Reaktor-brennelement Union Gmbh

Kraftwerk Union Aktiengesellschaft

Rbu, Reaktor-brennelment Union Gmbh

Thomas Sondermann

Martin Peehs

Gerhard Gradel

Wolfgang Dorr

Reinhard Schafer

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

Reconditioning ammonium nitrate-containing radioactive filtrates as produced in AUC or AU Pu C process by feeding preheated filtrate into the cathode chamber of an electrolysis cell containing boiling ammonium nitrate solution. The filtrate is brought to the boiling temperature with the assistance of the joulean heat of the electrolysis current. Ammonium carbonate and free NH.sub.3 in the filtrate are given off as gaseous CO.sub.2 and NH.sub.3 and steam and electrolytically formed NH.sub.3. The uranium and/or plutonium originally in solution as carbonate complexes is precipitated and separated by continuous circulation of the cell contents through a filter as well as electrolytically at the cathode.

Method of reconditioning radioactive filtrate

Mixed crystals containing uranium and gadolinium for conversion into nuclear fuels by introducing NH.sub.3, CO.sub.2 and a uranyl salt solution containing dissolved gadolinium into a body of an aqueous solution of ammonium carbonate. As a result salts of gadolinium and uranium complexes precipitate and during precipitation there is a lowering of the pH from 9 down to 8.2. The precipitate is separated and converted to uranium and gadolinium oxides. Preparing the mixed crystals in this manner results in the gadolinium being finely and homogeneously distributed into the oxidic nuclear fuel.

Method for manufacturing gadolinium-containing nuclear fuels

In the production of UO.sub.2, ammonium uranyl carbonate is an intermediate product wet with water and contaminated with ammonium carbonate and is washed with methanol to remove water and ammonium carbonate. The spent methanol containing 50% water and up to 10% ammonium carbonate is subjected to rectification in a column under subatmospheric pressure with cooling the top of the tower to a low temperature to retard decomposition of ammonium carbonate and condense a liquid water fraction. Clogging of the column, vapor lines and condenser by recombination of the decomposition products is prevented. The purified methanol contains less than 5% water and may be returned for further washing of ammonium uranyl carbonate.

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Kahl, Germany

Thomas Sondermann