Modeling of Radionuclide Releases From the Geological Repository for RBMK-1500 Spent Nuclear Fuel in Crystalline Rocks in Lithuania

During 2002–2005 the assessment of possibilities for disposal of spent nuclear fuel (SNF) in Lithuania was performed with support of Swedish experts. Potential geological formations for disposal of SNF were selected, disposal concept was developed, reference disposal site was defined and preliminary generic safety assessment was performed. Performing safety assessment the analysis of radionuclides migration from the repository as well as their impact to human and environment were also very important issues. In this paper results on the analysis of the radionuclide releases from the reference geological repository site for RBMK-1500 SNF in crystalline rocks in Lithuania are presented. For radionuclide migration in the near field region of the repository integrated finite difference method and the concept of compartments were used. For radionuclide migration in the far field the discrete channel network concept was used. The assessment of radionuclide migration in the near and far field region was performed using computer codes AMRER4.5 [1] and CHAN3D [2]. The results of analysis show that most of safety relevant radionuclides of RBMK-1500 SNF are effectively retarded in the near field region. The exposure due to possible release of the radionuclides from the crystalline rocks would be dominated by ¹²⁹I firstly while after app. 250 thousand years ²²⁶Ra is dominating already.