Aerodynamic Entrainment and Resuspension cont'd

DOE-HDBK-3010-94

5.0 Surface Contamination; Solid, Noncombustible Surfaces

There is still controversy over which basic resuspension concept to apply - force

balance or energy balance.

Due to an incomplete understanding of the turbulent boundary layer, and more

precisely of the bursting phenomenon, uncertainty exists as to the removal forces

acting on particles.

Some very important effects such as particle agglomeration on the surface (alters

the size of the particles to be suspended and raise questions as the

deagglomeration in flow), saltation (role of energy transfer from impacting

particles on suspension), and initial suspension have not been well studied.

The wide range of values for adhesive forces and the lack of models to explain

influence of roughness (both substrate and particle surface) results in great

uncertainty.

A few field studies have reported the suspension of particles from heterogeneous substrates.

Garland and Pigford (1992) reported a resuspension factor (K) of 1E-6 for fallout from

Chernobyl from the Harwell parking lot. If a sampling period of 24 to 72 hours is assumed,

the resuspension flux would be 1 to 4 E-8/hr. Sutter (1982) lists Ks reported for Bennett

(1976) of 2E-6 to 5E-9 for New York City and the United Kingdom and 6E-6 to 8E-9 for

paving stones. These are in the same range or less than reported by Garland and Pigford

(1992). Sutter reported K values for the study of resuspension of plutonium as oxide powder

or dried nitrate solution from various floor covering (Jones and Pond, 1967) ranging from

1E-10/hr to 1E-8/hr assuming an 16-hr sampling period for air movement only. The values

appear to be consistent with the bounding value assessed for homogeneous beds of powder of

4E-5/hr under process facility ventilation flow conditions and nominal outdoor conditions.

For particle deposits shielded from the ambient flow by debris or in a static (no induced

flow) facility, a resuspension flux an order of magnitude less, 4E-6/hr, is assessed to be

bounding.

Therefore, the ARR and RF values assessed to be bounding for aerodynamic entrainment

(resuspension) of surface contamination (sparse population) from a heterogeneous (hard,

unyielding) surfaces are:

Indoors or outdoors exposed to ambient conditions (normal process facility

ventilation flow or less, or nominal atmospheric windspeeds < 2 m/s with

gusts up to 20 m/s) following an event:

ARR 4E-5/hr; RF 1.0

Buried under debris exposed to ambient conditions or under static conditions

within the structure following an event:

ARR 4E-6/hr; RF 1.0

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