The RELAP/SCDAPSIM/MOD4.0 code is being developed as part of the international SCDAP Development Training Program (SDTP). SDTP consists of more than 90 organizations in 30 countries supporting the development of technology, software, and training materials for the nuclear industry. RELAP/SCDAPSIM/MOD4.0, which is the first version of RELAP5 completely rewritten to FORTRAN 90/95/2000 standards, has a number of unique options relative to previous versions of RELAP/SCDAPSIM including advanced numerical techniques and options, integrated uncertainty analysis, advanced graphical user interfaces, standardized interface for user supplied 3D reactor kinetics package, and advanced models and correlations for water and other fluids including Na, LiPb, PbBi, and molten salts. MOD4.0 has been used (a) for reactor simulation and analysis (LWR/HWRs, research reactors, Generation IV reactors), (b) for the design and analysis of experimental facilities and advanced fluid systems, and (c) as the general framework for advanced fluid systems model development activities. This paper describes the unique features of MOD4.0, discusses the validation and verification of the code, provides an overview of current applications of the code, and provides a more detailed discussion of the ongoing model development activities to support the design and analysis of alternative fluid systems such as the LiPb and Helium loops used in the thermal blanket modules for ITER being built in France and PbBi loops used in the MYRRHA accelerator-driven system proposed for Belgium.
