Penetration of HEPA filters by alpha recoil aerosols

Conference · Thu Jan 01 04:00:00 EST 1976

OSTI ID:7354855

McDowell, W J; Seeley, F G; Ryan, M T

Tests at Oak Ridge National Laboratory confirmed that alpha-emitting particulate matter does penetrate high-efficiency filter medium, identical to that used in HEPA filters, much more effectively than do non-radioactive or beta-gamma active aerosols. Filter retention efficiencies drastically lower than the 99.97 percent quoted for ordinary particulate matter have been observed with /sup 212/Pb, /sup 253/Es, and /sup 238/Pu sources, indicating that the phenomenon is common to all of these and probably to all alpha-emitting materials of appropriate half-life. Results with controlled air-flow through filters in series are consistent with the picture of small particles dislodged from the ''massive'' surface of an alpha-active material, and then repeatedly dislodged from positions on the filter fibers, by the alpha recoils. The process shows only a small dependence on the physical form of the source material. Oxide dust, nitrate salt, and plated metal all seem to generate the recoil particles effectively. The amount penetrating a series of filters depends on the total amount of activity in the source material, its specific activity, and the length of time of air flow. Dependence on the air flow velocity is slight. It appears that this phenomenon has not been observed in previous experiments with alpha-active aerosols because the tests did not continue for a sufficiently long time. A theoretical model of the process has been developed, amenable to computer handling, that should allow calculation of the rate constants associated with the transfer through and release of radioactive material from a filter system by this process.

• Research Organization: Oak Ridge National Lab., Tenn. (USA); Lowell Univ., Mass. (USA)
• DOE Contract Number: W-7405-ENG-26
• OSTI ID: 7354855
• Report Number(s): CONF-760822-5
• Country of Publication: United States
• Language: English

Related Subjects

500200 -- Environment
Atmospheric-- Chemicals Monitoring & Transport-- (-1989)
500300* -- Environment
Atmospheric-- Radioactive Materials Monitoring & Transport-- (-1989)
54 ENVIRONMENTAL SCIENCES
ACTINIDE ISOTOPES
ACTINIDE NUCLEI
ADSORPTION
AEROSOLS
AIR CLEANING SYSTEMS
AIR FILTERS
AIR POLLUTION
ALPHA DECAY RADIOISOTOPES
ALPHA PARTICLES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CHARGED PARTICLES
COLLOIDS
DAYS LIVING RADIOISOTOPES
DISPERSIONS
EFFICIENCY
EINSTEINIUM 253
EINSTEINIUM ISOTOPES
ENGINEERED SAFETY SYSTEMS
EQUIPMENT
EVEN-EVEN NUCLEI
FILTERS
HEAVY NUCLEI
HOURS LIVING RADIOISOTOPES
ISOTOPES
LEAD 212
LEAD ISOTOPES
NUCLEI
ODD-EVEN NUCLEI
PERFORMANCE TESTING
PLUTONIUM 238
PLUTONIUM ISOTOPES
POLLUTION
POLLUTION CONTROL EQUIPMENT
RADIOACTIVE AEROSOLS
RADIOISOTOPES
SOLS
SORPTION
TESTING
YEARS LIVING RADIOISOTOPES