Aerosol retention

R = Pore Radius r Particle Radius q = Face Velocity of Gas  

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IBR (1995). Aerosol Retention Efficiency, Vacuum Bags, Report No. 2866A to Hoover Company, Grass Lake, MI, USA, InterBasic Resources, Inc., Grass Lake, MI, USA. 

Figure 2.22 Aerosol retention on a capillary-pore membrane as a function of particle size and pore size.

C-4. J. Li, D. Leaver, and J. Metcalf, Aerosol Retention During An Unisolated Steam Generator Tube Rupture Severe Accident Event , Proceedings on the Fifth International Topical Meeting On Nuclear Thermal Hydraulics, Operations and Safety, Beijing, China, April 13-16, 1997. 

Roberts, D. L., Kiang, R. L., Witham, C. L. Aerosol retention in nuclear reactor components. Report EPRI NP-3705 (1984)... 

Regarding the aerosol retention in the steam generator. Phase B calculation results have demonstrated that trapping is mainly located along the first metres of this component and a h height mock-up is suffident in the PHEBUS fadlity. 

ThedifferencesbetweenRAFT and TRAPFRANCE are imder invest ation. The wall condensation models differ and the aerosol retention modelling in TRAPFRANCE are similar to those of VICTORIA. 

Aerosol physics during transport is modeled in MELCOR by MAEROS, which includes particle agglomeration and different retention mechanisms including thermophoresis, diffusiophoresis, brownian diffusion and gravitational deposition. Aerosol retention in water pools is of interest in the V-LPIS sequence, when water pools may exists above the ruptured pipe in the auxiliary building it could also be of interest in the water present in the secondary side of steam generators in the SGTR sequence. 

Sweeney TD, Brain JD, LeMott S. Anesthesia alters the pattern of aerosol retention in hamsters. J Appl Physiol 1983 54 37-44. 

Mitchel RE. Aerosol retention in the lungs as a function of respiration rate and particle size. Ph.D. dissertation. Ohio State University, 1971. 

Verification of the microbial retention efficiency of the membrane filters may be undertaken using either Hquid or aerosol challenge tests. A Hquid challenge test is more stringent. Furthermore, this test can provide retention information for process conditions such as extreme moisture after sterilization or air entrained with water drops. A Hquid challenge is performed using a protocol similar to that described for Hquid filtration. 

Fig. 2. Schematic of an experimental aerosol bacterial challenge setup for evaluation of bacterial retention.

The basic operations in dust collection by any device are (1) separation of the gas-borne particles from the gas stream by deposition on a collecting surface (2) retention of the deposit on the surface and (3) removal of the deposit from the surface for recovery or disposal. The separation step requires (1) application of a force that produces a differential motion of a particle relative to the gas and (2) a gas retention time sufficient for the particle to migrate to the coUecting surface. The principal mechanisms of aerosol deposition that are apphed in dust collectors are (1) gravitational deposition, (2) flow-line interception, (3) inertial deposition, (4) diffusional deposition, and (5) electrostatic deposition. Thermal deposition is only a minor factor in practical dust-collectiou equipment because the thermophoretic force is small. Table 17-2 lists these six mechanisms and presents the characteristic... 

Several groups investigated the use of liposomes for the intra-pulmonary delivery. Farr et al. (1985) showed that the deposition of aerosolized liposomes in the human lung depends on the aerosol particle size. Short-term retention profiles for MLVs and SUVs deposited in the lung were indicative of clearance via the mucociliary transport mechanism. 

Animal model Am specie s Exposure Exposure concentration3 Aerosol AMAD (pm GSD) Lung deposition (percent of dose) Lung retention or absorption half-time15 Reference... 

Monkey, 3-5 years 241Am02 Aerosol, nose-only No data 1.4 Jm 75 pCi/kg 23 pg/kg 0.1 days (32%) 160 days (68%) (retention) Mewhinney and Muggenburg 1985... 

The ICRP (1994b, 1995) developed a Human Respiratory Tract Model for Radiological Protection, which contains respiratory tract deposition and clearance compartmental models for inhalation exposure that may be applied to particulate aerosols of americium compounds. The ICRP (1986, 1989) has a biokinetic model for human oral exposure that applies to americium. The National Council on Radiation Protection and Measurement (NCRP) has also developed a respiratory tract model for inhaled radionuclides (NCRP 1997). At this time, the NCRP recommends the use of the ICRP model for calculating exposures for radiation workers and the general public. Readers interested in this topic are referred to NCRP Report No. 125 Deposition, Retention and Dosimetry of Inhaled Radioactive Substances (NCRP 1997). In the appendix to the report, NCRP provides the animal testing clearance data and equations fitting the data that supported the development of the human mode for americium. 

Mewhinney JA, Griffith WC, Muggenburg BA. 1982. The influence of aerosol size on retention and translocation of 241Am following inhalation of 241Am02 by beagles. Health Phys 42(5) 611-627. 

Stanley JA, Edison AF, Mewhinney JA, et al. 1978. Inhalation toxicology of industrial plutonium and uranium oxide aerosols II. Deposition, retention and dosimetry. Health Phys 35(6) 888. 

Stanley JA, Edison AF, Mewhinney JA. 1982. Distribution, retention and dosimetry of plutonium and americium in the rat, dog and monkey after inhalation of an industrial-mixed uranium and plutonium oxide aerosol. Health Phys 43(4) 521-530. 

TF Hatch, P Gross. Physical factors in respiratory deposition of aerosols. In Pulmonary Deposition and Retention of Inhaled Aerosols. New York Academic Press, 1964, pp. 27 43. 

Radon-222, a decay product of the naturally occuring radioactive element uranium-238, emanates from soil and masonry materials and is released from coal-fired power plants. Even though Rn-222 is an inert gas, its decay products are chemically active. Rn-222 has a a half-life of 3.825 days and undergoes four succesive alpha and/or beta decays to Po-218 (RaA), Pb-214 (RaB), Bi-214 (RaC), and Po-214 (RaC ). These four decay products have short half-lifes and thus decay to 22.3 year Pb-210 (RaD). The radioactive decays products of Rn-222 have a tendency to attach to ambient aerosol particles. The size of the resulting radioactive particle depends on the available aerosol. The attachment of these radionuclides to small, respirable particles is an important mechanism for the retention of activity in air and the transport to people. 

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