For the thermal analysis and the design of a prismatic gas-cooled reactor, local analyses have been widely used by modeling a unit cell or single assembly instead of a whole-core geometry. In spite of the recent rapid development of the computational fluid dynamics (CFD) technology, a whole-core CFD analysis for a prismatic reactor still requires tremendous computational expense and might be a heavy burden for designers desiring a large number of calculations with various design options.

This paper provides a practical method for the whole-core thermal analysis of a prismatic gas-cooled reactor. The method combines the merits of CFD and system approaches in order to provide the detailed analysis without much computational expense. It solves the three-dimensional heat conduction equation for a solid as in a CFD code. On the other hand, one-dimensional conservation equations are adopted for a fluid as in a system code. With such a combination, a significant reduction in the computational expense, as well as reasonable accuracy, is achieved. In addition, the present method adopts the basic unit cell concept, which eliminates an elaborate grid generation process. Detailed geometries and materials of the prismatic fuel and reflector blocks are efficiently modeled using the basic unit cells.