An Active Interrogation by Delayed Neutron Counting (AIDNEC) system for the assay of natural uranium in industrial waste in form of civil debris has been developed using the plasma focus (PF) device as a single-shot neutron source. The methodology of the technique involves irradiation of fissile mass by neutrons from a PF device and counting the delayed neutron emitted as a result of induced fission. In-house developed medium energy (17 kJ) PF device and ³He detector banks have been used for neutron irradiation of waste samples containing fissile masses and counting of the delayed neutrons respectively. The detector geometry and the moderators for the source and delayed neutrons have been optimized by Monte Carlo simulations. In this work, the results of these simulations and experimental observations are presented. The industrial radioactive waste samples used in this work were in the form of sand, bricks, chunks of concrete, etc. having a sample mass of few tens of kg. With ${\mathrm{D}}_2$ gas operated PF device (average yield (2.1 ± 0.8) $\times$10⁸ neutrons/shot) the detection limit is determined to be 170 g of natural uranium, i.e., 1.2 g of ²³⁵U. The feasibility of the technique using the same PF device operated with D–T gas (14.06 MeV neutrons) has been assessed by Monte Carlo simulations. As D–T fusion provides two orders more neutron yield as compared to ${\mathrm{D}}_2$ fusion, the detection limit of the present system with D–T gas is estimated to be 3.3 g of natural uranium in $\sim$40 kg waste. Considering this low detection limit, this technique can be used for the assay of nuclear material in all types of industrial radioactive waste produced in the fuel fabrication/handling or similar facilities.

使用等离子体聚焦（PF）装置作为单发中子源，已经开发出一种通过延迟中子计数（AIDNEC）进行主动询问的方法，用于分析工业垃圾中民用碎片形式的天然铀。该技术的方法论涉及由PF装置的中子辐照裂变物质，并计算由于诱导裂变而释放的延迟中子。内部开发的中能（17 kJ）PF设备和³探测器堆已用于中子辐照含有易裂变质量的废物样品，并分别计算了延迟中子的数量。通过蒙特卡洛模拟优化了源和延迟中子的探测器几何形状和调节剂。在这项工作中，提供了这些模拟和实验观察的结果。在这项工作中使用的工业放射性废物样品为沙子，砖块，混凝土块等形式，样品质量为几十公斤。和${\mathrm{d}}_{\mathrm{2个}}$ 气动PF装置（平均产量（2.1±0.8） $\times$10个⁸中子/次）的检测极限被确定为170克天然铀，即，将1.2g的²³⁵ U.使用相同的PF设备的技术的可行性与d-T气（14.06兆电子伏中子）已被操作由蒙特卡洛模拟评估。由于D–T聚变提供了比中子高出两个数量级的中子产${\mathrm{d}}_{\mathrm{2个}}$ 熔融，本系统用D–T气体的检出限估计为3.3 g天然铀 $〜$40公斤废物。考虑到这种低检测限，该技术可用于分析在燃料制造/处理或类似设施中产生的所有类型的工业放射性废物中的核材料。