Kraftwerk Union Aktiengesellschaft

Reaktor-Brennelement Union Gmbh

Wolfgang Dorr

Martin Peehs

Gerhard Gradel

Helmut Assmann

Georg Maier

Gerhard Dichtjar

Viktor Mathieu

Thomas Sondermann

Reinhard Schafer

Peter Wahode

Sieghard Hellmann

Heinrich Bayer

Egbert Brandau

Ulrich Jenczio

Jurgen Laucht

Method for manufacturing sintered oxidic nuclear fuel bodies by molding uranium oxide starting powder, a mixture of uranium oxide and plutonium oxide starting powder or of uranium-plutonium oxide mixed-crystal starting powder to form blanks and by a heat treatment of these blanks with a U.sub.4 O.sub.9 or (U, Pu).sub.4 O.sub.9 crystal phase developed in them to a degree which can be crystallographically detected at a sintering temperature in the range of 1000.degree. to 1400.degree. C. in an oxidizing and subsequently in a reducing gas atmosphere. The starting powder and/or the blanks are preroasted at a roasting temperature below the sintering temperature in a roasting gas atmosphere with oxidizing action and with an oxygen potential in which the U.sub.4 O.sub.9 (U, Pu).sub.4 O.sub.9 crystal phase is developed and cooled down subsequently to a starting temperature below the roasting temperature in an inert or oxidizing cooling-down gas atmosphere. Starting from this starting temperature, the blanks are heated to the sintering temperature in an inert or oxidizing heating gas atmosphere while maintaining the U.sub.4 O.sub.9 or the (U, Pu).sub.4 O.sub.9 crystal phase.

Method for the manufacture of oxide sintered nuclear fuel bodies

Method for sintering blanks into fuel pellets, in which the blanks are moved through the muffle of a tunnel furnace by pushing the blanks through the muffle on a guiding device which goes through the muffle and protrudes therefrom at least on the input side, in the form of a single-layer column of abutting blanks.

Method and tunnel furnace for sintering blanks

A sintered nuclear fuel compact of UO.sub.2 or the mixed oxides (U, Pu)O.sub.2 and (U, Th)O.sub.2, with which reactivity losses in a nuclear reactor having relatively long fuel element cycles are avoided, has in its sintered matrix neutron poison in the chemical compound form UB.sub.x with x=2; 4 and/or 12 and/or B.sub.4 C. A sintered nuclear fuel compact of this kind is produced by sintering from a compact comprising a mixture of at least one of the mixture components UO.sub.2, PuO.sub.2, (U, Pu)O.sub.2 and (U, Th)O.sub.2 powder with UB.sub.x powder, where x=2; 4 and/or 12 and/or B.sub.4 C powder.

Sintered nuclear fuel compact and method for its production

UO.sub.2 base powder exhibiting any specific surface and crystallite diameter properties is mixed with rare earth (SE) oxide-containing powder, the particles of which exhibit at least in one surface layer, a crystal lattice of the fluorite type, with the stoichiometric composition (SE.sub.0.5, U.sub.0.5) 0.sub.2.00 and/or form it in sintering; and is compacted to form compacts which are sintered in a gas atmosphere with reducing action at 1500.degree. C. to 1750.degree. C. to form high-density sintered bodies.

Method for producing oxidic sintered nuclear fuel bodies

Method for determining the contents of a fuel rod within a testing range extending in the longitudinal direction of the fuel rod, characterized by the features that

Method for determining the contents of a fuel rod

Method for the manufacture of oxidic nuclear fuel bodies by a heat treatment of blanks obtained from UO.sub.2 starting power or a mixture of UO.sub.2 and PuO.sub.2 starting powder at a treatment temperature in the range of 1000.degree. C. to 1400.degree. initially in a gas atmosphere with oxidizing action and subsequently in a gas atmosphere with reducing action. The oxygen potential of the gas atmosphere with oxidizing action is kept in a range in which a crystallographically demonstrable U.sub.4 O.sub.9 or (U, Pu).sub.4 O.sub.9 crystal phase is generated in the blanks during the heating to the treatment temperature in this gas atmosphere with oxidizing action.

Method for the manufacture of oxidic sintered nuclear fuel bodies

Method for the manufacture of oxidic sintered nuclear fuel bodies by compacting UO.sub.2 -starting powder or a mixture of UO.sub.2 -and PuO.sub.2 starting powder which contains up to 10% by weight rare-earth oxide, especially Gd.sub.2 O.sub.3, as an additive into blanks and subsequent densification of these blanks by a heat treatment in a sintering atomsphere with reducing action. The UO.sub.2 -starting powder used for compacting has a specific surface in the range of 2 to 4.5 m.sup.2 /g and/or a mean crystallite diameter in the range of 80 nm to 250 nm, and the heat treatment in the sintering atmosphere with reducing action is carried out at a temperature in the range of 1,500.degree. C. to 1,750.degree. C.

Method for manufacturing oxidic sintered nuclear fuel bodies

Manufacture of very dense oxidic fuel bodies of UO.sub.2 with rare earth oxides in which pressed blanks are subjected to sintering in an oxidizing atmosphere at relatively low temperature and are sintered in a reducing atmosphere at a higher temperature. This avoids sintering-inhibiting phases and permits very dense bodies with greater content of rare earth oxides to be produced.

Method for the manufacture of very dense oxidic nuclear fuel bodies

Manufacture of oxidic nuclear fuel bodies with oxygen-to-metal ratio of 2.0.+-.0.02 at relatively low sintering temperature in range of 1000.degree.-1400.degree. C. Nuclear fuel powder with an arbitrary oxygen-to-metal ratio is mixed with a grain-growth promoting additive (U.sub.3 O.sub.8) and pressed into blanks. The blanks are subjected to a two-stage operation in a furnace at 1000.degree.-1400.degree. C. - an oxidative-sintering stage in a carbon dioxide atmosphere and a reducing stage in a hydrogen containing atmosphere.

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Herzogenaurach, Germany

Wolfgang Dorr