20 5. CONCLUSIONS A method is described whereby the concentration of any radionuclide deposited on the ground can be derived from the exposure rates shown in the fallout pattern; fractionation is included specifically. Field data are consistent with calculations. The radionuclide composition of fallout within 160miles of ground zero can be adequately described as having all the volatile nuclides and half of the refractory nuclides present in unfractionated debris. The calculated surface concentrations (uCi/m?) of volatile nuclides are as accurate as the meter readings, which are accurate to +20%. The calculated surface concentrations of refractory nuclides are accurate to +30%.. Acknowledgements--The author wishes to extend his sincere thanks to Dr. Norman A. Bonner, who verified the algorithms, helped restructure the calculations, and provided many fruitful discussions during the course of the work; to Mr. Walter H. Martin who wrote the computer program; and to Dr. Lynn R. Anspaugh for his help in finding the necessary data and providing direction and encouragement. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48,