Uranium Trioxide - Production and Use

Production and Use

There are three methods to generate uranium trioxide. As noted below, two are used industrially in the reprocessing of nuclear fuel and uranium enrichment.

1. U₃O₈ can be oxidized at 500 °C with oxygen. Note that above 750 °C even in 5 atm O₂ UO₃ decomposes into U₃O₈.
2. Uranyl nitrate, UO₂(NO₃)₂·6H₂O can be heated to yield UO₃. This occurs during the reprocessing of nuclear fuel. Fuel rods are dissolved in HNO₃ to separate uranyl nitrate from plutonium and the fission products (the PUREX method). The pure uranyl nitrate is converted to solid UO₃ by heating at 400 °C. After reduction with hydrogen (with other inert gas present) to uranium dioxide, the uranium can be used in new MOX fuel rods.
3. Ammonium diuranate or sodium diuranate (Na₂U₂O₇·6H₂O) may be decomposed. Sodium diuranate, also known as yellowcake, is converted to uranium trioxide in the enrichment of uranium. Uranium dioxide and uranium tetrafluoride are intermediates in the process which ends in uranium hexafluoride.

Uranium trioxide is shipped between processing facilities in the form of a gel.

Cameco Corporation, which operates at the world's largest uranium refinery at Blind River, Ontario, produces high-purity uranium trioxide.

It has been reported that the corrosion of uranium in a silica rich aqueous solution forms both uranium dioxide and uranium trioxide. In pure water, schoepite (UO₂)₈O₂(OH)₁₂·12(H₂O) is formed in the first week and then after four months studtite (UO₂)O₂·4(H₂O) was produced. Reports on the corrosion of uranium metal have been published by the Royal Society.