Indonesia is about to enter the nuclear era by building several nuclear power plants in the near future. Numerous issues must be addressed to evaluate the impact on the environment of high-level radioactive waste (HLRW) generated by these plants. This consideration of HLRW management must be done in a timely manner;This dissertation discusses the methodology for the Genting repository site development plan. The approach to the development of the repository is divided into three main areas, the inventory of HLRW, the barrier systems (natural and engineered), and the physical conditions of the site. The radionuclide inventory and waste form require analyses of the waste package container that include selection of containment materials, the type of containment and its predicted performance, and radionuclide release models. Parameters pertinent to the repository site includes information from geology, hydrology, climatology, and water chemistry perspectives. These data are important to predict the long-term performance of the site;The integrated data relevant to the Indonesian repository site design are employed as the input to the total system performance assessment model completed using the Repository Integration Program (RIP). The methodology employs a "top-down" approach. The input is based on expert interpretation of available data. The possible pathways for radionuclides release are then calculated. In addition to normal site degradation, the disruptive event scenarios that are evaluated include earthquakes and flooding of the repository site. These analyses shows that the effect of earthquakes is significant for a high probability of occurrence (1x 10-2). However, for a low probability of occurrence (1x 10-7) the effect is not shown in this study;The combination of design assumptions and the RIP results are used to make suggestions for additional performance analyses and possible improvement in waste package and site designs that will enhance long-term repository performance and ensure the health and safety of the public.