Safety assessment of the Dukovany repository and waste acceptance criteria evaluation

The safety assessment of the Dukovany repository is based on the evaluation of two critical scenarios: groundwater transport; and intrusion and residence after institutional control (300 years after closure of the repository). These scenarios use source term values derived from the actual waste inventory and evaluation of data on engineered and natural barriers. Acceptance criteria are presented as volume activity limitations for various repository volume units (barrel, vault, two rows of vaults, i.e. 112 vaults). The mobile activity as the sum of the surface contamination, the leachability limit and the non-standard waste activity is also limited. The limits and conditions of operation do not directly include a limit on long term β nuclides. The State Organization for Nuclear Safety requested an impact evaluation to be done and the Nuclear Research Institute performed a safety analysis evaluating β nuclides. Model calculations proved that the migration curves are non-zero only for long lived radionuclides with high migration parameters, i.e. for 14C, 99Tc and 134Cs. Other radionuclides are limited by intrusion scenarios. In 1995, the operational safety report was completed. A realistic approach was adopted to evaluate the groundwater transport pathway using source term quantification. The release from the repository, considering the real properties of the barrier system, is very low and the limiting pathway for all radionuclides is then intrusion and residence. The probable doses are very low. Limits and conditions were derived in 1992 using the recommended limit of an annual dose of 10 μSv and unit activities for critical radionuclides. In 1995, the real inventory and real data from the repository and hydrogeological system were used to prove the safety of the repository. (author). 2 figs, 7 tabs