NUCLEAR FUEL ASSEMBLY LOADING MACHINE

Abstract

This machine for loading nuclear fuel assemblies (3) into a reactor vessel (1) of a nuclear reactor comprises a horizontally mobile trolley (5) to which a telescopic vertical mast (4) is attached. The mast includes a fixed drum (7) attached to the trolley and several vertically mobile drums (8-11) mounted coaxially with the fixed drum, allowing for telescopic extension. The innermost drum (11) is equipped with a grapple (12) for connecting to the upper end of a fuel assembly. The drums have a square cross-section. The drums are fitted with stops that cooperate to allow for individual deployment of the drums and their retraction by raising the innermost drum.Each drum, with the exception of the innermost drum, is equipped on its four lateral walls with pads designed to facilitate the deployment and retraction of the drums within one another. See Figure 1 for abbreviations.

Description

Title of the invention: NUCLEAR FUEL ASSEMBLY LOADING MACHINE Scope of the invention

[0001] The invention falls within the field of electricity production by nuclear energy, and therefore more specifically within the problem resulting from the handling of nuclear fuel used in such production plants.

[0002] It is aimed more particularly at one of the key elements of such a loading machine, and in general of handling, consisting of a mast, in this case telescopic, the lower end of which is classically equipped with a grapple capable of grasping nuclear fuel assemblies.

[0003] Such a telescopic mast comprises a plurality of elementary shafts designed to be deployed and retracted according to the required needs. Prior state of the art

[0004] As is known, the core of a nuclear reactor, whether boiling water or pressurized water, consists of fuel rods or needles grouped together to form assemblies, which can be handled independently of each other, both when they are placed in the core and when they are replaced after use.

[0005] The handling of such nuclear fuel assemblies is conventionally carried out by means of a so-called loading machine, equipped with a telescopic mast mounted on an overhead crane, and capable of moving on the one hand above the reactor core, and on the other hand above a temporary storage pool in particular of spent assemblies, i.e. after use within said core.

[0006] Such a loading machine is equipped with a control trolley, again capable of moving in a horizontal direction other than that of the overhead crane, typically perpendicular to it. The lower end of the mast is equipped with a grapple for coupling with the upper end of a fuel assembly, for the purpose of gripping and handling it.

[0007] In the more specific context of boiling water reactors, the telescopic mast travel is relatively long and can typically reach about twenty meters. This results in constraints in terms of maintaining the verticality of the mast, on the one hand, and the positioning accuracy of the grapple located at the lower end of said mast for coupling to a nuclear fuel assembly, on the other hand.

[0008] The objective of the present invention is to optimize the operation of such masts for loading machines, in particular having a high deployment stroke and more particularly adapted to boiling water nuclear reactors. Description of the invention

[0009] To this end, the invention relates to a machine for loading nuclear fuel assemblies into a reactor vessel, comprising a horizontally mobile trolley to which is associated a vertical telescopic mast comprising a fixed drum attached to the trolley and several vertically mobile drums, mounted coaxially with the fixed drum, so as to be able to deploy telescopically, the different drums having a square cross-section.

[0010] According to the invention: - the barrels are equipped with stops, capable of cooperating with each other in order to allow individual deployment of the barrels, and folding of said barrels by raising the innermost barrel; - each drum, with the exception of the innermost drum, is equipped at the level of the four lateral walls which define it, with pads, suitable for facilitating the guidance of the deployment and folding of the drums within each other.

[0011] In other words, the invention consists of facilitating the guidance of the grapple throughout the mast's travel, providing sufficient rigidity against horizontal forces, particularly those inherent in the movement of the loading machine, and being sufficiently slim to allow the tubes to fold within the available volume created by the fixed upper shaft. To this end, the stops, on the one hand, and the pads, on the other, play a role in facilitating this operation, especially for long deployment lengths of such a telescopic mast.

[0012] According to one feature of the invention, the fixed barrel is integral with a chassis resting on an orientation ring, itself received on the mobile carriage and capable of rotating relative to said carriage, so as to allow the desired orientation of the grapple.

[0013] According to another feature of the invention, the constituent material of the skates is made of ultra-high molecular weight polyethylene, typically with a very high molar mass greater than 106 g / mol. Brief description of the figures

[0014] The manner in which the invention can be implemented and the resulting advantages will be more apparent from the following examples of implementation, given by way of illustration and not limitation, in support of the attached figures.

[0015] Figure [1] is a schematic cross-sectional representation of a reactor vessel nuclear associated with its nuclear fuel assembly storage pool, and on which appears the loading machine according to the invention.

[0016] Fig. 2 is a schematic representation illustrating the trolley mounted on the slewing ring of the loading machine according to the invention.

[0017] Fig. 3 is a schematic perspective representation of two of the tubes constituting the telescopic mast of the loading machine of the invention and of the technical means implemented for its optimized operation. Detailed description of the invention

[0018] As already mentioned, the loading machine of the invention is intended to enable the handling of nuclear fuel assemblies within a nuclear power plant, and more specifically of a nuclear reactor core. In the example described, the characteristics apply to a loading machine more specifically dedicated to a nuclear reactor core operating according to BWR technology, i.e., boiling water.

[0019] To this end, the following has been represented: - the core (1) of the reactor, - the temporary storage pool (2) for said worn assemblies, - nuclear fuel assemblies (3), - the telescopic mast (4), - the trolley (5) of the loading machine, and - the rails on which the said trolley is likely to move in translation.

[0020] The mast (4) of the loading machine is therefore of a telescopic nature and in this case comprises a fixed upper shaft (7), attached to the trolley (5), and four telescopic shafts (8-11), capable of fitting one after the other into the fixed shaft (7).

[0021] These barrels have a square cross-section, facilitating the guidance of one another and ultimately the positioning accuracy of the grapple (12), positioned at the lower end of the lower tube (11), and intended to cooperate with the upper end of the assemblies (3) for the purpose of handling them.

[0022] These various constituent shafts of the telescopic mast are made of stainless steel and laser welded, and the walls which define them have a typical thickness of around 6 millimeters.

[0023] Each of the tubes, including the fixed shaft (7), has a length of approximately 6 meters, so that when the telescopic mast is fully extended, and due to the pairwise cooperation zones of each shaft, an effective mast deployment length of approximately 18 meters can be achieved, compatible in particular with the handling of nuclear fuel assemblies implemented in the boiling water reactors, which are known to require a greater displacement than those operating with pressurized water.

[0024] The fixed shaft (7) is attached to the carriage (5), and more specifically to a chassis (13), which is mobile in rotation by means of a dedicated motor (14), the chassis (13) resting on a slewing ring (15) fixed on the mobile carriage (5), as can be clearly seen in [Fig.2].

[0025] By doing so, it is possible to ensure the desired angular orientation of the mast (4) by the channel of this fixed shaft (7), and therefore corollarily of the grapple (12) according to reduced angular degrees over a continuous range of 330 degrees.

[0026] According to one feature of the invention, stops (20, 21) are fixed against the lateral walls defining said drums. More specifically, these stops are in the form of machined angle brackets and are joined by screwing, typically with two stops per drum at opposite corners in the lower part and two stops per drum in the upper part.

[0027] These stops are designed to allow the individual deployment and retraction of the drums, through the cooperation of said stops in pairs: being fixed to the outside of the drums at the top and to the inside of the drums at the bottom, they allow one drum to be placed on top of the other during mast deployment. Their thickness is adapted to the small space between the drums.

[0028] The deployment and re-deployment of the drums is ensured by lifting cables fixed at their end on the inner drum, and winding at their other end onto a lifting winch.

[0029] Furthermore, and in order to facilitate the sliding of said drums relative to one another without affecting the guidance, pads (22, 23) are used, in this case fixed by screws to the inner wall of the drums at the bottom of the drum, and to the outer wall at the top of the drum, with four pads per level, excluding the innermost drum (11). In the example described, these pads are fixed to two walls consecutive to the corners of the tubes, said pads being oriented at 90° from one tube to the other to avoid interference between drums.

[0030] Typically, these skates are made of very high density polyethylene, in particular known under the reference UHMW-PE, that is to say a polyethylene with a molar mass greater than 106 g / mol.

[0031] This particular choice of material constituting the pads makes it possible to optimize the wear resistance of said pads and therefore consequently of the telescopic mast, including as a result of their evolution in and out of water, and taking into account also their exposure to ionizing radiation, so that the maintenance operations on the telescopic tube of the invention are spaced out.

[0032] Consequently, due to the implementation of such skates, a reduction is ensured Maximum clearance between the drums optimizes the positioning accuracy of the grapple and, consequently, the handling of nuclear fuel assemblies. Furthermore, machining of the tubes is avoided.

[0033] So that combined with the possible rotation of the fixed upper drum (7), we get a loading machine combining both precision and optimization of the number of degrees of freedom in terms of handling nuclear fuel assemblies.

[0034] The invention also finds application in loading machines that may be used in new reactors known as SMRs (Small Modular Reactors). In this technology, the travel of the loading machine's mast is greater, typically reaching 30 meters. In this case, the telescopic mast described above is identical, except that two additional shafts are added, again equipped with guide pads and stops of the same design as those mentioned above, and located in the same way.

[0035] Due to the design of such a mast, and even for such a length of travel, the desired precision and modularity in terms of degree of freedom are still available.

Claims

Demands

1. A machine for loading nuclear fuel assemblies (3) into a reactor vessel (1) of a nuclear reactor, comprising a horizontally movable trolley (5) to which is associated a telescopic vertical mast (4) comprising a fixed drum (7) attached to the trolley and several vertically movable drums (8-11), mounted coaxially with the fixed drum, so as to be able to deploy telescopically, the innermost drum (11) being provided with a grapple (12) able to connect to the upper end of a fuel assembly, the different drums being of square cross-section, characterized: - in that the drums are provided with stops (20, 21), able to cooperate with each other in order to allow individual deployment of the drums, and the folding of said drums by raising the innermost drum;and - in that each barrel, with the exception of the innermost barrel, is equipped at the level of the four lateral walls which define it, with pads (22, 23) suitable for facilitating the guidance of the deployment and refolding of the barrels within each other.;

2. Loading machine according to claim 1, characterized in that the fixed drum (7) is integral with a chassis (13) resting on an orientation ring (15), itself received on the mobile carriage (5) and capable of rotating relative to said carriage (5), so as to allow the desired orientation of the grapple (12).

3. Loading machine according to any one of claims 1 and 2, characterized in that the constituent material of the pads (21, 22) is made of ultra-high molecular weight polyethylene.

4. Loading machine according to claim 3, characterized in that the polyethylene has a very high molar mass greater than 106 g / mol.

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