Multigroup Neutron Transport Monte Carlo Calculation

With deep research of particle transport problems and rapid development of computers, the applications and research fields of Monte Carlo method is further widened. Yet all of these studies want to get precise distribution for the neutron flux. Because of the rapid development of nuclear technology and more and more complex nuclear reaction processes, the general Monte Carlo calculation is difficult to provide high quality results in limited time. The lack of the accuracy has a direct impact on the subsequent calculations, so it is difficult to correctly simulate nuclear physics problem. But Monte Carlo adjoint calculation effectively solve part of those problems. In particular, the Monte Carlo adjoint method could give better calculated results in reasonable time for shield calculations, deep penetration problems, oil logging and reactor perturbation calculation and so on.Our research focuses on increase an multi-group neutrons adjoint transport calculation module on the base of MCMG that is aself-development MC particle transport code. Firstly, using perfect adjoint transport theory, we contrast the MCNP adjoint calculation to derive the multi-group neutron transport Monte Carlo adjoint equation; Secondly base on the MC MG multi-group P5neutrontransport program,using the cross-section producedby the collisio n mechanism for material transport, build a method of determine the fission exit energy group, scattering cross section-computing and the transfer matrix of energy group; Thirdly, contrast the MCMG multi-group forward calculation program combine the adjoint cross sec tion to give the MCMG adjoint program; Finally, the model Ⅰ test the correctness of MCMG adjoint program. The comparison shows that the calculated results are basically consistent with the results of the adjoint calculation and forward calculation. MCMG adjoint program have the at least time which is the half of MCMG forward calculation. The FOM value is abo ut four times the MCNP adjoint. The model Ⅱ research the applicability of the MCMG adjoint calculation for the different materials, and the results show that the adjoint calculation is unnecessary for the case of strong scattering. The model Ⅲ studies the application of generating important function by the MCMG adjoint calculation, and the results are compared with the weight window game. Although their important functions are produced by different mechanisms, the results of adjoint important functions are better than the results of important function from the weight windows. The FOM value is about1.5times the important function from the weight windows.