Development and verification of thermal-hydraulic/Reactor kinetics coupled code MARS/SNUNAC

Thermal-hydraulic/reactor kinetics coupled code MARS/SNUNAC was developed by combining best-estimate thermal hydraulic code MARS of KAERI and SNUNAC, SNU's reactor kinetics code. The validation of MARS/SNUNAC is examined by analyzing the OECD MSLB benchmark II problem and comparing the results of MARS/SNUNAC with those of other coupled codes. The computational effectiveness of the nodal core-reflector boundary conditions designed for transient reactor analysis is tested in terms of computational time taken for the benchmark problem results. It is shown that MARS/SNUNAC calculations are very similar to the computational results of other coupled codes and the use of core-reflector boundary conditions results in the 15% reduction of computational time with little or no effects on accuracy