Suspension of Material by Vehicular Traffic

DOE-HDBK-3010-94

4.0 Solids; Powders

exposure would be hours rather than seconds. Thus, a bounding ARR of 4E-5/hr with a RF

of 1.0 is recommended. However, as previously noted, the estimated respirable release

should not exceed the total respirable material in the source if known.

No experimental data on the effects of large debris over the deposited powder on

aerodynamic entrainment were found. Schmitt (May 1975) reported an approximate order of

magnitude reduction in particulate emissions from carbon microsphere used to extinguish a

fire. Due to the decrease in aerodynamic stress if the powder is shielded by remnants and

debris of the structure or exposed to static conditions within the structure, an ARR and RF

for powder under debris of 4E-6/hr and 1.0 are recommended.

Bounding ARR and RF, homogeneous bed of powder exposed to ambient

conditions (normal process facility ventilation flow or less, or nominal

atmospheric conditions <2 m/s with gusts up to 20 m/sec)

following an event:

4E-5/hr, 1.0

Bounding ARR and RF, homogenous bed of powder buried under structural

debris exposed to ambient conditions or under static conditions within the

structure following an event:

4E-6/hr, 1.0

It is noted that these values are for freshly deposited material in the immediate aftermath of

release. It would be inappropriate to use these values for cumulative summing of hourly

releases for long-term contamination (i.e., months to years).

4.4.4.2

Suspension of Material by Vehicular Traffic

In the event that radioactive materials in powder form are spilled onto a roadway during

transport or deposited by airborne transport during the accident, the deposited material may

be impacted by vehicular traffic unaware of the presence of the material or by evacuation of

personnel. Sehmel (1973) reported the results of experiments performed to measure the

suspension of material on an roadway from the passage of a vehicle (passenger car and

3/4-ton truck) through the deposited material and in an adjacent lane. Particles of ZnS

<25 m in diameter (MMD <5 m in diameter) were deposited on the asphalt surface of a

3-m by 30-m section of roadway (one lane of a two-lane road). The ZnS particle size

distribution during deposition is shown in Figure A.38a in Appendix A. Sampling towers

were located at three distances (3, 6, and 9 m) from the road with filter samplers at 0.3-m,

1-m, 2-m and 2.4-m heights. Realtime ZnS monitors were located at the 0.6-m level of each

tower. Deposition samplers were located between the towers on each row and at 1-m, 18-m

and 30-m. The arrangement is shown schematically in Figure A.38b in Appendix A.

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