Patent Description:
A nuclear fuel assembly (or "fuel assembly") comprises nuclear fuel rods (or "fuel rods") arranged in a bundle and a skeleton supporting the fuel rods.

Each fuel rod comprises a tubular cladding containing nuclear fuel pellets (e.g. UOz pellets), the two ends of the tubular cladding being closed by respective end plugs. Generally, a fuel rod spring is inserted in the fuel rod cladding for exerting a compression force on the pellets to avoid movement of the pellets inside the fuel rod. The pellets are for example obtained by compaction of nuclear fuel powder (e.g. UOz powder).

The skeleton comprises for example a bottom nozzle and an top nozzle spaced along a longitudinal axis, guide thimbles extending along the longitudinal axis between the bottom nozzle and the top nozzle with connecting the bottom nozzle and the top nozzle together, and spacer grids attached to the guide thimbles with being distributed along the guide thimbles. The fuel rods extend through the spacer grids and between the bottom nozzle and the top nozzle. The function of the spacer grids is to support the fuel rods.

Manufacturing fuel assemblies requires producing the nuclear fuel powder, pelletizing the nuclear fuel powder to obtain the nuclear fuel pellets (or "pellets"), producing fuel rods namely by loading the pellets into the cladding tubes and welding plugs at the ends of the cladding tubes, manufacturing the skeleton and inserting the fuel rods into the skeleton.

The thus manufactured fuel assemblies can be packaged for transportation to nuclear power plants.

Today, these operations are performed in a same nuclear fuel assembly manufacturing plant.

Besides, manual production is generally replaced progressively by automation to improve productivity, increase capacity and manage a more continuous flow of operations.

However, it is necessary to provide protections to the buildings and to the equipment to comply with risks such as fire, flooding, seism. Such protections increase when the manufacturing is automatized.

This leads to a nuclear fuel assembly manufacturing plant with a large footprint, the nuclear fuel assembly manufacturing plant being complex to operate and subject to numerous regulations.

Owing to these constrains, it appears difficult to construct new nuclear fuel assembly manufacturing plants, leading to difficulties of procurement for the nuclear power plant operators.

The documents "<NPL>, "<NPL> and <NPL>, disclose prior art examples of plants and methods for manufacturing nuclear fuel assemblies.

One of the aims of the invention is to propose a nuclear fuel assembly manufacturing method that allows constructing and operating a nuclear fuel assembly manufacturing plant more easily.

To this end, the invention proposes a method for manufacturing a nuclear fuel assembly according to claim <NUM>.

Specific embodiments are defined in claims <NUM>-<NUM>.

The invention also relates to a plant configured for manufacturing a nuclear fuel assembly as defined in claim <NUM>.

Specific embodiments are defined in claims <NUM> - <NUM>.

The invention also relates to a method of expanding a plant for manufacturing a nuclear fuel assembly as defined in claim <NUM>.

The invention and its advantages will be better understood upon reading the following description given solely by way of example and with reference to the appended drawings, in which:.

According to one aspect, the invention relates to a method for manufacturing a nuclear fuel assembly comprising nuclear fuel rods arranged in a bundle and a skeleton supporting the nuclear fuel rods.

The nuclear fuel assembly <NUM> of <FIG> comprises a bundle of nuclear fuel rods <NUM> and a skeleton <NUM> for supporting the fuel rods <NUM>. The fuel rods <NUM> extend parallel to each other and to an assembly axis L.

The skeleton <NUM> comprises a bottom nozzle <NUM>, a top nozzle <NUM>, a plurality of guide thimbles <NUM> and a plurality of spacer grids <NUM>.

The guide thimbles <NUM> extend parallel to the assembly axis L and connect the bottom nozzle <NUM> to the top nozzle <NUM> with maintaining a predetermined spacing along assembly axis L between the bottom nozzle <NUM> and the top nozzle <NUM>. The fuel rods <NUM> are received between the bottom nozzle <NUM> and the top nozzle <NUM>.

The spacer grids <NUM> are distributed along the bundle of fuel rods <NUM>. Each spacer grid <NUM> is fixedly attached to the guide thimbles <NUM> which extend through the spacer grid <NUM>.

Each spacer grid <NUM> is configured for supporting the fuel rods <NUM> in a spaced relationship. Each spacer grid <NUM> is configured for supporting the fuel rods <NUM> along the assembly axis L and transversely to the assembly axis L.

The fuel assembly <NUM> is configured for insertion of rods of a rod cluster control assembly (RCCA) and/or thimble plugs of a thimble plug assembly (TPA) into the guide thimbles <NUM>, the rods or thimble plugs being inserted through the top nozzle <NUM>.

A rod cluster control assembly (RCCA) includes a bundle of parallel control rods and possibly non-absorber rods arranged for insertion in the guide thimbles <NUM>, each control rod including neutron absorbing material. Such an RCCA is provided in a nuclear reactor and is for example vertically movable up and down for increasing or decreasing the reactivity of the fuel assembly <NUM> or fixedly inserted into a specific fuel assembly <NUM> for reducing reactivity of the nuclear reactor in the area of this fuel assembly <NUM>, e.g. in a peripheral area of the nuclear reactor.

A thimble plug assembly (TPA) is provided in a nuclear reactor and includes a plurality of plugs each configured for closing a respective guide thimble <NUM> of a fuel assembly <NUM> which is not provided with a RCCA in the nuclear reactor, in view of preventing bypass flow of coolant inside the guide thimbles <NUM> of this fuel assembly <NUM>.

In view of manufacturing a fuel assembly <NUM>, it is possible to provide the skeleton <NUM> without the bottom nozzle <NUM> or the top nozzle <NUM>, to insert the fuel rods <NUM> axially through the spacer grids <NUM> and to fixedly attach the bottom nozzle <NUM> or the top nozzle <NUM> to the guide thimbles <NUM> to complete the skeleton <NUM>.

The length of a fuel assembly <NUM> is for example of between <NUM> and <NUM> and the weight of a fuel assembly <NUM> is typically of between <NUM> and <NUM>.

The nuclear fuel assembly manufacturing method comprises the steps of inserting fuel rods <NUM> into the skeleton <NUM> to obtain a fuel assembly <NUM> and packaging the fuel assembly <NUM> in view of transportation, the steps being performed in a same nuclear fuel assembly manufacturing plant, preferably in a same nuclear fuel assembly manufacturing building.

In one particular embodiment, the method comprises a step of receiving fuel rods <NUM> transported from a nuclear fuel rod manufacturing plant separated by a non-confined area from the nuclear fuel assembly manufacturing plant, wherein these fuel rods <NUM> are used during the inserting step.

In the present invention, "separated by a non-confined area" means that the two plants or buildings are not connected in a confined manner. A transport of skeleton parts or nuclear fuel rods or nuclear fuel pellets or nuclear fuel powder or nuclear fuel powder precursor between the two plants or buildings separated by a non-confined area is performed e.g. via road, sea and/or air.

In this embodiment, the fuel rods <NUM> are not manufactured in the nuclear fuel assembly manufacturing plant. The fuel rods <NUM> are manufactured in a nuclear fuel rod manufacturing plant that is distinct from the nuclear fuel assembly manufacturing plant. The fuel rods <NUM> may be transported from the nuclear fuel rod manufacturing plant to the nuclear fuel assembly manufacturing plant via road, sea and/or air.

In one particular embodiment, the method comprises receiving skeleton parts from a skeleton manufacturing plant separated by a non-confined area from the nuclear fuel assembly manufacturing plant, using these skeleton parts in the insertion step.

In one particular embodiment, the method comprises receiving preassembled skeleton assemblies, each skeleton assembly comprising guide thimbles <NUM>, spacer grids <NUM> and only one among the top nozzle <NUM> and the bottom nozzle <NUM>, e.g. one among the top nozzle <NUM> and the bottom nozzle <NUM>, and, separately, the other one among the top nozzle <NUM> and the bottom nozzle <NUM>.

The method thus comprises, after the inserting step, a step of assembling the other among the bottom nozzle <NUM> or the top nozzle <NUM> to the preassembled skeleton assembly to complete the skeleton <NUM>.

Optionally, the method comprises receiving fuel rods <NUM> in a container and using this container in the packaging step for packaging a fuel assembly <NUM>.

Indeed, fuel rods <NUM> and fuel assemblies <NUM> can be transported in same containers, e.g. the fuel assembly containers of the Framatome company named "FCC".

For example, fuel rods <NUM> can be placed in a holster having substantially the same external dimensions as a corresponding fuel assembly <NUM>, the holster being placed in the container.

The reuse of the containers allows to limit the transport operations by using the same containers for transporting the fuel rods <NUM> from the nuclear fuel rod manufacturing plant to the nuclear fuel assembly manufacturing plant and then for transporting the fuel assemblies from the nuclear fuel assembly manufacturing plant to the nuclear power plant.

Alternatively, the method comprises using dedicated first containers for transporting nuclear fuel assemblies <NUM> and dedicated second containers for transporting fuel rods <NUM>, each second container being e.g. a first container equipped with additional equipment for allowing packaging of fuel rods <NUM> in the second containers.

The nuclear fuel assembly manufacturing plant <NUM> of <FIG> and <FIG> is configured for the implementation of the method of manufacturing a fuel assembly <NUM>.

The nuclear fuel assembly manufacturing plant <NUM> comprises a fuel assembly manufacturing unit <NUM> configured for manufacturing fuel assemblies <NUM> starting from fuel rods <NUM> and skeleton parts.

The fuel assembly manufacturing unit <NUM> comprises an inserting station <NUM> configured for insertion of fuel rods <NUM> into the skeleton <NUM> to obtain a fuel assembly <NUM> and a packaging station <NUM> configured for packaging the fuel assembly <NUM> into a fuel assembly container <NUM> in view of transportation, e.g. to a nuclear power plant. The fuel assembly container <NUM> is configured for receiving fuel assemblies <NUM> and for transporting them via road, air and/or sea.

The nuclear fuel assembly manufacturing plant <NUM> comprises an assembling hall <NUM> in which are located namely the inserting station <NUM> and the packaging station <NUM>. The inserting station <NUM> and the packaging station <NUM> are located in the same assembling hall <NUM>.

The fuel assembly manufacturing unit <NUM> comprises a crane <NUM> located in the assembling hall <NUM> for moving the nuclear fuel assemblies <NUM> between the stations located inside the assembling hall <NUM>.

The crane <NUM> is notably configured for moving the nuclear fuel assemblies <NUM> between the inserting station <NUM> and the packaging station <NUM>. Advantageously, the crane <NUM> is a bridge crane.

The fuel assembly manufacturing unit <NUM> optionally comprises a cleaning station <NUM> configured for cleaning a nuclear fuel assembly <NUM>.

The cleaning station <NUM> is for example located in the assembling hall <NUM>. Hence, the fuel assembly <NUM> can be loaded into and/or taken form the cleaning station <NUM> using the crane <NUM>.

The fuel assembly manufacturing unit <NUM> optionally comprises a fuel assembly inspection station <NUM> configured for the inspection of a fuel assembly <NUM>.

The fuel assembly inspection station <NUM> is for example located in the assembling hall <NUM>. Hence, the fuel assembly <NUM> can be loaded into and/or taken form the fuel assembly inspection station <NUM> using the crane <NUM>.

Advantageously, the cleaning station <NUM> is configured for cleaning of the fuel assembly <NUM> in a vertical position and/or substantially at ground level and/or the fuel assembly inspection station <NUM> is configured for inspection of the fuel assembly <NUM> in a vertical position and/or substantially at ground level.

The vertical position of the fuel assembly <NUM> for cleaning and/or inspection allows reducing the footprint of the fuel assembly manufacturing unit <NUM>.

Having the fuel assembly <NUM> at ground level instead of placing the fuel assembly <NUM> into a pit provided into the ground avoids the provision of such a pit which can be rendered difficult depending on the nature of the ground.

It however requires that the hall in which the cleaning station <NUM> or the fuel assembly inspection station <NUM> is located, here the assembling hall <NUM>, has a height which is sufficient for accommodating the fuel assembly <NUM> vertically.

Optionally, the cleaning station <NUM> is also configured for performing a rod cluster control assembly test (or "RCCA test") and/or a thimble plug assembly test (or "TPA test") while the fuel assembly <NUM> is in the cleaning position.

This allows reducing footprint of the fuel assembly manufacturing unit <NUM> by performing cleaning as well as RCCA test and/or TPA test in a same station instead of providing respective stations for cleaning, RCCA test and TPA test.

A RCCA test is a test of insertion the control rods of a RCCA into the fuel assembly <NUM> to ensure that, in operation, the RCCA will properly insert into the guide thimbles <NUM> of the fuel assembly <NUM>. A deformation of the fuel assembly <NUM> or a foreign body located in a guide thimble <NUM> may prevent proper insertion of the RCCA. Similarly, a TPA test is a test of insertion the thimble plugs of a TPA into the guide thimbles <NUM> of the fuel assembly <NUM>.

The fuel assembly inspection station <NUM> is configured for performing geometrical measurements and/or visual inspection.

Preferably, the fuel assembly inspection station <NUM> is configured for performing both geometrical measurements and visual inspection. This allows reducing footprint of the fuel assembly manufacturing unit <NUM> by performing geometrical measurements and visual inspection in a same station instead of providing respective stations for geometrical measurements and visual inspection.

Geometrical measurements may include for example a distance between fuel rods <NUM>, a distance between fuel rods <NUM> and guide thimbles <NUM>, an external envelope of the fuel assembly <NUM>, a verticality of the fuel assembly <NUM>.

Geometrical measurements are performed with instruments. The fuel assembly inspection station <NUM> comprises for example a measurement assembly which is vertically movable along a fuel assembly <NUM> received in the fuel assembly inspection station <NUM>, the measurement assembly comprising the instruments.

Visual inspection is performed for example for detecting any foreign body that may be present within the bundle of fuel rods <NUM>.

The fuel assembly manufacturing unit <NUM> optionally comprises a fuel rod inspection station <NUM> configured for the inspection of fuel rods <NUM> received from the nuclear fuel rod manufacturing plant. The fuel rod inspection station <NUM> is for example located in the assembling hall <NUM>.

The fuel assembly manufacturing unit <NUM> optionally comprises a fuel rod storage <NUM> configured for the storage of fuel rods <NUM> received from the nuclear fuel rod manufacturing plant. The fuel rod storage <NUM> is for example located in the assembling hall <NUM>. The fuel rod storage <NUM> comprises for example racks for storing the fuel rods <NUM> horizontally.

The fuel assembly manufacturing unit <NUM> optionally comprises a fuel assembly storage <NUM> configured for storing nuclear fuel assemblies <NUM> before cleaning, inspecting and/or packaging the nuclear fuel assemblies <NUM>.

The fuel assembly storage <NUM> is for example located in the assembling hall <NUM>. Hence, a nuclear fuel assembly <NUM> can be loaded into and/or taken from the fuel assembly storage <NUM> using the crane <NUM>.

The fuel assembly storage <NUM> is for example a room delimited inside the assembling hall <NUM>.

The fuel assembly storage <NUM> comprises for examples racks for storing each fuel assembly <NUM> in a vertical position.

Alternatively or optionally, the nuclear fuel assemblies <NUM> may be stored into fuel assembly containers <NUM>, preferably after cleaning and/or inspection. The nuclear fuel assemblies <NUM> stored in the fuel assembly containers <NUM> are ready to be sent to a nuclear power plant.

The fuel assembly manufacturing unit <NUM> optionally comprises a logistic area <NUM> configured for storing, receiving and/or sending transport containers.

The logistic area <NUM> is accessible from the exterior of the fuel assembly manufacturing unit <NUM> via a door <NUM> opening to the exterior. Preferably, the logistic area <NUM> is accessible to trucks and/or forklifts.

Optionally, the logistic area <NUM> is provided with a logistic area bridge crane <NUM> dedicated to the logistic area <NUM>. This logistic area bridge crane <NUM> is configured for example for lifting transport containers, notably fuel assembly containers <NUM> as well as fuel rod containers. The logistic area bridge crane <NUM> may be omitted, in which case handling operations may be performed using for instance a forklift. However, the logistic area bridge crane <NUM> provides more flexibility.

Preferably, the packaging station <NUM> is located in the assembling hall <NUM> with being adjacent to the logistic area <NUM>. Hence, a fuel assembly container <NUM> receiving a fuel assembly <NUM> can be moved from the packaging station <NUM> to the logistic area <NUM> easily.

In one particular embodiment, the logistic area <NUM> comprises a container storage zone <NUM> for storing transport containers. As illustrated on <FIG>, several fuel assembly containers <NUM> are present in the container storage zone <NUM>.

The nuclear fuel assembly manufacturing plant <NUM> optionally comprises a component area <NUM> which is configured for inspecting and storing skeleton parts.

As illustrated on <FIG>, the fuel assembly manufacturing unit <NUM> is housed in a building <NUM> made of two building modules <NUM>, <NUM> arranged side-by-side in an alignment direction A. For example, the two building modules <NUM>, <NUM> are each of rectangular shape and of substantially the same dimensions (length, width and height).

The stations (inserting station <NUM>, packaging station <NUM>. ) and equipment (crane(s), storages. ) of the fuel assembly manufacturing unit <NUM> are located in the two building modules <NUM>, <NUM>.

The logistic area <NUM> is located in a first building module <NUM> among the two building modules <NUM>, <NUM> and the inserting station <NUM> and the packaging station <NUM> are located in the second building module <NUM> among the two building modules <NUM>, <NUM>.

Where the case may be, as in the illustrated in <FIG>, the component area <NUM> is for example located in the same building module as the logistic area <NUM>, i.e. here the first building module <NUM>.

Where the case may be, as illustrated in <FIG>, the cleaning station <NUM>, the fuel assembly inspection station <NUM>, the fuel rod inspection station <NUM>, the fuel rod storage <NUM> and/or the fuel assembly storage <NUM> is/are for example located in the same building module as the inserting station <NUM> and the packaging station <NUM>, i.e. here the second building module <NUM>.

In the illustrated example, the logistic area <NUM> and the component area <NUM> located in the first building module <NUM> each communicate with the second building module <NUM>, and more particularly with the assembling hall <NUM>, via respective passages <NUM>, <NUM>.

The passage <NUM> between the logistic area <NUM> and the assembling hall <NUM> is adjacent the packaging station <NUM> and/or the passage <NUM> between the component area <NUM> and the assembling hall <NUM> is adjacent the inserting station <NUM>.

For example, the cleaning station <NUM>, the fuel assembly inspection station <NUM>, the fuel rod storage <NUM> and/or the fuel assembly storage <NUM> are located in the assembling hall <NUM> between these two passages <NUM>, <NUM>.

In the illustrated example, the method for manufacturing a nuclear fuel assembly <NUM> comprises:.

Insertion of the fuel rods <NUM> may be performed from top to bottom of the fuel assembly <NUM>, the top nozzle <NUM> being omitted or removed, or from bottom to top of the fuel assembly <NUM>, the bottom nozzle <NUM> being omitted or removed. Besides, insertion of the fuel rods <NUM> may be performed by pushing and/or pulling each fuel rod <NUM>.

In one exemplary embodiment, the insertion station <NUM> is configured for sequentially inserting groups of fuel rods into the skeleton <NUM>, each group of fuel rods being prepared manually and then inserted automatically into the skeleton <NUM>. The fuel rods of each group are to be inserted at a same elevation of the skeleton <NUM> lying on an insertion bench of the insertion station <NUM>.

In a specific exemplary embodiment, the insertion step comprises:.

In the case the fuel rods are inserted into the skeleton <NUM> by pulling, the insertion step may comprise:.

Optionally, the insertion step comprises, during insertion, checking that lubricant (e.g. water) is applied on the fuel rod, after insertion, checking the setting of the pulling assembly by measuring a distance between the fuel rod ends and shoulders of the guide thimbles plugs, checking the presence orientation and position of the fuel rods and/or checking visually the spacer grids and the fuel rods end plugs for damages.

These operations are repeated for each group of fuel rods according to the fuel rod position map, until all the necessary fuel rods are inserted into the skeleton <NUM>.

Optionally, the insertion step includes insertion of fuel rods containing a neutron poison. The neutron poison contains for example Gadolinium (Gd). In such case, the fuel rods without neutron poison and the fuel rods with neutron poison are preferably stored in different places. For example, the fuel rods containing neutron poison are stored on a dedicated trolley separated from storage for the fuel rods without neutron poison.

Upon preparing a group of fuel rods to be inserted at a same level in the skeleton <NUM>, the operator is guided by the fuel rod insertion map to place the fuel rods without neutron poison and the fuel rods with neutron poison at the appropriate place on the lift-table.

Hence, the groups of fuel rods with and/or without neutron poison are prepared manually on the lifting table with indication from the fuel rod insertion map displayed by a fuel assembly software executed by a computer.

The nuclear fuel assembly manufacturing method and the corresponding nuclear fuel assembly manufacturing plant <NUM> allows manufacturing fuel assemblies <NUM> efficiently and with minimized constrains.

The fuel rods <NUM> are not manufactured inside the nuclear fuel assembly manufacturing plant <NUM>. The manufacture of the nuclear fuel assembly <NUM> is operated using fuel rods <NUM> transported from a nuclear fuel rod manufacturing plant in a non-confined area. Fuel rods <NUM> can be easily transported by road, air and/or sea.

It is thus possible to produce fuel assemblies <NUM> simply and efficiently in a specific nuclear fuel assembly manufacturing plant <NUM> at proximity of one or several nuclear power plant(s).

Operations can be performed manually without the need to resort to automatization of some tasks. It is thus easier to start production of nuclear fuel assemblies and to invest in the nuclear fuel assembly manufacturing plant <NUM>.

In a specific embodiment, the nuclear fuel assembly manufacturing method comprises receiving pellets transported from a nuclear fuel pellet manufacturing plant separated by a non-confined area from the nuclear fuel assembly manufacturing plant <NUM>, using these pellets to manufacture fuel rods <NUM>, and using these fuel rods <NUM> to manufacture fuel assemblies <NUM> in the nuclear fuel assembly manufacturing plant <NUM>.

The nuclear fuel assembly manufacturing method comprises for example placing the pellets on pellet trays, optionally inserting the trays in an outgassing furnace for removing potential hydrogenous contamination from the pellets, loading the pellets from the pellet trays into a cladding tube in a fuel rod loading station, inserting a spring into the cladding tube, filling the cladding tube with helium gas and/or welding plugs at the ends of the cladding tubes for closing the fuel rod <NUM>.

The nuclear fuel assembly manufacturing plant <NUM> of <FIG> and <FIG> is configured for implementing such an embodiment of the fuel assembly manufacturing method.

The nuclear fuel assembly manufacturing plant <NUM> of <FIG> and <FIG> differs from that of <FIG> and <FIG> in that it further comprises a fuel rod manufacturing unit <NUM> configured for receiving pellets transported from a nuclear fuel pellet manufacturing plant separated by a non-confined area from the nuclear fuel assembly manufacturing plant <NUM> and to manufacture fuel rods <NUM> using these pellets, the fuel rods <NUM> being in turn used in the inserting step.

The fuel rod manufacturing unit <NUM> comprises for example a pellet receiving area <NUM> configured for receiving pellets, a pellet inspection area <NUM> configured for inspecting the pellets, an outgassing station <NUM> comprising at least one outgassing furnace <NUM> configured to expel potential hydrogenous contamination of the pellets, a cladding station <NUM> configured to receive cladding tubes and check the received cladding tubes, a fuel rod loading station <NUM> configured for loading the pellets into a cladding tube, a welding station <NUM> configured for welding plugs to the ends of the cladding tubes and/or a fuel rod inspection area <NUM> configured for inspecting the fuel rods <NUM>.

The pellet receiving area <NUM> is configured for receiving the pellets packed in pellet containers <NUM> and for temporarily storing the pellets with leaving the pellets in these pellet containers <NUM>.

Each pellet container <NUM> comprises for example a sealed casing containing several pellet transportation sheets and an outer shell, a structure, the outer shell structure being configured for packing the pellet containers <NUM> in an intermodal shipping container.

The pellet transportation sheets are metallic corrugated sheets which comprise several parallel ridges and furrows, each furrow being configured for receiving a column of nuclear fuel pellets.

The pellet inspection area <NUM> is configured for unpacking the pellet transportation sheets from the pellet containers <NUM>, transferring the pellets from a pellet transportation sheet onto a pellet tray and inspecting visually the nuclear pellets.

These operations are for example done manually. Placing the pellets on trays is for example performed by sliding manually all pellet columns from the pellet transportation sheet onto a pellet tray. Inspecting visually the pellets is for example performed by inspecting the visible surface of the pellets located on a pellet tray, then placing upside down a second pellet tray on the top of the pellets, returning both pellet trays together, removing the first pellet tray and finally inspecting the other visible surface of the pellets.

As illustrated on <FIG>, each pellet transportation sheet <NUM> has parallel furrows <NUM> configured for receiving pellets <NUM> arranged in pellet columns <NUM>.

Each pellet transportation sheet <NUM> is for example a metallic corrugated sheet comprising ridges alternating with the furrows <NUM>.

Each pellet tray <NUM> has for example parallel bars <NUM> defining between them grooves configured for receiving pellets <NUM> arranged in pellet columns <NUM>.

In a preferred embodiment, as illustrated on <FIG>, the pellet transportation sheets <NUM> and the pellet trays <NUM> are different but geometrically compatible to allow transfer of pellet columns <NUM> from a pellet transportation sheet <NUM> to a pellet tray <NUM>.

More specifically, the pitch P between the furrows <NUM> of a pellet transportation sheet <NUM> and the pitch P between the bars <NUM> of a pellet tray <NUM> are substantially equal, the pellet transportation sheet <NUM> and the pellet tray <NUM> comprise as many furrows <NUM> as grooves between the bars <NUM> and the length D of the furrows <NUM> of the pellet transportation sheet <NUM> is substantially equal to that of the bars <NUM> of the pellet tray <NUM>.

In one exemplary embodiment, transferring pellets <NUM> from a pellet transportation sheet <NUM> to a pellet tray <NUM> includes placing the pellet tray <NUM> side-by-side with the pellet transportation sheet <NUM> such that each furrows <NUM> of the pellet transportation sheet <NUM> is aligned with a respective groove between bars <NUM> of the pellet tray <NUM> as illustrated on <FIG>, and sliding each pellet column <NUM> of the pellet transportation sheet <NUM> into a groove of the pellet tray <NUM>.

Alternatively or optionally, as illustrated on <FIG>, transferring pellets <NUM> from a pellet transportation sheet <NUM> to a pellet tray <NUM> includes placing the pellet tray <NUM> upside down on the pellet transportation sheet <NUM> such that each pellet column <NUM> is received in a respective groove between the bars <NUM> of the pellet tray <NUM>, and then turning the assembly composed of the pellet transportation sheet <NUM> and the pellet tray <NUM> upside down such that the pellet tray <NUM> is below and the pellet transportation sheet <NUM> above, and removing the pellet transportation sheet <NUM>.

Such transferring with turning allows a visual inspection of both faces of the pellets <NUM> since a face is visible when the pellets <NUM> are on the pellet transportation sheet <NUM> and the other face of the pellets <NUM> is then visible the pellets <NUM> having been transferred to the pellet tray <NUM> with an upside down tuning.

Alternatively or optionally, as illustrated on <FIG>, such turning of pellets <NUM> is performed by using two pellet trays <NUM>. The pellets <NUM> are for examples transferred from a pellet transportation sheet <NUM> to a pellet tray as illustrated on <FIG> and then turned upside-down between two pellet trays <NUM> as illustrated on <FIG>.

Advantageously, as illustrated on <FIG>, the pellet trays <NUM> are configured for stacking the pellet trays <NUM>. This eases handling of the pellet trays <NUM>, namely transporting the pellet trays <NUM> and/or transferring them to outgassing furnaces <NUM>.

The pellet transportation sheets <NUM> and the pellet trays <NUM> are for example different in their design (e.g. material and/or structure), the pellet trays <NUM> being e.g. designed to resist to heating in the outgassing furnace <NUM>.

Advantageously, these pellet trays <NUM> are configured to be used for storing the pellets <NUM> and/or placing the pellets <NUM> into an outgassing furnace <NUM> and/or loading the pellets <NUM> into cladding tubes.

The pellets <NUM> can thus remain on the pellet trays <NUM> from the inspection to the loading into cladding tubes, without transfer of the pellets <NUM> from the pellet tray <NUM> to another support or container between the inspection and the loading. This limits manipulation of the pellets <NUM> and thus limits the risk of damaging the pellets <NUM>.

Optionally, the fuel rod manufacturing unit <NUM> comprises movable pellet storage vaults <NUM>, each storage vault <NUM> being configured for storing pellet trays <NUM> and movable to allow transferring pellet trays <NUM>.

As illustrated on <FIG>, each storage vault <NUM> is configured for receiving several pellet trays <NUM>, and comprises e.g. several compartments or cells <NUM>, each cell <NUM> being configured for receiving several pellet trays <NUM>.

Each storage vault <NUM> comprises for examples several cells <NUM>, each cell <NUM> being configured for receiving a stack of pellet trays <NUM> for example equivalent to the stack of pellet transportation sheets <NUM> from a pellet container <NUM>.

Each cell <NUM> is preferably provided with a door for closing the cell <NUM>.

Preferably, the cells <NUM> are distributed on two opposite faces 140A, 140B of the storage vault <NUM>. This allows improving stability of the storage vault <NUM>, increasing storage capacity and also loading two side-by-side outgassing furnaces <NUM> with pellet tray <NUM> from both sides of the storage vault <NUM>, without having to turn the storage vault <NUM>. The storage vault <NUM> is for example positioned between the two outgassing furnaces <NUM>, each outgassing furnace <NUM> being loading respectively with the pellet trays <NUM> of one side of the storage vault <NUM>.

Each storage vault <NUM> exhibits a parallelepiped shape with cells <NUM> located on two opposite faces 140A, 140B of the storage vault <NUM>.

Each storage vault <NUM> can be moved and/or elevated easily, e.g. with a standard pallet stacker <NUM>. The pallet stacker <NUM> allows moving the storage vaults <NUM> between pellet inspection area <NUM>, storage location, outgassing furnace <NUM> and fuel rod loading station <NUM>. Elevation eases the manual loading and unloading of pellet trays <NUM> inside and/or outside the storage vault <NUM>.

Pellet scraps (i.e. pellets with non-compliant surface flaws) may be unintentionally produced during handling of the pellets, namely during inspection, storing, outgassing and/or loading.

Optionally, the method comprises returning pellet scraps to the nuclear fuel pellet manufacturing plant in the pellet containers <NUM>. This allows benefiting from the return of the pellet containers <NUM> to the nuclear fuel pellet manufacturing plant knowing that the fuel rod manufacturing unit <NUM> is not configured for manufacturing nuclear fuel pellets and is deprived of equipment for processing pellet scraps.

Optionally, the method comprises temporarily storing pellet scraps in at least one pellet container <NUM> in the pellet receiving area <NUM> and/or in at least one cell <NUM> of a storage vault <NUM>. Pellet scraps may be stored in a can, the can being stored temporarily in a pellet container <NUM> or storage vault <NUM>. The outgassing station <NUM> comprises at least one outgassing furnace <NUM>. Each outgassing furnace <NUM> is configured for expelling potential hydrogenous contamination of the pellets.

Each outgassing furnace <NUM> is configured for receiving the pellet trays <NUM> containing the pellets, such that the pellets can be left in the pellet trays <NUM> for outgassing heating operation, without transfer of the pellets.

As illustrated on <FIG> and <FIG>, the outgassing station <NUM> is located in a room which is provided with dedicated locations for storing the storage vaults <NUM>.

In one embodiment, the method comprises receiving and inspecting cladding tubes to be filled with nuclear fuel pellets for obtaining the fuel rods <NUM>.

The cladding tubes are for example shipped in wooden boxes and unloaded manually.

The step of inspecting the cladding tubes comprises for example inspecting visually for transport damages (e.g. dents and scratches), checking that the cladding tube is empty and or drying the inside of the cladding tube to avoid presence of moisture.

Emptiness is checked e.g. using an optical emptiness checking device configured for projecting a light beam inside the cladding from one end and capturing light at the other end to check for any object obstructing propagation of the light.

Drying is performed e.g. by a drying device, blowing hot air inside the cladding tube.

As illustrated on <FIG>, the fuel rod manufacturing unit <NUM> comprises a cladding station <NUM>.

The cladding station <NUM> is configured for receiving the cladding tubes and performing the inspection of the received cladding tubes, and namely comprises for example an emptiness checking device and a drying device.

The welding station <NUM> and the fuel rod loading station <NUM> are configured to perform all the manufacturing steps of a fuel rod <NUM>.

The manufacturing of a fuel rod <NUM> comprises for example the following steps:.

Such loading including a turning step allows performing the loading with one single welding machine.

This allows minimizing the footprint of the welding station <NUM> and minimizing the cost of the fuel rod manufacturing unit <NUM> by avoiding the provision of two distinct welding machines. Turning the nuclear fuel rod <NUM> between welding of the plugs is time consuming but this is acceptable in the context of the rate of production foreseen for the fuel rod manufacturing unit <NUM>.

In addition, only one weighing device is needed. Weighing each cladding tube before and after filling with pellets allows to determine the uranium content.

Hence advantageously, the welding station <NUM> comprises one single welding machine and/or one single weighing device.

The loading of fuel rods <NUM> can advantageously be performed batchwise.

In such case, the empty weighing, plug welding, and pellet filling steps are operated for a batch of cladding tubes, theses cladding tubes are turned, and then the following steps of filled weighing, spring inserting, plug welding and releasing are performed for the batch of cladding tubes. Each batch of fuel rods <NUM> comprises for example approximately hundred fuel rods <NUM>.

The fuel rod loading station <NUM> is advantageously configured for creating pellet columns <NUM> and loading each pellet column <NUM> into a cladding tube. Preferably, the fuel rod loading station <NUM> is configured for creating a pellet column <NUM> at the specified length for loading into a next cladding tube while a previously created pellet column <NUM> is being loaded into a preceding cladding tube.

The method preferably comprises a step of inspecting the fuel rods <NUM>, i.e. once the fuel rods <NUM> are released from the welding station <NUM>.

The step of inspecting the fuel rods <NUM> may comprise scanning each fuel rod <NUM> for inspecting the fuel rod <NUM> in a nondestructive manner, testing helium leak of the fuel rod <NUM> and performing a final inspection including e.g. measuring the length of the fuel rod <NUM>, checking straightness of the fuel rod <NUM> and/or checking the fuel rod visual appearance.

Accordingly, the fuel rod inspection area <NUM> comprises one or several fuel rod inspection station(s).

A fuel rod inspection station is for example a leak testing station <NUM>, in particular a helium leak testing station. Such a leak testing station <NUM> is configured for identifying possible leaks of the fuel rod <NUM>, namely leaks of the fuel rod cladding, of the plugs and/or between the fuel rod cladding and one of the plugs.

Another fuel rod inspection station is for example a scanning station <NUM> configured for inspecting the fuel rods <NUM> in a nondestructive manner. The scanning station <NUM> is for example configured for passively scanning the gamma radiation emission count of the nuclear fuel pellets contained within the fuel rod <NUM> to check the enrichment level(s) and uniformity throughout the fuel rod <NUM>. Additionally, the scanning station <NUM> is for example configured for performing a gamma densitometer test to check the pellet column and plenum lengths, the presence of the required components such as the fuel rod spring and the absence of gaps between the pellets.

Another fuel rod inspection station is for example a final inspection station <NUM> configured for checking of geometrical characteristics of the fuel rod <NUM>, in particular measuring length of the fuel rod <NUM>, checking straightness of the fuel rod <NUM> and/or checking visual appearance of the fuel rod <NUM>. The final inspection station <NUM> comprises for example an inspection bench having a planar workplan.

The fuel rod manufacturing unit <NUM> optionally comprises a nuclear fuel rod rework station <NUM> configured for reworking a nuclear fuel rod <NUM> which has been identified as faulty during nuclear fuel rod inspection in the fuel rod inspection area <NUM> or during the fuel rod manufacturing in the welding station <NUM>.

The fuel rod manufacturing unit <NUM> comprises a controlled atmosphere enclosure <NUM> in which the atmosphere is controlled to ensure personnel safety and avoid the exit of particles of nuclear fuel that may arise from the pellets. The contour of the controlled atmosphere enclosure <NUM> is show in dotted lines of <FIG>.

The controlled atmosphere enclosure <NUM> extends to the stations where the pellets are not sealed into the fuel rods <NUM>.

In particular, in the present example, the pellet inspection area <NUM>, the outgassing station <NUM>, the fuel rod loading station <NUM> and the welding station <NUM> are located in the controlled atmosphere enclosure <NUM>.

The controlled atmosphere enclosure <NUM> is separated from the remaining of the fuel rod manufacturing unit <NUM>, namely from the pellet receiving area <NUM>, from the fuel rod inspection area <NUM> and from the cladding station <NUM>, including the emptiness checking device and the drying device.

The controlled atmosphere enclosure <NUM> is accessible to operators via a controlled entrance <NUM> and a controlled exit <NUM>.

As illustrated on <FIG>, the fuel rod manufacturing unit <NUM> is connected to the fuel assembly manufacturing unit <NUM> in a confined manner.

In the present invention two units or buildings or building modules are said to be connected "in a confined manner" when material can be transferred from one unit to the other of from one building to the other or from one building module to the other without transiting via the exterior.

The fuel rod manufacturing unit <NUM> and the fuel assembly manufacturing unit <NUM> are here placed side-by-side in a same building.

As illustrated on <FIG>, the building <NUM> includes four building modules including the first building module <NUM> and the second building module <NUM> housing the fuel assembly manufacturing unit <NUM> and a third building module <NUM> and a fourth building module <NUM> housing the fuel rod manufacturing unit <NUM>.

The welding station <NUM> and the fuel rod inspection area <NUM> are located in the third building module <NUM> which is side-by-side with the second building module <NUM>. The fuel rods <NUM> produced in the fuel rod manufacturing unit <NUM> can thus be transferred directly from the fuel rod inspection area <NUM> to the inserting station <NUM>.

The pellet receiving area <NUM>, the pellet inspection area <NUM> and the fuel rod loading station <NUM> are located in the fourth building module <NUM>.

In the present example, the outgassing station <NUM> and/or the rework station <NUM> are located in the fourth building module <NUM>.

The controlled atmosphere enclosure <NUM> extends in the fourth building module <NUM> and also to the third building module <NUM> such as to contain the welding station <NUM>. The third and fourth building modules <NUM>, <NUM> are here provided with internal walls for delimiting the controlled atmosphere enclosure <NUM> inside the third and fourth building modules <NUM>, <NUM>.

Advantageously, in a general manner, the nuclear fuel assembly manufacturing plant <NUM> comprises building modules arranged side-by-side with being aligned in the alignment direction A, the buildings modules housing several manufacturing units configured for implementation of respective steps of manufacturing a nuclear fuel assembly <NUM> (fuel rod manufacturing unit <NUM>, fuel assembly manufacturing unit <NUM>, etc.), each manufacturing unit being housed in one or several of the building modules dedicated to this manufacturing unit.

Manufacturing units of the nuclear fuel assembly manufacturing plant <NUM> may comprises a fuel assembly manufacturing unit <NUM> and/or a fuel rod manufacturing unit <NUM>, and also a fuel pellet manufacturing unit configured for manufacturing pellets from nuclear fuel powder and/or a fuel powder manufacturing unit configured for converting a nuclear fuel precursor into nuclear fuel powder, e.g. for converting gaseous UF<NUM> into UOz powder.

As visible on <FIG> and <FIG>, the fuel rod manufacturing unit <NUM> comprises conveyors for conveying the fuel rods <NUM> between the cladding station <NUM>, the welding station <NUM>, the fuel rod inspection area <NUM> and the inserting station <NUM>.

In the example, the fuel rod manufacturing unit <NUM> comprises a first conveying system <NUM> for conveying fuel rods <NUM> in a first direction and a second conveying system <NUM> for conveying fuel rods <NUM> in a second direction making a non-zero angle with the first direction. The second direction is here perpendicular to the first direction.

The fuel rod manufacturing unit <NUM> comprises a pivoting trolley <NUM> for transferring the fuel rods <NUM> from the first conveying system <NUM> to the second conveying system <NUM>. Preferably, the trolley is manually operated.

This arrangement allows conveying the fuel rods <NUM> easily without excessive automatization and with a low footprint of the fuel rod manufacturing unit <NUM> and the nuclear fuel assembly manufacturing plant <NUM> as a whole.

The second conveying system <NUM> is configured for transferring fuel rods <NUM> from the fuel rod inspection area <NUM> to the insertion station <NUM>. Besides, the second conveying system <NUM> may be used as buffer storage for storing fuel rods <NUM> temporarily between the fuel rod inspection area <NUM> and the inserting station <NUM>. Such storage avoids any supplementary manual operation.

In the illustrated embodiment, the first conveying system <NUM> is configured for conveying cladding tube from the cladding station <NUM> to the welding station <NUM> and for transferring fuel rods <NUM> from the welding station <NUM> successively to the fuel rod inspection stations <NUM>, <NUM>, <NUM> of the fuel rod inspection area <NUM>, and the second conveying system <NUM> is configured for conveying the fuel rods <NUM> from the pivoting trolley <NUM> to the inserting station <NUM>. Fuel rods <NUM> can be transferred manually from the last fuel rod inspection station (here final inspection station <NUM>) to the pivoting trolley <NUM>.

Each conveying system <NUM>, <NUM> comprise for example one or several transfer table(s), each transfer table comprising a slightly inclined ramp, whereby each cladding tube or fuel rod <NUM> can roll along the transfer table by gravity.

For example, one transfer table is provided between each pair of successive stations for transferring the cladding tube or fuel rod <NUM> from each station to the next one.

The first direction is parallel to the transverse direction T and the second direction is parallel to the alignment direction A such that the nuclear fuel rod <NUM> are conveyed towards the fuel assembly manufacturing unit <NUM>, more particularly towards the inserting station <NUM>.

In the illustrated example, at least one fuel rod inspection station is located beside the first conveying system <NUM> and/or a fuel rod inspection station is located at the end of the first conveying system <NUM>. For example, the final inspection station <NUM> is located at the end of the first conveying system <NUM> and the other fuel rod inspection station(s) is(are) located successively beside the first conveying system <NUM>.

Preferably, each fuel rod inspection station located beside the first conveying system <NUM> has its own specific conveying system for transferring a fuel rod <NUM> from the first conveying system <NUM> to the fuel rod inspection station and returning the inspected fuel rod <NUM> to the first conveying system <NUM>.

The placement of at least one fuel rod inspection station beside the first conveying system <NUM> has been chosen to optimize the footprint with still allowing good working conditions for the production and maintenance operators.

In the present case, the fuel rod inspection stations <NUM>, <NUM> are located beside the first conveying system <NUM> and distributed along the first conveying system <NUM> such that each fuel rod <NUM> is conveyed in register with the fuel rod inspection station <NUM>, <NUM>, inserted into the fuel rod inspection station <NUM>, <NUM> and transferred back the first conveying system <NUM> for being conveyed in register with the next fuel rod inspection station <NUM>, <NUM> or to the final inspection station <NUM> located at the end of the first conveying system <NUM>.

As indicated above, the nuclear fuel assembly manufacturing method comprises a step of cleaning a nuclear fuel assembly <NUM> and/or a step of inspecting a nuclear fuel assembly <NUM>.

The cleaning step and/or the inspecting step is/are performed with positioning the fuel assembly <NUM> in a vertical position and/or substantially at ground level.

The cleaning step is for example performed by air blowing cleaning and/or high pressure cleaning and/or washing with bubbling water and/or brushing cleaning, for example manual brushing cleaning.

The cleaning step and/or the inspecting step comprise(s) visually inspecting the fuel assembly <NUM> positioned vertically using at least one elevator for ascending and/or descending along the fuel assembly <NUM>.

As illustrated on <FIG>, a cleaning station <NUM> is configured for blowing with compressed air.

The cleaning station <NUM> comprises a telescopic enclosure <NUM> configured for receiving the fuel assembly <NUM> vertically.

The telescopic enclosure <NUM> comprises tubular segments <NUM> mounted telescopically one onto the others in a vertical direction such as to be movable between a retracted configuration and extended configuration in which the telescopic enclosure <NUM> defines a tube for receiving the fuel assembly <NUM>. The telescopic enclosure <NUM> is retracted and extended vertically. In the retracted position, the tubular segments <NUM> are for example retracted downwardly. Alternatively, they are retracted upwardly.

Retracting the telescopic enclosure <NUM> allows placing the fuel assembly <NUM> into the telescopic enclosure <NUM> without the need to lift the fuel assembly <NUM> at a high height. Extending the telescopic enclosure <NUM> allows enclosing the fuel assembly <NUM> for the blowing cleaning, with avoiding spreading of chips (generated during insertion of fuel rods <NUM> into the skeleton <NUM>) blown out of the fuel assembly <NUM> during blowing cleaning.

In view of deploying the telescopic enclosure <NUM>, the cleaning station <NUM> comprises for example a slide <NUM> vertically movable along a tower <NUM>, the slide <NUM> being connected to a tubular segment <NUM> of the telescopic enclosure <NUM> and to the blowing nozzle(s).

The cleaning station <NUM> comprises for example blowing nozzles <NUM> for blowing air through the fuel assembly <NUM>.

Advantageously, the blowing nozzles <NUM> are attached to a tubular segment <NUM> of the telescopic enclosure <NUM>, such that the blowing nozzles <NUM> are moved along the fuel assembly <NUM> upon closing the telescopic enclosure <NUM>. Hence, closure of the telescopic enclosure <NUM> and blowing cleaning can be performed simultaneously.

Advantageously, the cleaning station <NUM> is configured for performing insertion tests with a rod cluster control assembly (RCCA) and a thimble plug assembly (TPA).

In this view, as illustrated on <FIG>, the cleaning station <NUM> comprises a lifting tool <NUM> to which is suspended a dummy core component <NUM>, i.e. a RCCA or a TPA.

The lifting tool <NUM> comprises here a pivoting arm <NUM> which can pivot about a vertical pivoting axis B and a hoist which can slide along the pivoting arm <NUM> in view of placing the RCCA or TPA above the fuel assembly <NUM> received in the cleaning station <NUM> and lowering the RCCA or TPA into the fuel assembly <NUM> or moving the RCCA or TPA away. The RCCA or TPA can be moved up and down for example using a hoist for suspending the RCCA or TPA to the pivoting arm <NUM>.

As illustrated on <FIG>, optionally, the cleaning station <NUM> comprises an elevator <NUM> for moving an operator vertically along the fuel assembly <NUM> placed in the cleaning station <NUM>. This allows the operator to secure the top nozzle <NUM> before releasing the bridge crane <NUM>, to perform the RCCA & TPA tests, to supervise the cleaning operation and/or to perform a global visual inspection of the fuel assembly <NUM>. Such visual inspection would not be possible with a fixed enclosure instead of a telescopic enclosure <NUM>.

As visible on <FIG>, the fuel assembly inspection station <NUM> is configured for receiving the nuclear fuel assembly <NUM> vertically.

The fuel assembly inspection station <NUM> is configured for performing geometrical measurements on the fuel assembly <NUM> which is received in the fuel assembly inspection station <NUM>. Geometrical measurements may include length of the fuel assembly <NUM>, verticality of the fuel assembly <NUM>, distances between fuel rods <NUM>, distances between fuel rods <NUM> and guide thimbles <NUM>, twisting of spacer grids <NUM> and top nozzle <NUM> about the assembly axis L.

As illustrated on <FIG>, the fuel assembly inspection station <NUM> comprises a measuring assembly <NUM> comprising instruments configured for performing the geometrical measurements, the measuring assembly <NUM> being movable vertically along the fuel assembly <NUM> received in the fuel assembly inspection station <NUM>, such as to performed the measurements all along the fuel assembly <NUM>.

The measuring assembly <NUM> comprises for example a support frame <NUM> of annular shape which in use is fitted around the fuel assembly <NUM> and move along the fuel assembly <NUM>, the support frame <NUM> supporting instruments distributed on the circumference of the support frame <NUM>.

The instruments may comprise external probes to contact external surfaces of the fuel assembly <NUM> and measure external geometric parameters (external envelope, twisting, verticality. ) and/or internal probes configured for insertion between the fuel rods <NUM> to measure internal geometric parameters (distances between fuel rods <NUM>, distances between fuel rods <NUM> and guide thimbles <NUM>.

The fuel assembly inspection station <NUM> comprises an elevator <NUM> for moving an operator vertically along the fuel assembly <NUM> placed in the fuel assembly inspection station <NUM>. This allows the operator to perform a detailed visual inspection.

Optionally, the inspection station <NUM> is configured such that the fuel assembly <NUM> received in the inspection station <NUM> is rotatable around its vertical axis.

To this end, the inspection station <NUM> is for example equipped with a rotary support <NUM> which permit the operator to turn manually the fuel assembly <NUM> around its vertical axis L. This allows the operator to inspect visually each one of the four side faces of the fuel assembly <NUM>.

The support frame <NUM> is configured to allow rotation of the fuel assembly around its longitudinal axis L.

The rotary support <NUM> is configured to be blocked in a defined angular position during the geometrical measurements performed with the instruments supported by the support frame <NUM>.

In one embodiment, such a rotary feature is not implemented on the cleaning station <NUM>. The elevator <NUM> at the cleaning station <NUM> allows the operator to make a workmanship review of the fuel assembly <NUM> but not a detailed visual inspection on the four side faces of the fuel assembly as in the inspection station <NUM>. The elevator <NUM> of the station <NUM> is provided primarily for enabling the operator to secure the top nozzle before releasing the crane <NUM> and to perform the RCCA & TPA tests.

According to another aspect, the invention relates to a method of expanding a plant for manufacturing a nuclear fuel assembly <NUM> comprising fuel rods <NUM> arranged in a bundle and a skeleton <NUM> supporting the fuel rods <NUM>, the plant having a fuel assembly manufacturing unit <NUM> comprising a nuclear fuel rod inserting station <NUM> configured for insertion of fuel rods <NUM> into the skeleton <NUM> to obtain a fuel assembly <NUM> and a packaging station <NUM> configured for packaging the fuel assembly <NUM> into a fuel assembly container <NUM> in view of transportation, wherein said method includes a step of building at least one additional manufacturing unit and connecting the additional manufacturing unit to the fuel assembly manufacturing unit <NUM>.

The fuel assembly manufacturing unit <NUM> and the additional manufacturing unit are built sequentially. The fuel assembly manufacturing unit <NUM> is build and operated for a while (e.g. several months or several years) and then the additional manufacturing unit is build.

In the present invention, "connecting" manufacturing units means that the manufacturing units are connected such as to delimit together a confined area for the manufacture of nuclear fuel assemblies. The flow of material between the manufacturing units is operated in a continuous confined area, in particular without passing via the exterior to the open air.

According to one aspect, the method comprises adding an additional manufacturing unit configured for manufacturing components to be used in existing manufacturing unit(s) of the plant, in particular components to be used in the fuel assembly manufacturing unit <NUM>. These components have to be manufactured before performing the process steps performed in the already existing manufacturing units, in particular in the fuel assembly manufacturing unit <NUM>.

Hence, the plant is expanded in the upstream way when considering the process of manufacturing a nuclear fuel assembly <NUM>.

In a particular embodiment, an additional manufacturing unit is a fuel rod manufacturing unit <NUM> configured for manufacturing fuel rods <NUM> starting from pellets. These fuel rods <NUM> can thus be used in an inserting step performed in the inserting station <NUM> of the fuel assembly manufacturing unit <NUM>.

Further additional manufacturing units may be contemplated.

In one embodiment, the method includes a step of adding a fuel pellet manufacturing unit configured for manufacturing UOz based nuclear fuel pellets and connecting the fuel pellet manufacturing unit to the fuel rod manufacturing unit <NUM>.

The method may also include a step of adding a fuel powder manufacturing unit configured for converting a nuclear fuel precursor into nuclear fuel powder, e.g. gaseous UF<NUM> into UOz powder, and connecting the fuel powder manufacturing unit to the fuel pellet manufacturing unit.

In one embodiment, the method includes a step of adding a skeleton manufacturing unit configured for receiving separate skeleton parts and assembling the skeleton parts into skeleton <NUM>.

In one embodiment, the method includes a step of adding a pre-plugged cladding tube manufacturing unit configured for the manufacturing of cladding tubes having one plug welded at one end of the cladding tube. Such a pre-plugged cladding tube may be used directly in the fuel rod loading station <NUM>.

Each additional manufacturing unit may be located in the same building as an existing manufacturing unit or may be located in a new building that is connected to the building(s) of the existing the manufacturing unit(s).

In one embodiment, skeleton manufacturing unit and/or a pre-plugged cladding tube manufacturing unit is/are added to an existing nuclear fuel assembly manufacturing plant <NUM> comprising a fuel assembly manufacturing unit <NUM> and/or a fuel rod manufacturing unit <NUM>, with each being located in the same building as the fuel assembly manufacturing unit <NUM> or in the same building as the fuel rod manufacturing unit <NUM>.

For example, the added skeleton manufacturing unit and/or the added pre-plugged cladding tube manufacturing unit each can be located at a first floor of a fuel assembly manufacturing unit <NUM> and/or a fuel rod manufacturing unit <NUM>.

In one specific example, an added skeleton manufacturing unit is located at a first floor of an existing fuel assembly manufacturing unit <NUM> and/or an added pre-plugged cladding tube manufacturing unit is located at a first floor of an existing fuel rod manufacturing unit <NUM>.

In a specific embodiment, as illustrated on <FIG>, the method comprises sequentially building a fuel assembly manufacturing unit <NUM>, then adding a fuel rod manufacturing unit <NUM> to the existing fuel assembly manufacturing unit <NUM>, then, optionally, adding a fuel pellet manufacturing unit <NUM> and then, optionally, adding a fuel powder manufacturing unit <NUM>. Each addition is performed after operation the existing manufacturing unit(s) for a while, typically several months or several years.

According to one aspect, the method comprises adding an additional manufacturing unit which is a manufacturing unit of the same type as an existing manufacturing unit of the plant, i.e. a manufacturing unit configured for performing the same manufacturing steps.

In one embodiment, the additional manufacturing unit is a fuel assembly manufacturing unit <NUM> added to an existing fuel assembly manufacturing unit <NUM> for increasing production capacity.

In one embodiment the method includes a step of building an additional fuel pellet manufacturing unit <NUM> configured for manufacturing UOz based nuclear fuel pellets and connecting the additional fuel pellet manufacturing unit <NUM> to the additional fuel rod manufacturing unit <NUM>.

Optionally, the method includes a step of building an additional fuel powder manufacturing unit <NUM> configured for converting UF<NUM> into UOz and connecting the additional fuel powder manufacturing unit to the additional fuel pellet manufacturing unit <NUM>.

The method of expanding a nuclear fuel assembly manufacturing plant <NUM> avoids investing immediately in a complete nuclear fuel assembly manufacturing plant <NUM> including the fuel rod manufacturing unit <NUM>, and thus makes the starting investment easier. In addition, this allows gaining knowledge of the fuel assembly assembling before stepping to the fuel rod manufacturing starting from pellets which is more delicate.

Advantageously, complementary manufacturing units (fuel assembly manufacturing unit <NUM>, fuel rod manufacturing unit <NUM>, fuel pellet manufacturing unit <NUM> and fuel powder manufacturing unit <NUM>) are aligned in an alignment direction A and manufacturing units of the same type (e.g. two fuel assembly manufacturing units <NUM>) are placed side-by-side in the transverse direction T.

In addition, each pair of manufacturing units of the same type are preferably arranged symmetrically with respect to a vertical median plan S located between the two manufacturing units, in terms of location of their respective stations. The vertical median plan S extends vertically and along the alignment direction A.

In the example illustrated on <FIG> and <FIG>, the nuclear fuel assembly manufacturing plant <NUM> comprises two fuel assembly manufacturing units <NUM> and two fuel rod manufacturing units <NUM>. The two fuel assembly manufacturing units <NUM> are located side-by-side in the transverse direction T. Each fuel rod manufacturing unit <NUM> is aligned with a respective fuel assembly manufacturing unit <NUM> in the alignment direction A.

The manufacturing units are located in a 2x2 matrix pattern.

The two fuel assembly manufacturing units <NUM> are configured symmetrically with respect to a vertical median plan S, in terms of disposition of their respective stations. The two fuel rod manufacturing units <NUM> are configured symmetrically with respect to the vertical median plan S, in terms of disposition of their respective stations.

According to one aspect of the invention, e.g. for allowing to implement the method of expanding the nuclear fuel assembly manufacturing plant <NUM>, this latter is of modular construction.

The nuclear fuel assembly manufacturing plant <NUM> is for example configured for sequentially adding manufacturing units of different types for performing different steps of the manufacture of a fuel assembly <NUM> (fuel assembly manufacturing unit <NUM>, fuel rod manufacturing unit <NUM>.

The nuclear fuel assembly manufacturing plant <NUM> is configured for connecting the manufacturing units of different types in the alignment direction A, whereby the nuclear fuel assembly manufacturing plant <NUM> can be expanded with adding complementary manufacturing units (fuel rod manufacturing unit <NUM>, fuel pellet manufacturing unit <NUM> and fuel powder manufacturing unit <NUM>) in the alignment direction A.

The nuclear fuel assembly manufacturing plant <NUM> illustrated on <FIG> and <FIG> comprises a fuel assembly manufacturing unit <NUM> and a fuel rod manufacturing unit <NUM> and could be expanded by adding a fuel pellet manufacturing unit and optionally a fuel powder manufacturing unit.

Each manufacturing unit (fuel assembly manufacturing unit, fuel rod manufacturing unit. ) comprises utility systems each configured to provide a utility necessary for implementation of the method and the operation of the plant.

The utility systems of each manufacturing unit may include one or several among the following: an electric supply system, a computer network, a heating, ventilating and air conditioning system, a gaz supply system, a water supply network, a wastewater network, a compressed air supply system, a process ventilation system, an airborne contamination surveillance system, a criticality alarm system, a fire sections and doors system, a fire detector and alarm system.

Each manufacturing unit may comprise at least one utility system configured for interconnection with corresponding utility system of another manufacturing unit connected to said manufacturing unit and/or at least one utility system configured to operate independently from the corresponding utility system of another manufacturing unit connected to said manufacturing unit.

In one exemplary embodiment, at least one or each utility system of each manufacturing unit is natively configured for interconnection with a corresponding utility system of an upstream manufacturing unit that may potentially be constructed later side-by-side with the manufacturing unit.

Besides, each manufacturing unit is provided for interconnection with an additional manufacturing unit with delimiting a confined area.

Alternatively, at least one or each utility system of each manufacturing unit is independent from the corresponding utility system of each other manufacturing unit. This allows providing rightsized utility systems and thus limits the investment for the building of a manufacturing unit.

In a specific embodiment, each manufacturing unit comprises at least one utility system configured for interconnection with corresponding utility system of each other manufacturing unit and at least one utility configured to be independent from the corresponding utility system of each other manufacturing unit.

In such case, the utility system configured for interconnection is for example an alarm system, which is useful for propagating an alarm in all the manufacturing units or a computer network which is useful e.g. for transmission of information between manufacturing units, e.g. for traceability of the fuel assembly component during the manufacture of the fuel assembly.

In the example of <FIG> and <FIG>, the fuel assembly manufacturing unit <NUM> and the fuel rod manufacturing unit <NUM> are arranged side-by-side. The fuel assembly manufacturing unit <NUM> is configured for connecting a fuel rod manufacturing unit <NUM> on a side of the fuel assembly manufacturing unit <NUM>.

The fuel assembly manufacturing unit <NUM> and the fuel rod manufacturing unit <NUM> each comprise utility systems.

When constructed alone, each utility system of the fuel assembly manufacturing unit <NUM> is natively configured for connection with a corresponding utility system of the fuel rod manufacturing unit <NUM> that may potentially be constructed later side-by-side with the fuel assembly manufacturing unit <NUM>.

Besides, the fuel assembly manufacturing unit <NUM> is provided for interconnection with the fuel rod manufacturing unit <NUM> as regards the path of the fuel rods <NUM>.

Indeed, as it is visible on <FIG>, the final step of the nuclear fuel rod production is performed in the fuel rod inspection area <NUM> which is adjacent to the inserting station <NUM>. The fuel rods <NUM> can thus be transferred from the fuel rod inspection area <NUM> to the inserting station <NUM> easily, here via the second conveying system <NUM>.

Advantageously, the nuclear fuel assembly manufacturing plant <NUM> comprising a fuel assembly manufacturing unit <NUM> and a fuel rod manufacturing unit <NUM> is housed in a building made of several building modules, the fuel assembly manufacturing unit <NUM> and the fuel rod manufacturing unit <NUM> being housed in respective building module(s).

In other words, the fuel assembly manufacturing unit <NUM> is received in one or several building module(s) of the building which are distinct from the building module(s) receiving the fuel rod manufacturing unit <NUM>.

In a more general manner, advantageously, a nuclear fuel assembly manufacturing plant comprising a first manufacturing unit and a second manufacturing different from one another and configured for performing two distinct steps is housed in a building made of building modules, the first manufacturing unit being housed in one or several building module(s) distinct from building module(s) receiving the second manufacturing unit.

This allows constructing the manufacturing units sequentially, e.g. with constructing and operating a first manufacturing unit before adding the second manufacturing unit to the fuel assembly manufacturing plant. The different aspects of the invention are advantageous independently from each other. In addition, the specific features of the stations of the manufacturing unit are also advantageous independently from the manufacturing method and plant.

For example, the specific features of the pellet inspection area, the outgassing station, the fuel rod loading station, the welding station, the fuel rod inspection area, the fuel assembly cleaning station and/or the fuel assembly inspection station are advantageous in isolation or in combination. Hence the invention relates in a general manner to a fuel assembly inspection station configured for inspection of the fuel assembly positioned in a vertical position and/or comprising an elevator for an operator.

Besides, the invention also relates in a general manner to a fuel assembly cleaning station configured for inspection of the fuel assembly positioned in a vertical position and/or comprising an elevator for an operator and/or comprising a telescopic enclosure.

Claim 1:
Method for manufacturing a nuclear fuel assembly (<NUM>) comprising nuclear fuel rods (<NUM>) arranged in a bundle and a skeleton (<NUM>) supporting the fuel rods (<NUM>), the method comprising the steps of inserting fuel rods (<NUM>) into the skeleton (<NUM>) to obtain a fuel assembly (<NUM>) and packaging the fuel assembly (<NUM>) in view of transportation, the steps being performed in a same nuclear fuel assembly manufacturing plant (<NUM>),
wherein the steps of inserting fuel rods (<NUM>) and packaging the fuel assembly (<NUM>) are operated in a fuel assembly manufacturing unit (<NUM>)
wherein the nuclear fuel assembly manufacturing plant (<NUM>) comprises a fuel rod manufacturing unit (<NUM>) side-by-side with the fuel assembly manufacturing unit (<NUM>) such that fuel rods (<NUM>) produced in the fuel rod manufacturing unit (<NUM>) can be transferred directly from a fuel rod inspection area (<NUM>) of the fuel rod manufacturing unit (<NUM>) to the fuel rod insertion station (<NUM>) of the fuel assembly manufacturing unit (<NUM>),
characterized in that the fuel rod manufacturing unit (<NUM>) and the fuel assembly manufacturing unit (<NUM>) are placed side-by-side in a same building (<NUM>) including four building modules, the four building modules including a first building module (<NUM>) and a second building module (<NUM>) housing the fuel manufacturing unit (<NUM>) and a third building module (<NUM>) and a fourth building module (<NUM>) housing the fuel rod manufacturing unit (<NUM>), a welding station (<NUM>) and the fuel rod inspection area (<NUM>) of the fuel rod manufacturing unit (<NUM>) being located in the third building module (<NUM>) which is side-by-side with the second building module (<NUM>).