Free-Fall Spill with Enhanced Velocity Effects Normal to the Direction of Fall

DOE-HDBK-3010-94

4.0 Solids; Powders

3-m fall distance; the difference appears to diminish with fall distance probably due to the

greater consistency for the impact dispersion as the force increases).

The best available correlation for particle size of the airborne material is:

) + 7540(F)

(4-6)

AMMD = 12.1 - 3.29(

where:

AMMD = aerodynamic equivalent mass median diameter, m

F = fraction airborne

BP = bulk density powder, kg/m .

The equation only has a 46% correlation coefficient due to the variability in the data. The

GSD of the size distribution for all powders (based on the powders used in the experiments),

TiO2 and UO 2 are 4.82, 3.73 and 5.60, respectively.

The median and bounding ARFs and RFs are based on the experimental measurements

uncovered. For fall distances less than 3 m, the measured combination of ARF and RF

values that yield the highest fraction of material in the respirable fraction, 2E-3 and 0.3, are

assessed to be the bounding values. The median values are those determined considering

both powders, 3E-4 and 0.5. For fall distance greater than 3 m, the bounding value can be

estimated using the average airborne release fraction calculated by the model discussed in this

subsection multiplied by a factor of 2 provided the value calculated exceeds that obtained

with the ARF and RF combination of 2E-3 and 0.3.

4.4.3.2

Free-Fall Spill with Enhanced Velocity Effects Normal to the

Direction of Fall

The conditions represented here are extreme for the normal range of stresses normally

encountered in industrial-type accidents. The conditions may be found for powders

undergoing pneumatic transfers or for minute quantities of soil fines that sift/spill during

some earth moving operations such as digging with a backhoe or steam shovel in extremely

windy conditions. The factors derived are not meant to be applied unless there is reasonable

evidence that the conditions in the event or for the fraction of inventory indeed mimic the

experimental conditions. For example, this data is not intended for fine judgements about

low quantity releases from contaminated soil or for evaluating simple bulk powder spills in

an atmosphere of overall room/glovebox ventilation or typical ambient conditions.

Sutter (August 1980) reported results of experiments to measure the entrainment of dispersed

soil spilled into flowing air. Contaminated soil was collected, mixed and dried and pumped

into a 0.61-m by 0.61-m wind tunnel. The experimental setup is shown schematically in

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