DE3228971A1 - HOLDING TORSION SPRING WITH DOUBLE BEND - Google Patents

Description

Hold-down torsion spring with double bending

The present invention relates to fuel for a nuclear reactor and in particular a hold-down spring arrangement for "securing fuel assemblies or fuel assemblies in the Core of a nuclear reactor.

A nuclear reactor for the production of electrical energy normally has a core of fissile material to provide coolant flowing up through that core heat · The fissile material is elongated in Including fuel rods arranged in a square-shaped array, usually called fuel assemblies and by a number of spacer grids at intervals are held along the length of the assembly and in parallel relationship to one another. The fuel elements are held in an arrangement by .Kernlitterplatten at the top and bottom and are with an upper and a lower end piece for engagement with the tie plates

Mistake.

Normally, a hold-down spring device is arranged between the upper end piece and the upper core grid plate in order to provide a sufficient hold-down force which lifts against the hydraulic: i see) - hzvi. Lifting forces in the grain work. The springs also allow a growth of the fuel element in the axial direction due to either different thermal expansion or radiation-induced

Material change. The design problems therefore lie in the ability to provide sufficient hold-down force against to create the lift while there is sufficient room for growth. Within the inevitable Volumes must have sufficient material strength and rigidity. The stiffness / volume efficiency a spring becomes very important when used to hold down fuel elements.

There are currently two types of spring as hold-down devices common for fuel elements. This is where the helical spring is the most common. The other facility exists from a leaf spring arrangement. U.S. Patent 4,072,562 a device with a single torsion bar is disclosed. However, this facility is never in a nuclear reactor been used.

Helical springs attempt to solve the problem of stiffness / volume efficiency to solve that the spring

is placed in the center of the top tail assembly where most of the open space is available. Bad at This conception is the fact that the springs must be carefully positioned in order to gain access to the control rods to allow, and that the springs are fully exposed to the coolant flow, whereby the spring the dynamic loads of flow-induced vibrations is subject.

Leaf spring constructions are made by a manufacturer of 30

Used nuclear fuel. However, since these structures are stroke-limited, it is necessary to use the fuel element structure to unite with parts that are less susceptible to radiation-induced growth. In addition, must

these leaf springs are often interconnected or coupled 35

in order to achieve sufficient hold-down.

The torsion bar spring is an extremely effective device. With the same weight, it can have four times the energy of one

- 1-5-

¹ Save the leaf spring loaded in the same way. The difficulty with using torsion bars, however, is that there is not enough space in the fuel element to allow the bar to bend sufficiently. Typically, fuel elements are only 8 inches square. The size of the torsion arm is therefore limited to a length of less than 20.32 cm. The rod diameter, which ensures a sufficient hold-down force, cannot be subjected to stroke or loaded sufficiently without damage to absorb the growth when the Rod length is limited to less than 20, 32 cm.

The present invention overcomes the disadvantages of the known ones Facilities to a considerable extent by a hold-down torsion spring with double bending, which consists of a lever arm that acts on a torsion bar, which in turn acts on a torque tube. This facility is assembled in a "stick in a mantle" fashion. Of the Lever arm is attached to the torsion bar, which in turn

is connected to a torque tube by a limit connector. This border connector can be in one piece be with the torque tube or form a separate part. The entire device reacts - through a tensioning device

at the lever arm end of the torque tube. 25th

The present invention solves at least two major problems. The first problem relates to earlier torsion bar designs. Torsion springs with a

The only rods are flexible to the maxi-30

The number of installed peder lengths that are available within the upper end piece assembly are limited. Through the present Invention this is overcome in that a concentric torque tube is added, whereby the

Torsion spring length effective within the same dimension 35

is doubled. The resulting additional deflection or the resulting additional stroke is also eliminated some limitations on leaf springs. The second problem solved is fluid G induced vibration

»Β μ

iwulche mil. ik'.ljraubchf edern is connected. The coil springs act as cylinders on the cross flow; and vibrate either due to vortex shedding or due to turbulent shaking. This vibration tires the spring material and causes wear at the coil interfaces. The spring with double bent torsion bar can be largely enveloped by the flow and eliminates strömimgs ™ induced vibration problems. The advantages of the present invention are the elimination of the need to use coil springs for hold-down where a greater stroke, a "Ls .ihn leaf springs can provide. The torsion springs do not have any of the previously cited drawbacks of coil springs.

Another advantage is that the torsion springs can be made without special spring coiling equipment. You can do this in any well-equipped machine shop getting produced.

20In addition, allows the use of torsion springs other modifications to the upper end piece structure that are not possible with coil springs. There can be a reduction the pressure drop can be achieved. In addition, it is possible to design the end piece in such a way that it can be replaced or restore in situ is possible.

The aim of the present invention is to provide a hold-down spring for a fuel element of a nuclear reactor create, in particular, a torsion bar hold-down spring of increased effective length.

Further advantages, features and possible applications of the present invention emerge from the following description of an exemplary embodiment in conjunction with ^{FIG. 3} ^ of the drawing. Show in it:

Fig. 1 is a partially cut-away side view of an upper end piece; Fuel element with

" ¹ """'■"■"'^;'one'nie'de'rhä ^ tfe'federeinrlchtürtg according to ^! One »beiig ^^^ ■■ ^; vörll ^: egeriä'e ^: n" -Ei ^if f ^! indung _J

m .; Λ O i ;;: ..- ic:. V

ivisdhe Ärisieh-elneä fopsiönsstabs biegüng ^ according to ¹ de ^ ^i! be - present ^; Eh * find

^ along ^ the ^ Lihie-i «- ¹ ! -the ^ Mg. 3,

'xed'xuV ^! iose.i; b ί! θπ.1> .ιϋ ': u?:' ii ^; ji: ■■:.:; : < ^r : jä.i?;.: ■: · ..; ' ii: ^; .; ::!:? ·> Ι: Γ

Pig. 5 a EndänMöWb '-' äe-ö ^ Tbrsibhsstabs-der Pig * -3i ^; -'ΡΪ ^; ^r S ^{nO; ü} a '■ ^! the ^ci päg ^t i- ⁱ 5 ' ⁱ ätolicfie-looks ⁰ ' one * - ¹ other ^ ΰι

Fig. 7 is a side view

of the torsion bar according to Pig. I.

η "P ^{1 IGUI":;} Ψ is ^{i; eih;!} "Brennst of f element" shown 'nat ^f "fuel rods' ■ 'Ϊ1'^; mit-ij ^ ngsaohsen ^ ΐ2, - welDhe In parallel relation to each other ^f; · - ■■■ äifrxiU 'Ä'bs ^ anäiBhalt ^ lattice'^; lH ^l salary e'n- ^; We ^ rden ^ "ü ^; nd: with- a öTjerefn ¹ Eritstücir ' ^l ± fr ^ das ¹¹ "in the" core of a ^ nuclear reactor- between a-lower ^ Ke'rhgftter ^ latte ^ Cnich't shown)' and ^; an upper core grid plate 15 is arranged. The plate 15 is ISürtrhlÖciier't / -um 'to take the "Endstüc * l €" -and-- much of a projection "16" ^: ~' on \ 'äer ^>! Sö ^! Aligned ^ solderV ¹ to ά \ '& lever arms' 2fv ^{3 22v-; 23-!' Uend.} depress Jn ^^ aer hold-down spring ⁸ ^ Figure 2 is a plan view of the end piece ^ lOigezelgtV from '"' 30 _W hich the relative positions of the arms 21, 22 , 23 and 24 iigfe1i ^ / - ^{; 'ifö'ie:} - ^i> i ^{r fi;!} Pi '^ ^! ' ⁱ -l -gezelgt ^: iisiii, l ^ t'die ^ Tovrsibns ^ - 1 "5 ^ -nidPb * döp ^: peiLter ^i: Umbiegüng'in'eineir ¹ hole 17 of the end

³⁵ The spring 13 has a torsion tube 26 and a Torsjonr · .- ^: ''B-tab'SS'äüfV d ^! he 'within ^ the pipe 26 -ah / .issördnet and nnt dreöenr äh ^ his' ^J one end ^; a connecting piece 27 is connected. The other end of the tube 26 is with a

2-

1 socket rigidly connected to the pipe j> Ü provided, which Has spline teeth 29. The socket 30 has a bore 38 for receiving the rod 25 extending through the socket. At the open end of the bore 17 there are groove slots 31 for opening

5 Receipt of the spline teeth 29 of the bush 30 is formed. The lever arm

22 extends perpendicular to the rod 20 such that the depression of the arm by the projection 16 pushes the rod 25 and twist the tube 26. Block 37 is for receiving the

on the arm ? provided axial force exerted and transmits lO the axial force to the fuel element.

In Figure 3, the spring 13 is shown. Reference is made to a bend or elbow 39 which is provided therewith the arm 21 over the bore 17 of the adjacent spring

15 is achieved. The torsion bar 25 within the torsion tube 26 is connected to the latter by the connecting piece 27. FIG. K shows a section through the connecting piece 27, which has an opening 33 which is in engagement with one end 8 of the rod 25. The opening 33 and

20the arm or the end ? Ö edge shaped in such a way that rotation between them is excluded. In Fig. 5, a preferred embodiment is shown in which the opening 33 and the end 28 are square. In Fig. 6 a modified embodiment is shown in which the

25, the connecting piece 27 has an opening provided with grooves 36 for receiving spline teeth 32 of the rod 28. In FIG. ¹ I weld points are shown which connect the connecting piece 27 firmly to the torsion tube 26.

30lm operation is the depression of the lever arms 21, 22,

23 and 24 counteract the torsion spring force, which is caused by the twisting or twisting of the torsion bar 25 and the torsion tube 26 is generated, which is connected to the bar by the Connector 27 is rigidly connected and is rigidly connected to the socket, which is subject to rotation by splines 29 is prevented, which are received in slots 31 of the end piece 10. The axial force is applied via blocks 37 transmit the fuel element. The four opposite

Springs 13 exert torques on the fuel element, which are opposite to each other and therefore give zero resultant torque.

In Fig. 7 another modified embodiment is shown, which uses a retaining ring (not shown) which is arranged in the upper part of the end piece 10 and Has arms 35 which protrude through slots 3 ^. Of the Projection 16 acts on the arm 35, which in turn acts on the

lOHebelarm 20 acts on its inclined surface 19. If the arm 3i> the arm? 0 vu di; t · {/p:i1.ri the 1 1. {. ''. O / .tM rleti Po: ii t. i uri depressed, the arm bb slides along the surface 19, whereby the stroke length of the arm 35 is effectively increased relative to a straight arm. This allows a stiffer spring material to be used.

The above description and drawings illustrate only one exemplary embodiment which realizes the objects, features and advantages of the present invention. 20Modifications of the individual Κοπκ <; ρ1, (>;; I nd durohnu ;? im'if.li oh.

Claims (6)

PATENT AND LEGAL APPLICATION Tf: BARDEHLE, PAGENBSfT ^ ₁ J && £: MWN & UHG & LAWYERS PATENT AGENCIES! - EUROPEAN PATENT ATTORNEYS JOCHEN PAGENBERG DR jur.ll μ harvard - HEINZ BARDEHLE dii-i -ing BERNHARD FROHWITTER d.pl-ing- WOLFGANG A. DOST dr.dipl-chem GÜNTER FRHR. v. GRAVENREUTH dipl.-ing ₍ fh) UDO W. ALTENBURG dipl-phys POST BOX 86 0620, 8OOO MUNICH TELEPHONE (089) 980361 TELEX 522791 pad d CABLE: PADBÜRO MUNICH OFFICE: GALILEIPLATZ 1, 8 MUNICH DATE 3 AUGUST I982 M 2 * 178 Al / f '"'*"? patent claims Device for absorbing axial forces in a nuclear reactor with an upper and a lower tie plate, with projections protruding from the upper tie plate and fuel assemblies with end pieces, the fuel assemblies being arranged between the upper and lower tie plates, characterized in that at least one torsion spring ( 13) is provided with a torsion tube (26) and a torsion bar (25) which is arranged essentially concentrically within the torsion tube and at one end with this torsion tube and at the other end with a lever arm (21, 22) arranged essentially perpendicular to the torsion bar , 23, 2 * 1) is connected, that the torsion tube is rigidly connected to the end piece (10) and that the torsion spring (13) is arranged such that the lever arm is biased against the projection (16). 2. Device according to claim 1, characterized in that four torsion springs with a torsion tube (26) and a torsion bar (25) are provided, each parallel with a corresponding Edge of the end piece (10) are aligned. 3. Device according to claim 2, characterized in that g'e that a connector (27). is welded to one end of the torsion tube (26) and an opening for receiving the non-lever arm end (28) of the torsion bar (25), the non-lever arm end and the connector opening so shaped are that there is no rotation between them. Ij. Device as claimed in claim 3 _S, there is disposed £ the torsion tube (26) within a receiving bore (17) in the end piece (10). 5 · Device according to claim 4, characterized that a bushing (3) is attached to the end of the torsion tube (26) opposite the connecting piece is and has at least one spline projection (29) and that the receiving bore (17) for receiving * ° this at least one spline projection is slotted. 6. Device according to claim 5, d \ a characterized by that the end piece (10) with a number of elongated slots (34) through which a corresponding number of retaining rings (35) extend, the ring arms being positioned to act on the lever arms (20) and the lever arms having an inclined surface (19 ) provided to accommodate the action side of the ring arm r. Ind.