CA1038505A - Grid assembly structure for nuclear fuel bundle - Google Patents
Grid assembly structure for nuclear fuel bundleInfo
- Publication number
- CA1038505A CA1038505A CA226,956A CA226956A CA1038505A CA 1038505 A CA1038505 A CA 1038505A CA 226956 A CA226956 A CA 226956A CA 1038505 A CA1038505 A CA 1038505A
- Authority
- CA
- Canada
- Prior art keywords
- fuel
- grid
- tie rod
- bundle
- fuel bundle
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
- G21C—NUCLEAR REACTORS
- G21C3/00—Reactor fuel elements and their assemblies; Selection of substances for use as reactor fuel elements
- G21C3/30—Assemblies of a number of fuel elements in the form of a rigid unit
- G21C3/32—Bundles of parallel pin-, rod-, or tube-shaped fuel elements
- G21C3/34—Spacer grids
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E30/00—Energy generation of nuclear origin
- Y02E30/30—Nuclear fission reactors
Abstract
ABSTRACT OF THE DISCLOSURE
This invention relates to long nuclear fuel bundles which employ grids to support the fuel elements at intermediate points. More particularly it relates to a grid assembly feature to provide a long fuel bundle with variable rigidity.
A structure for attaching grids to a cage of tie rods which enables the rigidity of the whole assembly to be adjusted to give a wide variation from very stiff to relatively flexible.
the grids are joined to the tie rod cage by several straps of such a length and cross section so as to have a predetermined torsional rigidity and thereby provide the complete fuel bundle with the desired amount of flexability to cope with the out of straightness deviations of an actual fuel channel. The tie rods are attached to the grid by the flexible straps so as to prevent relative axial movement between the tie rods and grid. This invention provides the maximum stiffness at the point furtherest away from the axis of rotation which enables the fuel to be designated to fill the channel to the maximum possible extent, without the fuel bundle jamming in the fuel channel.
This invention relates to long nuclear fuel bundles which employ grids to support the fuel elements at intermediate points. More particularly it relates to a grid assembly feature to provide a long fuel bundle with variable rigidity.
A structure for attaching grids to a cage of tie rods which enables the rigidity of the whole assembly to be adjusted to give a wide variation from very stiff to relatively flexible.
the grids are joined to the tie rod cage by several straps of such a length and cross section so as to have a predetermined torsional rigidity and thereby provide the complete fuel bundle with the desired amount of flexability to cope with the out of straightness deviations of an actual fuel channel. The tie rods are attached to the grid by the flexible straps so as to prevent relative axial movement between the tie rods and grid. This invention provides the maximum stiffness at the point furtherest away from the axis of rotation which enables the fuel to be designated to fill the channel to the maximum possible extent, without the fuel bundle jamming in the fuel channel.
Description
1~385~s This invention relates to long nuclear fue~ bundles which employ grids to support the ~uel elements at intermediate points. More partlcularly it relates to a grid assembly feature to provide a long fuel bundle with variable rigidit~
With the present design of long fuel bundles, there must be an allowance made ~or the fact that the fuel channel may become warped and no line can be straight and true. If sufficient allow~
ance is not made for this, a fuel bundle may ~am ln the fuel . :
channel~ because, although the fuel bundles are relatively long, ~ -~
, . . . . ..
they may be fairly rigid and not bend to an appreciable extenk or ~;
alternatively too flexible for convenient handling. These long ~ -,:" ~j fuel bundles are a feature of many o~ the pre~e~t reactors. It would be advantageous if a sy tem could be provided which would enable the fuel to be desiened to ~ill the channel to the maximum possible extent~ without the attendant danger of the ~uel bundle -~
jamming in the fuel channel, as this would raise the burn up or channel power of the reactor without additional expense. Alter-natively it would be advantageous lf a system could be provided to give a predetermined stiffness to a fuel bundle.
It has been found that the above desiderata may be ob~
tained by attaching grids to a cage o~ tie rods so as to enable ~ ;
the rigidity of the whole assembly to be adjusted to give a wLde variation from very stiff to relatively flexible. The tie rod cage is attached to the grid by flexible strap means of such a length and cross-section so as to have a predetermined torsional rigidity and thereby provide a variable degree of stiffness to the whole assembly thus enabling the fuel designer to choose the des~
ired amount of flexibility to cope with the deviations and out of straightness of an actual fuel channel. ;
A preferred embodiment o~ the present invention provides a nuclear fuel assembly which has a plurality o~ fuel rods, a grid .~ - .
me~ns having apertures therein for receiving the fuel rods, the ~ 3 `"~.. ,~1 .
: .
~ 0 3~ 5 0 ~
fuel rods having c~n axis which is normally p0rpendicular to the plane of the grid means, tie rod means extending parallel to the fuel rods, flexible strap means attaching the tie rod means to the grid means so as to prevent relative axial movement between the tie rod means and the grid means so as to permi~ relative angular motion therebetween, the relative angular motion therebetween, the relative angular motion occurring when the Xul~l bundle is caused to bend in a longitudinal plane. One end of the ~lexible strap means ls attached ~o the tie rod means and another end to the grid means, with the intermediate portion having a predete~ined tor-sional rigidity tending to oppose the relative angular motion which occurs when the fuel bundle is caused to bend in the longi-tudinal plane.
The present inventlon will be more particularly described with re~erence to the figures in which:
Figure 1 is a view of a preferred embodiment o~ the fuel blmdle of the present invention;
Figure 2 is a cross-sectional view tc~ken a~ Section A-A
of the fuel bundle of the present invention;
Figure 3 shows a preferred embodiment of the means of providing variable rigidity~ and Figure 4 is an enlarged view of a pre~erred embodim~nt o~ the flexlble members exaggerated ~or clarit~.
., In Figure 1 there is shown a side view of the fuel bun-dle on which the present inven~ion is practised in which the ~uel ~ ;
bundle has end plates 10 and 12 at either end o~ the fuel bundle which along with the grids maintains the fuel elements in an accur-ately spaced configuration as shown in Figure '20 `
The indi~idual fuel elements 14, as shown in Fic~ure 1, ;
are fastened to end plate 10 b~, for example, hot upsetting the element end 16.
F~gure 2 is a cross-section view of Figure 1 tc~ken along
With the present design of long fuel bundles, there must be an allowance made ~or the fact that the fuel channel may become warped and no line can be straight and true. If sufficient allow~
ance is not made for this, a fuel bundle may ~am ln the fuel . :
channel~ because, although the fuel bundles are relatively long, ~ -~
, . . . . ..
they may be fairly rigid and not bend to an appreciable extenk or ~;
alternatively too flexible for convenient handling. These long ~ -,:" ~j fuel bundles are a feature of many o~ the pre~e~t reactors. It would be advantageous if a sy tem could be provided which would enable the fuel to be desiened to ~ill the channel to the maximum possible extent~ without the attendant danger of the ~uel bundle -~
jamming in the fuel channel, as this would raise the burn up or channel power of the reactor without additional expense. Alter-natively it would be advantageous lf a system could be provided to give a predetermined stiffness to a fuel bundle.
It has been found that the above desiderata may be ob~
tained by attaching grids to a cage o~ tie rods so as to enable ~ ;
the rigidity of the whole assembly to be adjusted to give a wLde variation from very stiff to relatively flexible. The tie rod cage is attached to the grid by flexible strap means of such a length and cross-section so as to have a predetermined torsional rigidity and thereby provide a variable degree of stiffness to the whole assembly thus enabling the fuel designer to choose the des~
ired amount of flexibility to cope with the deviations and out of straightness of an actual fuel channel. ;
A preferred embodiment o~ the present invention provides a nuclear fuel assembly which has a plurality o~ fuel rods, a grid .~ - .
me~ns having apertures therein for receiving the fuel rods, the ~ 3 `"~.. ,~1 .
: .
~ 0 3~ 5 0 ~
fuel rods having c~n axis which is normally p0rpendicular to the plane of the grid means, tie rod means extending parallel to the fuel rods, flexible strap means attaching the tie rod means to the grid means so as to prevent relative axial movement between the tie rod means and the grid means so as to permi~ relative angular motion therebetween, the relative angular motion therebetween, the relative angular motion occurring when the Xul~l bundle is caused to bend in a longitudinal plane. One end of the ~lexible strap means ls attached ~o the tie rod means and another end to the grid means, with the intermediate portion having a predete~ined tor-sional rigidity tending to oppose the relative angular motion which occurs when the fuel bundle is caused to bend in the longi-tudinal plane.
The present inventlon will be more particularly described with re~erence to the figures in which:
Figure 1 is a view of a preferred embodiment o~ the fuel blmdle of the present invention;
Figure 2 is a cross-sectional view tc~ken a~ Section A-A
of the fuel bundle of the present invention;
Figure 3 shows a preferred embodiment of the means of providing variable rigidity~ and Figure 4 is an enlarged view of a pre~erred embodim~nt o~ the flexlble members exaggerated ~or clarit~.
., In Figure 1 there is shown a side view of the fuel bun-dle on which the present inven~ion is practised in which the ~uel ~ ;
bundle has end plates 10 and 12 at either end o~ the fuel bundle which along with the grids maintains the fuel elements in an accur-ately spaced configuration as shown in Figure '20 `
The indi~idual fuel elements 14, as shown in Fic~ure 1, ;
are fastened to end plate 10 b~, for example, hot upsetting the element end 16.
F~gure 2 is a cross-section view of Figure 1 tc~ken along
- 2 -. , . . ~ .
S~ ~
Section A-A ~howing the tie rods 18 fastened to the grids 20 by the flexible strap means 22. The fuel elements 14 are shown disposed within the grids 20. ~ ~
Figure 3 is a partial view of two tie rods 18, a portion ~ ;
of the grid structure 20 and the flexible strap means 22 for ~asten ing the tie rods 18 to the grid 20. As shown in the preferred em-. ~
bodiment o~ Figure 3, the flexible strap means 22 may be strips o~
any suitable length wh~ch will provide the desired sti~fness or rigidity in the assembly. m e strap means 22 may be fastened to -the tie rod 18 at a point 24 by any suitable means, such as elec- ;
tron beam, resistance9 or arc welding as well as by brazing with an alloy compatible with the strip and tie rod. The strap means 22 may also be fastened to the grid 22 at a point 26 in a similar manner.
The action of the strap means 22 will be described in more detail with reference to Figure 4. In Figure 4 the strap means 22 is shown connected to a por~ion of the tie rod 18 and a portion of `~
the grid 20. The distance D found in Flgure 4 has been exaggerated for clarity. Any bending moment applied to the fuel bundle would result in a twisting moment being applied to the free portion L of ;~
the strap means 22.
Al~hough as shown in the preferred embodiment the strap mean8 22 i8 shown as having a greater dimension disposed in the radial direction and the narrow dimension being in a circumferen~
tial direction the strap means may assume other cross-sectional dimensions, such as round, trapezoidal or square.
Since a single fuel bundle will ha~e a large number of flexible strap means 22, the torsional rigidity of the indi~idual flexible strap means 22 will depend upon the stiffness desired for ~ , .
the fuel bundle as a whole as well as the number of flexible means which are effective in contributing to the stiffness of the bundle.
For instance, since the flexible strap means of the preferred em-It~
' 10;~505 bodiment have a rectangular shape, only those strips which are ~`
oriented to provide maximum ~orsional rigidity, i~e~ in ths present embodiment those located the furthest distance from the bending A-A will contribute significantly to the stiffness of the fuel element since those flexible means 22 c-ose t;o the axis A-A will be oriented along their axis of minimum torsional rigidity as shown in Figure 2~
In fact, in the preferred embodiment shown9 the flexible strap means 22 close to the æis A-A are subjec~ to substantially -~
pure bending about the narrow dimension and therefore ser~e mainly to prevent relative axial movement o~ the tie rod cage with res~
pect to the grids and contribu~e very little to the rigidity of the fuel bundle.
From th~ above description it can be seen that the con-tribution of each of the flexible means 22 depends on its location with respect to the axis of bending A-A and may be varied by changing the cross-sectional shape of the flexible strap means 22 to provide a predete~mined torsional rigidity necessary to achieve ;~
the desired bundle stif~ness.
In summary, it has been shown how a fuel bundle having a con~rolled rigidity or stiffness may be produced using in the preferred embodiment, a flexible strap means 22 o~iented in such a manner as to produce maximum stiffness at the point furthest away ~
~rom the axis of rotation. ~ -' ~
;~ .
- 4 ~
' ".
~. , . ~ , .. . .. . . . . .
S~ ~
Section A-A ~howing the tie rods 18 fastened to the grids 20 by the flexible strap means 22. The fuel elements 14 are shown disposed within the grids 20. ~ ~
Figure 3 is a partial view of two tie rods 18, a portion ~ ;
of the grid structure 20 and the flexible strap means 22 for ~asten ing the tie rods 18 to the grid 20. As shown in the preferred em-. ~
bodiment o~ Figure 3, the flexible strap means 22 may be strips o~
any suitable length wh~ch will provide the desired sti~fness or rigidity in the assembly. m e strap means 22 may be fastened to -the tie rod 18 at a point 24 by any suitable means, such as elec- ;
tron beam, resistance9 or arc welding as well as by brazing with an alloy compatible with the strip and tie rod. The strap means 22 may also be fastened to the grid 22 at a point 26 in a similar manner.
The action of the strap means 22 will be described in more detail with reference to Figure 4. In Figure 4 the strap means 22 is shown connected to a por~ion of the tie rod 18 and a portion of `~
the grid 20. The distance D found in Flgure 4 has been exaggerated for clarity. Any bending moment applied to the fuel bundle would result in a twisting moment being applied to the free portion L of ;~
the strap means 22.
Al~hough as shown in the preferred embodiment the strap mean8 22 i8 shown as having a greater dimension disposed in the radial direction and the narrow dimension being in a circumferen~
tial direction the strap means may assume other cross-sectional dimensions, such as round, trapezoidal or square.
Since a single fuel bundle will ha~e a large number of flexible strap means 22, the torsional rigidity of the indi~idual flexible strap means 22 will depend upon the stiffness desired for ~ , .
the fuel bundle as a whole as well as the number of flexible means which are effective in contributing to the stiffness of the bundle.
For instance, since the flexible strap means of the preferred em-It~
' 10;~505 bodiment have a rectangular shape, only those strips which are ~`
oriented to provide maximum ~orsional rigidity, i~e~ in ths present embodiment those located the furthest distance from the bending A-A will contribute significantly to the stiffness of the fuel element since those flexible means 22 c-ose t;o the axis A-A will be oriented along their axis of minimum torsional rigidity as shown in Figure 2~
In fact, in the preferred embodiment shown9 the flexible strap means 22 close to the æis A-A are subjec~ to substantially -~
pure bending about the narrow dimension and therefore ser~e mainly to prevent relative axial movement o~ the tie rod cage with res~
pect to the grids and contribu~e very little to the rigidity of the fuel bundle.
From th~ above description it can be seen that the con-tribution of each of the flexible means 22 depends on its location with respect to the axis of bending A-A and may be varied by changing the cross-sectional shape of the flexible strap means 22 to provide a predete~mined torsional rigidity necessary to achieve ;~
the desired bundle stif~ness.
In summary, it has been shown how a fuel bundle having a con~rolled rigidity or stiffness may be produced using in the preferred embodiment, a flexible strap means 22 o~iented in such a manner as to produce maximum stiffness at the point furthest away ~
~rom the axis of rotation. ~ -' ~
;~ .
- 4 ~
' ".
~. , . ~ , .. . .. . . . . .
Claims (5)
1. In a fuel assembly for a nuclear reactor a plurality of fuel rods, a grid means having apertures therein for receiving the fuel rods, the axis of said fuel rods being normally perpen-dicular to the plane of said grid means, tie rod means extending parallel to said fuel rods, flexible strap means attaching said tie rod means to said grid means so as to prevent relative axial movement between said tie rod means and said grid means while per-mitting relative angular motion therebetween, said relative angular motion occurring when said fuel bundle is caused to bend in a longitudinal plane, passing through said fuel bundle, one end of said flexible strap means being attached to said tie rod means and another end to said grid means, an intermediate por-tion having a predetermined torsional rigidity tending to oppose said relative angular motion which occurs when said fuel bundle is caused to bend in said longitudinal plane.
2. The fuel assembly of claim 1 wherein a pair of flex-ible strap means are attached to said tie rod on opposite sides thereof.
3. The fuel assembly of claim 2 in which said straps are rectangular and the relative angular motion of said tie rod means with the respect to said grids produces torsion in said straps.
4. The fuel assembly of claim 1 wherein a plurality of grid means are attached to a plurality of the rod means, and wherein each tie rod means has attached thereto a pair of flexible strap means.
5. The fuel assembly of Claim 4 in which substantially all torsional resiliency which opposes the bending of said fuel bundle in said longitudinal plane is produced by the pairs of flexible strap means closest to the longitudinal plane.
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA226,956A CA1038505A (en) | 1975-05-14 | 1975-05-14 | Grid assembly structure for nuclear fuel bundle |
| ES447892A ES447892A1 (en) | 1975-05-14 | 1976-05-13 | Reactor fuel assembly |
| JP51054490A JPS51140092A (en) | 1975-05-14 | 1976-05-14 | Reactor fuel assembly |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA226,956A CA1038505A (en) | 1975-05-14 | 1975-05-14 | Grid assembly structure for nuclear fuel bundle |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1038505A true CA1038505A (en) | 1978-09-12 |
Family
ID=4103079
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA226,956A Expired CA1038505A (en) | 1975-05-14 | 1975-05-14 | Grid assembly structure for nuclear fuel bundle |
Country Status (3)
| Country | Link |
|---|---|
| JP (1) | JPS51140092A (en) |
| CA (1) | CA1038505A (en) |
| ES (1) | ES447892A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2477754A1 (en) * | 1980-03-05 | 1981-09-11 | Kraftwerk Union Ag | Fuel element esp. for breeder or converter reactor - has local clamping bands around rod assembly and helical spacers |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BE774911A (en) * | 1971-11-04 | 1972-03-01 | Belgonucleaire Sa | SPACING GRID FOR COMBUSTIBLE BARS |
-
1975
- 1975-05-14 CA CA226,956A patent/CA1038505A/en not_active Expired
-
1976
- 1976-05-13 ES ES447892A patent/ES447892A1/en not_active Expired
- 1976-05-14 JP JP51054490A patent/JPS51140092A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2477754A1 (en) * | 1980-03-05 | 1981-09-11 | Kraftwerk Union Ag | Fuel element esp. for breeder or converter reactor - has local clamping bands around rod assembly and helical spacers |
Also Published As
| Publication number | Publication date |
|---|---|
| ES447892A1 (en) | 1977-12-16 |
| JPS51140092A (en) | 1976-12-02 |
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