Table 8.3. Interim Recommendations for Storage of Plutonium Metal and Plutonium Oxide - Continued

DOE-STD-1128-98

Guide of Good Practices for Occupational Radiological Protection in Plutonium Facilities

Table 8.3 (cont'd)

10.

Impure oxide from sources other than metal should be thermally stabilized at 1000100C for at

least an hour, or placed in a combination of a slightly lower temperature (-850C) for longer

heating time to result in the lowest loss on ignition (LOI) practicable with existing equipment.

This ensures complete conversion of substoichiometric material and aids small-particle

coalescence, which diminishes dispersal risk.

11.

Because plutonium oxide has greater potential for dispersion in severe accidents, it should have

priority over metal for storage in structurally robust vaults. Metal should be characterized to

ensure that it has not converted to oxide while in storage. Stored plutonium will have an

increasing radiation level because of the build-up of 241Am. Therefore, characterization of metal

should be done as soon as possible and should make full use of small-sample statistical methods

to minimize worker exposure. The results of characterization should be integrated with a site's

surveillance plan, as well.

12.

Quality assurance measures, labeling, and material characterization are essential. Material and

storage packaging specifics should be thoroughly documented.

(a)

A higher oxidation rate may occur if the contained metal exhibits a high surface-area configuration, such as sheet or

foil. The maximum annual increase for normal (uncatalyzed) oxidation of a given metal geometry can be calculated

using a reaction rate of 3 x 10-7 g oxygen/cm2-minute measured for alpha-phase plutonium under moist conditions at

50C.

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