diam., 5.5 nun; height, 5 mm; density, 9 g/cm 3) of a solid solution of 8570 UO 2 and 15% PuO 2 and produced by mixing the oxides by mechanical means, molding the tablets from the mix, and firing them in vacuo at 1750~The tablets of (U, Pu)O2 and the zircon cylinders were tested in a molybdenum ampoule in an inert atmosphere at 1500~ for 20 h with the specimens in contact under a load of 2 kgf/cm 2. Radiographic and chemical analyses revealed slight migration of U (up to 0.03%) and Pu (up to 0.02%) into the zircon composition and of the components of the refractory composition (Zr, Si, A1, and Cr) into the nuclear fuel (up to 0.01% of the original amount), and the absence of caking between the zircon specimens and the (U, Pu)O 2 tablets. These findings make it possible to recommend the ACP-bonded zircon composition for the production of crucibles for the melting unit of installations for the thermal stripping of spent fuel elements. CONCLUSIONSAn investigation was carried out of the physic,-and thermomechanical properties of ACP-bonded zircon ramming compounds, of the conditions for their drying and firing processes, and of their solid-solution interaction with a mixed (U, Pu)O 2 nuclear fuel.The optimal composition of the ramming compound is as follows: 95?0 zircon of particle-size fraction 0.06-3.0 ram, 5% refractory clay finer than 0.5 ram, and 7% ACP binder of density 1.5 g/cm 3 (on 100%). The composition is characterized by high strength and low porosity and water absorption.

Progress in the field of metallurgy has increased the demand for refractories and has demanded a constant improvement in their quality. Among the technical properties of refractories, one of the most important is slag-resistance, which characterizes the tendency of the refractory to resist the destructive effect of molten slags.Slag-resistance is evaluated from the loss in volume or mass of the refractory under the action of slag and from the depth of penetration of slag into the refractory.In recent years some studies have appeared in which the wear of a specimen in dynamic slag-resistance tests was estimated from the change in the chemical [I] or isotopic [2] composition of the melt or from the change in its physical properties, for example density [3]. Methods of determining the slag-resistance are constantly being reported and in these methods a larger and larger number of factors in the actual service of refractories, such as the gas medium, thermal shock, and large temperature gradients [4], act on the specimen to be tested. When reproducing the most important factors, there must always be a correlation between the results of the laboratory tests and the results in service.Equipment to determine the slag resistance at temperatures up to 1750~ has been developed at the All-Union Institute of Refractories.This equipment is based on a Tammantype high-temperature device made by the Experimental Workshop of the Urals Scientific Center of the Academy of Sciences of the USSR.The equipment includes: an electric furnace with a graphite heater with an internal diameter of 85 mm; a mechanism for inserting and removing the crucible; the insertion, removal, and rotation of the experimental specimen; systems for the electric supply, temperature measurement, cooling, inert-gas supply; and the automatic units.The layout of the equipment is shown in Fig. i.In the first adjustment period during furnace operation it was found that the working zone was insufficiently stable, its position depended on the quality of the assembly and it changed from one heating to the next.In order to increase the stability of the zone, heaters with a narrow throat in the middle, 115 mm long, 90 mm in external diameter, and with 96-98 mm diameter leads were used. This made it possible to have a stable working zone of a height of i00 mm and a temperature difference of < • and, for the same current and voltage, to reduce the warm-up time of the furnace.The furnace 1 was insulated with a charge of magnesite powder.The electric supply to the heater 2 is fed through the water-cooled leads 3 from the ac supply via the furnace transformer 4 whose primary winding is connected in series with the power unit and the thyristor voltage controller 5. The control makes it possible to change the voltage across the heater from 0 and 15 V. The system provides automatic control of the testing temperature using the Sh4501 contact millivoltmeter and the control unit (CU) of the thyristor voltage control.The maximum working voltage is established across the heater an...

The All-Union Institute of Refractories has developed the technology for producing periclase--lime clinkers based on natural raw materials: dolomite and magnesite [I].Some of the properties of these refractories prepared from clinkers with a CaO concentration of 2-60% have been studied.* The clinkers were prepared by firing briquettes made from raw powdered dolomite and magnesite at 1600~The chemical composition of these materials is given in Table I. The apparent density of the magnesite clinkers with I0, 20, or 40% CaO and the dolomite clinker was, respectively, 3.29, 3.33, 3.32, 3.24, and 3.24 g/cm 3.The specimens of refractory were made from a batch of the following grain composition [2]:40% fractions from 2-0.5 mm; 25% from 0.5-0.06 mm; and 35% <0.06 mm.As the bonding material, we used a "solid" carboniferous resin and paraffin as the temporary bonding in the preparation of the fired specimens.Before the study of their properties, the unfired specimens were heat-treated at higher temperatures in a nonoxidizing medium at 400~As the resistance of the resin-impregnated fired refractories during service are significantly higher than that of the unimpregnated, some of the specimens fired at 1700~ were impregnated with carboniferous pitch preceded by vacuum treatment [3].

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