Patent Description:
A nuclear fuel assembly generally comprises fuel rods containing fissile materials and an armature for supporting the fuel rods. The armature comprises generally a lower nozzle and an upper nozzle spaced along an assembly axis, guide thimbles (also named guide tubes) connecting the lower nozzle to the upper nozzle, and spacer grids distributed along the guide thimbles. The fuel rods are positioned between the lower nozzle and the upper nozzle with the guide thimbles extending though the spacer grids, the latter being configured for supporting the fuel rods axially and transversely with maintaining the fuel rods in a transversely spaced relationship.

Each spacer grid may be made of a plurality of tubular spacer grid elements assembled together to form a spacer grid, each spacer grid element being configured for receiving respectively one of the fuel rods.

<CIT> discloses a spacer grid made of a plurality of tubular spacer grid elements. Each spacer grid element is of hexagonal contour with fuel rod supporting features distributed at <NUM>°. An alternative spacer element is known from <CIT>.

A problem that may be encountered with spacer grids is the occurrence of fretting on the fuel rods at the points of contact of the fuel rods with the spacer grid, thus leading to fuel rod failure.

One of the aims of the invention is to provide a spacer grid element enabling to better support fuel rods, namely with improving fretting robustness and avoiding fuel rod failures.

To this end, the invention proposes a spacer grid element of a nuclear fuel assembly spacer grid, the spacer grid element defining a cell extending along an extension axis for receiving a nuclear fuel rod, the spacer grid element exhibiting a polygonal cross-section including at least three supporting sides distributed around the extension axis, wherein each supporting side comprises an inwardly protruding corrugation onto which is formed at least one spring for supporting a fuel rod extending through the spacer grid element.

A spring placed on an inwardly protruding corrugation has the advantage that the spring height can be easily adjusted to the cell and fuel rod dimensions. Besides, the corrugation limit the movability of the fuel rod in the cell. Furthermore, it provides a flow channel to improve the cooling of the fuel rod.

In other embodiments, the spacer grid element comprises one or several following optional features, taken individually or in any technically feasible combination:.

The invention also relates to a spacer grid for a nuclear fuel assembly, the spacer grid comprising a plurality of spacer grid elements as defined above, the spacer grid elements being assembled together to form the spacer grid.

The invention also relates to a spacer grid for a nuclear fuel assembly comprising a plurality of spacer grid elements as defined above and manufactured in a single piece of material, e.g. by additive manufacturing.

The invention also relates to a nuclear fuel assembly comprising a bundle of fuel rods and an armature for supporting the fuel rods, the armature comprising at least one spacer grid the spacer grids as defined above.

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

The nuclear fuel assembly <NUM> of <FIG> comprises a bundle of nuclear fuel rods <NUM> and an armature <NUM> for supporting the fuel rods <NUM>. The fuel assembly <NUM> is elongated along an assembly axis L.

The armature <NUM> comprises a lower nozzle <NUM>, an upper nozzle <NUM>, a plurality of guide thimbles <NUM> and a plurality of spacer grids <NUM>.

The lower nozzle <NUM> and the upper nozzle <NUM> are spaced along the assembly axis L. The guide thimbles <NUM> extend parallel to assembly axis L and connect the lower nozzle <NUM> to the upper nozzle <NUM>. Each guide thimble <NUM> opens upwards through the upper nozzle <NUM> for allowing insertion of a control rod (not shown) into the guide thimble <NUM>.

The spacer grids <NUM> are distributed along the guide thimbles <NUM> and are secured to the guide thimbles <NUM>, for instance by welding. Each spacer grid <NUM> extends transversely to the assembly axis L.

Each fuel rod <NUM> comprises for example a tubular cladding, pellets of nuclear fuel stacked inside the cladding and end plus closing the ends of the cladding (not shown).

Each fuel rod <NUM> extends parallel to the assembly axis L through the spacer grids <NUM>, with being supported transversely and longitudinally relative to assembly axis L by the spacer grids <NUM>. The fuel rods <NUM> are maintained in a transversely spaced relationship by the spacer grids <NUM>.

In operation, the fuel assembly <NUM> is placed in the core of a nuclear reactor with the lower nozzle <NUM> resting on a bottom plate <NUM> of the core and the assembly axis L being substantially vertical. A coolant flows upwardly from an inlet of the bottom plate <NUM>, through the lower nozzle <NUM> and between the fuel rods <NUM>, the spacer grids <NUM> and the upper nozzle <NUM> as illustrated by arrow F on <FIG>, with flowing along the fuel rods <NUM>.

The bundle of fuel rods <NUM> of the fuel assembly <NUM> exhibits preferably a hexagonal contour, the fuel rods <NUM> being maintained transversely in a space relationship with the fuel rod <NUM> located at the nodes on an imaginary hexagonal network.

The guide thimbles <NUM> are integrated in the bundle and received at nodes of the imaginary hexagonal network.

The nuclear fuel assembly <NUM> is for example designed for a VVER (acronym for Russian "Vodo-Vodianoï Energuetitcheski Reaktor"). The nuclear fuel assemblies <NUM> for VVER generally have fuel rods <NUM> arranged in a bundle having a hexagonal contour.

In the fuel assembly <NUM> represented on <FIG>, the spacer grids <NUM> are similar to each other and one spacer grid <NUM> will be further described with reference to <FIG>.

As illustrated on <FIG>, the spacer grid <NUM> comprises a plurality of spacer grid elements <NUM>. Each spacer grid element <NUM> is tubular and defines a respective cell of the spaced grid <NUM>, each spaced grid element <NUM> being configured for receiving a respective one of the fuel rods <NUM>.

<FIG> shows the spacer grid <NUM> only partially. More specifically, <FIG> shows only a seven cells unit formed of seven spacer grid elements <NUM>.

The spacer grid elements <NUM> are arranged at the nodes of an imaginary hexagonal network, and <FIG> illustrates a unit of seven cells including one central spacer grid element <NUM> surrounded by six spacer grid elements <NUM> located at the corners of an imaginary hexagon.

The spacer grid elements <NUM> of <FIG> are similar and only one of them will be further described with reference to <FIG> and <FIG>.

The spacer grid element <NUM> extends along a respective extension axis A that is perpendicular to the plane of the spacer grid <NUM> (plane of <FIG>). The extension axis A is substantially parallel to the assembly axis L. The fuel rod <NUM> received in each spacer grid element <NUM> extends through this spacer grid element <NUM> along the extension axis A.

The spacer grid element <NUM> has a polygonal cross-section including at least two supporting sides <NUM> distributed around the extension axis A.

More specifically, the spacer grid element <NUM> has a pseudo-polygonal cross-section including at least two supporting sides <NUM> distributed around the extension axis A.

The term "pseudo-polygonal" is used to account for the fact that the cross-section has sides defining a contour of general polygonal shape, some sides being however not rectilinear in cross-section but round or provided with shapes, in particular corrugations, as it will be explained below.

Each supporting sides <NUM> is configured to contact the fuel rod <NUM> extending through the spacer grid element <NUM> for supporting said fuel rod <NUM>.

In one embodiment, each side of the polygonal cross-section is a supporting side <NUM>.

Alternatively, the spacer grid element <NUM> comprises at least one non-supporting side <NUM>. Each non-supporting side <NUM> is configured for not contacting the fuel rod extending through the spacer grid element <NUM>.

The spacer grid element <NUM> comprises for example at least one non-supporting side <NUM> located between two supporting sides <NUM>.

The spacer grid element <NUM> comprises for example supporting sides <NUM> alternating with non-supporting sides <NUM>. In such an example, each supporting side <NUM> is located between two adjacent non-supporting sides <NUM> and each non-supporting side <NUM> is located between two adjacent supporting sides <NUM>.

In a particular embodiment, each spacer grid element <NUM> has a hexagonal cross-section with six sides including three supporting sides <NUM> distributed at <NUM>° around the extension axis A alternating with three non-supporting sides <NUM>.

Each supporting side <NUM> comprises an inwardly protruding central corrugation <NUM> located between two side walls <NUM>. Each side wall <NUM> connects one edge of the central corrugation <NUM> to the adjacent side. Each adjacent side is a supporting side <NUM> or a non-supporting side <NUM> as a function of the configuration of the cell. In the illustrated example, each adjacent side is a non-supporting side <NUM>.

Advantageously, the corrugation <NUM> extends all along the spacer grid element <NUM>, that is from one end to the other of the spacer grid element <NUM> along the extension axis A.

Preferably, the side walls <NUM> of the supporting side <NUM> extends along the polygonal contour of the spacer grid element <NUM>, and each central corrugation <NUM> is offset inwardly with respect to the polygonal contour of the spacer grid element <NUM>.

On each supporting side <NUM>, the central corrugation <NUM> comprises for example a central wall <NUM> and two lateral walls <NUM>, each lateral wall <NUM> connecting the contact wall <NUM> to a respective side wall <NUM> of the supporting side <NUM>.

The central wall <NUM> is offset inwardly with respect to side of the polygonal contour of the spacer grid element <NUM> corresponding to the supporting side <NUM>.

As represented in <FIG>, the contact wall <NUM> and the two edge walls <NUM> are substantially parallel.

Each lateral wall <NUM> extends for example obliquely with respect to said side of the polygonal contour of the spacer grid element <NUM> for connecting to the corresponding side wall <NUM>. The two lateral walls <NUM> extend from the central <NUM> with diverging one from the other towards the side walls <NUM>.

In a view along the extension axis A of the spacer grid element <NUM>, each lateral connection wall <NUM> is inclined relative to the contact wall <NUM>, for example at an angle of <NUM>°.

As the distance between the extension axis A and the spacer grid element <NUM> is at its minimum at each contact wall <NUM> of the corrugations <NUM>, the fuel rod <NUM> extending through the spacer grid element <NUM> along the extension axis A is in contact only with the inwardly protruding corrugations <NUM> of supporting sides <NUM> of the spacer grid element <NUM>.

Preferably, the corrugations <NUM> of the supporting sides <NUM> are identical. Only one of them will be further described.

At least one spring <NUM>, and preferably two springs <NUM>, are formed onto the corrugation <NUM>, the spring(s) <NUM> being configured for supporting the fuel rod <NUM> extending inside the spacer grid cell <NUM>.

Each spring <NUM> is for example elongated along the extension axis A and bridge-like.

As illustrated on <FIG>, each corrugation <NUM> is for example provided with a pair of springs <NUM>. The two springs <NUM> extend along each other.

Each pair of springs <NUM> is formed in the corrugation <NUM> for example between a central slot <NUM> formed in the contact wall <NUM> and two lateral slots <NUM> each formed in one of the two connection walls <NUM> of the corrugation <NUM>.

Each spring <NUM> is formed at the junction of a connection wall <NUM> and the contact wall <NUM>, more specifically between one central slot <NUM> formed in the contact wall <NUM> and one lateral slot <NUM> formed in the connection wall <NUM>.

As illustrated on <FIG>, in one exemplary embodiment, the central slot <NUM> is axially longer than the lateral slots <NUM>.

Each spring <NUM> comprises for example a longitudinal contact wing <NUM> formed in the contact wall <NUM> and a longitudinal lateral wing <NUM> formed in one of the connection wall <NUM>. The contact wing <NUM> and the lateral wing <NUM> extend over the whole length of the spring <NUM>. The lateral wing <NUM> is inclined relative to the contact wing <NUM>.

Advantageously, in an embodiment, each spring <NUM> has a non-rectilinear cross-section in each plane perpendicular to the extension axis A.

As illustrated on <FIG>, in each plane perpendicular to the extension axis A, the cross-section is arched with the concavity oriented inwardly providing on the contact wing <NUM> a convex contact surface for the contact with the fuel rod <NUM>.

In one exemplary embodiment, each contact wing <NUM> is arched lengthwise. The contact wing <NUM> describes an arch in the lengthwise direction of the spring <NUM>. The middle section of the contact wing <NUM> is closer to the extension axis A than the end sections of the contact wing <NUM>.

Optionally, each contact wing <NUM> is arched transversely. The transverse concavity of each contact wing <NUM> is directed radially outwardly relative to the extension axis A.

Optionally, each contact wing <NUM> is also arched laterally towards the associated spring <NUM> of the pair of springs. The springs <NUM> of each pair are closer at their middle than at their axial ends.

Each contact wing <NUM> is preferably of substantially constant width along the length of the spring <NUM>.

Each lateral wing <NUM> is preferably flat, with extending laterally from the corresponding contact wing <NUM> in the plane of the corresponding connection wall <NUM>.

In one embodiment, as illustrated in <FIG>, the width of the central slot <NUM> is of substantially constant width along its length and extends along a rectilinear line.

In one embodiment, as illustrated on <FIG>, each lateral slot <NUM> is C-shaped. Each lateral slot <NUM> has a width increasing from the ends of the lateral slot <NUM> towards the center of the lateral slot <NUM>. Each lateral slot <NUM> has a larger width in the center thereof.

The free longitudinal edge of each lateral wing <NUM> (along the lateral slot <NUM>) is curvilinear and curved away from the junction zone <NUM> between the lateral wing <NUM> and the contact wing <NUM>. The junction zone <NUM> is also curved away from the free longitudinal edge of each lateral wing <NUM> due to the curvature of the contact wing <NUM>.

Each lateral wing <NUM> has a width varying along the length of the spring <NUM> and reaches its maximal width at its center. Each lateral wing <NUM> is larger at the center than at the ends.

In one embodiment, as illustrated on <FIG> and <FIG>, each spacer grid cell <NUM> is defined by a respective spacer grid element <NUM>, the spacer grid element <NUM> being assembled to define the spaced grid <NUM>.

Each spacer grid element <NUM> defines a respective fuel cell <NUM>. Each spacer grid element <NUM> is a tube extending along the extension axis of the fuel cell <NUM> and having the cross-section of the spacer grid cell <NUM>.

The spacer grid elements <NUM> are preferably made of zirconium alloy. In an alternative embodiment the spacer grid elements <NUM> are made of Ni-based alloy or of another material with high mechanical characteristics such as for instance Ph13.

As illustrated in <FIG>, in order to form a spacer grid <NUM>, each side <NUM>, <NUM> of each spacer grid element <NUM> is placed in contact with a side <NUM>, <NUM> of another spacer grid element <NUM>.

In an exemplary embodiment shown in <FIG>, the spacer grid elements <NUM> are arranged such that, for each spacer grid element <NUM>, each supporting side <NUM> of the spacer grid element <NUM> in contact with a side of another spacer grid element <NUM> is in contact with a non-supporting side <NUM> of said other spacer grid element <NUM>. Each spacer grid element <NUM> is manufactured individually, for example by extruding or by sheet metal processing, bending and welding. A spacer grid <NUM> is then manufactured by welding a plurality of spacer grid elements <NUM> together. In an alternative embodiment, the spacer grid elements <NUM> are manufactured in a single piece of material, e.g. by additive manufacturing. The spacer grid elements <NUM> are all manufactured at once, thus forming the spacer grid <NUM>.

In a preferred embodiment, in each pair of adjacent spacer grid elements <NUM>, the two adjacent sides of the two spacer grid elements <NUM> are made in a single piece of material.

Advantageously, in case two spacer grid elements <NUM> are adjacent via two flat non-supporting sides <NUM>, only one flat wall common to the two spacer grid elements <NUM> and defining the two non-supporting sides <NUM> is provided. This allows reducing material and avoid internal corrosion in between adjacent sides.

Advantageously, in case two adjacent spacer grid elements <NUM> are adjacent via a supporting side <NUM> of one of the two spacer grid cells <NUM> and non-supporting sides <NUM> of the other one of the two spacer grid elements <NUM>, only one wall is manufactured.

This wall comprises a central corrugation <NUM> protruding inwardly with respect to one of the two spacer grid element <NUM> for defining the supporting side <NUM> and protruding outwardly with respect to the other spacer grid element <NUM> and defining the non-supporting side <NUM>.

As shown in <FIG> and <FIG>, each non-supporting side <NUM> is for example flat. Each non-supporting side <NUM> extends along one respective side of the polygonal contour of the spacer grid element <NUM>.

As illustrated on <FIG>, each fuel rod <NUM> is in contact with each spring <NUM> of each pair of springs of each corrugation <NUM> of the spacer grid element <NUM> in which the fuel rod <NUM> is inserted.

The springs <NUM> supports the fuel rod <NUM> transversely to the extension axis A to support the fuel rod <NUM> transversely and longitudinally by friction between the springs <NUM> and the fuel rod <NUM>.

The provision of each spring onto a corrugation <NUM> of the spacer grid element <NUM> allows obtaining a spacer grid <NUM> that has appropriate mechanical features for supporting the fuel rods <NUM>.

The corrugation <NUM> of each spacer grid element <NUM> reinforces the spacer grid, with forming box shaped structure, e.g. when applying a supporting side <NUM> of a spacer grid element to a non-supporting side <NUM> or a supporting side of another spacer grid element <NUM>.

The springs <NUM> exhibit a 3D-shape that provides satisfactory support with reduced fretting risks.

The widthwise curved elongated springs <NUM> provide sufficient flexion stiffness for obtaining at least one line contact between the fuel rod <NUM> and each spring <NUM> over a length sufficient for limiting local contact stress. The contact between the springs <NUM> of each pair of springs <NUM> and the fuel rod <NUM> must be sufficiently strong while avoiding fretting, namely when the fuel rod <NUM> vibrates in use due to the high velocity fluid flow.

The lateral wing <NUM> being inclined relative to the contact wing <NUM> imparts flexion stiffness to the spring <NUM>. The flexion stiffness of the spring <NUM> and the deformation of the spring <NUM> under load namely depend upon the inclination between the wings <NUM>, <NUM>, and upon the width of the lateral wing <NUM> along the spring <NUM>.

The embedding of the fuel rod <NUM> in each spacer grid element <NUM> by the springs <NUM> enables an additional clamping of the fuel rod <NUM>, which prevents the risk of fuel rod bow. This additional clamping enhances the overall fuel assembly stiffness and minimizes the sensitivity to fuel assembly bow.

The central slot <NUM> and the lateral slots <NUM> of each corrugation <NUM> define several openings in each spacer grid elements <NUM>, which enable a hydraulic exchange between the different cells of the spacer grid <NUM>.

The invention is not limited to the examples and variants presented above. Other examples and variants may be contemplated.

In the example presented above, each non-supporting side <NUM> of the spacer grid element <NUM> is flat or substantially flat.

In an alternative embodiment, as illustrated in <FIG>, each non-supporting side <NUM> of the spacer grid element <NUM> comprises an inwardly protruding central corrugation <NUM>. Such a corrugation <NUM> can reinforce the non-supporting side <NUM>.

In the example illustrated on <FIG>, the spaced grid element <NUM> exhibits a polygonal cross-section, in particular with a hexagonal cross-section, and comprises supporting sides <NUM> alternating with non-supporting sides <NUM>,.

In an alternative embodiment, as illustrated in <FIG>, the spaced grid element <NUM> exhibits a polygonal cross-section, in particular with a hexagonal cross-section, each sides of the polygonal cross-section being a supporting sides <NUM>.

In a particular embodiment, as illustrated on <FIG>, the spacer grid element <NUM> has a pseudo-hexagonal cross-section with six supporting sides <NUM> distributed at <NUM>° around the extension axis A. Each supporting side <NUM>, i.e. the six sides, is as described above, and comprises in particular an inwardly protruding central corrugation <NUM> located between two side walls <NUM> and provided with at least one spring <NUM>.

Advantageously, as illustrated on <FIG>, each spring <NUM> is configured for an elongated contact with the fuel rod <NUM> extending through the spacer grid element <NUM>.

In particular, when the spring <NUM> comprises a contact wing <NUM>, the contact wing <NUM> of each spring <NUM> is configured for contacting the fuel rod <NUM> along at least one line of contact <NUM> between the fuel rod <NUM> and the spring <NUM>.

In one embodiment, each spring <NUM> is configured for an elongated contact with the fuel rod <NUM> along a one single line of contact.

In particular, when the spring <NUM> comprises a contact wing <NUM>, the contact wing <NUM> of each spring <NUM> is configured for contacting the fuel rod <NUM> along a single line contact <NUM> between the fuel rod <NUM> and the spring <NUM>.

In another embodiment, as illustrated in <FIG>, each spring <NUM> is configured for an elongated contact with the fuel rod <NUM> along at least two separate lines of contact.

In particular, the spring <NUM> has a W-shaped contact surface (e.g. the contact wing <NUM>), so that two sections of the contact surface are closer to the extension axis A than the remainder of the spring <NUM> to define two separate contact lines <NUM> with the fuel rod <NUM>.

The central slot <NUM> provided in a supporting side <NUM> between two springs <NUM> may exhibit different shapes.

In on embodiment illustrated on <FIG>, the central slot <NUM> has a width that decreases from the axial ends of the central slot <NUM> to the middle of the central slot <NUM>.

In an alternative embodiment illustrated in <FIG>, the width of the central slot <NUM> increases from the axial end towards the middle of the central slot <NUM>.

In an alternative embodiment illustrated in <FIG>, the central slot <NUM> is I-shaped. The central slot <NUM> is of substantially constant width along its length and extends along a rectilinear line.

The laterals slots <NUM> provided in a supporting side <NUM> along springs <NUM> may exhibit different shapes.

In on embodiment illustrated on <FIG>, each lateral slot is C-shaped. It comprises a rectilinear edge and an arched edge opposed to the rectilinear edge. The arched edged is e.g. adjacent the spring <NUM>, the rectilinear edge being opposite the spring <NUM>.

In another embodiment illustrated on <FIG>, each lateral slot <NUM> is D-shaped. Each lateral slot <NUM> extends along an arcuate line.

In another embodiment illustrated on <FIG>, each lateral slot <NUM> is I-shaped. Each lateral slot <NUM> is of substantially constant width along its length and extends along a rectilinear line.

In an alternative embodiment illustrated in <FIG>, each lateral slot <NUM> is S-shaped. It extends along a curvilinear line having two opposed curvatures along its length.

The invention is not limited to the illustrated embodiments, and the different shapes of central slot <NUM> and lateral slots <NUM> illustrated on the figures may be combined differently.

As illustrated on <FIG>, each spring <NUM> is formed between one central slot <NUM> and one lateral slot <NUM>.

In an alternative embodiment, each spring <NUM> is formed between multiple central slots <NUM> and one lateral slot <NUM>. In particular, each spring <NUM> is formed between two central slots <NUM> and one lateral slot <NUM>. This embodiment allows to have a connection between the two springs <NUM>, forming an H or a X-shape.

In an alternative embodiment, each spring <NUM> is formed between one central slot <NUM> and multiple lateral slots <NUM>. The lateral slots <NUM> are, for example, I-shaped and are all aligned with each other.

The invention is not limited to the described embodiments and the different amounts of central slot <NUM> and lateral slots <NUM> described may be combined differently.

As illustrated on <FIG>, the corrugations <NUM> of the supporting sides <NUM> extends rectilinearly along the extension axis A.

Corrugations provided on the sides of the spacer grid elements <NUM>,that corrugations <NUM> of supporting sides <NUM> or corrugations <NUM> of non-supporting sides <NUM> define channels for the coolant and may be used to orientate the coolant flow at the exit of the spacer grid.

Indeed, a corrugation <NUM>, <NUM> provided in a supporting side <NUM> or a non-supporting side <NUM> of a spacer grid element <NUM> can be shaped such as to generate transverse flow of the coolant flowing through the spacer grid <NUM>.

In this view, the corrugation <NUM>, <NUM> can extend along the extension axis A with at least one end portion of the corrugation <NUM>, <NUM> (corresponding to the downstream end of the spacer grid element <NUM> when considering the direction of flow of the coolant through the spacer grid <NUM>) being inclined relative to the extension axis A. The angle of inclination is for example comprised between <NUM>° and <NUM>°.

In one example, the corrugation <NUM>, <NUM> extends along a rectilinear line inclined relative to the extension axis A.

As illustrated in <FIG>, in one example, a corrugation <NUM> of a non-supporting side <NUM> extends along a rectilinear line ("I-shaped corrugation") inclined relative to the extension axis A. The downstream end of the corrugation <NUM> is in particular inclined relative to the extension axis A at a downstream end 25A of the corrugation.

In another example, the corrugation <NUM>, <NUM> extends along a curvilinear line inclined relative to the extension axis A at least at the downstream end of the corrugation <NUM>, <NUM>.

As illustrated in <FIG>, in one example, a corrugation <NUM> of a non-supporting side <NUM> extends along a arcuate line ("C-shaped corrugation").

As illustrated on <FIG>, in one example, a corrugation <NUM> of a non-supporting side <NUM> extends along a curvilinear line with two opposed curvatures ("S-shaped" corrugation").

Claim 1:
Spacer grid element for
a nuclear fuel assembly spacer grid (<NUM>), the spacer grid element (<NUM>) defining a cell (<NUM>) extending along an extension axis (A) for receiving a nuclear fuel rod (<NUM>), the spacer grid element (<NUM>) exhibiting a polygonal cross-section including at least three supporting sides (<NUM>) distributed around the extension axis (A),
wherein each supporting side (<NUM>) comprises an inwardly protruding corrugation (<NUM>),
characterised in that at least one spring (<NUM>) is formed onto the corrugation (<NUM>), the spring (<NUM>) being configured for supporting a fuel rod (<NUM>) extending through the spacer grid element (<NUM>).