Patent Number: 047045396
Section: description

DETAILED DESCRIPTION OF THE INVENTION Reference is first made to FIGS. 2 and 3 showing cart 10 providing the transportation of container 12 to the various stations illustrated in FIGS. 1A through 1H. Said cart 10 is substantially made of a framework 26, placed on a rolling platform 28 via a sliding and/or rolling support 30 therebetween, designed such as to allow a limited displacement perpendicular to the rolling direction of the platform, between framework 26 and said rolling platform 28, during the introduction of cart 10 in a loading hall for receiving a container 12. Due to this feature, the cart can travel on running paths of the railway track type, with the necessary clearances for accommodating the stresses (radius of curvature, cant of the track, etc.) as well as on running paths made and mounted with accuracy, provided in the loading hall where the cart travels. The lateral centering is provided by side guiding rails 32 located on the walls of the hall and locking means 34 are provided, designed so as to allow or suppress the side motion freedom according to whether the cart is outside or inside the hall. Container 12 is positioned on the framework 26 of the cart via a plate 36 on which it is placed (FIG. 3) and which comprises means 38, for example jacks, for adjusting the height and levelness of the upper face on the container. The positioning of container with respect to the longitudinal and transverse axes thereof is obtained by a jig 40, fixed on the top of container 12, and cooperating with reference axes 42, 42 located on the upper portion of the cart framework 26, while setting means are provided for positioning the container 12 in the cart 10. In this embodiment, said setting means are in the form of screw-nut systems 44, 44' such as threaded shafts extending inwardly from opposite sidewalls of the framework 26 are respectively placed in register with the upper 46 and lower 46' support stubs on opposite sides container 12. According to the invention, the screw-nut systems 44, 44' not only ensure the container positioning, but they also maintain it in position and resist efforts to move it even due to an earthquake. Finally a resilient bumper system 48, 48', interposed between each support stub of the container and each screw-nut system, allows accomodation of displacement due to the radial expansion of the container, caused by heating, once the container has been loaded with irradiated fuel. During translation of the cart from the penetration shaft 20 (FIG. 1C) to the station for reinserting the container plug (FIG. 1G), it is necessary to provide protection against radiations emitted by the irradiated fuels loaded in the container, said container being then without its sealing plug. This radiation protection, according to another feature of this invention, is provided by a pair of movable armored protection plates shown schematically at 50 (FIG. 4) mounted on the upper platform of the framework 26 of cart 10 in such manner that a minimal distance e is obtained between the ceiling of the loading hall H and said protection plate 50, the value of said minimal spacing being set by a known mechanical device such as jacks 54 for example. According to the invention, said armored protection plates also allow reducing the radiations from the irradiated fuel when the latter is moved through penetration shaft 20, during loading of the container (station of FIG. 1E). According to the invention, the armored protection plates are provided with manual or mechanized control means, shown schematically at 52, allowing movement of the plates towards or away from each other, so as to close them against each other or in order to load and unload the container from the cart. The armored protection plates 50 fit against each other and cover in part the upper face of container 12, a clearance between the plates and the upper face container being provided for accommodating a vertical expansion of the container, due to its heating after having received the fuel. An extra armored protection can also be provided against the radiations, shown schematically at 56, fixed either on container 12 or on the framework 26 of the cart, or integrated to said framework, in order to complete a radiation shield at the top of the container when the container plug is removed. According to another feature of the invention (FIG. 5), there is provided a support trestle 58 for the container plug 14, said trestle being disposed on the cart framework 26. Trestle 58 allows depositing the container plug on the cart once it has been removed from the container, during the period when the latter is underneath the penetration shaft 20. This feature obviates having the sealing plug suspended during the container docking and loading operations, and facilitates checking and possibly changing the plug seals. According to the invention, it is possible to provide suction means such as a sucking device 60, on support trestle 58 (FIG. 5) for avoiding any discharge or dissemination of the contamination of the plug lower face. According to the invention, all the mechanisms of the cart, of the penetration shaft and for the plug removal are designed so as to be adaptable to the various types of containers, by a simple addition of adapters, allowing compensation for the differences in dimensions thereof and the needed protection from radiation. For safety reasons, notably in the case of an incidental shutdown of the installation, after the loading of a container with irradiated fuel, it is necessary to cool down said container. To this effect (FIG. 6), the invention provides a cooling device for container 12, comprising a tubing 64, integrated with or fixedly attached to the cart framework 26, and which covers the container over the entire height of its cooling fins 66, the cooling being provided by water circulating in the space between tubing 64 and the container, said circulation being provided by flexible ducts 68, 68'. The lower and upper fluid tightness of the tubing on the container is provided by standard seals 62. The fluid continuity of the tightness between the loading or unloading pit or tank 22 and container 12 is provided by means of a conventional metallic bellows 70 (FIG. 7) which is concentric with a sleeve 70' extending downwardly from the loading pit 22, the bellows 70 being held at an upper end thereof by a flange 71 connected to the underside of the loading pit 22. According to the invention, the fluid tightness is provided between the bellows 70 and container 12 at the level of the bearing surface 72 of the latter which receives the plug, in order to avoid any contamination of the upper part of said container. The system for maintaining the bellows is disclosed in French Pat. No. 80 26 360 filed on Dec. 12, 1980 and published under No. 2 496 329 in the name of the assignee of the present invention. This system includes a series of springs 74 maintaining the bellows 70 in its idle position, by exerting an upward force on shafts 76 the respective lower ends of which are rigidly connected to a flange 78, so-called movable abutment flange, which provides the connection between a gasket carrying flange 80 and the bellows lower end. According to the invention, the metallic bellows 70 can be disassembled from the bottom, without it being necessary to disassemble the springs 74 and flange 78, by disassembling a lower flange 82 maintaining the whole system in position. With reference to FIG. 8, a description will now be given of a bellows engaging means which, in this embodiment, are mounted on a tubing 84 of cart 10 and which allow, once the cart is positioned underneath penetration shaft 20, to engage the bellows 70 and pull it downwardly in order to hold gaskets 81 on the gasket carrying flange 80 against container upper bearing surface 72 and to ensure the fluid tightness provided by the bellows. Said bellows engaging means, which are similar to those disclosed in the hereabovementioned French patent, comprise four assemblies identical to that shown in FIG. 8, it being understood that their number can vary as a function of the efforts which have to be exerted for pulling the bellows. Each assembly includes a treated steel screw shaft 86, provided with an frustoconical insertion end 86', the lower end of said screw being provided with a roll or roller abutment 88 accommodating the axial stress. Each screw 86 cooperates with a spherical collar nut 90 provided on the movable abutment flange 78. In the embodiment shown here, each spherical collar nut 90 is held within a base 92 with prevents the collar nut 90 from rotation being rotated, while leaving a clearance affording a sufficient freedom for the motion of the collar nut 90. Each collar nut 90 is applied on base 92 by springs 94 exerting a slight pressure on the collar nut, for facilitating easy engagement of screw 86 at the beginning of the screwing operation, described below. Base 92 is mounted on an adjustment flange 96 via resilient devices, made here of spring washers 98 having a double function: 1--to protect step-down gears 100 of a driving mechanism for screws 86, described below, when stopped in mechanical abutment, and PA0 2--provide a free expansion of the container while remaining locked, without introducing a new excessive stress in the system. The adjustment flange 96 also allows positioning of the axis of nut 90 with respect to the axis of screw 86, the cart serving as a jig. According to the invention, the screw devices hereabove described are designed so as to accommodate a large offset between the axis of nut 90 and that of screw 86 in order to obtain a greater freedom of positioning of the cart underneath penetration shaft 20. To this effect, the collar of nut 90 is designed so as to allow a displacement of the cart of at least 4 mm with respect to the penetration shaft, when there is an earthquake, while still ensuring the thighness. Still according to the invention (FIG. 9), the resilient mounting devices for collar nuts 90 formed by the spring washers 98 are used as a force limiting system at the contact between the gasket carrying flange 80 collar 96 and the container 12, by measuring the relative displacement between the adjustment flange 96 and the base 92. To this effect, the invention provides cam means, such as a cam 102, mounted on the adjustment flange 96, and an electrical contact 104 on the base 92, for the detection of said relative displacement (of course, a reverse disposition can also be envisaged without departing from the scope of the invention by mounting cam 102 on base 92 and contact 104 on flange 96). The relative displacement thus detected corresponds to the force exerted between the container 12 and the bellows 70"; due to the compression effected by the screw device. Each screw 86 stops turning in a locked position due to the information provided to suitable control means by the electrical contact 104 operated by cam 102. Each screw 86 is driven in rotation by a motor 106 and a step-down gear 100 unit, said motor/step-down gear unit comprising a braking system 108 with manual unlocking 110. The driving of screw 86 is obtained via a sheath 112 keyed to the step-down gears 100, there being two grooves and two keys 114 providing a rotating connection between screw 86 and the sheath 112. The latter is guided by a hollow shaft of the step-down gear 100 and it comes to bear against the ball or roller abutment 88, fixed onto the tubing 84 of the cart, thereby allowing introducing all the axial efforts into the cart, and thereby protecting the step-down gear. The sheath 112 provides the angular adjustment of the first thread of screw 86 via a cam 116 and an electrical device 118, the synchronous motor 106 providing the rotation motion. The lower end of screw 86 is fixed by an articulated connection 120 at the end of the shaft 122 of a double action pneumatic jacket 124. The hereabove described system being identical to the corresponding system disclosed in the aforementioned French patent, its operation will not be described and the reader is invited to refer to the corresponding description of said prior patent. According to the invention, a revolution counting device 126 is provided for each screw system, such as adjacent screw 86, for detecting and signalling a possible lack of synchronization of the rotation of the screw systems, any lack of synchronization of one of the screw systems causing the stoppage of all the screws. According to the invention, when an incident occurs on a screw, it is possible to put out of order the screw which is diametrically opposite thereto and to go on operating all the other screws, either for locking them to obtain the fluid tightness, or for unlocking them in order to remove the container from the penetration shaft. According to the invention, an emergency manual control can be provided, which can be coupled to each screw so as to be able to effect a manual coupling or uncoupling thereof. Finally, according to the invention, when a screw is jammed in a corresponding nut, it is possible to cut off the jammed screw underneath the armored protection plates, said system being such that after disconnecting the bellows from the container the portion of the screw which is jammed in the nut does not prevent the translation of the container on its cart, and therefore a resetting of the system in a "safety" position is possible. Obviously, this invention is not limited to the various embodiments described and shown, and it encompasses all possible variations thereof.