[en] For the purpose of establishment of PHWR moderator and severe accident analysis system, the following works are performed. The main thermal-hydraulic phenomena are investigated and scaling analysis of the scaled down test facility design and fabrication are done to determine the scaling ratio based on the scaling law and practical constraints of the test facility. Theoretical background of the commercial CFD codes has been found out and their applicability and application conditions for the moderator circulation analysis are reviewed to develop the computer code requirement for the moderator 3-D analysis codes. Satisfactory analysis results against the STERN Lab. experiment showed the applicability of OpenFOAM and CUPID codes to moderator circulation analysis. For the development of various accident scenarios for establishing the DB for severe accident phenomena/progression, the level 1 and the level 2 PSA analysis results for Wolsong Unit 1 are reviewed and the most probable accident scenarios from the PDS event trees are selected. The latest ISAAC 4.03 version is used to predict the basic accident progression and the improvement items for the most up-to-date severe accident analysis issues analyzing function are derived. A basic system for the PHWR severe accident management decision making support system, SAMEX-CR is set up and requirement for the DB management system, SARDB-CR is derived to develop the implementation methodology for severe accident analysis DB management system