Plutonium Hydride Oxidation.

DOE-HDBK-3010-94

7.0 Application Examples; Dissolving Operations Examples

throughout an inert volume. It is noted, however, that the effects cannot realistically

be confined to one material. The TNT equivalent previously calculated for the

dissolving chamber was 2 g, which would release a corresponding 2 g of plutonium as

a respirable aerosol. It is emphasized again that the use of a detonation model to

bound the physical circumstances described in this example is unwarranted. The

maximum error of this type would be to assume that since 7.5 moles of hydrogen can

theoretically be generated over the entire dissolution process, this is the amount of

material involved in a detonation in proximity to the material. The resultant TNT

equivalent would be ~ 470 g, for which a 470 g release of plutonium could be

postulated. To use such an estimate as a meaningful estimate of potential

consequences would be ridiculous.

C. Plutonium Hydride Oxidation. If the dissolution temperature is less than 50 oC,

plutonium hydride sludge may be formed due to metal-hydrogen vapor interactions at

relatively slow reaction rates. Experience indicates that such sludge may account for,

at most, 5% of the original metal charge, or ~ 60 g. The hazard identification

indicates 100 g is a generally accepted upper limit due to the fact that sludge

formation must compete against the still thermodynamically favored normal

dissolution reaction even at lower temperatures. This sludge will also dissolve if

dissolution temperature exceeds 50 oC during the overall process.

The plutonium hydride sludge produced in the dissolver is actually a damp oxide +

hydride mixture. As long as it has been passivated by dilute nitric acid and remains

damp, it can be recycled into the dissolution process without risk. If, however, the

material becomes dry, highly exothermic reactions may result. Finely divided

hydride is pyrophoric in air at room temperature. This is due to the rapid oxidation

reaction that produces PuO2 and H2. The reaction has been observed in materials

contaminated with hydride once exposure to air occurs. The hydride is not a

detonable material, nor is the hydrogen generated expected to be an explosive hazard

unless unusual confinement conditions exist.

It is assumed that 100 g of hydride sludge was generated in the process and has been

incorrectly handled, allowing it to dry in the glovebox atmosphere. Several

phenomena could be used to model the potential airborne release from initiation of the

oxidation reaction. The main concern is that the material could become a fire source,

but that would not be a major problem in the metal dissolution glovebox, which

contains very little combustible material. The release phenomena could be considered

similar to heating of reactive powders, for which the ARF and RF are 1E-2 and 1E-3

(subsection 4.4.1.2). However, the phenomena is a combustion reaction, and the

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