Alkem Gmbh

Peter Funke

Rainer Lob

Karl Ennerst

Wihelm Konigs

Dietmar Hanus

Production of mixed-oxide nuclear fuel pellets of uranium dioxide (UO.sub.2+x) and plutonium dioxide (PuO.sub.2) which are soluble in nitric acid. The powder mixture of oxides is added to a halogen-free milling aid, such as propane diol, then is milled and subsequently granulated, pressed and sintered. The milling aid is expelled by subsequent drying processes or heat treatments (sintering). The milling process is controlled to obtain a primary grain size of less than two micrometers.

Method of producing mixed-oxide nuclear fuel pellets soluble in nitric

Production of UO.sub.2 nuclear fuel pellets containing PuO.sub.2 in set amounts, which pellets are soluble in nitric acid and suitable for reprocessing without the aid of a special additive. Uranium oxide powder is mixed with 15 to 50% by weight of the mixture of plutonium oxide powder; the mixture milled and pressed into pellets. The pellets are sintered, comminuted, pressed to form pellets and the pellets comminuted to free-flowing granules. The free-flowing granules are mixed with UO.sub.2 granules to obtain a desired UO.sub.2 /PuO.sub.2 ratio, and the mixture pressed into pellets and sintered to form UO.sub.2 nuclear fuel pellets containing PuO.sub.2 soluble in nitric acid.

Method of producing PuO.sub.2 /UO.sub.2 /-nuclear fuels

Method for controlling desired redox potential in hydrogencontaining protective gases used in high-temperature furnaces in powder-metallurgical processes. A sample of the protective gas is withdrawn from the furnace and the redox potential of the sample measured at the high temperature to produce treated bodies of good quality. Humidifying the gases blowing through the furnace is employed to erase or minimize a deviation of the redox potential of the sample from a predetermined redox potential. Ax oxygen-hydrogen mixture may be obtained by electrolysis of water as a function of the measured redox potential and this mixture may be used for humidification. In this manner good quality end products are assured despite fluctuations in throughput and properties of material entering the furnace.

Setting and controlling desired redox potentials in gases

Sintering nuclear fuel pellets of nuclear fuel oxides having oxygen in stoichiometric excess of the dioxides by passing the nuclear fuel pellets through a reduction furnace having a reducing atmosphere under regulated exposure time or residence time to produce reduced nuclear fuel oxides of desired oxygen content. The reduced pellets are cooled and sent to an intermediate station for checking or holding. The cooled pellets from the intermediate station are sent through a sintering furnace with means for independently regulating the exposure time or residence time in the sintering furnace. Additional features are the independent control of the atmospheres and temperature as well as the humidity concentration in each furnace. Less expensive nitrogen gas may efficiently be used in the process.

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Rodenbach, Germany

Peter Funke