Security Classification DOCUMENT CONTROL DATA - R&D {Security classification of title, body of abstract and indexing annotation must be entered when the overall reportia classified) 1. ORIGINATING ACTIVITY (Corporate authar) Fe. REPORT SECURITY U.S. Naval Research Laboratory Washington, D.C, 20390 3 C LASSIFICA TION Unclassified lab GRouP REPORT TITLE THE EXTENT OF RADIOACTIVE EQUILIBRIUM BETWEEN RADON ANDITS SHORT-LIVED DAUGHTER PRODUCTS IN THE ATMOSPHERE 4. DESCRIPTIVE NOTES (Type of report and inclusive dates) An interim report on the problem. §. AUTHOR(S) (Last name. firat name, initial) Lockhart, L.B., Jr., and Patterson, R.L., Jr. 6. REPORT DATE Ja. TOTAL NO. OF PAGES 8a. CONTRACT OR GRANT NO. 9a. ORIGINATOR'S REPORT NUMBER(S) April 5, 1966 NRL Problem AQ2-13 & 7b. NO. OF AEFS 290 3 NRL Report 6374 PROJECT NO. RR 004-02-42-5151 ¢. and AEC AT 49-7(2435) 9b. OTHER REPORT NO(S) (Any other numdera that may be assigned thie report d. 10. AVAILABILITY /LIMITATION NOTICES Distribution of this document is unlimited. 11. SUPPL EMEN TARY NOTES 12. SPONSORING MILITARY ACTIVITY Departmentof the Navy (Office of ‘ Naval Research) Washington, D.C. 13. ABSTRACT A set of experimental conditions has been derived which optimizes the accuracy with which the radon contentof the atmosphere andits apparent residence timethere can be determined from measurementof the filterable gross 8 activity during two separate 10-minute periods following the end of a 20-minute collection period. The 20-minute collection is made ona filter of essentially 100% retentivity (glass fiber filter) and countedfor @ activity through a 10-mil (70. mg/cm?) aluminum absorber on equipmentof knownefficiency for the 8 particles emitted by RaB and RaC. Theratio of measured counts during the 61-through-71-minute decay period to that during the 1-through-11-minute period is emnloyed to obtain the atom ratio of RaC to RaB (p) in the air sar pled, the apparent age (r) of the conglomerate of radon andits daughters, and the total counts to be expected from any given radon concentration in the air. Extensive examples of atmospheric measurements are given which suggest that under most conditions in the free atmosphere radonis essentially at secular equilibrium with its daughter products. Other collections made following addition of radon to a restricted volume show the expected increase in p with time, which confirms the basic validity of the procedure. DD .2%. 1473 7 Security Classification