WO1994005012A1 - Fuel pellet for liquid cooled nuclear reactors - Google Patents

Fuel pellet for liquid cooled nuclear reactors Download PDF

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Publication number
WO1994005012A1
WO1994005012A1 PCT/DE1993/000756 DE9300756W WO9405012A1 WO 1994005012 A1 WO1994005012 A1 WO 1994005012A1 DE 9300756 W DE9300756 W DE 9300756W WO 9405012 A1 WO9405012 A1 WO 9405012A1
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WO
WIPO (PCT)
Prior art keywords
fuel
pellet
nuclear
fuel pellet
temperature
Prior art date
Application number
PCT/DE1993/000756
Other languages
German (de)
French (fr)
Inventor
Günter LOHNERT
Herbert Reutler
Original Assignee
Siemens Aktiengesellschaft
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Filing date
Publication date
Application filed by Siemens Aktiengesellschaft filed Critical Siemens Aktiengesellschaft
Publication of WO1994005012A1 publication Critical patent/WO1994005012A1/en

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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
    • G21C3/02—Fuel elements
    • G21C3/04—Constructional details
    • G21C3/16—Details of the construction within the casing
    • G21C3/20—Details of the construction within the casing with coating on fuel or on inside of casing; with non-active interlayer between casing and active material with multiple casings or multiple active layers
    • 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

Definitions

  • the invention relates to a fuel pellet for a liquid-cooled nuclear reactor, in which one fuel is subjected to a nuclear reaction, which fuel pellet can be arranged alone or in groups in a cladding tube to form a fuel rod.
  • the fuel for liquid-cooled nuclear reactors is usually provided in the form of pellets, in particular tablets, made of uranium oxide and / or uranium carbide, which are pressed and sintered from the corresponding powder; these pellets are usually arranged in large numbers in cladding tubes to form fuel rods.
  • Cladding tubes generally consist of zirconium or alloyed zirconium and, under normal operating conditions, ensure essentially complete retention of the Reaction products that are released during the nuclear reaction taking place in the fuel.
  • spherical fuel elements instead of the fuel rods in liquid-cooled nuclear reactors, in which fuel particles containing uranium oxide with an average size of about 500 ⁇ m, which are embedded in a graphite matrix, are used .
  • the fuel particles are coated with silicon carbide and are known as "coated particles".
  • the coating of the fuel particles very reliably fulfills the function of safely retaining the reaction products formed in the fuel by the nuclear reaction. It could also be shown experimentally that such fuel particles can be tur prolonged exposure (for example, 500 hours) a Tempera ⁇ up to 1600 C ⁇ without the safe retention is limited.
  • a helium-cooled high-temperature nuclear reactor has been described in DE-C 30 16 402, which is so limited in its dimensions and consequently also in its output that the disturbances described above, in particular when completely shut down ⁇ case of all active cooling systems, the fuel elements never reach a temperature that is above the temperature of a safe retention of the fission products by the coating of the fuel particles.
  • the high-temperature nuclear reactor is updated ⁇ staltet that at each possible fault, the fuel reach a temperature of at most about 1600 * C.
  • a fuel assembly for a water-cooled nuclear reactor is described for example in DE 37 36 565 AI. This fuel assembly has fuel rods made of zircon or a zirconium alloy and containing fuel pellets.
  • the fuel rods serve, in particular, as already mentioned, to safely retain the reaction products formed by the nuclear reaction in the actual fuel.
  • the temperature resistance of the fuel element is therefore largely determined by the temperature resistance, in particular the melting point of the fuel rods. Therefore the safe retention of the reaction products is guaranteed up to this melting point.
  • the invention is based on the object of specifying a fuel pellet for a liquid-cooled nuclear reactor in which one fuel is subjected to a nuclear reaction, which fuel pellet can be arranged alone or in groups in a cladding tube to form a fuel rod, in which the reaction products are reliably retained even in the event of a malfunction that causes the core of the reactor to melt.
  • a fuel pellet which is intended for use in a liquid-cooled nuclear reactor and in which a fuel is subjected to a nuclear reaction and which can be arranged alone or in groups in a cladding tube to form a fuel rod and off there are a large number of fuel-containing fuel particles, each of which is provided with a coating which is essentially impenetrable for reaction products of the nuclear reaction even when the fuel pellet is exposed to a temperature which occurs when a nuclear reactor melts Temperature corresponds.
  • the term “essentially” means that the release of reaction products from a fuel pellet is limited to a few percent of the total reaction products present in the fuel pellet.
  • the fuel in the fuel pellet advantageously has uranium oxide and / or uranium carbide, and the covering of each fuel particle has a layer of zirconium carbide. Resistance up to 3000 ° C in hydrogen atmosphere has been demonstrated for such fuel particles.
  • the fuel pellet is conveniently shaped into a tablet and can therefore be used in a conventional fuel rod
  • Fuel element for a liquid-cooled, in particular water-cooled, nuclear reactor can be arranged.
  • the fuel particles of the fuel pellet are advantageously stored in a matrix of a binder; graphite is particularly suitable as a binder.
  • the fuel particles in the fuel pellet are, without prejudice to other configurations of the fuel pellet, advantageously approximately spherical and are therefore particularly suitable for powder-metallurgical processes for producing the fuel pellet.
  • the coating of each fuel particle is in the pellet Brennstoff ⁇ preferably up to a temperature of about 2500 * C substantially impenetrable, whereby the secure retention of reaction products in virtually any imaginable accident core melt is secured.
  • the invention also relates to the use of a fuel pellet in a nuclear reactor cooled with a liquid, in particular water, the fuel pellet being able to be arranged on its own or in a cladding tube to form a fuel rod and having a multiplicity of fuel-containing fuel particles, each of which are provided with a covering which is essentially impenetrable for fission products of the nuclear reaction even when the fuel pellet is exposed to a temperature which corresponds to a temperature in the event of a meltdown of the nuclear reactor.
  • the properties of the essentially impenetrable sheathing are exploited in such a way that a reliable retention of reaction products of the nuclear reaction is ensured in a liquid-cooled nuclear reactor for every conceivable disturbance.
  • the fuel is a substance that can be split by thermal neutrons, in particular uranium, and the nuclear reaction is a nuclear fission. Accordingly, a nuclear reactor in which uranium or a comparable substance is split by thermal neutrons can be operated practically completely safely with a view to avoiding the release of reaction products.
  • design parameters of a liquid-cooled nuclear reactor in which a fuel pellet according to the invention is to be used should be changed in such a way that that the time and temperature limits set by the properties of the coating of the fuel particles are not exceeded in the event of a fault. This can be done by reducing the power density of the nuclear reactor.
  • a suitable design of a basin intended for receiving a molten reactor core for the purpose of cooling the melt as quickly as possible, for example by enlarging a surface of the basin that is in contact with the soil, would also reduce the load on the coating of the fuel particles, namely in that shortly after the disturbance occurs, the temperature of the melt is significantly reduced.
  • the single figure shows a fuel pellet 1 in the form of a tablet, specifically a tablet with chamfered edges with respect to an axis 6.
  • the fuel pellet 1 has approximately spherical fuel particles 2 which are embedded in a matrix 5 consisting of a binder, in particular graphite.
  • Each fuel particle 2 contains fuel 3 inside, which is surrounded by an envelope 4.
  • Materials for the cladding 4 are selected so that even at a temperature which is a maximum temperature in the event of a core meltdown of a nuclear reactor in which the fuel pellet 1 is used and the fuel 3 of a nuclear reaction, in particular nuclear fission by thermal neutrons , is subjected, corresponds to, is essentially impenetrable for reaction products which have formed or are formed in the fuel 3 as a result of the nuclear reaction.
  • the fuel pellet according to the invention for a liquid-cooled nuclear reactor makes it possible to ensure safe retention of reaction products from a nuclear reaction to which the fuel has been subjected to the fuel pellet, even when the fuel pellet is exposed to a temperature which occurs when a nuclear reactor melts Temperature corresponds.

Abstract

A fuel pellet (1) for a liquid cooled nuclear reactor in which fuel (3) undergoes a nuclear reaction can be arranged by itself or together with a plurality of fuel pellets into a fuel rod inside a cladding tube. The fuel pellet (1) has a plurality of fuel particles (2) containing fuel (3), each provided with a cladding (4) impenetrable by nuclear reaction products even when the fuel pellet (1) is exposed to a temperature which corresponds to the temperature occurring when an accident causes fusion of the reactor core. This fuel pellet (1) ensures that the reaction products are reliably retained in any imaginable emergency situation even in the case of a water-cooled nuclear reactor.

Description

Brennstoffpellet für einen flüssigkeitsgekühlten KernreaktorFuel pellet for a liquid-cooled nuclear reactor
Die Erfindung betrifft ein Brennstoffpellet für einen flüssigkeitsgekühlten Kernreaktor, in dem ein Brennstoff einer Kernreaktion unterworfen wird, welches Brennstoff¬ pellet allein oder zu mehreren in einem Hüllrohr zu einem Brennstab anordenbar ist.The invention relates to a fuel pellet for a liquid-cooled nuclear reactor, in which one fuel is subjected to a nuclear reaction, which fuel pellet can be arranged alone or in groups in a cladding tube to form a fuel rod.
In Risikostudien wird die hauptsächliche, wenn auch äußerst geringe, von flüssigkeitsgekühlten Kernreaktoren ausgehende Gefahr darin gesehen, daß im Kernreaktor eine Störung stattfinden könnte, die zum Schmelzen des den Brennstoff enthaltenden Reaktorkerns führt, sei es durch eine Lei- stungsexkursion oder durch einen wie auch immer hervorge¬ rufenen Ausfall der Kühlung. Bei einer derartigen Störung können in der aus dem Reaktorkern entstandenen Schmelze Temperaturen bis zu 2500βC erreicht werden, wodurch Reak¬ tionsprodukte aus der in dem Reaktorkern oder der Schmelze stattgefundenen bzw. stattfindenden Kernreaktion freige¬ setzt werden.In risk studies, the main, albeit extremely low, risk from liquid-cooled nuclear reactors is seen in the fact that a malfunction could occur in the nuclear reactor that could cause the reactor core containing the fuel to melt, be it through a performance excursion or whatever caused cooling failure. In such an interference temperatures may be up to 2500 C β reached in the resulting melt from the reactor core, thereby Reak¬ tion products of which took place in the reactor core or the melt or nuclear reaction taking place freige¬ sets are.
Der Brennstoff für flüssigkeitsgekühlte Kernreaktoren wird üblicherweise in Form von Pellets, insbesondere Ta- bletten, aus Uranoxid und/oder Urancarbid bereitgestellt, welche aus entsprechendem Pulver gepreßt und gesintert werden; diese Pellets werden üblicherweise jeweils viel- zählig in Hüllrohren zu Brennstäben angeordnet. Hüllrohre bestehen in der Regel aus Zirkon oder legiertem Zirkon und sorgen in dem Reaktorkern unter normalen Betriebsbedingun¬ gen für eine im wesentlichen vollständige Rückhaltung der Reaktionsprodukte, die bei der in dem Brennstoff stattfin¬ denden Kernreaktion freigesetzt werden.The fuel for liquid-cooled nuclear reactors is usually provided in the form of pellets, in particular tablets, made of uranium oxide and / or uranium carbide, which are pressed and sintered from the corresponding powder; these pellets are usually arranged in large numbers in cladding tubes to form fuel rods. Cladding tubes generally consist of zirconium or alloyed zirconium and, under normal operating conditions, ensure essentially complete retention of the Reaction products that are released during the nuclear reaction taking place in the fuel.
Für gasgekühlte Hochtemperatur-Kernreaktoren kommen vor- zugsweise kugelförmige Brennelemente anstelle der Brenn¬ stäbe in flüssigkeitsgekühlten Kernreaktoren in Betracht, bei denen Uranoxid enthaltende Brennstoffpartikel mit einer mittleren Größe von etwa 500 μm , die in einer Ma¬ trix aus Graphit eingebettet sind, zum Einsatz kommen. Die Brennstoffpartikel sind mit einer Umhüllung aus Si- liziumcarbid versehen und unter der Bezeichnung "coated particles" bekannt. Die Umhüllung der Brennstoffpartikel erfüllt sehr zuverlässig die Funktion einer sicheren Rückhaltung der durch die Kernreaktion in dem Brennstoff gebildeten Reaktionsprodukte. Es konnte auch experimentell nachgewiesen werden, daß solche Brennstoffpartikel über längere Zeit (beispielsweise 500 Stunden) einer Tempera¬ tur bis zu 1600βC ausgesetzt werden können, ohne daß die sichere Rückhaltung eingeschränkt wird.For gas-cooled high-temperature nuclear reactors, preference is given to using spherical fuel elements instead of the fuel rods in liquid-cooled nuclear reactors, in which fuel particles containing uranium oxide with an average size of about 500 μm, which are embedded in a graphite matrix, are used . The fuel particles are coated with silicon carbide and are known as "coated particles". The coating of the fuel particles very reliably fulfills the function of safely retaining the reaction products formed in the fuel by the nuclear reaction. It could also be shown experimentally that such fuel particles can be tur prolonged exposure (for example, 500 hours) a Tempera¬ up to 1600 C β without the safe retention is limited.
Ausgehend von dieser Kenntnis ist in der DE-C 30 16 402 ein mit Helium gekühlter Hochtemperatur-Kernreaktor be¬ schrieben worden, der in seinen Abmessungen und demzufolge auch in seiner Leistung so begrenzt ist, daß bei den oben beschriebenen Störungen, insbesondere beim völligen Aus¬ fall aller aktiven Kühlsysteme, die Brennelemente zu keinem Zeitpunkt eine Temperatur erreichen, die oberhalb der Temperatur einer sicheren Rückhaltung der Spaltpro¬ dukte durch die Umhüllung der Brennstoffpartikel liegt. Insbesondere ist der Hochtemperatur-Kernreaktor so ausge¬ staltet, daß bei jeder möglichen Störung die Brennelemente eine Temperatur von höchstens etwa 1600*C erreichen. Ein Brennelement für einen wassergekühlten Kernreaktor ist beispielsweise in der DE 37 36 565 AI beschrieben. Dieses Brennelement weist Brennstäbe auf, die aus Zirkon oder einer Zirkonlegierung bestehen und Brennstoffpellets ent- halten. Die Brennstäbe, dienen insbesondere, wie bereits erwähnt, der sicheren Rückhaltung der durch die Kernreaktion im eigentlichen Brennstoff gebildeten Reaktionsprodukte. Die Temperaturbeständigkeit des Brennelementes ist somit wesentlich bestimmt durch die Temperaturbeständigkeit, ins- besondere den Schmelzpunkt der Brennstäbe. Daher ist die sichere Rückhaltung der Reaktionsprodukte höchstens bis zu diesem Schmelzpunkt gewährleistet.Based on this knowledge, a helium-cooled high-temperature nuclear reactor has been described in DE-C 30 16 402, which is so limited in its dimensions and consequently also in its output that the disturbances described above, in particular when completely shut down ¬ case of all active cooling systems, the fuel elements never reach a temperature that is above the temperature of a safe retention of the fission products by the coating of the fuel particles. In particular, the high-temperature nuclear reactor is ausge¬ staltet that at each possible fault, the fuel reach a temperature of at most about 1600 * C. A fuel assembly for a water-cooled nuclear reactor is described for example in DE 37 36 565 AI. This fuel assembly has fuel rods made of zircon or a zirconium alloy and containing fuel pellets. The fuel rods serve, in particular, as already mentioned, to safely retain the reaction products formed by the nuclear reaction in the actual fuel. The temperature resistance of the fuel element is therefore largely determined by the temperature resistance, in particular the melting point of the fuel rods. Therefore the safe retention of the reaction products is guaranteed up to this melting point.
Der Erfindung liegt die Aufgabe zugrunde, ein Brennstoff- pellet für einen flüssigkeitsgekühlten Kernreaktor anzu¬ geben, in dem ein Brennstoff einer Kernreaktion unterworfen wird, welches Brennstoffpellet allein oder zu mehreren in einem Hüllrohr zu einem Brennstab anordenbar ist, bei dem eine sichere Rückhaltung der Reaktionsprodukte auch im Fall einer Störung, bei der es zum Schmelzen des Reaktorkerns kommt, gewährleistet ist.The invention is based on the object of specifying a fuel pellet for a liquid-cooled nuclear reactor in which one fuel is subjected to a nuclear reaction, which fuel pellet can be arranged alone or in groups in a cladding tube to form a fuel rod, in which the reaction products are reliably retained even in the event of a malfunction that causes the core of the reactor to melt.
Die Lösung dieser Aufgabe erfolgt erfindungsgemäß dadurch, daß ein zur Verwendung in einem flüssigkeitsgekühlten Kern- reaktor, in dem ein Brennstoff einer Kernreaktion unterwor¬ fen wird, bestimmtes Brennstoffpellet, welches allein oder zu mehreren in einem Hüllrohr zu einem Brennstab anorden¬ bar ist und aus einer Vielzahl von Brennstoff enthaltenden Brennstoffpartikeln besteht, die je für sich mit einer Um- hüllung versehen sind, welche für Reaktionsprodukte der Kernreaktion auch dann im wesentlichen undurchdringlich ist, wenn das Brennstoffpellet einer Temperatur ausgesetzt wird, welche einer bei einem Kernschmelzunfall eines Kern¬ reaktors auftretenden Temperatur entspricht. Unter dem Begriff "im wesentlichen" ist zu verstehen, daß die Freisetzung von Reaktionsprodukten aus einem Brenn¬ stoffpellet begrenzt ist auf wenige Prozent der insgesamt in dem Brennstoffpellet vorhandenen Reaktionsprodukte. Da, wie oben ausgeführt, die bei einem Kernschmelzunfall aus dem Reaktorkern entstehende Schmelze eine Temperatur in der Größenordnung von 2500*C erreicht, sind die zur Verwendung in einem gasgekühlten Hochtemperatur-Kernreaktor bekannten Brennstoffpartikel mit Umhüllungen aus Siliziumcarbid für diesen Zweck ungeeignet.This object is achieved according to the invention in that a fuel pellet which is intended for use in a liquid-cooled nuclear reactor and in which a fuel is subjected to a nuclear reaction and which can be arranged alone or in groups in a cladding tube to form a fuel rod and off there are a large number of fuel-containing fuel particles, each of which is provided with a coating which is essentially impenetrable for reaction products of the nuclear reaction even when the fuel pellet is exposed to a temperature which occurs when a nuclear reactor melts Temperature corresponds. The term “essentially” means that the release of reaction products from a fuel pellet is limited to a few percent of the total reaction products present in the fuel pellet. Since, as stated above, the resulting in a nuclear meltdown from the reactor core melt, a temperature of the order of 2500 * C reached, for use in a high temperature gas cooled nuclear reactor known fuel particles with sheaths made of silicon carbide for this purpose are suitable.
Der Brennstoff in dem Brennstoffpellet weist günstigerwei¬ se Uranoxid und/oder Urancarbid auf, und die Umhüllung jedes Brennstoffpartikels weist eine Schicht aus Zirkon- carbid auf. Für derartige Brennstoffpartikel konnte eine Beständigkeit in Wasserstoffatmosphäre bis zu 3000°C nachgewiesen werden.The fuel in the fuel pellet advantageously has uranium oxide and / or uranium carbide, and the covering of each fuel particle has a layer of zirconium carbide. Resistance up to 3000 ° C in hydrogen atmosphere has been demonstrated for such fuel particles.
Das Brennstoffpellet ist günstigerweise zu einer Tablette geformt und kann somit in einem Brennstab eines üblichenThe fuel pellet is conveniently shaped into a tablet and can therefore be used in a conventional fuel rod
Brennelementes für einen flüssigkeitsgekühlten, insbesonde¬ re wassergekühlten, Kernreaktor angeordnet werden.Fuel element for a liquid-cooled, in particular water-cooled, nuclear reactor can be arranged.
Vorteilhafterweise sind die Brennstoffpartikel des Brenn- stoffpellets in einer Matrix aus einem Bindemittel eingela¬ gert; als Bindemittel kommt insbesondere Graphit in Frage.The fuel particles of the fuel pellet are advantageously stored in a matrix of a binder; graphite is particularly suitable as a binder.
Die Brennstoffpartikel in dem Brennstoffpellet sind unbe¬ schadet anderweitiger Ausgestaltungen des Brennstoffpellets vorteilhafterweise etwa kugelförmig und eignen sich damit besonders für pulvermetallurgische Prozesse zur Herstellung des Brennstoffpellets. Die Umhüllung jedes Brennstoffpartikels in dem Brennstoff¬ pellet ist vorzugsweise bis zu einer Temperatur von etwa 2500*C im wesentlichen undurchdringlich, womit der sichere Rückhalt für Reaktionsprodukte in praktisch jedem denkbaren Kernschmelzunfall gesichert ist.The fuel particles in the fuel pellet are, without prejudice to other configurations of the fuel pellet, advantageously approximately spherical and are therefore particularly suitable for powder-metallurgical processes for producing the fuel pellet. The coating of each fuel particle is in the pellet Brennstoff¬ preferably up to a temperature of about 2500 * C substantially impenetrable, whereby the secure retention of reaction products in virtually any imaginable accident core melt is secured.
Die Erfindung betrifft auch die Verwendung eines Brenn¬ stoffpellets in einem mit einer Flüssigkeit, insbesondere Wasser, gekühlten Kernreaktor, wobei das Brennstoffpellet allein oder zu mehreren in einem Hüllrohr zu einem Brennstab anordenbar ist und eine Vielzahl von Brennstoff enthalten¬ den Brennstoffpartikeln aufweist, die je für sich mit einer Umhüllung versehen sind, die für Spaltprodukte der Kern¬ reaktion auch dann im wesentlichen undurchdringlich ist, wenn das Brennstoffpellet einer Temperatur ausgesetzt wird, welche einer Temperatur bei einem Kernschmelzunfall des Kernreaktors entspricht. Auf diese Weise werden die Eigen¬ schaften der im wesentlichen undurchdringlichen Umhüllung in der Weise ausgenutzt, daß in einem flüssigkeitsgekühlten Kernreaktor bei jeder denkbaren Störung ein sicherer Rück¬ halt von Reaktionsprodukten der Kernreaktion gesichert ist. Von besonderer Bedeutung ist 'diese Verwendung dann, wenn der Brennstoff ein durch thermische Neutronen spaltbarer Stoff, insbesondere Uran, und die Kernreaktion eine Kern- Spaltung ist. Dementsprechend kann ein Kernreaktor, in dem Uran oder ein vergleichbarer Stoff durch thermische Neutro¬ nen gespalten wird, unter dem Aspekt der Vermeidung der Freisetzung von Reaktionsprodukten praktisch vollkommen sicher betrieben werden.The invention also relates to the use of a fuel pellet in a nuclear reactor cooled with a liquid, in particular water, the fuel pellet being able to be arranged on its own or in a cladding tube to form a fuel rod and having a multiplicity of fuel-containing fuel particles, each of which are provided with a covering which is essentially impenetrable for fission products of the nuclear reaction even when the fuel pellet is exposed to a temperature which corresponds to a temperature in the event of a meltdown of the nuclear reactor. In this way, the properties of the essentially impenetrable sheathing are exploited in such a way that a reliable retention of reaction products of the nuclear reaction is ensured in a liquid-cooled nuclear reactor for every conceivable disturbance. This use is of particular importance if the fuel is a substance that can be split by thermal neutrons, in particular uranium, and the nuclear reaction is a nuclear fission. Accordingly, a nuclear reactor in which uranium or a comparable substance is split by thermal neutrons can be operated practically completely safely with a view to avoiding the release of reaction products.
Unter Umständen sind Konstruktionsparameter eines flüssig¬ keitsgekühlten Kernreaktors, in dem ein erfindungsgemäßes Brennstoffpellet eingesetzt werden soll, so zu verändern, daß die durch die Eigenschaften der Umhüllung der Brenn- stoffpartikel zeitlich und temperaturmäßig gesetzten Gren¬ zen im Fall einer Störung nicht überschritten werden. Dies kann durch eine Verringerung der Leistungsdichte des Kern- reaktors geschehen. Eine geeignete Ausgestaltung eines zur Aufnahme eines geschmolzenen Reaktorkerns vorgesehenen Beckens zum Zwecke einer möglichst raschen Abkühlung der Schmelze, beispielsweise durch Vergrößerung einer mit dem Erdreich in Kontakt stehenden Oberfläche des Beckens, würde ebenfalls die Belastung der Umhüllung der Brennstoffpar¬ tikel verringern, nämlich dadurch, daß kurz nach Eintritt der Störung eine deutliche Absenkung der Temperatur der Schmelze bewirkt wird.Under certain circumstances, design parameters of a liquid-cooled nuclear reactor in which a fuel pellet according to the invention is to be used should be changed in such a way that that the time and temperature limits set by the properties of the coating of the fuel particles are not exceeded in the event of a fault. This can be done by reducing the power density of the nuclear reactor. A suitable design of a basin intended for receiving a molten reactor core for the purpose of cooling the melt as quickly as possible, for example by enlarging a surface of the basin that is in contact with the soil, would also reduce the load on the coating of the fuel particles, namely in that shortly after the disturbance occurs, the temperature of the melt is significantly reduced.
Ein Ausführungsbeispiel der Erfindung ist in der Zeichnung dargestellt.An embodiment of the invention is shown in the drawing.
Aus der einzigen Figur geht ein Brennstoffpellet 1 in Form einer Tablette, und zwar einer bezüglich einer Achse 6 etwa zylindrischen Tablette mit angefasten Kanten, her¬ vor. Das Brennstoffpellet 1 weist etwa kugelförmige Brenn- stoffpartikel 2 auf, die in einer aus einem Bindemittel, insbesondere Graphit, bestehenden Matrix 5 eingelagert sind. Jeder Brennstoffpartikel 2 enthält im Inneren Brenn- stoff 3, welcher von einer Umhüllung 4 umgeben ist. Werk¬ stoffe für die Umhüllung 4 sind so ausgewählt, daß auch bei einer Temperatur, welcher einer Maximaltemperatur bei einem Kernschmelzunfall eines Kernreaktors, in dem das Brenn¬ stoffpellet 1 eingesetzt ist und der Brennstoff 3 einer Kernreaktion, insbesondere einer Kernspaltung durch ther¬ mische Neutronen, unterworfen wird, entspricht, im wesent¬ lichen undurchdringlich ist für Reaktionsprodukte, die sich durch die Kernreaktion in dem Brennstoff 3 gebildet haben oder bilden. Das erfindungsgemäße Brennstoffpellet für einen flüssig¬ keitsgekühlten Kernreaktor ermöglicht es, einen sicheren Rückhalt von Reaktionsprodukten aus einer Kernreaktion, der der Brennstoff dem Brennstoffpellet unterworfen wurde, auch dann zu gewährleisten, wenn das Brennstoffpellet einer Temperatur ausgesetzt ist, welche einer bei einem Kernschmelzunfall eines Kernreaktors auftretenden Tempera¬ tur entspricht. The single figure shows a fuel pellet 1 in the form of a tablet, specifically a tablet with chamfered edges with respect to an axis 6. The fuel pellet 1 has approximately spherical fuel particles 2 which are embedded in a matrix 5 consisting of a binder, in particular graphite. Each fuel particle 2 contains fuel 3 inside, which is surrounded by an envelope 4. Materials for the cladding 4 are selected so that even at a temperature which is a maximum temperature in the event of a core meltdown of a nuclear reactor in which the fuel pellet 1 is used and the fuel 3 of a nuclear reaction, in particular nuclear fission by thermal neutrons , is subjected, corresponds to, is essentially impenetrable for reaction products which have formed or are formed in the fuel 3 as a result of the nuclear reaction. The fuel pellet according to the invention for a liquid-cooled nuclear reactor makes it possible to ensure safe retention of reaction products from a nuclear reaction to which the fuel has been subjected to the fuel pellet, even when the fuel pellet is exposed to a temperature which occurs when a nuclear reactor melts Temperature corresponds.

Claims

Patentansprüche Claims
1. Brennstoffpellet (1) für einen flüssigkeitsgekühlten Kernreaktor, in dem ein Brennstoff (3) einer Kernreaktion unterworfen wird, welches Brennstoffpellet (1) allein oder zu mehreren in einem Hüllrohr zu einem Brennstab anordenbar ist und eine Vielzahl von Brennstoff (3) enthaltenden Brennstoffpartikeln (2) aufweist, die je für sich mit einer Umhüllung (4) versehen sind, welche für Reaktionsprodukte der Kernreaktion auch dann im wesentlichen undurchdring¬ lich ist, wenn das Brennstoffpellet (1) einer Temperatur ausgesetzt wird, welche einer bei einem Kernschmelzunfall eines Kernreaktors auftretenden Temperatur entspricht.1. fuel pellet (1) for a liquid-cooled nuclear reactor in which a fuel (3) is subjected to a nuclear reaction, which fuel pellet (1) can be arranged alone or in a cladding tube to form a fuel rod and a plurality of fuel particles (3) containing fuel (2), each of which is provided with a covering (4), which is essentially impenetrable for reaction products of the nuclear reaction even when the fuel pellet (1) is exposed to a temperature which would occur in the event of a meltdown of a nuclear reactor occurring temperature corresponds.
2. Brennstoffpellet (1) nach Anspruch 1, bei dem der2. Fuel pellet (1) according to claim 1, wherein the
Brennstoff (3) Uranoxid und/oder Urancarbid aufweist und bei dem die Umhüllung (4) jedes Brennstoffparti<els (2) eine Schicht aus Zirkoncarbid aufweist.Fuel (3) has uranium oxide and / or uranium carbide and in which the casing (4) of each fuel part (2) has a layer of zirconium carbide.
3. Brennstoffpellet (1) nach Anspruch 1 oder 2, welches zu einer Tablette geformt ist.3. Fuel pellet (1) according to claim 1 or 2, which is shaped into a tablet.
4. Brennstoffpellet (1) nach einem der vorhergehenden An¬ sprüche, bei dem die Brennstoffpartikel (2) in einer Ma- trix (5) aus einem Bindemittel, insbesondere Graphit, ein¬ gelagert sind.4. Fuel pellet (1) according to one of the preceding claims, in which the fuel particles (2) are embedded in a matrix (5) made of a binder, in particular graphite.
5. Brennstoffpellet (1) nach einem der vorhergehenden An¬ sprüche, bei dem die Brennstoffpartikel (2) etwa kugelförmig sind.5. Fuel pellet (1) according to one of the preceding claims, in which the fuel particles (2) are approximately spherical.
6. Brennstoffpellet (1) nach einem der vorhergehenden An¬ sprüche, bei dem die Umhüllung (4) jedes Brennstoffpartikels (2) bis zu einer Temperatur von etwa 2500"C im wesentlichen undurchdringlich ist. 6. Fuel pellet (1) according to one of the preceding claims, in which the casing (4) of each fuel particle (2) is essentially impenetrable up to a temperature of approximately 2500 ° C.
7. Verwendung eines Brennstoffpellets (1), in dem ein Brennstoff (3) einer Kernreaktion unterworfen wird, wel¬ ches allein oder zu mehreren in einem Hüllrohr zu einem Brennstab anordenbar ist und welches eine Vielzahl von Brennstoff (3) enthaltenden Brennstoffpartikeln (2) auf¬ weist, die je für sich mit einer Umhüllung (4) versehen sind, die für Reaktionsprodukte der Kernreaktion auch dann im wesentlichen undurchdringlich ist, wenn das Brennstoff¬ pellet (1) einer Temperatur ausgesetzt wird, welche einer Temperatur in einem Kernschmelzunfall eines Kernreaktors entspricht, in einem Kernreaktor, der mittels einer Flüs¬ sigkeit gekühlt ist.7. Use of a fuel pellet (1) in which a fuel (3) is subjected to a nuclear reaction, which alone or in groups can be arranged in a cladding tube to form a fuel rod and which contains a large number of fuel particles (2) containing fuel particles (2) has, which are each provided with a covering (4) which is essentially impenetrable for reaction products of the nuclear reaction even when the fuel pellet (1) is exposed to a temperature which is the temperature in a core meltdown of a nuclear reactor corresponds in a nuclear reactor which is cooled by means of a liquid.
8. Verwendung nach Anspruch 7, wobei der Kernreaktor mit- tels Wasser gekühlt wird.8. Use according to claim 7, wherein the nuclear reactor is cooled by means of water.
9. Verwendung nach Anspruch 7 oder 8, wobei der Brennstoff (3) ein durch thermische Neutronen spaltbarer Stoff ist und wobei die Kernreaktion eine Kernspaltung ist. 9. Use according to claim 7 or 8, wherein the fuel (3) is a fissionable material by thermal neutrons and wherein the nuclear reaction is a fission.
PCT/DE1993/000756 1992-08-21 1993-08-19 Fuel pellet for liquid cooled nuclear reactors WO1994005012A1 (en)

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Publication number Priority date Publication date Assignee Title
DE4433032C1 (en) * 1994-09-16 1996-01-04 Forschungszentrum Juelich Gmbh Safer nuclear reactor with combined water coolant and moderator
FR2807563B1 (en) * 2000-04-07 2002-07-12 Framatome Sa NUCLEAR FUEL ASSEMBLY FOR A LIGHT WATER-COOLED REACTOR COMPRISING A NUCLEAR FUEL MATERIAL IN THE FORM OF PARTICLES

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1074426A (en) * 1964-09-28 1967-07-05 Minnesota Mining & Mfg Improvements in or relating to nuclear fuels
GB1376365A (en) * 1973-02-07 1974-12-04 Atomic Energy Authority Uk Nuclear fuel compacts
JPH02159597A (en) * 1988-12-12 1990-06-19 Nuclear Fuel Ind Ltd Coated fuel particle coated with hardened over-coat and manufacturing of nuclear fuel using it
EP0376583A1 (en) * 1988-12-29 1990-07-04 General Atomics Nuclear fuel particles and method of making nuclear fuel compacts

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3039944A (en) * 1959-05-13 1962-06-19 Zumwalt Lloyd Robert Fuel element
DE2207655C3 (en) * 1972-02-18 1979-04-12 Kernforschungszentrum Karlsruhe Gmbh, 7500 Karlsruhe Process for improving the compatibility of oxidic nuclear fuels with the materials of the surrounding fuel element cladding
DE3016402A1 (en) * 1980-04-29 1981-11-05 GHT Gesellschaft für Hochtemperaturreaktor-Technik mbH, 5060 Bergisch Gladbach HIGH-TEMPERATURE REACTOR IN MODULAR DESIGN
DE3736565C2 (en) * 1987-10-28 1995-12-14 Siemens Ag Nuclear reactor fuel element

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1074426A (en) * 1964-09-28 1967-07-05 Minnesota Mining & Mfg Improvements in or relating to nuclear fuels
GB1376365A (en) * 1973-02-07 1974-12-04 Atomic Energy Authority Uk Nuclear fuel compacts
JPH02159597A (en) * 1988-12-12 1990-06-19 Nuclear Fuel Ind Ltd Coated fuel particle coated with hardened over-coat and manufacturing of nuclear fuel using it
EP0376583A1 (en) * 1988-12-29 1990-07-04 General Atomics Nuclear fuel particles and method of making nuclear fuel compacts

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 014, no. 415 (P - 1102) 7 September 1990 (1990-09-07) *

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