prrncssctewnne pasorarone ATFICIALUSE ONLY po LOS ALAMOS. NEW MEXICO OFFICE MEMORANDUM TO : €, L. Shipman, H-Division Office FROM : ¥W, 8. Johnson _ aed | tf ACL by | DATE: May 24, 195% REPOSITORY COLLECTION. SUBJECT: RESULTS OF ATMOSPHERIC SAMPLING PROGRAM SYMBOL : He5 BOX No FOLDER Since 2/19/54, nearly continuous monitoring has been in progress for the detection of contamination of possible Pacific origin, This has consisted of air sampling for concentration and size of radioactive fall-out particles and a recording G.-M, tube instrument for observing . changes in surface activity. Samples prier to 3/1/54 were used to develop a standard decay curve for normal background radiation and all succeeding samples were compared to this curve. Filter samples were changed twice daily throughout the period of concern, " Two periods of significant change in normal background were observed, by The first occurred between 0600-1620 4/5/54 when the air concentration approached ten times normal background, The rise and fall of the air cone centration took place within a 24-hour period, Successive counts indicated that the material decayed with a slope of -2.0 on the basis of a 3/26/54 x te z # i F E origin, The second period of interest is not yet completed, Ke ey about five times normal were observed on 5/10/54. Air concentrations A heavy rain occurred @uring this day also, which contained approximately 0.3 pe of beta activity per liter. Rain water from succeeding showers was radio-assayed but the highest concentration found was only about 0.03 pe/liter. Surface beta activity was noted to be 4 — 5 times normal background when measured with open~shield G,-M, instruments, c. a a The contamination resulting from this latest incident is still in the i air and on the ground in detectable quantities, Ten representative air samples have been observed for decay. Five of the decay curves exhibited ee: 8 a slope between -1.0 and «1,5 on the basis of 5/4/54 origin while the re- a1 = maining five fell eff more rapidly with slopes of =§-4 or greater. The water sample of highest concentration decayed as t™ wsing the same shot “as its zero time, os Sc a ay _ fe cee Sampling will be continued antil normal. background air concentrations are obtained, a a ee me: e mo 7 uate re =. = Wie . me we EP . , a, Me RC gs aa Teyokh ae ee ee ; Bey ee a a woe ote ee ON , ~Lo no ne ie oof . i auf ro” ‘ Hot 5 . “ : . > . _Ff ; ve nn “ra ‘ ‘ : 4 vo ’ a . “ . Lf. * ! 1 oveDAFCULUSE 7 ‘ be. hy # : 4 se . oy pal woe . . 2 Q oS * + Pin . a os . ee . : i s * . ~ ec:* ‘z.eo #e ¥. ‘Schult ® f. Te . 4 vot #5 ” fu