Small-Scale Spray Releases: Initial Aerosol Test Results

Abstract

One of the events postulated in the hazard analysis at the Waste Treatment and Immobilization Plant (WTP) and other U.S. Department of Energy (DOE) nuclear facilities is a breach in process piping that produces aerosols with droplet sizes in the respirable range. The current approach for predicting the size and concentration of aerosols produced in a spray leak involves extrapolating from correlations reported in the literature. These correlations are based on results obtained from small engineered spray nozzles using pure liquids with Newtonian fluid behavior. The narrow ranges of physical properties on which the correlations are based do not cover the wide range of slurries and viscous materials that will be processed in the WTP and across processing facilities in the DOE complex.Two key technical areas were identified where testing results were needed to improve the technical basis by reducing the uncertainty due to extrapolating existing literature results. The first technical need was to quantify the role of slurry particles in small breaches where the slurry particles may plug and result in substantially reduced, or even negligible, respirable fraction formed by high-pressure sprays. The second technical need was to determine the aerosol droplet size distribution and volume from prototypic breaches and fluids, specifically including sprays from larger breaches with slurries where data from the literature are scarce.To address these technical areas, small-and large-scale test stands were constructed and operated with simulants to determine aerosol release fractions and net generation rates from a range of breach sizes and geometries. The properties of the simulants represented the range of properties expected in the WTP process streams and included water, sodium salt solutions, slurries containing boehmite or gibbsite, and a hazardous chemical simulant. The effect of antifoam agents was assessed with most of the simulants. Orifices included round holes and rectangular slots. For the combination of both test stands, the round holes ranged in size from 0.2 to 4.46 mm. The slots ranged from (width × length) 0.3 × 5 to 2.74 × 76.2 mm. Most slots were oriented longitudinally along the pipe, but some were oriented circumferentially. In addition, a limited number of multi-hole test pieces were tested in an attempt to assess the impact of a more complex breach. Much of the testing was conducted at pressures of 200 and 380 psi, but some tests were conducted at 100 psi. Testing the largest postulated breaches was deemed impractical because of the much larger flow rates and equipment that would be required.This report presents the experimental results and analyses for the aerosol measurements obtained in the small-scale test stand. It includes a description of the simulants used and their properties, equipment and operations, data analysis methodologies, and test results. The results of tests investigating the role of slurry particles in plugging small breaches are reported in Mahoney et al. (2012). The results of the...

Large-Scale Spray Releases: Initial Aerosol Test Results

“…The results of tests investigating the role of slurry particles in plugging of small breaches are reported in Mahoney et al (2012a). The results of the aerosol measurements in the small-scale test stand are reported in Mahoney et al (2012b). Table S.1 provides a summary of each large-scale aerosol test objective, whether the objective was met, and a discussion of the test results.…”

“…0.2 apply to orifice plugging and small-scale aerosol testing. These objectives and the results of studies to address them are discussed by Mahoney et al (2012aMahoney et al ( , 2012b. Determine the size distribution of aerosol droplets and the total droplet volume concentration as a fraction of the total spray volume for a range of circular and rectangular breach sizes (up to the largest postulated breach in a 3-in.…”

“…Initial testing to obtain aerosol release fraction and generation rates has recently been completed in small-and large-scale test stands and are discussed in this report and in the small-scale aerosol report (Mahoney et al 2012b). These tests were conducted with simulants representing the expected WTP process stream properties over a range of orifice sizes and geometries and line pressures.…”

“…A broad range of simulants were developed and tested in the small-scale aerosol test stand (Mahoney et al 2012b). However, because of the hazards and costs associated with some of the simulants developed, only a small subset of the simulants was used in the large-scale test stand.…”

“…The effect of reduced surface tension resulting from the use of antifoam agents (AFA) (i.e., blends of surface-active agents) was addressed by testing in the small-scale test system (Mahoney et al 2012b), which is the companion to this study. The breakup of fast moving droplets into smaller droplets depends on the magnitude of the aerodynamic forces acting on the droplet.…”