Preparation of Refractories from Uranium Dioxide
The preparation of refractories from uranium dioxide is governed by certain properties of the material that require special consideration. Significant among these properties are (1) the oxidation characteristics, which necessitate firing in a hydrogen atmosphere, (2) the nonplastic nature, which presents forming problems, (3) the chemical reactivity, and (4) the radioactivity, which necessitates special precautions in handling to avoid health hazards. Crucibles and shapes are formed both by pressing and by slip casting. Pressing is performed without binders of any kind and therefore entails limitations in die design, close control of water content and pressure, and extreme care in handling the green ware. Slip casting is made possible by leaching the finely ground UO2 in concentrated hydrochloric acid solution, followed by thorough washing to remove the excess acid. A binder to increase dry strength is helpful and may assist in deflocculation. If Carbowax‐4000W is used as a binder, very thin crucibles (1/16 in. thick) can be cast. The slip must be carefully controlled for successful casting and special attention must be given to mold design and casting technique. A molybdenum furnace with a hydrogen atmosphere is used for firing all UO2 refractories. The usual firing temperature is 1750°C. At this temperature shrinkage is approximately 15% and density is more than 80% of the maximum theoretical density. Shrinkage and density increase abruptly at higher temperatures.
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Document Type: Research Article
Affiliations: Argonne National Laboratory, Chicago, Illinois
Publication date: 1953-04-01