Active Coincidence Neutron Method Of Measuring The Quality Of Depleted Shaft Member

In the process of nuclear disarmament, nuclear warhead detection is an important verification technology of nuclear disarmament treaty. Because the structure of warhead core concerns to the secrets of nuclear weapons'design, it isn't allowed to take the core out for direct measurement during the verification of the nuclear material. So it becomes an important part of arms control verification that how to certain the attributes of the nuclear material in the sealed containers, the non-destructive measurement technique appears and develops from this.Uranium is an important nuclear weapons material, but because of its weak radioactivity and low emission rate of the spontaneous fission neutrons, the passive method is difficult to measure generally, and active method is more effective. Therefore, the attributes measurement of uranium components is a difficult in arms control verification.The attributes of uranium is still no clear definition, but it is undoubtedly that the mass and the enrichment of uranium components are the most important two attributes. So the research of uranium components non-destructive measurement technique is quite important in arms control verification. At present, there are four methods of the mass measurement of uranium components, they are:time-correlated coincidence, active delayed neutron counting method, neutron multiplicity counting method, and active coincidence neutron counting method which is studied in this thesis. Active coincidence neutron counting method is to induce the fissile nuclides for fission reaction by external neutrons firstly, and then measure the fission neutron coincidence counting to determine the mass of nuclear material.The research of this thesis is through the measurement of the depleted uranium components with the active coincidence neutron counting method to explore the relationship between the coincidence neutron counting rate and the mass of the depleted uranium components. A well neutron coincidence detector including 62 3He counters is used, an Am-Be source is selected as the external neutron source for induced fission, and a shield is optimized to reduce influence of the accidental coincidence counts. As a result of the experiments, there is a linear relationship between the coincidence neutron counting rate and the mass of the depleted uranium components. In the 132cm distance conditions, the maximum deviation of the linear fit mass from the nominal mass of is 7.34%, and the main impact factor is the outer diameter of the depleted uranium components. In addition, relying on the detection equipments used in this experiment, the passive measurement is also finished successfully, and the linear correlation is better than that in the active measurement, because of the elimination of the influence of outer diameter. The maximum deviation of the linear fit mass is only 4.05% and it proves that it is feasible to measure the depleted uranium components with the passive method.The measurement of the highly enriched uranium components with the active coincidence neutron counting method under the same conditions is also carried out, which proves that the high enriched uranium components are also able to be measured in this experimental system. For highly enriched uranium, the relationship between the coincidence neutron counting rate and the mass of the components is exponential, the maximum deviation of the fit mass is 12.16%, and the thickness of the components has become the greater impact factor.