A NEW METHOD FOR COLLECTION OF FALLOUT MATERIAL FROM NUCLEAR DETONATIONS* George A. Welford and John H. Harley Heaith and Safety Laboratory ABSTRACT . A collection system is presented and evaluated for the off-site measurementof fallout material. The collector consists of a funnel, ion-exchange column, and leveling device —all constructed of polyethylene. The ion-exchange column is packed with paper pulp, anion exchange resin, and cation exchange resin. This unit may be exposed for monthly periods, and the column may be conveniently shipped to a central laboratory for analysis of the fissionproduct content. The results of a six-month evaluation period are reported and are compared with the openpot method of collecting fallout material at the same physicalsite. The total activity may be collected by ashing the paper pulp and resin. Individual isotopes may be eluted, or the three absorbents may be separated for gamma spectral analysis and later chemical analysis. 1 INTRODUCTION The Health and Safety Laboratory (HASL) of the Atomic Energy Commission has been involved in the off-site collection of radioactive debris from nuclear detonations since 1951. In order to estimate the distribution of fallout, the total beta activity and some individual isotopes are measured per unit area at a sufficient number of stations to permit a world-wide evaluation. Various systems have been devised to collect this material simply and efficiently. The three systems presently in use and their main difficulties are: 1. Direct analysis of surface soil:! The low specific activity requires sampling of a relatively large area of virgin soil and makes the analytical problems extremelydifficult. 2. Settled dust on gummed paper:’ This is the largest system in operation at the present time because of the convenience of operation by untrained personnel. Only total beta activity may be measured, and doubt has been expressed concerning the efficiency of this system. This doubt may be erased by comparison with collection systems whose efficiency could be more simply evaluated. 3. Open-pot collectors:? This system requires some laboratory facilities at the collection site for transfer from the collector. The possibility of sample loss in transfer and shipment is considerable. The ion-exchange collection system was first described by B. Aler and K. Edvarson of the Swedish ResearchInstitute of National Defense.’ Their work was directed toward the collection of a sample for gammaspectroscopy, and no data were shownfor collection efficiency. The *Prepared for presentation at the American Chemical Society, San Francisco, April 1958. 355