Selection of Filter Media in Alpha Air Monitors for Emergency ...

P-4a-262
Table 2 Relative background counts of radon decay products in a plutonium region obtained for the test filters
Filter Type and Designation
Relative background counts of radon decay products
in a plutonium region
MEMBRANE( PTFE with backing TYPE)
MILLIPORE FSLW (3.0 µm pore size) 0.006 ± 0.002
PREFILTER FOR MEMBRANE FILTER
MILLIPORE AW19 (5.0 µm pore size) 0.04 ± 0.005
On the basis of these results, we examined background counts in a plutonium energy region about two filters. We
selected FSLW and AW19 out of PTFE membrane filters with backing and prefilters. The relative background counts
of radon decay products obtained for the test filters are shown in Table 2. This also showed that PTFE membrane filters
with backing such as FSLW is suitable for alpha monitoring because of lower background counts.
SUMMARY
Some characteristics of commercial air filters were studied so as to select the suitable filter media in an alpha air
monitor for emergency environmental monitoring .
Cellulose acetate membrane filters and PTFE membrane filters without baking showed high surface collection
efficiency, but these filters are not suitable for alpha air sampling because of high pressure drop. It was found that the
PTFE membrane filter with backing had a high surface collection efficiency and low pressure drop. Further research on
the particle collection efficiency for the PTFE membrane filters with baking of various pore sizes is required in order to
make a choice of the optimum pore size.
(This research was conducted under Science Technology Agency Contract. )
REFERENCES
1. L.B.Lockhart,Jr., R.L.Patterson,Jr. and W.L.Anderson, Characteristics of Air Filter Media Used for Monitoring
Airborne Radioactivity. NRL Report 6054, U.S. Naval Research Laboratory, Washington D.C., USA (1964)
2. M.D.Hoover and G.J.Newton, Update on Selection and Use of Filter Media in Continuous Air Monitors for Alpha-
Emitting Radionuclides. in Inhalation Toxicology Research Institute Annual Report, LMF-138, Albuquerque,
USA (1992)
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