DE3221270C1

DE3221270C1 - Nuclear reactor fuel element

Info

Publication number: DE3221270C1
Application number: DE3221270A
Authority: DE
Inventors: Hans Ing.(grad.) 8521 Effeltrich Lettau; Matthias Ing.(grad.) 8551 Hemhofen Rudolph
Original assignee: Kraftwerk Union AG
Current assignee: Kraftwerk Union AG
Priority date: 1982-06-04
Filing date: 1982-06-04
Publication date: 1983-10-20

Abstract

In order to reduce the fuel can waste for a nuclear reactor fuel element, one (7a) of the fuel rods (7) has on the outside two ducts (15a; 15b) which are mutually offset in the axial direction and between which a spacer (8) is positioned; connected in a form-fitting fashion to the lower end of this fuel rod (7a) having the ducts (15a; 15b) is a drop safety part (17) which is arranged extending transversally trough the axial drop path of other fuel rods (7) and delimits an axial movement of the other fuel rods (7) in dropping direction. <IMAGE>

Description

Da die anderen Brennstäbe keine Stollen tragen, kann bei ihrer Herstellung auch kein Hüllrohrausschuß durch Bestollen auftreten. Im Falle eines Hüllrohrbruches an einem keine Stollen tragenden Brennstahes während des Betriebes in einem Kernreaktor wird der untere Teil dieses Brennstabes durch das quer in seinem axialen Fallweg verlaufenden Fallsicherungsteil am Herausgleiten in Fallrichtung aus dem Brennelement in das Kühlmittelführungsrohr gehindert.Since the other fuel rods do not have studs, it can be used in their manufacture there is also no cladding scrap due to burrowing. In the event of a jacket tube rupture at a fuel steel that does not carry any tunnels during operation In a nuclear reactor, the lower part of this fuel rod is crossed in its axial fall path running fall protection part on sliding out in the direction of fall prevented from the fuel assembly in the coolant guide tube.

Aus der DE-OS 21 56 171 ist zwar ein Kernreaktorbrennelement mit Brennstäben bekannt, von denen einer auf der Außenseite zwei in Achsrichtung versetzte Stollen aufweist, zwischen denen ein Abstandshalter positioniert ist. Hierdurch wird jedoch nur ein Verschieben oder Kriechen des Abstandshalters im Reaktorbetrieb verhindert, ein Herausgleiten des unteren Teiles eines gebrochenen Hüllrohres eines Brennstabes in das Kühlmittelführungsrohr kann nicht vermieden werden. From DE-OS 21 56 171 is a nuclear reactor fuel element with Known fuel rods, one of which on the outside two offset in the axial direction Has studs between which a spacer is positioned. Through this however, there is only a shifting or creeping of the spacer during reactor operation prevents the lower part of a broken cladding tube from sliding out Fuel rod in the coolant pipe cannot be avoided.

Von Vorteil ist es, wenn in Weiterbildung der Erfindung an der Außenseite der Außenhülse des Abstandshalters Gleitschuhe mit Winkelabstand voneinander angeordnet sind, von denen einer in radialer Richtung federnd ist und die anderen starr sind. Auf diese Weise brauchen auch keine elastischen Gleitschuhe außen an einem Brennstab angebracht zu werden, so daß der Hüllrohrausschuß noch weiter verringert wird. It is advantageous if, in a further development of the invention, on the outside the outer sleeve of the spacer sliding blocks arranged at an angular distance from one another are, of which one is resilient in the radial direction and the other are rigid. In this way there is also no need for elastic sliding shoes on the outside of a fuel rod to be attached, so that the cladding tube committee is reduced even further.

Andererseits können alle Brennstäbe des Kernreaktorbrennelementes mit Kernbrennstoff gefüllt sein.On the other hand, all fuel rods of the nuclear reactor fuel assembly be filled with nuclear fuel.

Die Erfindung und ihre Vorteile seien anhand der Zeichnung an einem Ausführungsbeispiel näher erläutert: F i g. 1 zeigt die Seitenansicht eines erfindungsgemäßen Kernreaktorbrennelementes. The invention and its advantages are based on the drawing on one Exemplary embodiment explained in more detail: F i g. 1 shows the side view of an inventive Nuclear reactor fuel assembly.

F i g. 2 zeigt einen Querschnitt des Kernreaktorbrennelementes nach F i g. 1 entsprechend der strichpunktierten Linien II-II. F i g. 2 shows a cross section of the nuclear reactor fuel assembly according to FIG F i g. 1 corresponding to the dash-dotted lines II-II.

F i g. 3 zeigt eine Draufsicht auf die Unterenden der Brennstäbe des Kernreaktorbrennelementes nach Fig. 1. F i g. Figure 3 shows a plan view of the lower ends of the fuel rods of the nuclear reactor fuel assembly according to FIG. 1.

Das Kernreaktorbrennelement nach F i g. 1 weist an seinem oberen Ende ein Kupplungsteil 2 auf, mit dem das Brennelement mit einem nicht dargestellten Füllkörper gekuppelt werden kann, welcher einen ebenfalls nicht dargestellten Verschlußkörper für ein vertikales Kühlmittelführungsrohr eines Schwerwasser-Kernreaktors aufweist, in das das Kernreaktorbrennelement mit vertikaler Längsachse hängend eingesetzt wird und das von einem Kühlmittel durchströmt wird. The nuclear reactor fuel element according to FIG. 1 points at its upper End of a coupling part 2, with which the fuel assembly with a not shown Filler body can be coupled, which has a closure body, also not shown for a vertical coolant duct of a heavy water nuclear reactor, in which the nuclear reactor fuel element is inserted hanging with a vertical longitudinal axis and through which a coolant flows.

Am Kupplungskörper 2 ist auf dessen Unterseite ein Gestängeteil 3 angebracht,welches an seinem Unterende einen Gestängering 4 aufweist. Dieser Gestängering 4 ist auf der Unterseite mit achsparallelen Stäben 5 versehen, an deren Unterenden eine Stabhalteplatte 6 befestigt ist, die außen am Mantel Gleitschuhe 6a aufweist. An dieser Stabhalteplatte 6 sind auf deren Unterseite befindliche Brennstäbe 7, 7a festgeschraubt. A rod part 3 is located on the underside of the coupling body 2 attached, which has a rod ring 4 at its lower end. This rod ring 4 is provided on the underside with axially parallel rods 5, at their lower ends a rod holding plate 6 is attached, which has sliding shoes 6a on the outside of the jacket. On this rod holding plate 6 are located on the underside of fuel rods 7, 7a screwed tight.

Das Kernreaktorbrennelement ist mit über seiner Länge gleichmäßig verteilten Abstandshaltern 8 versehen, von denen jeder, wie Fig. 2 zeigt, eine Außenhülse 9 mit kreisförmigem Querschnitt aufweist. Ferner weist jeder Abstandshalter 8 eine in F i g. 2 nicht dargestellte Innenhülse ebenfalls mit kreisförmigem Querschnitt auf, die zur Außenhülse 9 koaxial ist. Außerdem sind noch koaxiale Zwischenhülsen vorgesehen, von denen in F i g. 2 nur eine einzige Zwischenhülse 10 dargestellt ist. The nuclear reactor fuel element is uniform over its length distributed spacers 8, each of which, as shown in FIG. 2, has an outer sleeve 9 has a circular cross-section. Furthermore, each spacer 8 has a in Fig. 2 inner sleeve, not shown, also with a circular cross-section which is coaxial with the outer sleeve 9. There are also coaxial intermediate sleeves provided, of which in F i g. 2 only a single intermediate sleeve 10 is shown is.

Die Außenhülse 9, die Zwischenhülsen 10 und die Innenhülsen sind durch hochkant angeordnete Radialstege 11 miteinander verbunden, so daß durch diese Hülsen und die Radialstege 11 in den Abstandshaltern 8 Maschen 12 gebildet sind, durch die jeweils ein Brennstab 7 geführt ist. In jeder Masche 12 befinden sich drei Noppen 13 und 14, an denen der jeweilige Brennstab 7 mit seiner Mantelfläche anliegt. Diese Noppen 13 und 14 sind an den Seiten der Außenhülse 9, der Zwischenhülse 10, der nicht dargestellten Innenhülse und/oder der Stege 11*ausgebildet. Zwei Noppen 13 sind starr, während die dritte Noppe 14 federnd ausgebildet ist.The outer sleeve 9, the intermediate sleeves 10 and the inner sleeves are through Radial webs 11 arranged on edge are connected to one another, so that these sleeves and the radial webs 11 in the spacers 8 meshes 12 are formed by each of which a fuel rod 7 is guided. There are three knobs in each stitch 12 13 and 14, on which the respective fuel rod 7 rests with its outer surface. These Knobs 13 and 14 are on the sides of the outer sleeve 9, the intermediate sleeve 10, the inner sleeve not shown and / or the webs 11 * formed. Two knobs 13 are rigid, while the third knob 14 is resilient.

Ein Brennstab 7a weist auf seiner äußeren Mantelfläche in Achsrichtung zueinander versetzte Stollen 15a und 15b auf, zwischen denen jeweils ein Abstandshalter 8 positioniert ist. A fuel rod 7a points on its outer circumferential surface in the axial direction offset studs 15a and 15b, between which a spacer 8 is positioned.

Auf der Außenseite der Außenhülsen 9 weisen die Abstandshalter 8 drei Gleitschuhe 16 und 17 auf, die voneinander einen gleichen Winkelabstand von 1200 haben und von denen zwei Gleitschuhe 16 starr sind und der dritte Gleitschuh 17 in radialer Richtung federnd ist. The spacers 8 point on the outside of the outer sleeves 9 three sliding blocks 16 and 17, which are at an equal angular distance from each other 1200 and of which two sliding shoes 16 are rigid and the third sliding shoe 17 is resilient in the radial direction.

Diese Gleitschuhe 16 und 17 liegen am Kühlmittelführungsrohr eines Kernreaktors an und halten dort das Kernreaktorbrennelement schwingungsfrei in bezug auf das Kühlmittelführungsrohr.These sliding shoes 16 and 17 are located on the coolant guide tube of a Nuclear reactor and keep there the nuclear reactor fuel element vibration-free in relation on the coolant pipe.

Am Unterende des Brennstabes 7a mit den in Achsrichtung versetzten Stollen 15a und 15b ist ein Quergitter 17 als Fallsicherungsteil mit einer Klammer 18 mit Abstand und getrennt von den Abstandshaltern 8 sowie ohne ein zusätzliches Verbindungsteil zu diesen Abstandshaltern 8 formschlüssig befestigt. Dieses Quergitter 17 weist von Radialstegen gehaltene Hülsen auf, die konzentrisch zueinander derart angeordnet sind, daß sie quer durch den axialen Fallweg anderer Brennstäbe 7 verlaufen, Abstand von diesen anderen Brennstäben 7 haben und eine Axialbewegung dieser anderen Brennstäbe 7 in Fallrichtung begrenzen. At the lower end of the fuel rod 7a with the axially offset Lugs 15a and 15b is a crossbar 17 as a fall protection part with a clamp 18 at a distance and separate from the spacers 8 and without an additional one Connecting part attached to these spacers 8 in a form-fitting manner. This crossbar 17 has sleeves held by radial webs which are concentric to one another in such a way are arranged so that they run transversely through the axial fall path of other fuel rods 7, Have a distance from these other fuel rods 7 and an axial movement of these others Limit fuel rods 7 in the direction of fall.

Günstigerweise ist dieses Quergitter 17 noch an den Unterenden eines weiteren Brennstabes 7, vorzugsweise zweier weiterer Brennstäbe 7 mit Klammern 18 formschlüssig befestigt. Von Vorteil ist, wenn auch diese weiteren Brennstäbe 7, an denen das Fallsicherungsteil befestigt ist, Positionierstollen für die Abstandshalter 8 an ihrer Außenseite aufweisen. Ferner ist es günstig, wenn das Fallsicherungsteil nur an Brennstäben formschlüssig befestigt ist, von denen ein annähernd gleiches strahleninduziertes Differenzlängenwachstum während des Betriebes im Kernreaktor erwartet werden kann.Conveniently, this transverse grid 17 is also at the lower ends of one further fuel rod 7, preferably two further fuel rods 7 with clamps 18 positively attached. It is advantageous if these further fuel rods 7, to which the fall protection part is attached, positioning studs for the spacers 8 have on their outside. It is also advantageous if the fall protection part is only positively attached to fuel rods, one of which is approximately the same Radiation-induced difference in length growth during operation in the nuclear reactor can be expected.

Anstelle eines Quergitters 17 kann als Fallsicherungsteil auch ein Draht vorgesehen sein, der durch Querbohrungen an den Unterenden des die Stollen 15a und 15b aufweisenden Brennstabes 7a und der anderen Brennstäbe 7 geführt ist. Günstigerweise wirft der Draht zwischen zwei Brennstäben einen Bogen. Instead of a cross grating 17, a fall protection part can also be used Wire may be provided through transverse bores at the lower ends of the cleats 15a and 15b having fuel rod 7a and the other fuel rods 7 is guided. Conveniently, the wire casts an arc between two fuel rods.

Beide erwähnten Fallsicherungsteile gestatten eine unterschiedliche Längenänderung der Brennstäbe 7 und 7a während des Betriebes in einem Kernreaktor, sie verhindern aber auch, zusammen mit den Positionierstollen für die Abstandshalter 8, daß beim Hüllrohrbrucheines der Brennstäbe 7 und 7a das untere Teil des betreffenden Stabes aus dem Brennelement heraus in das Kühlmittelführungsrohr im Kernreaktor gleitet. Both mentioned fall protection parts allow a different one Change in length of the fuel rods 7 and 7a during operation in a nuclear reactor, but they also prevent, together with the positioning studs for the spacers 8, that when the cladding tube breaks one of the fuel rods 7 and 7a, the lower part of the relevant Rod out of the fuel assembly into the coolant pipe in the nuclear reactor slides.

Claims

Claims: 1. Nuclear reactor fuel element, in particular for use in a vertical coolant duct with one another located in a nuclear reactor axially parallel, elongated, nuclear fuel containing fuel rods with their upper ends are supported on a rod holding plate, and with one on the fuel rods positioned spacer that has an outer sleeve with sliding shoes on the outside as well as a coaxial inner sleeve, between which a coaxial intermediate sleeve and radial webs connected to the outer, inner and / or intermediate sleeve Are arranged upright and with the outer, the inner and / or the intermediate sleeve Form meshes through which the fuel rods are guided axially parallel and resting against knobs are on the sides of the radial webs and the outer, inner and / or intermediate sleeve are designed, characterized in that one of the Fuel rods (7a) on the outside have two axially offset tunnels (15a; 15b), between which the spacer (8) is positioned, and that with the lower end of the lugs (15a; 15b) having fuel rod (7a) Fall protection part (17) is positively connected, which transversely through the axial Falling path of other fuel rods (7) is arranged to run and an axial movement this other fuel rods (7) limited in the direction of fall.

2. Nuclear reactor fuel element according to claim 1, characterized in that that the fall arrester part through transverse bores in the lower ends of the cleats (15a; 15b) having fuel rod (7a) and the other fuel rods (7) guided Metal wire is.

3. Nuclear reactor fuel element according to claim 1, characterized in that that the fall protection part is opposite to the lower ends of the other fuel rods (7) arranged transverse grid (17) is.

4. Nuclear reactor fuel element according to claim 1, characterized in that that on the outside of the outer sleeve (9) of the spacer (8) sliding shoes (16; 17) are arranged at an angle! From each other, one of which (17) in a radial Direction is resilient, while the other (16) are rigid.

The invention relates to a nuclear reactor fuel element in particular for Insertion into a vertical coolant duct located in a nuclear reactor with axially parallel, elongated fuel rods containing nuclear fuel, which are held with their upper ends on a rod holding plate, and with one on the fuel rods positioned spacers, the an outer sleeve with sliding shoes has on the outside and a coaxial inner sleeve, between which a coaxial Intermediate sleeve and connected to the outer, the inner and / or the intermediate sleeve Radial webs are arranged upright and with the outer, the inner and / or the Form intermediate sleeve meshes through which the fuel rods are axially parallel and on knobs are guided adjacent to the sides of the radial webs as well as the outer, inner and / or the intermediate sleeve are formed.

Such a nuclear reactor fuel element is from the German patent 20 19 271 known. This known fuel assembly is particularly suitable for heavy water moderators Nuclear reactors all of its fuel rods point outside at the level of the spacers each on tunnels that are offset by 1200. These studs are for positioning the spacer in this spacer or in the spacer mesh. This results in a different change in length of the individual fuel rods Nuclear reactor fuel assembly within an operating nuclear reactor is not with special needs. Furthermore, the spacers each have on the outside of the outer sleeve two rigid sliding shoes and one of the fuel rods on the outer circumference of the nuclear reactor fuel assembly several axially offset, elastic sliding shoes in the radial direction which rest on the inside of the coolant guide tube in the nuclear reactor and thus together with the rigid sliding shoes, the entire fuel assembly bridging manufacturing tolerances keep the coolant guide tube free from vibrations caused by the coolant disturbance could be caused. The elastic sliding shoes are on the relevant Fuel rod each with the help of a mechanical connection such. B.

attached to a tear-off rivet. The application of these mechanical connections however, on the fuel rod can lead to a leak in the cladding tube, which is why the fuel rod carrying the elastic sliding shoes is not filled with nuclear fuel is.

The ones on the outside of the fuel rods of the nuclear reactor fuel assembly The studs located not only position the spacers, they prevent them also that if the cladding tube of a fuel rod breaks during operation in a nuclear reactor, the lower part of the fuel rod from the nuclear reactor fuel assembly slides out into the coolant guide tube and blocks this coolant guide tube.

Attaching the studs on the outside of the ducts for the However, fuel rods are particularly complex and can cause high costs, since z. B.

Incorrectly attached studs cannot be repaired by welding or soldering are, so that the cladding tube in question is scrap.

The invention is based on the object in a further development of the known Nuclear reactor fuel element the cladding tube committee and thus also the cladding tube costs to reduce considerably in the manufacture of the nuclear reactor fuel element.

To solve this problem, a nuclear reactor fuel element is the initially mentioned type according to the invention characterized in that in a known manner one of the fuel rods on the outside two mutually offset in the axial direction Has studs, between which the spacer is positioned, and that with the lower end of the fuel rod having the lugs a fall protection part in a form-fitting manner is connected, which extends transversely through the axial fall path of other fuel rods is arranged and an axial movement of these other fuel rods in the direction of fall limited.

In this way, only a single one or at most a few need The fuel rods of the nuclear reactor fuel element are provided with cleats on the outside to be.