#Half life sourcefilter series

(USA) OSTI Identifier: 7354855 Report Number(s): CONF-760822-5 TRN: 76-020040 DOE Contract Number: W-7405-ENG-26 Resource Type: Conference Resource Relation: Conference: 14. « lessĪuthors: McDowell, W J Seeley, F G Ryan, M T Publication Date: Research Org.: Oak Ridge National Lab., Tenn. 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. It appears that this phenomenon has not been observed in previous experiments with alpha-active aerosols because more » the tests did not continue for a sufficiently long time. Dependence on the air flow velocity is slight.

#Half life sourcefilter series

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. Oxide dust, nitrate salt, and plated metal all seem to generate the recoil particles effectively. The process shows only a small dependence on the physical form of the source material. 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.

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. 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.