Blast Effects

DOE-HDBK-3010-94

4.0 Solids; Powders

appropriate source for evaluating powders. The lesser values obtained from this data are

considered to confirm that the bounding ARF x RF values assigned for liquids and solids,

based on an assumed GSD of 8, are very conservative.

4.4.2.2

Blast Effects

The impact of gas flow upon powder deposited upon a surface is dependent upon the

characteristics of the gas flow, powder and surface. The experiments performed by Royster

and Fish (1967) illustrates the importance of the angle the air flow impacts the surface on the

efficiency of suspension. Experiments were performed where air was drawn into an

apparatus at a 30 angle and directed upon sparse populations of particles freshly deposited

on various surfaces. The apparatus is shown in Figure A.31 in Appendix A. The material

entrained was collected on a filter sealing the inlet to the air blower. The fraction of activity

removed by the apparatus compared to other estimation techniques as shown in Table A.38

in Appendix A. This illustrates the fact that, under ordinary circumstances of parallel flow

to surface, aerodynamic forces are not very effective for removal of particles deposited upon

surfaces. Figure 4-15 reproduced from the referenced article shows the effect of velocity

impacting at an angle to surface upon the fraction of 5 and 0.5 m diameter particles

entrained from a stainless steel surface. Removal is relatively complete at fairly low

velocities impacting the surface.

Entrainment from blast effects is divided into two categories:

Unshielded blast effects from detonations and large volume, confined

deflagrations. The dominant effect in either case is accelerated air impacting

powder and supporting surfaces from many angles.

Shielded blast effects from detonations and large volume, confined

deflagrations. The dominant effect in either case is accelerated air flow

parallel to powder and supporting surfaces.

4.4.2.2.1 Unshielded Blast Effects From Detonations and Large Volume,

Confined Deflagrations. Deflagration of a system filled with a flammable mixture may

accelerate to a detonation if the system configuration induces high turbulence during the

burning. Typically, this can occur in piping lines sized incorrectly with regard to National

Fire Protection Association Standards, inadequate use of flame arrestors in piping systems, or

confinement of the flammable mixture. In a study of flammable gas detonations in plutonium

storage facilities (Fry, 1991), it was concluded that an actual detonation, as opposed to a

deflagration, was highly unlikely. That study reiterated common assumptions that effective

confinement of vapor cloud explosions requires a flammable gas volume at least half the size

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