Neutron transport numerical simulation of different energy of neutron sources is performed in hypothetical nuclear warhead models.Three methods of actively warhead detection are analyzed and the feasibility of actively detecting warheads with three types of neutron sources is studied.With 14.1 MeV pulse neutron source,distribution of delayed neutron flow with time is studied.Results show that the warheads can be detected without exposing the sensitive information of nuclear weapons by detecting the delayed neutrons.

It is devoted to study the physical feasibility of nondestructively detecting and identifying fissile material or concerned nuclear device.The key point of the technique is to measure characteristic γ radiation emitted spontaneously from the nuclear fissile material,and to extract the useful information of nuclear fissile materials to be measured.By using simulated γ-spectra data,this method is tested and the results show that the isotopic composition and other characteristic information can be extracted from the measured γ-ray spectrum of fissile materials with accuracy better than 2%.Also,it is indicated by this study that the geometric self-shielding correction (the γ-ray self-absorption)of the measured fissile materials is one of the key factors to improve the accuracy of calculations.And simplified semi-empirical expressions are also presented for the self-shielding correction factors of certain simple geometric configurations.The mathod discussed applies to the nuclear material safeguard techniques such as monitor,verifying and account etc.