Lee M H, Clark S B
Nuclear Chemistry Research Division, Korea Atomic Energy Research Institute, Post Office Box 150, Daejon, Yusong, Republic of Korea.
Environ Sci Technol. 2005 Aug 1;39(15):5512-6. doi: 10.1021/es0486115.
An accident and fire at the former McGuire Air Force Base and Boeing Michigan Aeronautical Research Center (BOMARC) site in New Jersey resulted in dispersion of weapons-grade plutonium in particulate form to the local environment. Soil samples collected at the BOMARC site were measured for their activities and isotopic ratios of Pu and Am isotopes by radioanalytical techniques. The activities of the Pu and Am isotopes in the BOMARC soil were markedly higher than fallout levels, and they decreased nearly exponentially with increasing particle size of the soil. The measured (241)Am activity was compared to calculated values based on decay of (241)Pu. The activity ratios of (238)Pu/(239,240)Pu, (241)Pu/(239,240)Pu, and (241)Am/(239,240)Pu observed in the BOMARC soil were much lower than those attributed to nuclear reprocessing plants and Chernobyl fallout. From the activity ratios of (241)Pu/(239,240)Pu and (241)Am/(239,240)Pu, the origin of the Pu isotopes was identified as weapons-grade and the time since production of the material was estimated. Furthermore, the atomic ratio of (240)Pu/(239)Pu in the BOMARC soil was remarkably lower than the fallout value influenced by nuclear weapons testing and the Chernobyl accident. The atomic ratio of (240)Pu/(239)Pu was very close to the value of the weapons-grade Pu detected from the Thule accident in Greenland. This work demonstrates the utility of radioanalytical measurements and decay calculations for defining characteristics of the source term and discriminating multiple processes that contribute to a source. Such an approach would also be needed to respond to a terrorist event involving an improvised nuclear device or radiological dispersal device.
新泽西州前麦圭尔空军基地和波音密歇根航空研究中心（BOMARC）所在地发生的一起事故及火灾，导致武器级钚以颗粒形式扩散到当地环境中。通过放射分析技术对在BOMARC场地采集的土壤样本进行了钚和镅同位素的活度及同位素比率测量。BOMARC土壤中钚和镅同位素的活度明显高于沉降水平，且它们随土壤颗粒尺寸增大几乎呈指数下降。将测得的（241）镅活度与基于（241）钚衰变计算的值进行了比较。在BOMARC土壤中观察到的（238）钚/（239,240）钚、（241）钚/（239,240）钚和（241）镅/（239,240）钚的活度比率远低于归因于核后处理厂和切尔诺贝利沉降物的比率。根据（241）钚/（239,240）钚和（241）镅/（239,240）钚的活度比率，确定钚同位素的来源为武器级，并估算了该材料的生产时间。此外，BOMARC土壤中（240）钚/（239）钚的原子比率明显低于受核武器试验和切尔诺贝利事故影响的沉降值。（240）钚/（239）钚的原子比率非常接近在格陵兰图勒事故中检测到的武器级钚的值。这项工作证明了放射分析测量和衰变计算在定义源项特征以及区分对源有贡献的多个过程方面的实用性。应对涉及简易核装置或放射性散布装置的恐怖事件也需要这样一种方法。
