* cedars oh hak 6 wn Unk NRL REPO RT 6374 TABLE 3 Calculated 8 Counts Obtainable From 20-Minute Collections of Radon Daughters on Glass Fiber Filters for a Radon Concentration of 100 pCi/m' and a Filtration Rate of | m*/min ar the | fol- Disintegrations During 10-Minute x 100 in at Periods 3 for it 61 fii for p= 0.048 rber vals the | as RaB RaC Total Ratio (tet-71/t1-11) ited ods p= 0.190 uct otal RaB Rac Total Ratio (te1-71/f1-11) BOURSESarn: p = 0.390 RaB RaC Total Ratio (te1-71/t1-11) p = 0.564 RaB RaC Total Ratio (tga-71/£1-11) p= 0.735 RaB RaC Total Ratio (te1-71/t1-11) tev 3798 1687 5485 864 1594 2458 0.448 13170) 8233 21403 2879 5640 8519 0.398 22700 19562 42962 4903 10279 15182 0.359 28946 30758 59704 6227 13775 20002 0.335 33221! 41689 74910 7136 16562 23698 0.316 Total Counts During 10-Minute Periods No Absorber faut 61-71 518] 244) 762 118 231 349 0.458 1795 1192] 2987 392 817 1209 0.405 30941 2833 5927 668 1488 2156 0.364 3945] 4454 8399 849 1995 2844 0.339 4528). 973 6037 2398 10565 3371 0.319 the true values. With no absorption except for that inherent in the counting tube window, maxi- mum count rates are obtained but also decreased sensitivity results because both RaB and RaC are counted simultaneously; moreover, the effect of the large quantity of low-energy conver- sion electrons associated with RaB cannot be accurately assessed. Since a 10-mil aluminum absorber will remove nearly all response to the conversion electrons from the RaB and_ also 5-mil Absorber fee fe1-71 171 180 35] 39 170 209 0.595 594] 879 1473 130 602 732 0,497 1024 2089 3113 291 1098 1319 0.424 1305] 3285 4590 281 1471 1752 0.382 1498 445? 5950 322 1769 2091 0.351 10-mil Absorber fia f61-71 71 137 208] 16 130 146 0.702 246 670 916} 54 459 513 0.560 494 1592 2016 92 837 929 0.461 541 9504 3045 116 1121 1237 0.406 621 3393 4014; 133 1348 1481 0.369 30-mil Absorber feu 0 54{ 54] £61-71 0 51 51 0.945 0 264 264 0 181 181 0.685 0 628 628 0 330 330 0.525 0 987 987 0 442 442 0.448 «0 1338 1338 0 532 532 0.397 reduce to a considerable extent the counter response to the RaB itself, use of an absorber of this 10-mil thickness is considered to be a practical compromise. Estimations of the overall errors (standard deviations) based on the counting statistics to be expected from use of this procedure to determine the radon concentration have been made for the conditions of an air flow of 0.5 m/min, a back- ground of 30 counts/min, and a 5% contribution