Alpha migration through air filters: A numerical simulation

Technical Report · Wed Dec 11 04:00:00 EST 1991

OSTI ID:10151952

Biermann, A H; da Roza, R A; Chang, Yun

This theoretical study investigates the migration of alpha-emitting particles through high-efficiency particulate air (HEPA) filters. As part of the study, a review of previous research relating to the alpha-migration phenomena was conducted. As a result of the literature review, a numerical model was developed to simulate the migration of alpha-emitting radionuclide aerosols through HEPA filters. This model predicts the filter performance with regard to particle penetration. It can be used to better estimate the penetration of alpha radioactive species through filter systems for environmental concerns, to aid in the use of current filter systems, and to design new filter systems. It is obvious from the review of the literature that evidence exists of migration of alpha radionuclide species through high-efficiency filter media. The theories suggest that nanometer-size particles can eventually penetrate fibrous filters because of gradual movement through the filter matrix. It is conjectured that this movement may be induced by energies caused by the alpha recoil from the decay process by thermal energies. It is further hypothesized that such nanometer-size particles, containing radionuclide species can be formed from larger particles already captured within the filter. The penetration of such small particles through high-efficiency filter media is so low that experimental corroboration of these mechanisms by penetration measurements is difficult at best. A number of items were identified that affect the migration of alpha-emitting particles through a filter. These include the size distribution of aerosol particles entering the filter, the size distribution of fragment particles produced by alpha recoil, the penetration of the challenge aerosols and fragment particles, the velocity through the filter, the radionuclide specific activity, the alpha recoil energy, and the surface-binding energies between the particle and the filter matrix.

• Research Organization: Lawrence Livermore National Lab., CA (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 10151952
• Report Number(s): UCRL-LR--109866; ON: DE92015631
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420202
54 ENVIRONMENTAL SCIENCES
540130
AEROSOLS
AIR
AIR FILTERS
ALPHA PARTICLES
EMISSION
NUMERICAL ANALYSIS
PARTICLE RESUSPENSION
PERFORMANCE
PROTECTIVE STRUCTURES AND EQUIPMENT
RADIOACTIVE MATERIALS MONITORING AND TRANSPORT
RADIONUCLIDE MIGRATION
RECOILS
TEMPERATURE EFFECTS
VAN DER WAALS FORCES