Patent Number: 046831061
Section: description

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT FIG. 1 shows a nuclear vessel reactor 1 closed at its upper end by a cover 2. Clusters (not shown) which may be conventional in nature and construction are located in the reactor vessel for controlling the core. Sensors are provided for measuring the position of the clusters as well as mechanisms for actuating the clusters and thermocouples for monitoring the temperature in the core. Such elements are quite conventional and have not therefore been shown. What is important here is that these elements are connected to the outside of the reactor by electric cables or wires: the sensors for measuring the position of the clusters and the thermocouples must be provided with means for conveying their output signals to signal processing systems placed outside the reactor vessel. The mechanisms for actuating the clusters require electric power. Each of the electric devices is therefore provided with at least one cable which is guided to the outside of the reactor, through the cover, by a guide 3 and which ends with a fixed connector 4. As shown in FIG. 4, cables connected to the electric devices situated in the reactor vessel are guided inside fluid tight guide tubes 3 up to the fixed connectors 4. Those connectors 4, which correspond to similar electric devices inside the reactors, have a similar arrangement. For example, the fixed connectors 4 to which the control cluster position sensors are connected are all disposed in a same plane, perpendicular to the vertical axis of the reactor vessel, at the upper end of each tube 3 situated vertically above each cluster, and are evenly distributed around the end portion of the tubes 3 at 90.degree. (if the number of measuring sensors is four). Thus, the arrangement with respect to each other of the connectors 4 associated with the sensors measuring the position of the clusters is similar to the arrangement of the sensors inside the reactor vessel. Similarly, the fixed connectors corresponding to the actuating mechanisms of the control clusters are all situated similarly at the upper part of tubes 3 and the fixed connectors corresponding to the thermocouples are all disposed in a same plane with an arrangement similar to the arrangement inside the core. In FIG. 4 only those fixed connectors have been shown which correspond to the sensors measuring the position of the clusters (four connectors situated at the end of tube 3) and a fixed connector corresponding to a cluster actuating mechanism (situated in a plane slightly below the four preceding connectors). Referring again to FIG. 1, two layers 5 and 5' of conduits 6 are shown. Sections of cables connecting fixed connectors 4 to fixed connectors 7 situated on plates 8 placed at a distance from the reactor extend along the conduits 6. As seen in FIG. 4, the cables comprise a first section which connects a fixed connector 4 to a fixed connector 10, also fixed, constituting an inlet into one of ducts 6. The first sections are identified as a whole as 9. Referring to FIG. 3, a second section 11 of the cable connects each of the inlet connectors 10 to a lead-out connector 12 constituting an outlet from conduit 6. Referring to FIGS. 1 and 2, third sections 13 connect the lead out connectors 12 from conduits 6 to connectors 7 carried on plates 8 located at a distance from the reactor vessel. The third sections are supported by bridges 14 (FIGS. 1 and 2). Referring to FIG. 2, the conduits are arranged in planar layers pependicular to the axis of the reactor vessel; in each layer, the conduits are mutually parallel. Thus layers 5 and 5' have conduits 6 orientated in directions at 90.degree. from each other. Layer 5" has conduits orientated at 45.degree. from those in layers 5 and 5'. Referring to FIG. 3, a conduit 6 is parallelepipedic in shape. The associated lead-in connectors 10 are situated on the larger surfaces 15 and 15' whereas the lead-out connectors 12 are situated on end faces 16 and 17. Conduit 6 is divided longitudinally into two separate compartments 18 and 19 each comprising a larger lateral surface 15 or 15' and an end surface 16 or 17 of the conduit 6. Thus, the sections 11 in one of compartments 18 or 19 are not in contact with the sections 11 in the other compartment. The number of lead-in connectors 10 on each lateral surface 15 or 15' may typically be equal to the number of lead-out connectors 12 corresponding to each lead-in connector 10 and conversely. It is however, possible for the connectors 12 to be less in number than the connectors 10, several sections 11 being connected to a same lead-out connector 12. FIG. 3, shows a conduit 6 which has four lead-in connectors 10 on each lateral surface 15 or 15' and four lead-out connectors 12 on each end surface 16 or 17. However, the number may be higher, in particular on conduits 6 situated close to the axis where the conduits 6 have a length close to the diameter of the reactor core. Referring to FIG. 4, each fixed connector 4 above the cover is associated with a connector 10 leading into a conduit 6 and close to connector 4; thus, the first sections 9 connecting fixed connectors 4 to the associated lead-in connectors 10 and corresponding to similar electric devices have the same length. In FIG. 4, all first sections identified as 9a are of the same length, and sections 9b, 9c or 9d also have the same length as all those similar thereto. In addition, in the particular case of FIG. 4, sections 9a and 9c are equal to each other; the same goes for sections 9b and 9d. The identity of the lengths of the respective sections comprising sections 9 makes these sections interchangeable; when a malfunction occurs in one of sections 9, it may be very quickly changed since sections 9 are all prepared beforehand to a suitable length, so that all that is required is to connect each of the mobile connectors situated at the ends of the section on the one hand to the fixed connector 4 and on the other to the fixed connector 10. The arrangement of the first sections 9 is, moreover, such that, in the case where several electric devices are redundant, which is the case for the sensors measuring the position of the clusters, conduit lead-in connectors 10 situated in separate conduits 6 are associated with the fixed connectors 4 situated above the top cover at the ends of the first cables relative to these devices. Thus, the second sections 11 of the cables relative to these redundant electric devices are necessarily in separate conduits 6; should a malfunction occur in one or even more of these conduits 6, at least one of the conduits containing one of the sections relative to these redundant devices will not be damaged and will fulfill its function. The assembly of the third sections 13 extending from ducts 6 in the same plane, and hence parallel to each other, extends from reactor 1 parallel to the direction of the conduits 6, in two opposite directions, since the sections 13 extend from each conduit 6 through two opposite end faces 16 or 17. The third sections 13 from the same end 16 or 17 of the same conduit 6 are grouped together at the outlet of conduit 6 into a single cable. This single cable is formed in a way conventional in the nuclear field, i.e., it generally comprises a first sheath which is an electric insulator (this sheath may, for example, be formed from chlorosulfonated polyethylene), a second sheath forming a heat screen, made, for example, from glass wool, a third sheath having a metal screen function, formed, for example, from a steel or copper strip or braid, and a fourth insulating sheath made, for example, from chlorosulfonated polyethylene. These sheaths allow the cable to suitably resist heat, radiation, sprinkling with boron-containing water and earthquakes. Finally, the assembly of cables extending in the same direction from conduits 6 parallel to each other is of a fairly limited number, since this number is equal to the number of conduits situated in the same plane. The assembly of these cables may therefore rest on the bridge 14 which supports it as far as plate 8 situated away from the reactor while only forming a single layer of cables. The number of bridges 14 is of course equal to twice the number of layers of conduit 6 (there are, for example three layers 5, 5' and 5" in the drawings). The direction of the conduit 6 of each layer 5, 5' or 5" is of course provided so that the bridges 14 may be evenly distributed around the reactor. The cabling installation of the invention has numerous advantages: positioning of the cables is easy since the second cables connecting the fixed connectors 14 situated above the top cover to the fixed connectors 7 situated on plates 8 at a distance from the reactor are formed from several independent sections, of well defined lengths, which may be prepared beforehand and thus need only be connected very simply, using connectors situated at each of their ends. Similarly, dismantling of the cables is very easy. Replacement of the cables is also facilitated, since it is sufficient to change the damaged section of each of the cables which no longer fulfill their function; these sections are readily accessible, in particular the cables grouping together the third sections are disposed in a single layer on the bridges 14; in addition, the replacement sections are prepared beforehand. The facility of fitting, removing and replacing cables allows the operators to minimize their stay in the contaminated environment and to work under easy and more comfortable conditions, without requiring special tools. An additional result is a more reliable assembly. Furthermore, the installation of the invention allows the use of electric devices, in particular sensors for measuring the position of the clusters, which are redundant. In fact, it is only the very rational arrangement of the cables of the installation of the invention which allows a high number of cables to be used. Furthermore, since the cables extending from redundant devices must be disposed so as to comply with prevailing safety standards since the electric power supplies for these redundant devices must have different origins and be mechanically separate, since the paths of the transmission, cables must be different and since minimum distances are imposed between the paths of the cables, only a very precise organization of the arrangement of these cables makes it possible to use these redundant devices. The installation of the invention further allows cables corresponding to devices having similar functions, without however being redundant, to be placed in the same compartment, so that all the third sections extending in the same direction from conduits parallel to each other correspond to electric devices having the same function. Thus analog signal processing devices may be grouped together on the same plate 8 at a distance from the reactor. In the conduits, the sections may exist together at small distances, thus allowing a high concentration of the cables. A cabling installation according to the invention is furthermore very resistant to earthquakes, to radiation and to sprinkling with boron-containing water, for the cables used are constructed so as to resist these environmental conditions in the reactor, each of the sections being surrounded, in a manner known per se by protective sheaths similar to the sheaths of the third sections described above. As for circuits 6, these are made of stainless steel and thus withstand very well the environmental conditions inside the reactor.