Heating of Pools

DOE-HDBK-3010-94

3.0 Liquids; Aqueous Solutions

The data are limited but do appear to consistently indicate a gradual increase in airborne

release with temperature until boiling or near boiling temperatures. The air velocity range is

very limited although the air velocity probably represents a much greater aerodynamic stress

on the surface than the nominal velocity indicates. Air velocity measurements are usually at

much greater distances from the surface than in the experimental apparatus, and, air being a

fluid, the velocity decreases with distance from the surface due to frictional forces. The

extremely small liquid sample sizes would also enhance effective stress as well. The

concentrated plutonium nitrate solution used represents a very important class of liquids found

in DOE facilities but its fluid characteristics (higher density, surface tension) may not make it

bounding for other aqueous solutions.

3.2.1.2

H eatin g of P ools

ARFs were also measured during the evaporation of 90% of the volume of aqueous solutions

at three surface disturbance levels: simmering, disturbed surface, and boiling (Mishima,

Schwendiman and Radasch, November 1968). The results from the source document are

reproduced in Table A.2, and the experimental apparatus is shown in Figure A.2, both in

Appendix A. In the experiments, 100 ml of a dilute Pu(NO3)4 solution (0.25 M HNO3)

containing 0.7 mg Pu was placed in a 180 ml borosilicate beaker. The surface area of the

liquid was 11.5 cm2. The beaker was held in the center of a transite support ring that

positioned the beaker in a aluminum plate set upon a hot plate. A screen supporting a glass

fiber filter filled the annular area between the support ring and beaker and allowed air to be

drawn through the 4-liter borosilicate glass bell jar to entrain particulate material escaping

from the beaker. The velocity through the annular filter was estimated to be 3 cm/s. The

air was drawn out of the top of the bell jar via a water-cooled condenser to remove moisture.

The condensate was collected. Airborne material was collected on an in-line glass fiber

filter.

The pertinent results are shown in Table 3-2. The ARFs for the four runs at boiling ranged

from 4.5E-7 to 1.8E-3. Three of the four values ranged from 3E-4 to 1.8E-3. The two

highest values (1.1E-3 and 1.8E-3) were estimated by the sum of the filter acid leach and

from acid washes of the equipment downstream of the filter position due to loss of the filter.

These values include solution splattered from the vessel onto the glassware. The values are

almost certainly high, but it is not known how high. Two of the runs (ARFs 4.5E-7 and

1.1E-3) used a 0.70 mg Pu source without an airflow. The two runs performed at

simmering (no surface breaking) resulted in ARFs of 1.3E-6 and 4.5E-6 that are bounded by

the evaporation value of 3E-5 quoted in subsection 3.2.1.1. The four experiments with

heating rates resulting in disturbed surfaces generated ARFs ranging from 5.8E-5 to 8.4E-4:

an order of magnitude variation in estimates. A bounding value for boiling of aqueous

solutions of 2E-3 is selected, and, in the absence of a measured particle size distribution, a

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