3D-cylinder reactor core neutron space-time kinetics is simulated with an improved quasi-static method. The program is developed. In a supposable 250 MW modular HTGR model, the core neutron space-time kinetics is simulated. Calculated results obtained from this program and CITATION code agree well with each other at initiatory state. Variance of the core reactivity, average neutron flux of each group, and relative power with time is computed.

To solve the three-dimensional transient problems,the Improved Quasi Static Method(IQS) is adopted to deal with the temporal problem,and an improvement of synthesis method(YN) is also introduced.By factorizing the neutron flux,the time step of this method is enlarged so as to decrease the number of spatial calculations.For spatial calculations,Nodal Green's Function Method(NGFM) is used to determine the distribution of shape function,so the spatial mesh of IQSYN/NGFM can be about twenty times as large as that of finite difference method.

A calculational method is presented about the simulation of flow pattern of fuel elements in the physics calculation for Pebble Bed HTR. Then detailed calculation on 10MW HTR is described along with comparison of its results with that of a simplified computation without close simulation of the flow pattern of fuel elements in the reactor core.

Descriptions are on situations about the fuel ball flow in curvilineal channel of High Temperature Gas Pebble Bed Reactor, and on the method of solving that problem by using the programs with rectangular meshes. This method has been used for the physical design of HTR-10MW Test Module and can be spread over other problems with curvilineal meshes.

This paper studies the problems about buckling feedback of spectral calculations in physical calculations of the reactor and presents a useful method by which the buckling feedback of spectral calculations is implemented. The effect of the buckling feedback in spectra and the broad group cross scetion, comvergence of buckling feedback iteration and the effect of the spcetral zones dividing are discussed in the calculations. This method has been used for the physical design of HTR-10MW Test Module.