Reactor core analysis method and medium in which reactor core analysis program is recorded

If a calculation code and physical amount data to be treated in analytic calculation are formed as an object, and analytic calculation is conducted based on an object-indicating programming method, calculation codes based on different calculation method or different calculation meshes can be combined. With such procedures, different calculation methods or calculation mesh determination can be combined freely depending on the structure of a reactor core to be an object of the analysis, thereby enabling to obtain calculation results at high accuracy. In addition, the calculation time can be shortened, and the memory capacity used in a computer can be reduced. Since the calculation class is determined on every calculation code based on different calculation methods, maintenance such as program changing operation in future can be facilitated to thereby improve maintainability. (N.H.)