A simplified model of aerosol removal by containment sprays

Abstract

Spray systems in nuclear reactor containments are described. The scrubbing of aerosols from containment atmospheres by spray droplets is discussed. Uncertainties are identified in the prediction of spray performance when the sprays are used as a means for decontaminating containment atmospheres. A mechanistic model based on current knowledge of the physical phenomena involved in spray performance is developed. With this model, a quantitative uncertainty analysis of spray performance is conducted using a Monte Carlo method to sample 20 uncertain quantities related to phenomena of spray droplet behavior as well as the initial and boundary conditions expected to be associated with severe reactor accidents. Results of the uncertainty analysis are used to construct simplified expressions for spray decontamination coefficients. Two variables that affect aerosol capture by water droplets are not treated as uncertain; they are (1) ^Q', spray water flux into the containment, and (2) "H', the total fall distance of spray droplets. The choice of values of these variables is left to the user since they are plant and accident specific. Also, they can usually be ascertained with some degree of certainty. The spray decontamination coefficients are found to be sufficiently dependent on the extent of decontamination that the fraction of the initial aerosol remaining in the atmosphere, m^^, is explicitly treated in the simplified expressions. The simplified expressions for the spray decontamination coefficient are: X(hr ~h = X(mf = 0.9) [X(mf)/X(mf = 0.9

Heat, Mass and Aerosol Transfers in Spray Conditions for Containment Application

“…At the same time, measurements obtained for t > 1500 s are not considered due to the increase of the online turbidimeter accuracy observed for lower aerosol mass concentration presents in draining water. According to the result presented on the Fig.15, the aerosol removal rate is equal to 0.0019 during the period 200 s to 1500 s. In this condition, the droplet collect efficiency computed with the relation (2) is equal to 0.0108 which is in good agreement between Powers's results for droplet size of 200 µm (15) and with Ducret's results (16) for monodisperse droplet size of 280 µm. Let's point out the fact that Ducret's results were obtained during steady state thermal-hydraulic conditions and aerosol mass concentration in suspension in the CARAIDAS vessel, and the single droplet efficiency is constant during the test, as opposed to the TOSQAN vessel where the aerosol population changes all along the test.…”

Development of rapid atmospheric source term estimation system for AP1000 nuclear power plant

“…In 1993, U.S. NRC released A Simplified Model of Aerosol Removal by Containment Sprays (Powers and Burson, 1993). In the report, aerosol removal mechanisms by water droplets, such as impaction, interception and diffusion, were analyzed in detail, and based on the analysis, a mechanistic model was established.…”

Removal of Sarin Aerosol and Vapor by Water Sprays

“…all mechanisms A number of correlations for these mechanisms are reported by Rimberg and Peng (1977), Hidy (1984), and Seinfeld (1986). Powers and Burson (1993) have developed a simplified model for the removal of aerosols from reactor containments by water sprays. The correlations selected for use in these scoping calculations are certainly adequate for that purpose but further searching of the literature would be warranted for follow-on work.…”