Removal of Iodine and Particles by Sprays in the Containment Systems Experiment

MELCOR 1.8.3 assessment: CSE containment spray experiments

“…Based on data from earlier tests in the CSE series on natural removal of suspended cesium and uranium aerosol particles [22], significantly larger particles (up to 16 pm diameter) would be required to match the observed natural depleiion rates such as those found before the first spray period. Particle size was measured by cascade impactors at selected intervals during the spray tests; for test A-9, the measured mass median particle diameter was 0.5 pm for cesium and 0.6 pm for uranium before the first spray period, and 0.4 pm for both cesium and uranium after the second spray period [14]. At longer times, more of the material penetrated the impactor, indicating a shift to smaller sizes.…”

“…The experimentalists [14] attributed this effect to two causes: (1) the Maypack is not a perfect discriminator of iodine forms and some of the iodine called inorganic might be in forms less readily removed, and (2) absorption of inorganic iodine by aqueous sprays is a reversible process and back diffusion into the gas space can occur from liquid films which contain high concentrations of iodine.…”

“…To this end, a number of assessment calculations have been and are being done [3-131. One of these assessment activities is analysis of a series of eight large-scale containment spray experiments performed in the Containment, Systems Experiment (CSE) vessel [14], to evaluate the performance of aqueous sprays as a means of decontaminating containment atmospheres. Measurements were obtained which provide a suitable basis for judging the ability of various mathematical models to predict spray performance in large nuclear power plant buildings.…”

Effect of Spray Flow Rate on Washout of Gases and Particles in the Containment Systems Experiment.

“…The amount of solute absorbed per unit volume of liquid flowing down the wall at deck level is (10) where Q w = mass absorption rate for entire wall film, kw = gas phase mass transfer coefficient for transfer to wall film, A = total film surface exposed to containment atmosphere, w C = mass' concentration of solute in the bulk gas phase. g Equation (10) indicates that the absorption rate is independent of flow rate. Knudsen and Hilliard(7) suggested a method for estimating the gas phase mass transfer coefficient for transfer to vertical wall films.…”

“…The concentration of elemental iodine, C g1 , can be estimated from Equations (1), (4), and (10). Assuming an instantaneous release and no interroom transport or vapor phase reactions, these equations combine to give (16) where C I = concentration at time zero, 18 (17) • .…”