Approximately 22 600 spent nuclear fuel (SNF) assemblies originating from the RBMK-1500 reactor of the Ignalina nuclear power plant in Lithuania need to be managed and disposed of safely. Generic investigations of RBMK-1500 SNF disposal options in Lithuania were initiated. This paper presents insights on RBMK-1500 SNF disposal in crystalline rocks gained during participation in the International Atomic Energy Agency Coordinated Research Project “The Use of Numerical Models in Support of Site Characterization and Performance Assessment Studies for Geological Repositories,” as well as in the Lithuanian Science Development Program. The research was focused on the analysis of disposal behavior of different SNF types under generic geological conditions and for a one-canister defect scenario with two different corrosion rates. A comparison of peak fluxes from the near field for Lithuanian RBMK-1500 and Swedish boiling water reactor SNF revealed differences that are not directly proportional to the differences in SNF inventory.