DISTRIBUTION OF LOCAL FALLOUT FROM THE HIROSHIMA A-BOMB - ANALYSIS OF U-235/U-238 RATIO

原子弹的黑雨内容对于澄清核战争造成的健康和环境危害很重要。我们分析了广岛原子弹(小男孩)留下的唯一黑色雨的实物遗迹，这是一面带有黑色条纹的抹灰墙。在墙上的黑色残留物中检测到过量的^&lt；137&gt；Cs和异常的^&lt；235&gt；U/^&lt；238&gt；U；确认墙上的黑色条纹来自小男孩。结果还表明，过量的^&lt；235&gt；U可以作为指纹，以澄清从小男孩排放到环境中的物质的分布。在黑雨样本中也检测到了高浓度的铅和锌，这可能导致了降雨区的一定程度的重金属污染。另一方面，在广岛原子弹爆炸三天后收集的土壤中没有发现U-235/U-238同位素比值偏离自然比值，那里应该排放了大约50公斤的铀-235。土壤中U-234/U-238比值的变化与土壤颗粒大小和土壤消化过程有关。

Contents of black rain from the A-bomb are important to clarify the health and environmental hazard caused by nuclear warfare. We analyzed the only existing physical remains of the black rain from Hiroshima A-bomb (Little Boy), a plastered wall with black streaks. Excess ^<137>Cs and anomalous ^<235>U/^<238>U ratios detected in the black residues on the wall confirmed that the black streaks on the wall originated from Little Boy. The results also showed that excess ^<235>U could be used as a fingerprint to clarify the distribution of materials discharged from Little Boy into the environment. High concentrations of Pb and Zn, which may have caused a degree of heavy metal pollution in the area where the rain fell, were also detected in the black rain sample..Deviation in U-235/U-238 isotope ratio from natural ratio, on the other hand, was not found in soil collected three days after A-bomb detonation in Hiroshima, where approximately 50 kg of U-235 should have been discharged. U-234/U-238 ratio variation in soil that was dependent on the soil particle size and soil digestion procedure was found.