【摘要】 根据美国Small Boy试验的近场远爆心区域(Off-site)剂量场分布图,计算了不同区域内沉降至地面的放射性活度累积份额,结合动力学沉降预报程序给出的不同粒径粒子落地范围,计算得到了不同放射性活度累积份额下的粒子粒径下限。结果表明,试验产生的百微米以上粒径的粒子携带的放射性活度份额约为Bridgeman方程估算结果的86%。本方法可以扩展至不同爆高的地面爆炸场景,分析其近区沉降物的放射性份额,对于优化放射性沉降预报程序具有一定价值;对于发展分凝模型、分析放射性物质在各种粒子中的分布规律等具有重要意义。更多还原

【Abstract】 Background: Activity-size distribution of fallout particles plays an important role in fallout prediction project. It also suggests how radioactive nuclides attached by carriers such as soil particles or debris and helps us know why fractionation happens. It should be determined by sampling, measurement and analysis, but not all this work well done in each ground explosion. Purpose: Feasibility of work to calculate the lower limit of particle size with special cumulate activity fraction by off-site contours of residual gamma radiation and dynamic model that can trace fallout particles was examined. Methods: Off-site contours of residual gamma radiation from Small Boy test were digitized, and the cumulative activity fraction in each area was estimated. Based on the spatial distribution of particles of different sizes deposited on the ground surface, which is calculated with a dynamic fallout prediction code, the lower limit of particle size with special cumulate activity fraction was discovered. Results: The results show that cumulative activity contribution from particles with diameter of a few hundred micrometer was 14% less than obtained with Bridgeman Equation. Conclusion: It’s feasible to calculate cumulative activity-size distribution of fallout particles from off-site contours of residual gamma radiation, and this work can help us to know activity-size distribution in different ground nuclear explosions.更多还原