotally coupled to the upper extremity of the bundle-type assembly 34 and a second lever-arm 38 pivotally mounted on a pin 40 having a vertical axis with respect to the first arm 36 and with respect to a second vertical pivot-pin 42 which is rigidly fixed to the containment casing 24 of the nuclear reactor. The length of the vertical portion 32a of the hanger 32 is such that a height H is left free above the small rotating shield plug, thus making it possible to position a number of different devices 22. The cables and tubes which are intended to pass through the small rotating shield plug are fixed respectively on the two guiding arms 36 and 38, extend vertically downwards so as to constitute the bundle-type assembly 34 and are guided by the two elements of the hanger 32 to the different points of the small rotating shield plug 18 at which said cables or tubes are intended to penetrate through this latter. Before proceeding to a more detailed description of the guiding device according to the first embodiment, the advantage and the general operation of the device may already be understood by referring more particularly to FIGS. 2 and 3. During the combined movement of rotation of the small shield plug 18 and of the large shield plug 20, the two lever-arms 36 and 38 are caused to pivot about pins 46 and 42 in such a manner that the vertical axis of the bundle-type assembly 34 remains in coincident relation with the axis of rotation of the small shield plug. It is understood in particular that, by virtue of the presence of these two lever-arms, irrespective of the position of the small rotating shield plug with respect to the large shield plug and more specifically irrespectively of the position of the point at which the hanger 32 is fixed on the small shield plug, the extremity of the lever-arm 36 can be maintained in the line of extension of the axis X--X' of the small shield plug by pivotal displacement of the lever-arms 36 and 38 with relative angles of pivotal motion which are of small amplitude irrespective of the movements of rotation of the small and large shield plugs with respect to a reference position. It can be understood that this limitation of angular displacements is a particularly important feature of the invention since cables or tubes which have a certain degree of stiffness must pass around the different articulations. As will be explained hereinafter, this makes it possible in particular to limit the dead length of cables and tubes while also limiting the value of stress induced in the tubes or cables under the action of the twisting effort produced by rotational displacement of the small and large shield plugs. It is readily apparent that one of the problems to be solved is that of twisting of the cables or tubes in the vertical guiding portion corresponding to the bundle-type assembly 34. In more precise terms, the problem is to control the degree of twist in order to prevent introduction of excessive localized stresses in said tubes or cables since the repetitive character of such stresses would be liable to result in damage. The construction of this portion of the device will now be described in greater detail in order to provide a clearer idea of its originality. For the purpose of guiding in the vertical direction in the bundle-type assembly 34, the different cables or tubes 50 are fixed on annular guide-plates such as the plate 52 and these latter are uniformly spaced between the horizontal portion 32b of the hanger 32 and the arm 36. In fact, a distinction must be drawn between a bottom guide-plate 52a which is rigidly fixed to the arm 32b of the hanger 32, a top guide-plate 52b which is associated with the arm 36 and intermediate guide-plates 52c. At least in the portion corresponding to the bundle-type assembly 34, the cables or tubes 50 are fixed on the guide-plates 52 in uniformly spaced relation and thus constitute the equivalent of a squirrel cage. As will become apparent hereinafter, the different guide-plates are positioned relative to each other by means of three cables secured to the bottom ring 52a and to the top ring 52b. It is further apparent that twisting of the cables 50 is produced at the time of rotation of the upper arms 36 and 38. This twisting movement in one direction or in the other is clearly accompanied by a reduction in the vertical height H' between the bottom guide-plate 52a which is rigidly fixed to the arm 32b and the top guide-plate 52b with respect to an intermediate value. As will be explained in detail below, the guide-plate 52b is consequently not directly secured to the arm 36 but is coupled to this latter through the intermediary of a vertical jack which permits displacements of the top guide-plates 52b in order to absorb the reductions or increases in said height H' with respect to an intermediate value. In FIG. 4, there is shown in greater detail one example of construction of an intermediate guide-plate 52c. This latter is designed in the form of a ring, the external face of which is provided with semicylindrical recesses 60. The cables such as the cable 50 are placed at the level of the guide-plate within a circular sleeve 62. Said sleeve is in turn placed within a recess 60 and clamped in position by means of an individual clamping member such as the member 64. Said clamping member 64 is fixed in the guide-plate 52 by means of four screws such as the screw 66. It is apparent that the imbricated shape 68 of said clamping members makes it possible to reduce the space between two consecutive cables 50 while fixing the clamping member 64 in position on each side of the sleeve 62. As can readily be understood, each clamping member has a semi-cylindrical bore 69 which cooperates with the bore 60 of the intermediate guide-plate 52c. It is further apparent that exactly the same nethod is adopted for fixing the cables or tubes 50 in the guide-plates 52a and 52b. Furthermore and as mentioned earlier, the different intermediate guide-plates 52c are maintained in position by means of supporting cables 70. By way of example, provision is made for three supporting cables. As will be explained hereinafter, said cables are fixed on the top guide-plate 52a and on the bottom guide-plate 52b and are, of course, also fixed within the intermediate guide-plates 52c. In FIG. 4, there is also shown a preferred mode of clamping of the cables 70. This clamping operation is carried out by placing two semi-cylindrical half-shells 74a and 74b within a bore 72 formed in the guide-plate 52. Clamping of the cable within the guide-plate 52 is carried out, for example, by means of two cone-point set-screws 76 which are intended to clamp one of the half-shells in position (namely the half-shell 74a, for example) with respect to the upper half-shell. It is apparent that the cables 70 are then secured to each intermediate guide-plate. It is important to lay emphasis on the double function performed by the supporting cables 70. The first function is to maintain equality of spacing between two consecutive guide-plates during relative movement of the arm 36 with respect to the hanger 32 in the vertical direction. The other function is to ensure uniform distribution between the different intermediate guide-plates 52c of the angle through which the top guide-plate 52b rotates with respect to the bottom guide-plate 52a which is rigidly fixed to the hanger. It may be stated in more precise terms that, by virtue of the supporting cables 70, if the top guide-plate 52b rotates through an angle A with respect to the bottom guide-plate 52a, the angle between two consecutive guide-plates will be substantially equal to A/(n+1) if there are n intermediate guide-plates 52c. It should be added that the second function could be performed in a different way. For example, provision could be made in the case of each guide-plate for two stops which are rigidly fixed to the guide-plate located immediately beneath and limit the movement of rotation of the guide-plate considered to a maximum angle, taking into account the maximum angle which can appear between the bottom guide-plate 52a and the top guide-plate 52b. In more general terms, the guide-plates are connected to each other in such a manner as to ensure that the total angle of rotation between the top guide-plate and the bottom guide-plate is distributed between the different guide-plates in proportion to the distance between the plates in the vertical direction and that they retain a common axis of symmetry of revolution. In FIG. 5, there is shown the articulation between the bundle unit 34 and the arm 36, and more precisely the mode of compensation for variations in length resulting from twisting of the cables or tubes 50. The top guide-plate 52b is not rigidly fixed to the arm 36 but coupled to this latter by means of the operating rod of a jack designated by the general reference 80. The jack body is designated by the reference 80a, the jack piston is designated by the reference 80b and the operating rod of the jack is designated by the reference 80c. Said operating rod is rigidly fixed to a yoke 82 which is guided in vertical translational motion as a result of cooperation of guides 84 and rollers 86 attached to the yoke 82 which is rigidly fixed to a transmission rod 88. Said rod is fixed on the one hand on the top guide-plate 52b and on the other hand on the yoke 82 by means of a system 90 forming a universal-joint assembly. It is thus apparent that the top guide-plate 52b is in fact rotationally coupled to the arm 36 but capable of displacement in a vertical direction with respect to the arm 36. More specifically, the jack 80 is controlled in such a manner as to exert a constant force. Thus, under the action of rotation of the top guide-plate 52b with respect to the bottom guide-plate 52a, displacement of the guide-plate 52b takes place progressively only during the course of twisting of all the cables 50. Moreover, FIG. 5 shows diagrammatically the upper extremity 70a of the suspension cable 70 associated with a nut system 92 which makes it possible to carry out the adjustment. FIG. 3 is a top view showing diagrammatically the complete device for guiding cables or tubes. There are again shown the horizontal arm 32b of the hanger 32, the arm 36 which is pivotally mounted with respect to said hanger, the arm 38 which is pivoted about the pin 40 with respect to the arm 36, the arm 38 being in turn pivoted about the pin 42 with respect to a support bracket 100 which is rigidly fixed to the dome 24. The movements of the arms 36 and 38 in order to follow the movements of the small and large rotating shield plugs are produced by two actuating devices designated by the reference 102 for the movement of the arm 36 with respect to the arm 38 about the pivot-pin 40 and by the reference 104 for the movement of the arm 38 about the pivot-pin 42 with respect to the fixed support bracket 100. In the embodiment shown in FIG. 3, each actuating means 102 or 104 consists of a hydraulic jack 106 which is rigidly fixed to the arm 36, for example, and the operating rod 108 of which is adapted to carry a toothed rack 110. Said toothed rack is disposed in meshing engagement with a toothed pinion 112 which is rigidly fixed to the arm 38 and the shaft of which is coaxial with the pivot-pin 40. It can readily be understood that, by initiating operation of the jack 106, the arm 36 is displaced in pivotal motion with respect to the arm 38. Furthermore, the device comprises a mechanical detector as designated for example by the reference 114 for detecting any movement of the arm 36 with respect to the arm 38. A signal which is representative of said movement is transmitted by said detector to the control unit. Exactly the same principle of operation applies to the actuating device 104. In this embodiment, it is apparent that the control unit includes follow-up control devices for causing the actuating devices 102 and 104 to displace the extremity of the arm 36 in such a manner as to ensure that said extremity remains vertically above the center of the small rotating shield plug. It will naturally be understood that other actuating means could be employed. This result can readily be obtained in accordance with well-known control techniques involving the use of detectors 114, for example, and achieving follow-up control between said mechanical means 104 and 102 and the mechanical means for producing displacements of the small and large rotating shield plugs. It is therefore unnecessary to describe this follow-up control system in greater detail. In the foregoing description, it has been considered that the hanger 32 was rigidly fixed on the small rotating shield plug or in other words that there did not exist any possibility of pivotal displacement of the vertical portion 32a with respect to the small rotating shield plug. However, for certain handling operations in the nuclear reactor, it may prove advantageous to provide maximum clearance within the entire space which extends above the small rotating shield plug. It is for this reason that, in accordance with an improved alternative embodiment, provision can be made for a possibility of pivotal displacement of the hanger about its vertical axis Z--Z'. This form of construction will now be described in greater detail with reference to FIG. 6. In this embodiment, the horizontal arm 32'b is capable of rotating in a horizontal plane about the vertical column 32'a. It is apparent that, under these conditions, the same problem arises in regard to twisting of the cables or tubes 50 which are placed along this portion of the guiding device. This problem is solved substantially in the same manner as in the case of the bundle portion 34. It should nevertheless be borne in mind that rotational displacement of the hanger takes place at much less frequent intervals than the bundle portion 34 and that the applied forces are also of much lower value. The vertical column 32'a is provided with a base 32c which is rigidly fixed to the small rotating shield plug 18. The arm 32'b of the hanger is pivotally mounted on the upper extremity of the vertical column 32'a in known manner. Guiding of the cables or tubes 50 is carried out by means of annular plates which are similar to the plates 52. There is thus shown a bottom annular guide-plate 52'a which is rigidly fixed to the base 32c, a top annular guide-plate 52'b which is rigidly fixed to the arm 32'b and one or a number of intermediate annular plates 52'c, said intermediate annular plate or plates being capable of moving freely in translational motion and in rotational motion with respect to the vertical column 32'a. The cables or tubes 50 are fixed at uniform intervals on the periphery of the guide-plates so as to form the equivalent of a squirrel cage. As in the case of the bundle portion 34, the intermediate annular plate or plates are connected to the top plate 52'b by means of supporting cables 70'. Said cables 70' are fixed on the top guide-plate 52'b by means of resilient devices 125 which perform much the same function as the jack 80 while taking into account that the movements take place at a much lower frequency. Moreover, the vertical column 32'a passes through the horizontal arm 32'b. An actuating device 120 makes it possible to cause rotational displacement of the arm 32'b about the vertical column 32'a. Said actuating device can consist of a jack 122, the operating 122a of which is rigidly fixed to a toothed rack 122b in cooperating relation with a pinion 124 which is rigidly fixed to the upper extremity of the vertical column 32'a. The actuating device is associated with a sensor for detecting rotational motion of the arm 32'b (not shown). It is readily apparent that, when inititiating a movement of rotation of the vertical column 32'a, it is also necessary to initiate the corresponding movements of rotation of the arms 36 and 38. This function is performed by the general control unit of the device. It would not constitute any departure from the invention if the vertical column 32'a were rotatable with respect to the base 32c which is rigidly fixed to the small rotating shield plug 18, in which case the arm 32'b would be rigidly fixed to the vertical column 32'a. It can readily be understood in this case that the actuating device 120 is rigidly fixed to the small rotating shield plug and transmits its movement to the foot of the vertical column 32'a. It should be added that, taking into account the weight of the assembly constituted by the two guiding arms 36 and 38 and by the cables and tubes 50 which are secured to said arms, it may be preferable to support the arms 36 and 38. Provision can accordingly be made for a cable which is attached at its lower end to the pivot-pin 40 of the arm 38 and is secured at its upper end to a slide-block, said slide-block being capable of moving within a circular guide rail which is rigidly fixed to the dome 24. It can be mentioned by way of example that, by virtue of the two supporting arms 36 and 38, the maximum movements of rotation of the large shield plug are followed with maximum angles of pivotal displacement at the level of the articulations or pivot-pins 40 and 42, these angles being equal respectively to 45.degree. and 62.degree.. It is apparent that the reduced value of these angles considerably simplifies the problem of the flexibility loops or "slack" which the cables and tubes must possess at the level of said articulations. It is understood that, by means of the device according to the invention, the space which extends above the small and large rotating shield plugs can be freed to the maximum extent in order to facilitate positioning of the different mechanisms on the shield plugs. Furthermore, the guiding means make it possible to limit the degrees of curvature or of twist applied to the cables or tubes during the different movements, thus considerably reducing the stresses applied to said cables or tubes and increasing the useful life of these latter. The device further permits accessibility of the cables, with the result that these latter are conveniently interchangeable. In the foregoing description, the bottom guide-plate 52a is rigidly fixed to the hanger 32 in order to provide maximum clearance for the small rotating shield plug. However, in some cases or in other applications of the device, it would be possible to dispense with the hanger. The bottom guide-plate 52a would then be directly fixed on the small shield plug 18 at its center of rotation. The system would then be simplified in the case of the first alternative embodiment. In the second alternative embodiment of the invention which will now be described, the hanger is in fact dispensed with. The bundle-type assembly described earlier is replaced in this case by a "rigid axis" assembly which provides a direct connection between the center of rotation of the small rotating shield plug and the free end of the horizontal articulated arm. Moreover, the general problem to be solved is again the same since it remains necessary to avoid twisting of the cables or ducts. The central portion of the rigid vertical mast 150 is shown in FIGS. 7a and 7b and the upper end of said mast is shown in FIG. 9. It is recalled that the lower end of the mast is rigidly fixed at the center of the small rotating shield plug 18 and that the axis of the mast coincides with the axis of rotation of the plug. FIGS. 7a and 7b show one form of construction of the intermediate guide-plates 52'c. The external periphery of the guide-plate 52' is identical with the external periphery of the intermediate guide-plates 52c and therefore does not call for any further description. Similarly, horizontality of the guide-plates is achieved by means of cables 70 as in the previous embodiments. The difference lies in the cooperation between the intermediate guide-plate and the mast 150; this cooperation permits equal distribution of the total rotation between the intermediate guide-plates. The guide-plate 52'c is pierced by a central bore 152. Within the interior of said bore 152 and around the mast 150, provision is made for a ring 154 in which is formed a central bore 156. The ring 154 is coupled for translational motion with the guide-plate 52'c on the one hand by means of its flat portion 154' which penetrates into the recessed portion 158 of the guide-plate 52'c and on the other hand by means of circlips 160. However, the ring 154 is capable of rotating with respect to the guide-plate. The flat portion 154' of the ring is provided at its external periphery with at least one recess 162 corresponding to an angle .alpha. at the center. Said recess 162 is adapted to cooperate with a stud 164 which is rigidly fixed to the guide-plate. Provision could naturally be made for a plurality of recesses 162 and for a plurality of studs 164. The internal face of the ring 154 corresponding to the bore 156 is also provided with a recess 166 corresponding to an angle at the center equal to .beta.. This second recess 166 is adapted to cooperate with a key 168 fixed on the mast by any known means. It will readily be apparent that provision can be made for a plurality of recesses 166 and for a plurality of keys 168 in order to accommodate applied stresses. It is therefore apparent that two assemblies are provided for limiting the angle of rotation of the guide-plate 52c with respect to the mast 150, the effects of which are added. The total possible range of angular displacement has the value .alpha.+.beta.. In FIG. 8, there is shown a simplified form of construction of the guide-plate 52"c. Provision is made simply for a key 168' which is rigidly fixed to the mast 150 and for a recess 170 formed in the internal face of the guide-plate 152"c. There is thus obtained only one possibility of rotation equal to .beta.. The top guide-plate 52'b is shown in FIG. 9. As already explained with reference to FIG. 5, the guide-plate 52'b must be capable of displacement in the vertical direction under the action of a jack and is rotationally coupled to the extremity of the horizontal arm 36. The upper extremity 150a of the mast 150 is rotatably mounted in the extremity of the arm 36, for example by means of two ball-type or roller-type thrust bearings. The extremity 150a is fitted internally with the body 174a of a pneumatic jack 174, the operating rod 174b of which is rigidly fixed to a horizontal guide-plate 176 by means of the ball thrust bearing 175. The pipe 174c for supplying the jack 174 is also shown. The guide-plate 176 is connected to the top guide-plate 52'c by means of rods such as the rod 178. Said rods 178 traverse the arm 36 through bores 180. It is therefore apparent that the top guide-plate 52'b is rotationally coupled to the arm 36 but that the top guide-plate 52b is capable of vertical displacement along the mast 150 under the action of the jack 174. Under the action of a movement of rotation of the mast 150, the ducts or pipes 50 assume a helical configuration and the jack moves downwards. The tensile load does not change since the pneumatic circuit comprises either a large volume of gas or an expansion and overflow system. As already mentioned, the intermediate guide-plates 52'c or 52"c serve to ensure equal distribution of the total angle of rotation between the bottom guide-plate which is rigidly fixed to the shield plug and the top guide-plate 52'b which is rotationally coupled to the arm. The intermediate guide-plate 52"c of FIG. 8 permits a maximum rotation .beta.=100.degree. if it is desired to provide three keys 168' and three recesses 170. By means of guide-plates of the type designated by the reference 52"c, it is therefore possible to obtain all values of angular displacement up to .+-.50.degree.. The system constituted by the recess 162 and the stud 164 of FIG. 7a permits a maximum angle of rotation .alpha.=340.degree.. It is in fact necessary to take into account the diameter of the stud 164 and the length of the heel or projecting portion to be left on the periphery of the ring. If the guide-plate is intended to have an angular displacement within the range of .+-.50.degree. to .+-.170.degree., it is clearly unnecessary to make use of the angle .beta.. The recess 166 will therefore have a width equal to the width of the key 168. The angle .alpha. is zero. If the guide-plate is intended to have an angular displacement within the range of .+-.170.degree. to .+-.220.degree., the guide-plate 52'c is put to use by employing the two rotation-limiting systems. By way of example, if five intermediate guide-plates are employed and the total angle of displacement has a value of .+-.150.degree., the following intermediate guide-plates can be employed successively: In the case of the two intermediate guide-plates located nearest the bottom guide-plate, plates of the type designated by the reference 52"c will be employed with respective values in respect of .beta.=0; in the case of .alpha., the respective values will be .+-.75.degree., .+-.100.degree. and .+-.125.degree.. There is then obtained an accurate distribution of the helix of the ducts 50 of the bundle over the entire length of the vertical mast 150, especially under the most exacting conditions which correspond to maximum design values of angular displacement which cannot be exceeded. Contraction of a bundle unit calls for adapted ducts and, as in any system which works in torsion, the ducts 50 will be judiciously arranged so as to ensure that the center of torsion of the bundle unit corresponds as closely as possible to the principal axis of the guide-plates and of the mast. It should nevertheless be added that the horizontal arms 36 and 38 could be replaced by other means for supporting the cables and ducts between the fixed point and the upper extremity of the main bundle portion 34. It would also be possible to employ conventional flexible connections such as festoons or garlands as employed in known manner for linear displacements of traveling bridge cranes, whether these latter are combined with sliding linear arms or not. Furthermore, the device according to the invention and in particular the structure of its main bundle portion is applicable to fields other than nuclear reactors equipped with eccentric rotating shield plugs. The fuel assembly storage pools associated with fast reactors can be mentioned by way of example. Ducts arranged in a bundle can also be used to supply fuel assembly storage magazines of the rotary drum or carousel type. Broadly speaking, the invention is applicable whenever a bundle of cables, pipes or ducts having a certain degree of stiffness is intended to pass through a rotating component.