Oxides - Continued - std3028

DOE-STD-3028-2000

system is generally a mixture of oxides with a O/U ratio between 2 and 3. Uranium

oxides in this range are considered stable and suitable for storage.

1. The criterion of 0.5 wt % volatiles provides a reasonable balance between the

difficulty of achieving lower volatiles contents (primarily moisture) and the cost (of

both the container and any ancillary impact on storage facility size) of providing a

container that will withstand the overpressure theoretically postulated by a higher

volatiles content. Correlation of the volatiles criterion with bounding pressures in

storage containers is established in Appendix B (Derivation of Pressure Equation)

and other sections of this Appendix.

2. Most of the stored 233U oxide powders were assayed for volatiles content at varying

heating temperatures at the times they were formed, then stored in closed

containers. Testing each batch for volatiles content according to Criterion 6.1.2.3 will

verify if the historic measurements are still reliable. Existing material failing to meet

the 0.5 wt% requirement must then be treated as specified in Section 6.1.2.2 and be

subject to subsequent verification.

3. The stabilization requirements of this Standard accomplish the following primary

objectives:

reduce the residual moisture (volatiles) content to less than 0.5 wt% and similarly

reduce equivalent quantities of species such as hydrates that might produce

pressurizing gases during long-term storage via radiolysis;

minimize potential for water readsorption above the 0.5 wt% threshold; and

stabilize reactive volatile 233U species.

There are also secondary objectives that are desirable, but not absolutely necessary.

If the material is treated to meet a primary objective, then the following secondary

objectives should also be considered:

convert to U3O8

enhance particle size

If the volatiles content cannot be shown to be less than 0.5 wt %, this Standard

specifies that oxide material will be placed in a continuously oxidizing atmosphere at

a material temperature of greater than 750C (1382F) for a minimum of one hour.