omg, 6 INTERPRETATION OF SURVEY~aTER DATA, a. The purpose of this oxperiment was to obtain information concerning the interpretation of survey-metor readings in terms of hazard, For this purpose, it is nocessary to know not only the ionization associated with the fission-product activity, but also the beta and gamma ray energies which produce the lonization. b, The effective gamma ray energy of the radiation field surrounding ground zero ranged from 0.1 to 0.2 Mev for two shots, Since the average energy of the inci- dent radiation was around 0,7 lev, it is clear that a very high flux of relatively low-energy radiation must heve been present ns a result of scattering and degradation of the incident photons, . since it is well established that, except for properly de- signed ion-chamber instruments, radlation-detccting instruments are unreliable for cnergics below 0,2 Mev and because much low-cnergy gamma-ray activity is present in fission fields, it is important that great care be oxercised in the future design of survey instruments for use in contaminated areas, Ce Seven types of survey instruments were testod to determine their res~ ponse to radiation ficlds amanating from samples of fission-preduct aggregate, The famma dose rate in roentzens and the beta dose rate in oquivalont roentgens were calix brated with sccondary standards at heights ranging from 20 centimeters to 1 meter above the surface of radioactive plaques, these calivrated fields, Survey instruments were then exposed te The work is continuing and the results will be fully tabu- lated in the final report, 7. VALUATION OF FILTER MATERIALS, &, The objective of this project was to evaluate the filtration cfficiency of five standard and developmental filter materials against the airborne particulete contamination present in the atomic bomb cloud. porated in gas These filter materials are incor- masks, collective protectors, and othcr devices designed for res- piratory protection and air filtration. The project participated in the first three shots; twenty-three out of twenty-four satisfactory samplos were obtaincd from the filter collecting B-L7 drones which penetrated the atomic cloud, b, So far, all samples have been counted for beta activity, and decay data are being taken over a period of 8 wecks on selected samples. Radio-autographs are being made, and information on alpha activity is being gathered, The data are cur- rently being corrected for counting errors and decay, prior to final compilation and analysis of results, ~m evragep SURREY AYPduds pan RTEASD Muti ala