[en] To perform Total System Performance Assessment(TSPA) of a potential HLW repository, it is necessary to develop the TSPA code. KAERI has developed the one-dimensional PSA code MASCOT-K since 1997 and verified special modules dedicated for the dissolution of spent nuclear fuel. In the second R and D phase, MASCOT-K is once again verified as a part of the confidence building for TSPA. The AMBER code based on the totally different mathematical approach, compartment theory is used together with MASCOT-K to assess the annual individual doses for given K- and Q- scenarios. Results indicate that both AMBER and MASCOT-K simulate the annual individual doses to a potential biosphere. And the MASCOT-K is more flexible to describe the natural barrier such as a fracture for sensitivity studies. In the third R and D phase, MASCOT-K will be actively used to check whether the proposed KAERI reference disposal concept is solid or not