High order fast neutron multiplicity measurement equations based on liquid scintillation detector.

Fast neutron multiplicity counting (FNMC) analysis method is a new nondestructive analysis method for nuclear materials. It uses a fast neutron detector array to detect the neutrons emitted by the sample. The quality of plutonium in the sample is obtained by recording the neutron coincidence counting of fast neutron multiplicity. At present, the first three multiplets widely studied including singlets, doublets and triplets can no longer meet the needs of the research. In this paper, The derivation process of fast neutron multiplicity measurement equation for liquid scintillation detector is studied in detail based on the basic principle, neutron counting method, by using the methods of the factorial moments, probability generating functions and parameter estimation method, and considering the influence of scattering crosstalk. Finally, the fast neutron multiplicity measurement equation including singlets, doublets, triplets, quadruplets and pentuplets are established according to the parameter estimation method and the two kinds of solution methods of this equation are given. The work in this paper lays a theoretical and analytical foundation for the research of fast neutron multiplicity measurement system based on liquid scintillation detector.

Simulation study on neutron multiplicity of plutonium based on liquid scintillation detector.

Fast neutron multiplicity counting (FNMC) is a new method of non-destructive analysis for nuclear materials. Using fast neutron detector array to detect the neutrons emitted from a sample, it obtains measurements according to the multiple counting method and analyzes the mass of plutonium in the sample. In this paper, A FNMC measuring device model has been constructed for simulation study in reference to the most advanced FNMC experimental device in the world. A series of typical plutonium sample models, including samples of plutonium metal and samples of plutonium oxide with different isotopic abundance and in different mass, have been designed. The correctness of the newly established fast neutron multiplicity measuring equation and the necessity of modifying the classical measuring equation have been verified by the computer simulated measurements. Compared with the calculation result from the equation developed in this paper and the calculation result from the classical NMC model, the simulated result shows that the new method is better than the classic method in result deviation.

Fast-neutron multiplicity analysis based on liquid scintillation.

In this study, according to the establishment of the classical neutron multiplicity measurement equation, a fast-neutron multiplicity analysis and measurement equation is established, considering the influence of neutron scattering cross-talk, by means of theoretical analysis and computer simulation. Moreover, the fission rate F, multiplication M, and (α, n) reaction rate α in the established equation were solved. A new measurement method of scattering cross-talk was established and the established equation was validated using Geant4 simulation. The fast-neutron multiplicity counting equation has only a smaller deviation from the fast-neutron multiplicity counting system based on liquid scintillation detector, and it has a wider application prospect.