Study Of The Eigenvalue Problem Of Neutron Transport And The Detection Efficiency Of γ-ray By MC Method

The nuclear fissile reaction system, which provides nuclear energy or neutrons, theoretically demands its criticality safety and neutron energy spectrum to be predicated. Generally, those are realized by calculating the k-eigenvalue problem. Because Monte Carlo Method, for short MC method, has been known as accurate numerical methods for calculating particle transport, a number of general Monte Carlo Code have been developed abroad, for example KENO and MCNP are MC code. But these code only can calculate the k eigenvalue problem, and not calculate such as the λ. and a eigenvalue problem. However, for some special nuclear fissile systems, those eigenvalue problem are more important comparing to the k eigenvalue problem, for instance, using λ -eignevalue problem may obtain more accurate neutron spectrum than using k-eigenvalue problem. Therefore, we have constructed the calculations model of λ -eignevalue problem, and on the basis ofKENO code, developed the MC code of λ -eigenvalue problem.The unhealthful radioactivity in environment has increasingly been an interest problem. In the radioactivity measure of the environment samples, HPGe γ -spectrometer can expediently analyze the species and content of the radionuclide in the environment samples. Those demands the detection efficiency corresponding to the different energy y -ray in the various environment samples. We are used to gain the detection efficiency by making the standard samples, because of the different source of the environment samples, the component and density and volume of the samples can't entirely match those of the standard samples, so it is very difficult to make the standard samples, thereby, in order to conquered experiment difficulty, this article has calculated the detection efficiency of HPGe γ -spectrometer by existing Monte Carlo code.Aim at the above problem, this article obtained following creative results:1.Base on the KENO-IV code, λ-keff iteration model has been constructed in this thesis. By this model, the λ-eigenvalue problem can be treated as a series of k eigenvalue problems with a certain λ number which is adjusted by keff. The Monte Carlo code for calculating λ eigenvalue problem has been developed in this thesis. This code has been used to calculate the λ-eigenvalue problem and the calculation results of λ-eigenvalue, correspond spectra and correspond reaction rates are consistent with the predication of the theory, and gained the practical results.2.Using the MCNP-4B code, this article has calculated the efficiency calibration curves of the HPGe -spectrometer ,compared with the results of experiment. The results have shown that the Monte Carlo simulation calculation has been a convenient and reliable method for the efficiency calibration of the HPGe γ, -spectrometer. We have calculated the variety rules of detection efficiency with the samples of various components and densities and sizes on different energy points, gained the factual results, and resolved the difficulty of the experiment.