无源中子符合计数法测量MOX中钚质量铀干扰修正方法研究  

Research on Correction Method for Uranium Interference in Passive NeutronCoincidence Counting Method for Pu Measurement in MOX Fuel

作　　者：张俞奇 许小明[1] ZHANG Yuqi;XU Xiaoming(Department of Radiochemistry,China Institute of Atomic Energy,Beijing 102413,China)

机构地区：[1]中国原子能科学研究院放射化学研究所,北京102413

出　　处：《原子能科学技术》2024年第6期1372-1379,共8页Atomic Energy Science and Technology

摘　　要：无源中子符合计数法可以在不破坏MOX(mixed oxide)燃料的前提下,测量其中子信号进行符合分析而得出Pu含量,但在MOX燃料的测量应用过程中,Pu自发裂变中子会诱发U产生显著诱发中子信号,对于Pu的测量产生干扰。通过蒙特卡罗模拟与MSR数据处理方法,开展了无源中子符合计数法测量MOX燃料中Pu质量时U产生的诱发中子信号干扰比例模拟研究。模拟结果分别给出了U诱发信号干扰占比随MOX燃料样品PuO_(2)质量含量、密度、质量的变化关系,得到了明确的函数关系式。该方法适用于样品密度在1.5~9.0 g/cm^(3)、质量在10~500 g、PuO_(2)含量在1%~44%范围的MOX燃料无源中子符合计数法测量的修正,修正因子为0.64%~8.49%,适用于快堆及热堆以及不同生产阶段MOX燃料中U、Pu含量的测量分析。The closed cycle requires the recovery of valuable fuels such as uranium and plutonium after spent fuel reprocessing and recycling in different forms like MOX fuel.With the improvement of spent fuel reprocessing capabilities and the advancement of integrated fast reactors,the measurement of MOX fuel characteristics has become increasingly important.In the production process of MOX fuel,the mass of uranium and plutonium must be accurately measured for nuclear material accounting requirements.Passive neutron coincidence counting method can perform a non-destructive analysis of the plutonium mass in the material,reduce the influence of environmental and other geometric factors through time-correlated neutron signal analysis,and calculate the plutonium mass with the abundance information obtained by the gamma-ray spectroscopy method.Combined with the U/Pu ratio obtained by the X-ray fluorescence analysis method,the mass of uranium and plutonium in MOX fuel can be calculated.In the neutron measurement,there is a large induced fission reaction cross-section for uranium in the energy range of spontaneous fission neutrons of plutonium.The induced fission neutrons caused by 235U affect the spontaneous fission neutron signal measurement and must be corrected.Based on the method,confirmatory experiments were conducted through PuO_(2)powder and U3O8 powder standard samples to confirm the significant impact and a geometric model of MCNP was established.The deviation of the neutron counting rate obtained by comparative analysis of the experiment and simulation was within the acceptable range.Multiplicity shift register logic programs were used to analyze the simulation results of samples with different U/Pu ratios and abundances.The R+A and A signals were obtained by calculating the number of neutron pulses within the gates of the front and rear of the long delay.Coincident count rates can be calculated by combining the real signals and simulation time.MCNP simulated a series of MOX fuel powder samples with different PuO_(2)ma

关 键 词：MOX 蒙特卡罗模拟 无源中子符合计数法 

分 类 号：TL273[核科学技术—核燃料循环与材料]