Distribution and behavior of some radionuclides associated with the Trinity nuclear test

The activities of Ba-133, Cs-137, Eu-152, Eu-154, Eu-155, Pu-239, and Am-241 were determined by gamma spectroscopy on the largest sample set (n = 49) of bulk trinitite to date. The range in activity for all isotopes is large. For example, the activity of Am-241 (normalized to the time of detonation) ranges between 1 and 42 Bq/g. Comparison of activities for isotopes derived from the device, Am-241 versus Cs-137, Eu-155, and Pu-239, indicate positive trends. Correlations were not observed between the activities of the soil-derived activation products Eu-152 and Eu-154 and the radioisotopes from the device. The calculated ratio of fission products (Eu-155/Cs-137) is 0.012 +/- A .006 (1 sigma, n = 3), which is lower than predicted for the thermal neutron-induced fission of Pu-239 (similar to 0.03). This discrepancy may be attributed to the spontaneous fission of the natural U tamper resulting in mixing between fission products from Pu-239 and U-235. The spatial distribution of the trinitite samples relative to ground zero has been modeled based on the activity of Eu-152. The calculated distances do not correlate with any of the activities for the radioisotopes investigated here, and suggest a relatively homogeneous distribution. However, trinitite samples with the highest activities for Cs-137, Pu-239, and Am-241 yield the shortest calculated distances of 50-60 m away from ground zero.