Reduce the water content to less than 0.5 wt% and similarly reduce equivalent - Continued

DOE-STD-3013-2004

A notably desirable result of 950oC calcination is that metal impurities are

expected to be converted largely or entirely to binary oxides (e.g., Fe2O3, Cr2O3,

and Ga2O3) and complex oxides containing more than one metal cation.

Thermodynamics strongly favors reduction of high valent oxides such as Fe2O3

and U3O8 by hydrogen, thereby providing a large potential chemical sink for

elemental hydrogen generated by chemical or radiolytic means. To illustrate the

potential magnitude of this effect, consider that 3 wt% of Fe in a maximum 5 Kg

charge or impure oxide corresponds to about 214 grams (about 1.3 moles) of

Fe2O3. This amount of ferric oxide theoretically is capable of converting about 45

atmospheres (about 660 psi) of hydrogen at 150oC to water in a typical storage

package, assuming about one liter of gas void space.

In this Standard, the maximum allowable package heat generation rate (19

watts) is reduced substantially from the 30 watts permitted by DOE-STD-3013-

96. As a result, bounding container and material temperatures will be

substantially lower. Recent calculations of thermal profiles for one bounding

scenario (exposure of a 19 watt 9975 shipping container to diurnal insulation)

indicates maximum container and oxide temperatures of 147oC (297oF) and

275oC (527oF) respectively [Hensel 1999a,b] (see Table A-1, Section A.6.3.2.2).

From these and related analyses, a solar influence of about 46oC (83oF ) on oxide

temperature can be deduced. Using a straight line extrapolation from the 30 and

19 watt cases, peak oxide temperatures near 150oC (302oF) and 205oC (401oF )

can be estimated for 6 and 12 watt oxide packages, respectively. When the solar

factor is subtracted, the resulting temperatures for "normal" storage in 9975

packages (near 105oC at 6 w and 160oC at 12 w) are seen to be within or close

to the range experienced during typical vault storage of plutonium oxides.

Significantly, the heat generation rates for 5 kg of the 30-50 wt% plutonium

materials studied to date in the MIS program are less than 6 watts. All MIS

materials studied to date in the 50-80 wt% range have wattage under 12 watts

for 5 kg, as should be expected since the wattage of 4.4 kg of typical weapons

grade plutonium metal is about 12.5 watts (see Section B.4 in Appendix B).

Therefore, impure materials packaged under this Standard with weapons grade

isotopic compositions will never experience the bounding temperatures calculated

for the 19-watt solar scenario. The vast preponderance of higher specific wattage