Development of a multi-dimensional thermal-hydraulic system code, MARS 1.3.1

A multi-dimensional thermal-hydraulic system code MARS has been developed by con- solidating and restructuring the RELAP5/MOD3.2.1.2 and COBRA-TF codes. The two codes were adopted to take advantage of the very general, versatile features of RELAP5 and the realistic three-dimensional hydrodynamic module of COBRA-TF. In the course of code development, major features of each code were consolidated into a single code first. The resulting source programs were rewritten in standard fortran 90, and then were restructured using modular data structures based on ``derived type variablesʹʹ and a new ``dynamic mem- ory allocationʹʹ scheme. In addition, the Windows graphics features were implemented for user friendliness. This paper presents the developmental activities up to mars version 1.3.1 including the code consolidation, the code restructuring and modernization, and the results of the developmental assessment