Large Falling Object Impact or Induced Air Turbulence

DOE-HDBK-3010-94

4.0 Solids; Powders

powder, the same value for the ARF, 1E-3, is recommended but the RF is reduced to 0.1 due

to the difficulty of deagglomerating powders.

Large Falling Object Impact or Induced Air Turbulence. Under

4.4.3.3.2

some circumstances (e.g., seismic events) substantial portions of structural features and

equipment may fall into radionuclide-bearing-powders released from confinement. If the fall

of the objects generates a substantial air movement, the powder impacted may be suspended

by the aerodynamic stress imposed.

Langer (1987) dropped three rocks (1.29 kg, 1.17 kg, and 1.82 kg) 3.7-m onto powder on a

plywood sheet (called the "impact area") or held in a can in a vented metal box placed on the

impact area. The experimental apparatus is shown schematically in Figure A.36 and the

results are reproduced in Table A.42 in Appendix A. Air (430 cfm) was drawn into the box

via a filter that removed particles >5 m in diameter and passed through the impact area at

a velocity of 0.8 mph (0.36 m/s). Most of the air (91%, 390 cfm) was drawn through a

8-in. diameter cyclone with a 10 m AED cutoff. The particles penetrating the cyclone were

collected on a special high volume filter paper. The remainder of the air (~ 9%, 40 cfm)

was passed through a cyclone with a 5 m AED cutoff, a one-stage impactor that removed

all particles >0.5 m AED, and the particles penetrating the system were collected on a glass

fiber filter. Two optical spectrometers (1 l/min. instrument that classified particles 5 to 100

m into 4 classes and a 3 l/min. instrument that divided particles 0.2 to 12 m into 16

classes) provided real-time aerosol particle size distributions and number concentrations.

Four powders were tested - sand (<2000 m and <500 m), sand plus Al2O3, Al2O3, and

nickel metal. An indication of the size of the powders is reproduced in Table A.42. The

intent of the experiments was to determine the release of plutonium powders impacted by

building debris. For typical plutonium dioxide powder formed in the foundry, ~ 0.01% is

in the respirable size range (defined by the author as particle <3 m AED), 0.3% in the

inhalable range (defined by the author as particles <10 m AED) and ~ 2.2% was

<25 m AED (based on data from optical sizing of the powder). All three materials used as

surrogates were free-flowing (non-cohesive) powders unlike fine PuO2. The size distribution

of both Al2O3 (gritty, free-flowing, large proportions of fines) and nickel (hard, nearly

spherical metal, free-flowing) were finer than that for foundry PuO2. Airborne releases for

non-cohesive powders should be greater than for cohesive powders, with Al2O3

characteristics most closely paralleling the PuO2. The density of Al2O3 is 3.965 g/cm3,

approximately one-third that of PuO2, and the density of nickel is 11.5 g/cm3. The relevant

data from the experiments are tabulated in Table 4-15.

The highest measured ARF for all materials is 1E-3 for the Al2O3 uncontained on the pad.

The RF associated with this configuration is 0.3, a value near the middle of the RFs

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