Measurement of Nagasaki Pu Global Transport Rates, Comparing with SO₂ from Historic Volcanic Eruptions

Abstract

An artificial single dose contaminant was released at Nagasaki, Japan on August 9, 1945 detonating plutonium (10-15 kg) atomic bomb. A portion, 1.2 kg of 23~was fissioned releasing 21 kt TNT energy along with various fission products. The rest of the unexpended fissile material, 239+24~, 13.8 kg (3.49 x 1013 Bq), was dispersed into the atmosphere along with a fission product, 137CS, 23.4 g (7.44 x 1013 Bq). The fate of 239+24~and 137CS was investigated by analysing both local and global fallout.The highest concentration of 239+24~was 64.5 mBq/g (181 mBq/cm 2 ) while it was 188 mBq/g (526 mBq/cm 2 ) for 137CS both at 2.8 km east from the hypocentre. The total amount of deposition in the local fallout region of 264 km 2 was 37.5 g (9.48 xl0 1 0Bq) for 239+24~and 3.14 mg (5.88 x 10 10 Bq) for 137CS. The ratio of the local fallout against the total amount of the radionuclides released was 0.27 % for 239+24~and 0.134 % for 137CS.Recent advancements in analytical technology made it possible for artificial radionuclides released from the Nagasaki explosion to be detected in the Arctic ice core layer of 1945. The 239+24~and the 137CS, were measured by collecting 10 ice cores on the Agassiz ice cap, Ellesmere Island, Canada. The deposition was 0.16 JlBq/cm 2 for 239+24~and 20 JlBq/cm 2 for 131CS. During the atmospheric testing, the deposition of 239+24OpU and 131CS varied more than 100 times with the highest peaks of over 50 JlBq/cm 2 for 239+24~and over 800 JlBq/cm 2 for 137CS both occurred in 1962. Analyzing Arctic data, there are many new information for long global transport, the history of nuclear weapons development etc.