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: Additional Aerosol Test Results

“…To address the second technical area, the testing program collected aerosol generation data at two scales, commonly referred to as small-scale and large-scale testing. The small-scale testing and resultant data are described in Mahoney et al (2013), and the large-scale testing and resultant data are presented in Schonewill et al (2012). In tests at both scales, simulants were used to mimic the relevant physical properties projected for actual WTP process streams.…”

“…Initial testing to obtain aerosol release fraction and generation rates was completed during Phase I in small-and large-scale test stands and presented in the large-scale aerosol report (Schonewill et al 2012) and the small-scale plugging and aerosol test reports (Mahoney et al 2012 andMahoney et al 2013). These tests were conducted with simulants representing the expected WTP process stream properties over a range of orifice sizes, geometries, and line pressures.…”

“…The fluids tested include Newtonian salt solutions with increased density and viscosity, slurries of gibbsite or boehmite in water that are essentially Newtonian fluids, and non-Newtonian slurries of clays and a chemical simulant with rheology targets for Bingham yield stress and consistency of 6 Pa/6 cP and 30 Pa/30 cP (Schonewill et al 2012(Schonewill et al , 2013Mahoney et al 2013). In general, the aerosol generation rates from the water sprays are always the same or higher than each of these other fluids.…”

“…The objective of this first phase of testing (hereafter called Phase I testing) was to improve the technical basis for predicting the size and concentration of aerosols produced from a spray leak by reducing the uncertainty introduced by extrapolating existing literature results. The results of Phase I testing (which are documented in Mahoney et al (2012), Mahoney et al (2013), and Schonewill et al (2012) and which are briefly summarized in Section 1.1) led to a conclusion that a second phase of testing was needed, with the primary goal of improving confidence of the release fraction results when extrapolating (i.e., scaling) those results to postulated spray leak scenarios in the WTP. In addition to this primary goal for testing in the large-scale test stand, the Phase II spray leak testing was conducted to address areas of uncertainty remaining from Phase I testing with respect to aerosol behavior (namely aerosol release fraction and generation rates) for:  simulant(s) near the WTP rheological boundaries of (6 Pa/6 mPa·s and 30 Pa/30 mPa·s)  simulant(s) with solids loadings greater than 20 wt%  simulant(s) with a small solids fraction of particles that have a relatively high density  lower spray pressures (i.e., specifically 100 and 200 psig in the small-scale tests)  in-spray measurements.…”

“…Other objectives identified in Test Plan TP-WTPSP-031, Rev. 1.0, are not discussed in this report as they apply either to Phase I test objectives completed in previous testing and discussed in Mahoney et al (2012Mahoney et al ( , 2013 and Schonewill et al (2012) or to objectives addressed by Phase II small-scale testing and discussed in Schonewill et al (2013). …”