EP0720766A1 - Nuclear fuel sintered body and process for producing it - Google Patents

Nuclear fuel sintered body and process for producing it

Info

Publication number
EP0720766A1
EP0720766A1 EP94926937A EP94926937A EP0720766A1 EP 0720766 A1 EP0720766 A1 EP 0720766A1 EP 94926937 A EP94926937 A EP 94926937A EP 94926937 A EP94926937 A EP 94926937A EP 0720766 A1 EP0720766 A1 EP 0720766A1
Authority
EP
European Patent Office
Prior art keywords
nuclear fuel
sintered body
surface film
boron
particles
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.)
Ceased
Application number
EP94926937A
Other languages
German (de)
French (fr)
Inventor
Gerhard Gradel
Alfons Roppelt
Martin Peehs
Harald Cura
Klaus Koebke
Erhard Ortlieb
Richard A. Perkins
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Siemens AG
Original Assignee
Siemens AG
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Siemens AG filed Critical Siemens AG
Priority to EP94926937A priority Critical patent/EP0720766A1/en
Publication of EP0720766A1 publication Critical patent/EP0720766A1/en
Ceased legal-status Critical Current

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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
    • G21C3/42—Selection of substances for use as reactor fuel
    • G21C3/58—Solid reactor fuel Pellets made of fissile material
    • G21C3/62—Ceramic fuel
    • G21C3/623—Oxide fuels
    • 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
    • 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
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S376/00—Induced nuclear reactions: processes, systems, and elements
    • Y10S376/90—Particular material or material shapes for fission reactors
    • Y10S376/901—Fuel

Definitions

  • the invention relates to a nuclear fuel sintered body according to claim 1, a nuclear reactor fuel element according to claim 13 and a method for producing a nuclear fuel sintered body according to claim 14.
  • EP-A1-0 239 843 discloses a nuclear fuel sintered body made of U ⁇ 2 (U, Pu) ⁇ 2 and (U, Th) ⁇ 2.
  • This known nuclear fuel sintered body is obtained by producing a mixture of uranium oxide powder or uranium mixed oxide powder with uranium boride or boron carbide powder and pressing it into compacts, which are then sintered in a sintering furnace in a reducing sintering atmosphere to form nuclear fuel sintered bodies.
  • the boron is thus distributed uniformly everywhere in the sintered matrix.
  • Boron in uranium-containing nuclear fuel sintered bodies is a neutron absorber that can be burned off in terms of physical physics and, after a certain period of use, these nuclear fuel sintered bodies lose their property as an absorber for thermal neutrons in a nuclear reactor.
  • Nuclear reactor fuel elements with fuel rods which contain uranium-containing nuclear fuel sintered bodies are used in the nuclear reactor, for example, during four successive, generally equally long fuel element cycles. At the end of a fuel element cycle, some of the nuclear reactor fuel elements in the nuclear reactor are replaced by fresh, unirradiated nuclear reactor fuel elements.
  • the fresh, unirradiated nuclear reactor fuel elements would bring about a relatively high reactivity in the nuclear reactor compared to the already irradiated nuclear reactor fuel elements.
  • the boron in the nuclear fuel sintered bodies of these fresh, unirradiated nuclear reactor fuel elements initially dampens the reactivity brought about by these nuclear reactor fuel elements by initially absorbing thermal neutrons.
  • the nuclear fuel of fresh and unirradiated nuclear reactor fuel elements gradually burns off in the nuclear reactor by nuclear fission, but at the same time a combustible neutron absorber present in this nuclear fuel gradually burns off neutron physically, so that this neutron absorber finally has little or no thermal energy Neutrons absorb. That is why even freshly inserted unirradiated nuclear reactor fuel elements in the nuclear reactor can have about the same reactivity in the nuclear reactor during their entire service life in the nuclear reactor as the nuclear reactor fuel elements that have already undergone a fuel element cycle in the nuclear reactor.
  • Boron as a neutron absorber in the nuclear fuel is compared to other combustible neutron absorbers such as rare earths
  • the fuel element cycles are relatively long, e.g. are longer than 12 months, since boron prevents heat build-up in the nuclear fuel.
  • the invention is based on the object of developing the known nuclear fuel sintered body so that there is no increase in reactivity which is too rapid and too high when starting up a nuclear reactor if this nuclear fuel sintered body is freshly introduced into this nuclear reactor in the unirradiated state .
  • the particles of boron or a chemical boron compound with a are provided surface film that holds back boron, this boron cannot escape from the nuclear fuel sintered body according to the invention. This ensures an increase in reactivity which is damped with regard to its speed and height.
  • the surface film advantageously contains no boron at all.
  • Claims 2 to 12 are directed to advantageous further developments of the nuclear fuel sintered body according to claim 1.
  • the further development according to claim 9 ensures good retention of boron
  • the further development according to claim 10 ensures a largely uniform distribution of the particles of boron or chemical boron compound in the sintered matrix of the nuclear fuel sintered body enables.
  • Claim 13 relates to a nuclear reactor fuel element with a fuel rod which contains such a nuclear fuel sintered body in a cladding tube.
  • the method according to claim 14 allows a relatively simple production of a nuclear fuel sintered body which contains particles of boron and / or a chemical boron compound provided with the surface film.
  • Claims 14 and 15 are directed to advantageous developments of this method.
  • UO2 powder is used as the powdered starting oxide and is obtained, for example, in accordance with the ammonium uranyl carbonate or AUC process (for example, Gemelin Handbook of Inorganic Chemistry, Uranium, Supplement Volume A3, 1981, pplOl to 104).
  • This U ⁇ 2 "powder has an average particle diameter of 15 to 20 .mu.m.
  • the U ⁇ 2 ⁇ powder can also by another method, such as the ammonium diuranate (ADU) process (e.g.
  • crystalline boron powder 300 ppm of crystalline boron powder, the average particle diameter of which is 20 to 25 ⁇ m, is added to the U ⁇ 2 ⁇ powder.
  • the particles of this crystalline boron powder have a surface film made of metallic molybdenum, the film thickness of which is approximately 5 ⁇ m. This surface film is in a sputtering device (e.g. E. Lang, "Coatings For High Temperature
  • the sputtering device has an electrically conductive anode body, for example made of aluminum, on which crystalline boron powder was located. Furthermore, a cathode body is made of The crystalline starting boron powder with a mean starting particle size of about 15 ⁇ m is treated between anode and cathode body in a argon atmosphere at a direct electrical voltage of about 2000 V during a sputtering time of about 2.
  • the crystalline boron powder rolls again and again during this sputtering on an inclined plane from the anode body, so that a uniformly thick, firmly adhering and all-round dense surface film of molybdenum is achieved on the boron powder particles.
  • the surface film can also consist of at least one of the metals, ruthenium, tungsten and chromium or of at least one of the alloys molybdenum-based alloy, ruthenium-based alloy, tungsten-based alloy and chromium-based alloy. It is favorable if this surface film from a
  • Chromium-nickel alloy or a molybdenum-niobium alloy exists.
  • the metals of these two alloys all have one relatively small capture cross section for thermal neutrons.
  • the metals rhenium, rhodium and hafnium and the base alloys of these metals are also suitable for the surface film, since these metals have a large initial cross section for thermal neutrons, but do not burn out neutron physically as quickly as boron Therefore, in conjunction with boron, particularly long fuel element cycles are possible.
  • the surface film can also consist of at least one of the non-metals tantalum carbide, niobium carbide, titanium carbide, tantalum carbide, niobium carbide, titanium carbide, zirconium carbide, chro carbide, vanadium carbide, tungsten carbide, molybdenum carbide, tantalum nitride, niobium nitride, titanium nitride, zirconium nitride, zirconium nitride Vanadium silicide, tungsten silicide, molybdenum silicide, zirconium silicide, magnesium oxide, beryllium oxide, chromium oxide, calcium oxide, cerium oxide and zirconium oxide exist.
  • the surface film consists of at least one of the substances silicon carbide and silicon nitride, preferably Si3N4.
  • the capture cross section for thermal neutrons of these non-metals is particularly small.
  • These non-metals are advantageously applied in the form of a surface film to the boron powder particles by precipitating the reaction product of a chemical gas phase reaction of chemical compounds which contain the components of the surface film (for example chemical vapor deposition (CVD) processes according to E. Lang , “Coating For High Temperature Applications", 1983, Applied Science Publishers, London and New York, pp.33 to 78). In this way, however, a metallic surface film can also be applied to the boron powder particles.
  • CVD chemical vapor deposition
  • 0.2% by weight of powdered zinc stearate is also added to the UO2 powder with the added crystalline boron powder as a pressing aid.
  • powdered aluminum distearate can also be used as a pressing aid.
  • the UO2 powder with the added boron powder and the added pressing aid is then mixed intimately in a tumbling mixer for 15 minutes.
  • about 5% powdered U3O3 can be added to the powder in the tumble mixer as a pore former.
  • compacts are pressed from the mixture obtained by intimate mixing, which are sintered in a hydrogen atmosphere at a sintering temperature of 1750 ° C. for three hours.
  • the nuclear fuel sintered bodies After cooling, the nuclear fuel sintered bodies have a specific density of approximately 10.30 g / cm 3 to 10.55 g / cm 3 while the specific density of the boron particles in the sintered matrix is 7 to 9 g / cm 3 , that is to say in the favorable range of 5 g / cm 3 to 10 g / cm 3 .
  • Boron analysis of the nuclear fuel sintered bodies after sintering shows a boron concentration of 295 ppm, that is to say only a very small boron loss within the measuring accuracy.
  • the equivalent diameter of the boron particles (diameter of a sphere whose spherical volume is equal to the boron particle volume) in the sintered matrix is in the favorable range from 5 ⁇ m to 300 ⁇ m.
  • the thickness of the surface film on these boron particles, which consists of a different material than the sinter matrix and the boron particles is in the favorable range from 0.3 ⁇ m to 30 ⁇ m.
  • Such boron particles show practically no tendency to segregate, in particular in UO2 powder which has been obtained by the processes indicated above. No boron escapes from them during sintering.
  • the boron concentration in the sinter matrix of the nuclear fuel sintered body is in the range from 100 ppm to 10,000 ppm; because on the one hand a strong damping of the speed and amount of the increase in reactivity can be achieved in a nuclear reactor into which such nuclear fuel sintered bodies are introduced as part of a fresh nuclear reactor fuel element, but on the other hand the formation of cracks in the sintered matrix of the nuclear fuel sintered body is avoided.
  • the isotope B] _Q in the boron in the boron or in the boron-containing chemical compounds used is enriched compared to the natural isotope composition of boron. This can be achieved in a known manner, for example by cyclotron, diffusion or separation nozzle enrichment. This isotope B I _ Q practically absorbs the thermal neutrons. Due to its accumulation in the boron, which is located in the sintered matrix of the nuclear fuel sintered body, the concentration of this boron can be chosen to be relatively low.
  • a nuclear reactor fuel element for a nuclear reactor.
  • a nuclear reactor fuel element is advantageously provided for a light water nuclear reactor, in particular for a pressurized water nuclear reactor or a boiling water nuclear reactor.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Ceramic Engineering (AREA)
  • Plasma & Fusion (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Powder Metallurgy (AREA)
  • Monitoring And Testing Of Nuclear Reactors (AREA)

Abstract

A nuclear fuel interbody of UO2 or one of the mixed oxides (U, Pu)O2, (U, Th)O2, (U, RE)O2, (U, Pu, RE)O2, (U, Th, RE)O2 and (U, Pu, Th, RE)O2 (RE = rare earth) has particles of boron and/or a chemical boron compound in the sintered matrix. To retain the boron, these particles are coated with a surface film consisting of a different substance from the sinter matrix and the particles. A nuclear reactor fuel element has a fuel rod containing such a nuclear fuel sintered body in a jacket rod.

Description

Beschreibungdescription
KERNBRENNSTOFFSINTERKÖRPER UND VERFAHREN ZU SEINER HERSTELLUNGNUCLEAR FUEL INTERBODE AND METHOD FOR THE PRODUCTION THEREOF
Die Erfindung betrifft einen Kernbrennstoffsinterkörper nach Patentanspruch 1, ein Kernreaktorbrennelement nach Patentan¬ spruch 13 und ein Verfahren zum Herstellen eines Kernbrenn- stoffsinterkörpers nach Patentanspruch 14.The invention relates to a nuclear fuel sintered body according to claim 1, a nuclear reactor fuel element according to claim 13 and a method for producing a nuclear fuel sintered body according to claim 14.
Aus der EP-A1-0 239 843 ist ein Kernbrennstoffsinterkörper aus Uθ2 (U,Pu)θ2 und (U,Th)θ2 bekannt. In der Sintermatrix dieses Kernbrennstoff-Sinterkörpers ist Bor als Neutronengift in der chemischen Verbindung UBX mit x=2 ; 4 und/oder 12 und/oder B4C eingebaut. Dieser bekannte Kernbrennstoffsinter¬ körper wird gewonnen, indem ein Gemisch aus Uranoxidpulver oder Uranmischoxidpulver mit Uranborid- oder Borcarbidpulver hergestellt und zu Preßlingen gepreßt wird, die anschließend in einem Sinterofen in einer reduzierend wirkenden Sinterat¬ mosphäre zu Kernbrennstoffsinterkörpern gesintert werden. In diesen Kernbrennstoffsinterkörpern ist somit das Bor in der Sintermatrix überall gleichmäßig verteilt.EP-A1-0 239 843 discloses a nuclear fuel sintered body made of Uθ2 (U, Pu) θ2 and (U, Th) θ2. In the sintered matrix of this nuclear fuel sintered body, boron is a neutron poison in the chemical compound UB X with x = 2; 4 and / or 12 and / or B4C installed. This known nuclear fuel sintered body is obtained by producing a mixture of uranium oxide powder or uranium mixed oxide powder with uranium boride or boron carbide powder and pressing it into compacts, which are then sintered in a sintering furnace in a reducing sintering atmosphere to form nuclear fuel sintered bodies. In these nuclear fuel sintered bodies, the boron is thus distributed uniformly everywhere in the sintered matrix.
Bor in uranhaltigen Kernbrennstoffsinterkörpern ist ein neu¬ tronenphysikalisch abbrennbarer Neutronenabsorber, der nach einer gewissen Einsatzzeit dieser Kernbrennstoffsinterkörper in einem Kernreaktor seine Eigenschaft als Absorber für ther¬ mische Neutronen verliert.Boron in uranium-containing nuclear fuel sintered bodies is a neutron absorber that can be burned off in terms of physical physics and, after a certain period of use, these nuclear fuel sintered bodies lose their property as an absorber for thermal neutrons in a nuclear reactor.
Kernreaktorbrennelemente mit Brennstäben, die uranhaltige Kernbrennstoffsinterkörper enthalten, werden z.B. während vier aufeinanderfolgender, in der Regel gleichlanger Brenn¬ element-Zyklen im Kernreaktor eingesetzt. Am Ende eines Brennelement-Zyklus wird jeweils ein Teil der Kernreaktor¬ brennelemente im Kernreaktor durch frische, unbestrahlte Kernreaktorbrennelemente ersetzt . Die frischen, unbestrahlten Kernreaktorbrennelemente würden im Kernreaktor verglichen mit den bereits bestrahlten Kern¬ reaktorbrennelementen eine verhältnismäßig hohe Reaktivität bewirken. Das Bor in den Kernbrennstoff-Sinterkörpern dieser frischen, unbestrahlten Kernreaktorbrennelemente dämpft zu¬ nächst jedoch die durch diese Kernreaktorbrennelemente be¬ wirkte Reaktivität, in dem es anfänglich thermische Neutronen absorbiert.Nuclear reactor fuel elements with fuel rods which contain uranium-containing nuclear fuel sintered bodies are used in the nuclear reactor, for example, during four successive, generally equally long fuel element cycles. At the end of a fuel element cycle, some of the nuclear reactor fuel elements in the nuclear reactor are replaced by fresh, unirradiated nuclear reactor fuel elements. The fresh, unirradiated nuclear reactor fuel elements would bring about a relatively high reactivity in the nuclear reactor compared to the already irradiated nuclear reactor fuel elements. However, the boron in the nuclear fuel sintered bodies of these fresh, unirradiated nuclear reactor fuel elements initially dampens the reactivity brought about by these nuclear reactor fuel elements by initially absorbing thermal neutrons.
Der Kernbrennstoff frischer und unbestrahlter Kernreaktor¬ brennelemente brennt im Kernreaktor durch Kernspaltung all¬ mählich ab, zugleich brennt aber auch ein in diesem Kern¬ brennstoff vorhandener abbrennbarer Neutronenabsorber neutro- nenphysikalisch allmählich ab, so daß dieser Neutronenabsor¬ ber schließlich keine oder nur noch wenige thermische Neutro¬ nen absorbier .Deshalb können auch frisch in den Kernreaktor eingesetzte unbestrahlte Kernreaktorbrennelemente während ih¬ rer gesamten Standzeit im Kernreaktor etwa gleiche Reaktivi- tat im Kernreaktor wie die Kernreaktorbrennelemente bewirken, die schon einen Brennelement-Zyklus im Kernreaktor hinter sich haben.The nuclear fuel of fresh and unirradiated nuclear reactor fuel elements gradually burns off in the nuclear reactor by nuclear fission, but at the same time a combustible neutron absorber present in this nuclear fuel gradually burns off neutron physically, so that this neutron absorber finally has little or no thermal energy Neutrons absorb. That is why even freshly inserted unirradiated nuclear reactor fuel elements in the nuclear reactor can have about the same reactivity in the nuclear reactor during their entire service life in the nuclear reactor as the nuclear reactor fuel elements that have already undergone a fuel element cycle in the nuclear reactor.
Bor als Neutronenabsorber im Kernbrennstoff ist gegenüber an- deren abbrennbaren Neutronenabsorbern wie Seltene Erden vonBoron as a neutron absorber in the nuclear fuel is compared to other combustible neutron absorbers such as rare earths
Vorteil, wenn die Brennelemen -Zyklen verhältnismäßig lang, also z.B. länger als 12 Monate sind, da mit Bor Wärmestau im Kernbrennstoff vermieden wird.Advantage if the fuel element cycles are relatively long, e.g. are longer than 12 months, since boron prevents heat build-up in the nuclear fuel.
Der Erfindung liegt die Aufgabe zugrunde, den bekannten Kern¬ brennstoff-Sinterkörper weiterzubilden, so daß kein zu schneller und zu hoher Reaktivitätεanstieg beim Anfahren ei¬ nes Kernreaktors bewirkt wird, wenn dieser Kernbrennstoffsin¬ terkörper im unbestrahlten Zustand frisch in diesen Kernreak- tor eingebracht ist.The invention is based on the object of developing the known nuclear fuel sintered body so that there is no increase in reactivity which is too rapid and too high when starting up a nuclear reactor if this nuclear fuel sintered body is freshly introduced into this nuclear reactor in the unirradiated state .
Da beim erfindungsgemäßen Kernbrennstoffsinterkörper die Par¬ tikel aus Bor oder einer chemischen Borverbindung mit einem Oberflächenfilm versehen sind, der Bor zurückhält, kann die¬ ses Bor nicht aus dem erfindungsgemäßen Kernbrennstoff-Sin¬ terkörper austreten. Damit ist ein Reaktivitätsanstieg ge¬ währleistet, der hinsichtlich seiner Geschwindigkeit und Höhe gedämpft ist .Günstigerweise enthält der Oberflächenfilm über¬ haupt kein Bor.Since in the nuclear fuel sintered body according to the invention the particles of boron or a chemical boron compound with a Are provided surface film that holds back boron, this boron cannot escape from the nuclear fuel sintered body according to the invention. This ensures an increase in reactivity which is damped with regard to its speed and height. The surface film advantageously contains no boron at all.
Die Patentansprüche 2 bis 12 sind auf vorteilhafte Weiterbil¬ dungen des Kernbrennstoffsinterkörpers nach Patentanspruch 1 gerichtet .Insbesondere die Weiterbildung nach Patentanspruch 9 gewährleistet ein gutes Zurückhalten des Bors, während die Weiterbildung nach Patentanspruch 10 eine weitgehend gleich¬ mäßige Verteilung der Partikel aus Bor bzw. der chemischen Borverbindung in der Sintermatrix des Kernbrennstoff-Sinter- körpers ermöglicht. Patentanspruch 13 betrifft ein Kernreak¬ torbrennelement mit einem Brennstab, der in einem Hüllrohr einen solchen Kernbrennstoffsinterkörper enthält.Claims 2 to 12 are directed to advantageous further developments of the nuclear fuel sintered body according to claim 1. In particular, the further development according to claim 9 ensures good retention of boron, while the further development according to claim 10 ensures a largely uniform distribution of the particles of boron or chemical boron compound in the sintered matrix of the nuclear fuel sintered body enables. Claim 13 relates to a nuclear reactor fuel element with a fuel rod which contains such a nuclear fuel sintered body in a cladding tube.
Das Verfahren nach Patentanspruch 14 erlaubt ein verhältnis- mäßig einfaches Herstellen eines Kernbrennstoffsinterkörpers, der mit dem Oberflächenfilm versehene Partikel aus Bor und/oder einer chemischen Borverbindung enthält. Die Patent¬ ansprüche 14 und 15 sind auf vorteilhafte Weiterbildungen dieses Verfahrens gerichtet .The method according to claim 14 allows a relatively simple production of a nuclear fuel sintered body which contains particles of boron and / or a chemical boron compound provided with the surface film. Claims 14 and 15 are directed to advantageous developments of this method.
Die Erfindung und ihre Vorteile seien anhand von Ausführungs- beispielen näher erläutert:The invention and its advantages are explained in more detail with reference to exemplary embodiments:
Als pulverförmiges Ausgangsoxid wird UO2-Pulver verwendet, das beispielsweise entsprechend dem Ammoniumuranylcarbonat- bzw. AUC-Verfahren (z.B. Gemelin Handbuch der Anorganischen Chemie, Uran, Ergänzungsband A3, 1981, pplOl bis 104) gewon¬ nen wird. Dieses Uθ2"Pulver hat einen mittleren Partikel¬ durchmesser von 15 bis 20 um. Das Uθ2~Pulver kann auch nach einem anderen Verfahren, z.B. dem Ammoniumdiuranat- (ADU-) Verfahren (z.B. Gmelin Handbuch der Anorganischen Chemie, Uran, Ergänzungsband A3, 1981, pp 99 bis 101) , dem IDR-Verfah- ren oder dem DC-Verfahren (z.B. Gmelin Handbuch der Anorgani¬ schen Chemie, Uran, Ergänzungsband A3, (1981), pp 104 bis 115 "Trockenchemische Prozesse") gewonnen werden. Bei dem pulver- för igen Ausgangsoxid kann es sich auch um die Mischoxide (U,Pu)02, (U,Th)02, (U,RE)02, (U,Pu,RE)02, (U,Th,RE)02 oder (U, Pu,Th,RE)θ2 mit RE=Seltene Erde (insbesondere wenigstens eines der Elemente Gadolinium, Europium und Samarium) han¬ deln.UO2 powder is used as the powdered starting oxide and is obtained, for example, in accordance with the ammonium uranyl carbonate or AUC process (for example, Gemelin Handbook of Inorganic Chemistry, Uranium, Supplement Volume A3, 1981, pplOl to 104). This Uθ2 "powder has an average particle diameter of 15 to 20 .mu.m. The Uθ2 ~ powder can also by another method, such as the ammonium diuranate (ADU) process (e.g. Gmelin Handbook of Inorganic Chemistry, Uranium, Supplement A3, 1981 , pp 99 to 101), the IDR process Ren or the DC method (eg Gmelin handbook of inorganic chemistry, uranium, supplement volume A3, (1981), pp 104 to 115 "dry chemical processes"). The powdery starting oxide can also be the mixed oxides (U, Pu) 0 2 , (U, Th) 0 2 , (U, RE) 0 2 , (U, Pu, RE) 0 2 , (U , Th, RE) 0 2 or (U, Pu, Th, RE) θ2 with RE = rare earth (in particular at least one of the elements gadolinium, europium and samarium).
Dem Uθ2~Pulver wird 300 ppm kristallines Borpulver zugesetzt, dessen mittlerer Partikeldurchmesser 20 bis 25 μm beträgt. Die Partikel dieses kristallinen Borpulvers haben einen Ober¬ flächenfilm aus metallischem Molybdän, dessen Filmdicke etwa 5 um beträgt. Dieser Oberflächenfilm wird in einer Sputter- Vorrichtung (z.B. E. Lang, "Coatings For High Temperature300 ppm of crystalline boron powder, the average particle diameter of which is 20 to 25 μm, is added to the Uθ2 ~ powder. The particles of this crystalline boron powder have a surface film made of metallic molybdenum, the film thickness of which is approximately 5 μm. This surface film is in a sputtering device (e.g. E. Lang, "Coatings For High Temperature
Applications", 1983, Applied Science Publishers, London und New York, pp.79-120) hergestellt. Die Sputtervorrichtung hat im vorliegenden Fall einen elektrisch leitenden Anodenkörper z.B. aus Aluminium, auf dem sich kristallines Ausgangsborpul- ver befand. Ferner ist ein Katodenkörper aus Molybdänblech vorhanden. Das kristalline Ausgangsborpulver mit einer mitt¬ leren Ausgangspartikelgröße von etwa 15 um wird während einer Sputterzeit von etwa 2 Stunden in Argonatmosphäre bei einer elektrischen Gleichspannung von etwa 2000 V zwischen Anoden- und Katodenkörper behandelt. Während dieses Sputterns rollt das kristalline Borpulver immer wieder auf einer schiefen Ebene am Anodenkörper ab, so daß ein gleichmäßig dicker, fest haftender und allseitig dichter Oberflächenfilm aus Molybdän auf den Borpulverpartikeln erzielt wird.Applications ", 1983, Applied Science Publishers, London and New York, pp.79-120). In the present case, the sputtering device has an electrically conductive anode body, for example made of aluminum, on which crystalline boron powder was located. Furthermore, a cathode body is made of The crystalline starting boron powder with a mean starting particle size of about 15 μm is treated between anode and cathode body in a argon atmosphere at a direct electrical voltage of about 2000 V during a sputtering time of about 2. The crystalline boron powder rolls again and again during this sputtering on an inclined plane from the anode body, so that a uniformly thick, firmly adhering and all-round dense surface film of molybdenum is achieved on the boron powder particles.
Der Oberflächenfilm kann auch aus mindestens einem der Me¬ talle , Ruthenium, Wolfram und Chrom oder aus mindestens ei¬ ner der Legierungen Molybdänbasislegierung, Rutheniumbasisle¬ gierung, Wolframbasislegierung und Chrombasislegierung beste- hen. Günstig ist, wenn dieser Oberflächenfilm aus einerThe surface film can also consist of at least one of the metals, ruthenium, tungsten and chromium or of at least one of the alloys molybdenum-based alloy, ruthenium-based alloy, tungsten-based alloy and chromium-based alloy. It is favorable if this surface film from a
Chrom-Nickel-Legierung oder einer Molybdän-Niob-Legierung be¬ steht. Die Metalle dieser beiden Legierungen haben alle einen verhältnismäßig geringen Einfangsquerschnitt für thermische Neutronen. Geeignet für den Oberflächenfilm sind auch die Me¬ talle Rhenium, Rhodium und Hafnium, sowie die Basislegierun- gen dieser Metalle, da diese Metalle zwar einen großen Ein- fangsquerschnitt für thermische Neutronen haben, aber nicht so schnell neutronenphysikalisch ausbrennen wie Bor. Sie kön¬ nen daher in Verbindung mit Bor besonders lange Brennele¬ mentzyklen ermöglichen.Chromium-nickel alloy or a molybdenum-niobium alloy exists. The metals of these two alloys all have one relatively small capture cross section for thermal neutrons. The metals rhenium, rhodium and hafnium and the base alloys of these metals are also suitable for the surface film, since these metals have a large initial cross section for thermal neutrons, but do not burn out neutron physically as quickly as boron Therefore, in conjunction with boron, particularly long fuel element cycles are possible.
Der Oberflächenfilm kann auch aus mindestens einem der Nicht¬ metalle Tantalcarbid, Niobcarbid, Titancarbid, Tantalcarbid, Niobcarbid, Titancarbid, Zirkoniumcarbid, Chro carbid, Vana- diumcarbid, Wolframcarbid, Molybdäncarbid, Tantalnitrid, Niobnitrid, Titannitrid, Zirkoniumnitrid, Vanadiumnitrid, Tantalsilizid, Niobsilizid, Vanadiumsilizid, Wolframsilizid, Molybdänsilizid, Zirkoniumsilizid, Magnesiumoxid, Beryllium¬ oxid, Chromoxid, Calciumoxid, Ceroxid und Zirkoniumoxid be¬ stehen. In besonders vorteilhafter Weise besteht der Oberflä¬ chenfilm aus mindestens einem der Stoffe Siliziumcarbid und Siliziumnitrid, vorzugsweise Si3N4. Der Einfangsquerschnitt für thermische Neutronen dieser Nichtmetalle ist besonders gering. Diese Nichtmetalle werden günstigerweise in Form ei¬ nes Oberflächenfilms auf die Borpulverpartikel durch Nieder¬ schlagen des Reaktionsprodukts einer chemischen Gasphasen- reaktion von chemischen Verbindungen aufgebracht, die die Komponenten des Oberflächenfilms enthalten (z.B. Chemical Vapour Deposition- (CVD-) Verfahren nach E. Lang, "Coating For High Temperature Applications", 1983, Applied Science Publishers, London und New York, pp.33 bis 78) . Auf diese Weise kann aber auch ein metallischer Oberflächenfilm auf die Borpulverpartikel aufgebracht werden.The surface film can also consist of at least one of the non-metals tantalum carbide, niobium carbide, titanium carbide, tantalum carbide, niobium carbide, titanium carbide, zirconium carbide, chro carbide, vanadium carbide, tungsten carbide, molybdenum carbide, tantalum nitride, niobium nitride, titanium nitride, zirconium nitride, zirconium nitride Vanadium silicide, tungsten silicide, molybdenum silicide, zirconium silicide, magnesium oxide, beryllium oxide, chromium oxide, calcium oxide, cerium oxide and zirconium oxide exist. In a particularly advantageous manner, the surface film consists of at least one of the substances silicon carbide and silicon nitride, preferably Si3N4. The capture cross section for thermal neutrons of these non-metals is particularly small. These non-metals are advantageously applied in the form of a surface film to the boron powder particles by precipitating the reaction product of a chemical gas phase reaction of chemical compounds which contain the components of the surface film (for example chemical vapor deposition (CVD) processes according to E. Lang , "Coating For High Temperature Applications", 1983, Applied Science Publishers, London and New York, pp.33 to 78). In this way, however, a metallic surface film can also be applied to the boron powder particles.
Dem UO2-Pulver mit dem zugesetzten kristallinen Borpulver wird ferner 0.2 Gew.-% pulverförmiges Zinkstearat als Preß- hilfsmittel zugefügt. Anstelle von Zinkstearat kann auch pul¬ verförmiges Alu iniumdistearat als Preßhilfsmittel verwendet werden. Das UO2-Pulver mit dem zugesetzten Borpulver und dem zugesetzten Preßhilfsmittel wird sodann in einer Taumelmisch¬ anlage 15 Minuten lang innig vermischt. Auch kann dem Pulver in der Taumelmischanlage noch etwa 5 % pulverförmiges U3O3 als Porenbildner zugesetzt werden. Die Tatsache, daß mit Molybdän beschichtete Partikel des kristallinen Borpulvers etwa die gleiche Dichte haben wie die Partikel des Uθ2~Pul- vers, fördert die innige Vermischung dieser beiden Pulver miteinander und steht einer Entmischung beim späteren Trans¬ port und Lagern des Gemisches entgegen.0.2% by weight of powdered zinc stearate is also added to the UO2 powder with the added crystalline boron powder as a pressing aid. Instead of zinc stearate, powdered aluminum distearate can also be used as a pressing aid. The UO2 powder with the added boron powder and the added pressing aid is then mixed intimately in a tumbling mixer for 15 minutes. Also, about 5% powdered U3O3 can be added to the powder in the tumble mixer as a pore former. The fact that particles of the crystalline boron powder coated with molybdenum have approximately the same density as the particles of the UO 2 powder promotes the intimate mixing of these two powders with one another and prevents segregation during the subsequent transport and storage of the mixture.
Aus dem durch inniges Vermischen gewonnenen Gemisch werden schließlich Preßkörper gepreßt, die in Waserstoff-Atmosphäre bei einer Sintertemperatur von 1750° C drei Stunden lang ge¬ sintert werden. Nach dem Abkühlen haben die Kernbrennstoff- Sinterkörper eine spezifische Dichte von etwa 10.30 g/cm3 bis 10.55 g/cm3 während die spezifische Dichte der Borpartikel in der Sintermatrix 7 bis 9 g/cm3 beträgt, also im günstigen Be¬ reich von 5 g/cm3 bis 10 g/cm3 liegt.Finally, compacts are pressed from the mixture obtained by intimate mixing, which are sintered in a hydrogen atmosphere at a sintering temperature of 1750 ° C. for three hours. After cooling, the nuclear fuel sintered bodies have a specific density of approximately 10.30 g / cm 3 to 10.55 g / cm 3 while the specific density of the boron particles in the sintered matrix is 7 to 9 g / cm 3 , that is to say in the favorable range of 5 g / cm 3 to 10 g / cm 3 .
Bei metallischem, silizidischem oder oxidischem Oberflächen¬ film auf den Partikeln des Borpulvers wird außer in H2-Atmo¬ sphäre vorteilhafterweise auch in Inertgas, z.B. Argon, ge¬ sintert, während bei einem carbidischen Oberflächenfilm das Sintern günstigerweise in CO und /oder CO2 und bei nitridi- sehen Oberflächenfilm in Stickstoffe und/oder einer gasför¬ migen Ammoniakverbindung vorgenommen wird, so daß ein Zerset¬ zen des Oberflächenfilms durch die Sinteratmosphäre praktisch vermieden wird. Da überdies die Sintertemperatur kleiner als der Schmelzpunkt des Oberflächenfilms aus den angegebenen Me- tallen, Metall-Legierungen und Nichtmetallen auf den Borpar¬ tikeln ist, bleibt dieser Oberflächenfilm gleichmäßig dicht.In the case of metallic, silicidic or oxidic surface film on the particles of the boron powder, in addition to the H2 atmosphere, it is advantageously also carried out in inert gas, e.g. Argon, sintered, while in the case of a carbide surface film the sintering is advantageously carried out in CO and / or CO2 and in the case of nitride surface film in nitrogen and / or a gaseous ammonia compound, so that the surface film is decomposed by the sintering atmosphere is practically avoided. Since, moreover, the sintering temperature is lower than the melting point of the surface film made of the specified metals, metal alloys and non-metals on the boron particles, this surface film remains uniformly dense.
Eine Boranalyse der Kernbrennstoffsinterkörper nach dem Sin¬ tern ergibt eine Borkonzentration von 295 ppm, also nur einen sehr geringen Borverlust innerhalb der Meßgenauigkeit. Der äquivalente Durchmesser der Borpartikel (Durchmesser einer Kugel, deren Kugelvolumen dem Borpartikelvolumen gleich ist) in der Sintermatrix liegt im günstigen Bereich von 5 μm bis 300 um. Ferner liegt die Dicke des Oberflächenfilms auf die¬ sen Borpartikeln, der aus einem anderen Stoff als die Sinter¬ matrix und die Borpartikel besteht, im günstigen Bereich von 0.3 μm bis 30 μm. Derartige Borpartikel zeigen insbesondere in UO2-Pulver, das nach den oben angegebenen Verfahren gewon¬ nen wurde, praktisch keine Entmischungstendenz. Während des Sinterns entweicht aus ihnen auch kein Bor.Boron analysis of the nuclear fuel sintered bodies after sintering shows a boron concentration of 295 ppm, that is to say only a very small boron loss within the measuring accuracy. The equivalent diameter of the boron particles (diameter of a sphere whose spherical volume is equal to the boron particle volume) in the sintered matrix is in the favorable range from 5 μm to 300 μm. Furthermore, the thickness of the surface film on these boron particles, which consists of a different material than the sinter matrix and the boron particles, is in the favorable range from 0.3 μm to 30 μm. Such boron particles show practically no tendency to segregate, in particular in UO2 powder which has been obtained by the processes indicated above. No boron escapes from them during sintering.
Beim Verwenden von pulverförmigem Zirkoniumdiborid ZrB2 als borhaltige Verbindung anstelle des kristallinen Bors wurden ähnlich geringe Borverluste beim Sintern erzielt.When using powdered zirconium diboride ZrB2 as the boron-containing compound instead of the crystalline boron, similarly low boron losses were achieved during sintering.
Es ist vorteilhaft, wenn die Borkonzentration in der Sinter- matrix des Kernbrennstoffsinterkörpers im Bereich von 100 ppm bis 10 000 ppm liegt; denn dadurch kann einerseits eine star¬ ke Dämpfung von Geschwindigkeit und Höhe des Reaktivitätsan- stiegs in einen Kernreaktor erzielt werden, in den solche Kernbrennstoffsinterkörper als Bestandteil eines frischen Kernreaktorbrennelements eingebracht werden, andererseits wird aber auch eine Ausbildung von Rissen in der Sintermatrix des Kernbrennstoffsinterkörpers vermieden.It is advantageous if the boron concentration in the sinter matrix of the nuclear fuel sintered body is in the range from 100 ppm to 10,000 ppm; because on the one hand a strong damping of the speed and amount of the increase in reactivity can be achieved in a nuclear reactor into which such nuclear fuel sintered bodies are introduced as part of a fresh nuclear reactor fuel element, but on the other hand the formation of cracks in the sintered matrix of the nuclear fuel sintered body is avoided.
Es ist günstig, wenn in dem verwendeten Bor bzw. in den ver- wendeten borhaltigen chemischen Verbindungen das Isotop B]_Q im Bor verglichen mit der natürlichen Isotopenzusammenset- zung des Bors angereichert ist. Dies kann in bekannter Weise z.B. durch Zyklotron-, Diffusions- oder Trenndüsenanreiche¬ rung erzielt werden. Dieses Isotop BI_Q absorbiert praktisch die thermischen Neutronen. Durch seine Anreicherung im Bor, das sich in der Sintermatrix des Kernbrennstoffsinterkörpers befindet, kann die Konzentration dieses Bors verhältnismäßig gering gewählt werden.It is favorable if the isotope B] _Q in the boron in the boron or in the boron-containing chemical compounds used is enriched compared to the natural isotope composition of boron. This can be achieved in a known manner, for example by cyclotron, diffusion or separation nozzle enrichment. This isotope B I _ Q practically absorbs the thermal neutrons. Due to its accumulation in the boron, which is located in the sintered matrix of the nuclear fuel sintered body, the concentration of this boron can be chosen to be relatively low.
Es ist vorteilhaft, die erfindungsgemäßen Kernbrennstoff-Sin¬ terkörper in ein Hüllrohr, in der Regel aus einer Zirkonium- basislegierung oder rostfreiem Stahl, eines Brennstabs einzu- bringen und dieses Hüllrohr gasdicht zu verschließen. Dieser Brennstab ist günstigerweise Bestandteil eines Kernreaktor¬ brennelements für einen Kernreaktor. Vorteilhafterweise ist ein solches Kernreaktorbrennelement für einen Leichtwasser- kernreaktor vorgesehen, insbesondere für einen Druckwasser¬ kernreaktor oder einen Siedewasserkernreaktor.It is advantageous to insert the nuclear fuel sintered bodies according to the invention into a cladding tube, usually made of a zirconium-based alloy or stainless steel, of a fuel rod. bring and seal this cladding gas-tight. This fuel rod is advantageously part of a nuclear reactor fuel element for a nuclear reactor. Such a nuclear reactor fuel element is advantageously provided for a light water nuclear reactor, in particular for a pressurized water nuclear reactor or a boiling water nuclear reactor.
Versuche an einem solchen Hüllrohr, die die Bedingungen in einem Kernreaktor simulierten, ergaben, daß Bor sogar bei Temperaturen von 800 °C und mehr nicht aus den Kernbrenn¬ stoff-Sinterkörpern entweicht. Experiments on such a cladding tube, which simulated the conditions in a nuclear reactor, showed that boron does not escape from the nuclear fuel sintered bodies even at temperatures of 800 ° C. and higher.

Claims

Patentansprüche claims
1. Kernbrennstoffsinterkörper aus UO2 oder einem der Misch¬ oxide (U,Pu)θ2» (U,Th)02, (U,RE)02, (U,Pu,RE)02, (U,Th,RE)02, und (U,Pu,Th,RE)02 (RE=Seltene Erde) mit Partikeln aus Bor und/oder einer chemischen Borverbindung in der Sintermatrix und mit einem Oberflächenfilm auf diesen Partikeln, der aus einem anderen Stoff als die Sintermatrix und die Partikel be¬ steht und Bor zurückhält.1. Nuclear fuel sintered body made of UO2 or one of the mixed oxides (U, Pu) θ2 »(U, Th) 0 2 , (U, RE) 0 2 , (U, Pu, RE) 0 2 , (U, Th, RE ) 0 2 , and (U, Pu, Th, RE) 02 (RE = rare earth) with particles made of boron and / or a chemical boron compound in the sintered matrix and with a surface film on these particles made of a different material than the sintered matrix and the particles exist and retain boron.
2. Kernbrennstoffsinterkörper nach Anspruch 1, bei dem der Oberflächenfilm aus einem Metall und/oder einer Metall-Legie¬ rung besteht.2. Nuclear fuel sintered body according to claim 1, wherein the surface film consists of a metal and / or a metal alloy.
3. Kernbrennstoffsinterkörper nach Anspruch 2, bei dem der3. Nuclear fuel sintered body according to claim 2, wherein the
Oberflächenfilm aus mindestens einem Metall der Gruppe Molyb¬ dän, Rhenium, Ruthenium, Rhodium, Wolfram und Chrom besteht.Surface film consists of at least one metal from the group molybdenum, rhenium, ruthenium, rhodium, tungsten and chromium.
4. Kernbrennstoffsinterkörper nach Anspruch 2, bei dem der Oberflächenfilm aus mindestens einer Metall-Legierung der4. Nuclear fuel sintered body according to claim 2, wherein the surface film of at least one metal alloy
Gruppe Molybdänbasislegierung, Rheniumbasislegierung, Ruthe¬ niumbasislegierung, Rhodiumbasislegierung, Wolframbasislegie- rung und Chrombasislegierung besteht.Group of molybdenum-based alloy, rhenium-based alloy, ruthenium-based alloy, rhodium-based alloy, tungsten-based alloy and chromium-based alloy.
5. Kernbrennstoffsinterkörper nach Anspruch 4, bei dem der5. Nuclear fuel sintered body according to claim 4, wherein the
Oberflächenfilm aus mindestens einer Metall-Legierung aus der Gruppe Chrom-Nickel-Legierung und Molybdän-Niob-Legierung be¬ steht.Surface film consists of at least one metal alloy from the group of chromium-nickel alloy and molybdenum-niobium alloy.
6. Kernbrennstoffsinterkörper nach Anspruch 1, bei dem der6. Nuclear fuel sintered body according to claim 1, wherein the
Oberflächenfilm aus mindestens einem Stoff der Gruppe Tantal¬ carbid, Niobcarbid, Titancarbid, Zirkoniumcarbid, Chromcar- bid, Vanadiumcarbid, Wolframcarbid, Molybdäncarbid, Tantalni¬ trid, Niobnitrid, Titannitrid, Zirkoniumnitrid, Vanadiumni- trid, Tantalsilizid, Niobsilizid, Vanadiumsilizid, Wolframεi- lizid, Molybdänsilizid, Zirkoniumoxid, Magnesiumoxid, Beryl- liumoxid, Chromoxid, Calziumoxid, Ceroxid und Zirkoniumoxid besteht .Surface film made of at least one substance from the group tantalum carbide, niobium carbide, titanium carbide, zirconium carbide, chromium carbide, vanadium carbide, tungsten carbide, molybdenum carbide, tantalum nitride, niobium nitride, titanium nitride, zirconium nitride, vanadium nitride, tantalum silicide, tungsten silicide, niobium silicide, ni-silicon silicide, ni-silicon silicide, ni-silicon silicide, ni-silicon silicide, ni-silicon silicide, ni-silicon silicide, ni-silicon silicide , Molybdenum silicide, zirconium oxide, magnesium oxide, beryl lium oxide, chromium oxide, calcium oxide, cerium oxide and zirconium oxide.
7. Kernbrennstoffsinterkörper nach Anspruch 1, bei dem der Oberflächenfilm aus mindestens einem Stoff aus der Gruppe7. Nuclear fuel sintered body according to claim 1, wherein the surface film of at least one material from the group
Siliziumcarbid und Siliziumnitrid, vorzugsweise Si3N4^ be¬ steht .Silicon carbide and silicon nitride, preferably Si3N4 ^ be¬.
8. Kernbrennstoffsinterkörper nach Anspruch 1, bei dem der äquivalente Durchmesser der Partikel im Bereich von 5 μm bis8. Nuclear fuel sintered body according to claim 1, wherein the equivalent diameter of the particles in the range of 5 microns to
300 μm liegt.300 μm.
9. Kernbrennstoffsinterkörper nach Anspruch 1, bei dem die Dicke des Oberflächenfilms 0.3 μm bis 30 μm beträgt.9. Nuclear fuel sintered body according to claim 1, wherein the thickness of the surface film is 0.3 microns to 30 microns.
10. Kernbrennstoffsinterkörper nach Anspruch 1, bei dem die spezifische Dichte der Partikel 5 g/cm3 bis 10 g/cm3 beträgt.10. Nuclear fuel sintered body according to claim 1, wherein the specific density of the particles is 5 g / cm 3 to 10 g / cm 3 .
11. Kernbrennstoffsinterkörper nach einem der Ansprüche 1 bis 10, bei dem die Borkonzentration im Bereich von 100 ppm bis11. Nuclear fuel sintered body according to one of claims 1 to 10, wherein the boron concentration in the range of 100 ppm to
10 000 ppm liegt.10,000 ppm.
12. Kernbrennstoffsinterkörper nach einem der Ansprüche 1 bis 11, bei dem das Isotop B]_Q im Bor verglichen mit der natür- liehen Isotopzusammensetzung angereichert ist.12. Nuclear fuel sintered body according to one of claims 1 to 11, in which the isotope B] _Q is enriched in boron compared to the natural isotope composition.
13. Kernreaktorbrennelement mit einem Brennstab, der in einem Hüllrohr einen Kernbrennstoffsinterkörper entsprechend einem der Patentansprüche 1 bis 12 enthält.13. Nuclear reactor fuel element with a fuel rod which contains a nuclear fuel sintered body in a cladding tube according to one of the claims 1 to 12.
14. Verfahren zum Herstellen eines Kernbrennstoffsinterkör¬ pers nach einem der Ansprüche 1 bis 12 aus pulverförmigem Ausgangsoxid, dem die mit dem Oberflächenfilm versehenen Par¬ tikel aus Bor und/oder der chemischen Borverbindung zuge- mischt werden und das zu Preßkörpern gepreßt wird, die an¬ schließend gesintert werden. 14. A process for producing a nuclear fuel sintered body according to one of claims 1 to 12 from powdered starting oxide, to which the particles of boron and / or the chemical boron compound provided with the surface film are mixed and which is pressed into pressed bodies which are pressed on ¬ are finally sintered.
15. Verfahren nach Anspruch 14, bei dem dem pulverförmigen Ausgangsoxid vor dem Pressen ein Preßhilfsmittel zugesetzt wird.15. The method according to claim 14, wherein a pressing aid is added to the powdered starting oxide before pressing.
16. Verfahren nach einem der Ansprüche 14 und 15, bei dem das Sintern in einer Sinteratmosphäre durchgeführt wird, die bei einem metallischen, silizidischen oder oxidischen Oberflä¬ chenfilm auf den Partikeln Wasserstoff und/oder ein Inertgas, bei einem carbidischen Oberflächenfilm auf den Partikeln CO und/oder CO2 und bei einem nitridischen Oberflächenfilm auf den Partikeln Stickstoff und /oder eine Ammoniakverbindung enthält. 16. The method according to any one of claims 14 and 15, in which the sintering is carried out in a sintering atmosphere which, in the case of a metallic, silicidic or oxidic surface film on the particles, hydrogen and / or an inert gas, in the case of a carbidic surface film on the particles CO and / or CO2 and, in the case of a nitridic surface film, contains nitrogen and / or an ammonia compound on the particles.
EP94926937A 1993-09-22 1994-09-13 Nuclear fuel sintered body and process for producing it Ceased EP0720766A1 (en)

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FR2814584B1 (en) * 2000-09-27 2002-10-31 Commissariat Energie Atomique NUCLEAR FUEL COMPRISING A CONSUMABLE POISON AND ITS MANUFACTURING METHOD
EP1345239B1 (en) 2002-03-11 2008-06-04 Urenco Nederland B.V. Nuclear fuel comprising a uranium-molybdenum alloy
KR101436499B1 (en) * 2012-11-05 2014-09-01 한국원자력연구원 Fabrication method of burnable absorber nuclear fuel pellet using rapid sintering, and the burnable absorber nuclear fuel pellet thereby

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FR1414598A (en) * 1963-11-25 1965-10-15 Int Research & Dev Co Ltd Improvements in materials containing boron and in the processes for their production
US3917768A (en) * 1969-02-25 1975-11-04 Fiat Spa Sintered nuclear fuel and method of preparing same
US4671927A (en) * 1984-12-03 1987-06-09 Westinghouse Electric Corp. Nuclear fuel rod containing a hybrid gadolinium oxide, boron carbide burnable absorber
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ES2002719A6 (en) * 1986-07-22 1988-10-01 Westinghouse Electric Corp Nuclear fuel pellets
JPH01155294A (en) * 1987-12-14 1989-06-19 Toshiba Corp Neutron absorber
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