wate ee ee —_ e Platinum Screen Collections This is a Naval Research Laboratory experimental eollector. An uncharged platinum screen is mounted vertically and held normal to surface winds by a large vane, Two week total activity collegtions made by NRL with this collector range up to that for 0.5 x 10° cubic feet of air, For individual twenty-four hour periods, total activities as high as 20 times that for gummed paper collectors have been observed, 1. Sample Total Sr90 tn dpm CL 536-P: 1.0 sq. ft., 80 mesh platinum screen, Washington, D.C., collected 1600, February 1h, 26.0 + 1.7 1955 to 1600, February 21, 1955. 2. CL 537-P: 1,0 sq. ft., 80 mesh platinum screen, 1.9 + 0,8 Washington, D. Cs, collected 1600, February 21, 1955 to 1600, February 28, 1955. 3. CL 538-P: 1.0 sq/ ft., 80 msh platinum screen, 37.2 + 1.6 Washington, D.C., collected 1600, February 28, oo meh 1955 to 1600, March 7, 1955. DOE ARCHIVES (70