RE: airfilters and radon daughters

["Bauman, Rodney L. (84U) " <84u@BECHTELJACOBS.ORG>]

For sites using alpha DAC values of  ~ E-11 uCi/ml or less, a 3 to 5 day air

filter decay period is usually required.  This is to allow for the decay of

Pb-212, a thoron daughter with a 10.6 hr half-life.  Although the thoron

daughter products normally have initial concentrations much less than the

radon daughters, they can still cause a problem when using uranium

(class-Y), thorium, or TRU DAC values. 



Rodney Bauman, CHP, RRPT

Bechtel Jacobs Company, LLC

Project Health Physicist

ETTP and Y-12 Waste Operations

Y-12 National Security Complex

Voice: 865.241.5344

Pager: 865.417.0561

Fax: 865.576.3946

84u@bechteljacobs.org

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