Residue Impaction

DOE-HDBK-3010-94

7.0 Application Examples; Feed Preparation Example

anticipated to be 1.0, but that value can be assumed for the sake of simplicity. Other

batches are not affected by the localized combustion.

The ARF and RF assigned for self-sustained oxidation of plutonium metal are 5E-4 and

0.5 (subsection 4.2.1.1.4). The maximum initial respirable source term is:

2000 g * 1.0 * 5E-4 * 0.5 = 0.5 g

The source term decreases to 3E-2 g if the maximum expected DR of 0.05 is used.

As opposed to the plutonium powder spill, it is anticipated that a fines fire would

occur inside glovebox confinement, unless the container that spilled outside the box

contained fines, a highly unlikely conjunction of events given that the number of

containers with significant fines accumulation is small.

C. Residue Impaction. Residue impaction is not an accident. It is part of normal

operations. Small amounts of material are driven airborne within the impactor but do

not escape the device in significant quantities. The only accident that might release

material is a catastrophic failure that results in a large shrapnel pattern from the unit.

The design of the unit is supposed to preclude that possibility, but it is included as an

example of using release fraction data for unusual circumstances.

Based on the size of a residue batch for the residue dissolver, one feed cycle of the

device would not process more than 1000 g as plutonium, and would typically process

much less. For the sake of example, it is also assumed that after years of operation,

holdup monitors indicate 50 g of plutonium present when the unit is shutdown.

Only a small fraction of the feed material would be in the impaction zone at any one

time. The rest would be loaded into the feed hopper, in the rubble output chamber,

or in a can at the impactor station waiting to be cycled into the feed hopper. Very

complicated models and algorithms could be developed to try and describe the

situation. However, a rigorously defensible definition of the exact nature of the

catastrophic failure, vis-a-vis the plutonium, is likely unattainable and, in any case,

not worth seeking. It provides no new insight into a problem inherent in a mature

technology that is already well understood. A bounding MAR of 1050 g with a DR

of 1.0 can simply be assumed.

The shock to material when the unit flies apart is not greater than the shock from

internal impaction when the unit is operating properly. If release fractions even

approaching 1% were experienced in normal operations, significant accountability and

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