Free-Fall Spill - h3010v10073

DOE-HDBK-3010-94

3.0 Liquids; Aqueous Solutions

3.2.3

F ree-F all S p ill

Aqueous solution, slurries, and viscous liquids (non-Newtonian fluids) spilled onto a hard,

unyielding surface can be subdivided into drops by the instability/shear stress at the surface

of the liquid during the fall and by impact upon striking the surface (splashing). The passage

of the falling material through the air space creates airflow patterns and turbulence that aids

in suspension.

3.2.3.1

S olu tion s

Experiments have been performed to determine the airborne release from the free-fall spill of

aqueous solutions with densities of ~ 1.0 (uranine) and ~ 1.3 g/cc (UNH). Materials that

may represent airborne material deposited on the walls were measured in some experiments.

The fall distance was limited, less than 3 m, and the initial dispersion of the material was

uncontrolled; material was released by inverting a glass beaker holding the liquid. The

experimental apparatus is shown schematically in Figure A.7 and the measured results

reproduced in Tables A.10 through A.13 in Appendix A. Measured ARFs and RFs are

tabulated in Table 3-6.

The ARFs for the uranine solution under these conditions ranged from 4E-6 to 2E-4 and

1E-6 to 2E-5 for the UNH. The fraction of the source airborne as particles 10 m AED and

less ranged from 2E-6 to 1E-4 for the uranine solution and from 2E-7 to 1E-5 for UNH.

Both the fraction airborne and the fraction in the respirable size range appear to vary with

fall distance and source size. A conservative bounding value for the ARF for aqueous

solution with a density near 1 would be 2E-4 with an RF of 0.5. For TRU solutions with

greater densities, a bounding ARF of 2E-5 with an RF of 1.0 (based on a high value that

may be anomalous) is considered conservative. The median ARF and RF for aqueous

solutions are 4E-5 and 0.7 and 1E-6 and 0.3 for the concentrated heavy metal solutions.

As previously noted in subsection 3.2.2.3.2, for the sake of simplicity a gross density

distinction is made for determining which ARF and RF values to use for solutions. Any

solution containing heavy metal salts where the liquid alone has a density in excess of

~ 1.2 g/cm3 is considered a "concentrated heavy metal solution" for assigning ARF and RF

values. Any solution containing heavy metal salts where the solution alone has a density less

than ~ 1.2 g/cm3 is considered an "aqueous solution" for assigning ARF and RF values.

An empirical model of ARF and droplet size distribution from free-fall spills of liquids

beyond the fall distance range encompassed in the experiments has been developed by

Ballinger, et al. (January 1988). In this model, the ARF value is defined by the following

equation:

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