论文标题
使用有机闪烁体和主动中子多样性计数的$^{237} $ np的无损测定
Measured Nondestructive Assay of $^{237}$Np Using Organic Scintillators and Active Neutron Multiplicity Counting
论文作者
论文摘要
在核保障措施的背景下，非破坏性测定的目的是精确验证在非抑制量的时间内宣布的核材料样本的质量。 237NP是一个扩散的问题，有效测定样本的能力是验证和保障工具箱中缺少的部分。该材料具有与235U相同的保障措施，可按照克数量报告，并被归类为“其他核材料”。鉴于每年在美国生产3000千克237NP，而裸球临界质量为40-60 kg，因此希望通过在20分钟测量中以10 g区分10 g的237np的系统来增强保障工具箱。一种测量方式是中子多重性计数，将检测到的多重计数率与可裂变材料的量相关联。先前的仿真工作表明，基于有机闪烁体的多样性计数器可以达到设计标准，而基于旗舰的3HE系统，即表皮中子多数次数计数器，需要更长的测量时间才能达到相同的精度。在这项工作中，使用有机闪烁体和基于3HE的系统对6公斤球的同时测量237NP，用于确认仿真研究的趋势。基于有机闪烁体的系统在几分钟的顺序上达到了中子双重率的1％不确定性，而基于3HE的系统则需要几天才能达到相同的精度。总之，国际原子能局应考虑开发和部署有机闪烁体的多样性计数器
The purpose of nondestructive assay in the context of nuclear safeguards is to precisely verify the declared mass of a sample of nuclear material in a noninhibitive amount of time. 237Np is a proliferation concern, and the capacity to efficiently assay samples of it is a missing piece in the verification and safeguards toolbox. The material is subject to the same safeguards as 235U, is reportable in gram quantities, and is classified as "other nuclear material" according to the United States Department of Energy. Given that 3000 kg of 237Np is annually produced in the US and the bare sphere critical mass is 40-60 kg, it is desirable to augment the safeguards toolbox with a system capable of distinguishing 10 g of 237Np in a 20-minute measurement. One measurement modality is neutron multiplicity counting, which relates the detected multiplicity count rates to the amount of fissionable material. Prior simulation work shows that an organic scintillator-based multiplicity counter can achieve the design criteria, whereas the flagship 3He-based system, the Epithermal Neutron Multiplicity Counter, requires much longer measurement times to achieve the same precision. In this work, simultaneous measurements of a 6-kg sphere of 237Np by organic scintillator- and 3He-based systems are used to confirm the trends in the simulation study; the organic scintillator-based system achieves 1% uncertainty in the neutron double multiplicity rate on the order of minutes, while the 3He-based system requires days to reach the same precision. In conclusion, the International Atomic Energy Agency should consider the development and deployment of an organic scintillator-based multiplicity counter
