Small-Scale Spray Releases: Orifice Plugging 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 published 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 present 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 introduced by extrapolating existing literature results. The first technical need was to quantify the role of slurry particles in small breaches in which 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 largely absent.To address these technical areas, small-and large-scale test stands were constructed and operated with simulants to determine the aerosol release fractions and aerosol 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 anti-foam agents (AFA) was assessed with most of the simulants. Orifices included round holes and rectangular slots. 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.The purpose of the study described in this report is to provide experimental data for the first key technical area, potential plugging of small breaches, by performing small-scale tests with a range of orifice sizes and orientations representative of the WTP conditions. The simulants used were chosen to represent the range of process stream properties in the WTP. Testing conducted after the plugging tests in the small-and large-scale test stands addresses the second key technical area, aerosol generation. The results of the small-scale aerosol generation tests are included in Mahoney et al. (2012). The area of spray generation from large breaches is covered by large-scale testing in Schonewill et al. (2012). S.1 Objective S.2 Results and Performance Against Success Criteria...

Large-Scale Spray Releases: Additional Aerosol Test Results

“…The first technical area was to quantify the role of slurry particles in small breaches where slurry particles may plug the hole and prevent high-pressure sprays. The results from an effort to address this first technical area can be found in Mahoney et al (2012). The second technical area was to determine aerosol droplet size distribution and total droplet volume from prototypic breaches and fluids, including sprays from larger breaches and sprays of slurries for which literature data are mostly absent.…”

“…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.…”

“…These constraints included chemical cost, disposal cost, time for preparation, time for cleaning, and chemical hazards. A greater number of simulants were tested in the small-scale spray leak tests, including the chemical slurry simulant (Mahoney et al 2012. The non-hazardous slurry simulant chosen for Phase II large-scale testing was an 80/20 solids blend of a kaolin/bentonite clay slurry simulant.…”

“…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). …”