Strategy of detailed history method is summarized, depending on which code ITR(ions transport and reaction) was developed. Both basic method and impulse approximation method to select flight path of ions are complemented respectively. Numerical results agree with CORTEO and TRIM very well. Relation between two methods is discussed. We found reason of CORTEO results differ from TRIM's by limiting maximum of flight length derived by impluse approximation method. ITR has advantages of TRIM and CORTEO. Impluse approximation method reduces nuclear collisions simulated. Index technique is used to calculate scattering angle, which significantly improves efficiency of ITR.

Principles of ion interaction with target atoms including nucleus and electrons are introduced. We study "detail history" Monte Carlo method. An ion Monte Carlo simulation code ITR (ions transport and reaction) was developed. It shows that our code perform good results compared with TRIM and Corteo. It is faster than TRIM.

For NDP,we produce an iteration method derived from probability iteration.It is compared with linear regularization(LR) method for unfolding of NDP.Both produce good results without counts random errors.Iteration method's result is none-negative.LR method is better at the position where source distributions change steeply.Iteration method produce better results as we consider count random errors.It shows that amplifying matrix elements exponentially brings acceleration.

In practice of homogenization with Monte Carlo method,critical effect is studied and B_N theory is applied taking critical effect into account.Fundamental mode with buckling B is used as a measure of finite size.A critical spectrum in solution of fine-group Bl equations is used to correct weighted spectrum for homogenization.A PWR prototype core is examined to verify that the method generates few group constants effectively.In addition,a zero power physical experiment verification is performed.Numerical validations show that B_N theory is adequate for critical correction in multi-group constants generation via Monte Carlo method.

Generalized coarse-mesh finite difference(GCMFD) method,which uses generalized-geometry coarse meshes to speed up the method of characteristics(MOC),is proposed.A method adjusting width factor automatically is adopted in the GCMFD method.The GCMFD method is adopted in a 3-D neutron transport MOC code TCM.Numerical tests are used to verify acceleration effect of GCMFD in TCM.It shows that the GCMFD method can use generalized-geometry coarse meshes to accelerate MOC iteration,and the GCMFD method with automatically adjusting width factor has good acceleration effect.

A reconstruction method is described for hexagonal assemblies. The program named JXJS has been encoded based on the model; The JXJS results are compared with calculated results by solving the equations in reference[1](61tri/hexagonal assembly) and analysis of error has been also performed.