**Abstract**

The reactor core system consists of many materials, involving multi-physics processes, and can be analyzed and simulated at multi-scales. With the evolution of cluster computer, traditional programs and models could be translated into new program structure and modified in detail, so that more complex problems can be solved. Based on existing theory, programs of sub-channels analysis, two-dimensional (2D) method of characteristic (MOC), fuel temperature approximation, and threedimensional (3D) discrete ordinate method (SN) are developed and analyzed. The different approach is that the reusable software structure of core calculation is established, with more well-defined storage of nuclear data, control layers, and more effective parallel algorithm for computation. The features of parallel algorithm for these programs are listed succinctly in the discussion. Additionally, the corresponding testing on parallel algorithm and computing results are given.

**Keywords:** reactor core, modeling and simulation, nuclear data, software structure, parallelism
