322 FEELY AND BAZAN but during 1963 '4sb was used as a unique tracer for certain December 1962 events. SUMMARY The distribution of °°Sr and of other components of nuclear debris in the stratosphere may be determined with fair accuracy by using data from the balloon-sampling program and the Project Star Dust WU-2 aircraft sampling program. The distributions of *"Sr observed during 1962 to 1964 provide information on the initial altitude of injection of debris from U.S.S.R. polar tests andon the seasonal nature of changes in the stratospheric distribution. Specifically, it would appear that little debris injected into the polar stratosphere, even by events of very high yield, stabilizes at altitudes above 70,000 ft. Movement of debris from the northern-hemisphere source regions into the southern hemisphere appears to occur preferentially during the autumn and winter seasons of the southern hemisphere. Measurements of other fission products and of a number of products of neutron activation should also be useful for studying atmospheric motions. REFERENCES 1. L. P. Saiter, High Altitude Balloon Sampling Program, in Fallout Program Quarterly Summary Report, USAEC Report HASL-140, pp. 166-214, Health and Safety Laboratory, Oct. 1, 1963. 2. L. P. Salter, High Altitude Balloon Sampling Program, in Fallout Program Quarterly Summary Report, USAEC Report HASL-149, pp. 54-99, Health and Safety Laboratory, Oct. 1, 1964. 3. H.W. Feely, B. Davidson, J. P. Friend, R. J. Lagomarsino, and M. W. M. Leo, Ninth Quarterly Report on Project Star Dust, Report DASA-1309, Defense Atomic Support Agency, Sept. 1, 1963. 4. H. W. Feely and F. Bazan, Second Interpretive Report on the High Altitude Balloon Sampling Program, USAEC Report NYO-10498, Isotopes, Inc., June 10, 1964, 5. F. Bazan and H.W. Feely, First Quarterly Report on the High Altitude Balloon Sampling Program, USAEC Report NYO-10496, Isotopes, Inc., Feb. 1, 1964. 6. L. P, Salter, Results of Measurements Made at HASL and Reported at a Conference Held at the New York Operations Office, AEC, on Dec. 6, 1963. 7. M. I. Kalkstein, Rhodium-102 High Altitude Tracer Experiment, Science, 137: 645-652 (1962). 8. J. P. Friend, H.W. Feely, P. W. Krey, J. Spar, and A. Walton, The High Altitude Sampling Program, Report DASA-1300, Defense Atomic Support Agency, Aug. 31, 1961. 9. U.S, Weather Bureau, Announced Nuclear Detonations, 1945-1962, in Fallout Program Quarterly Summary Report, USAEC Report HASL-142, pp. 218-242, Health and Safety Laboratory, November 1963.

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