STRAIN OF LID BOLTS OF TYPE B PACKAGES DURING 9 M DROP TESTS – RESULTS OF REAL TESTS AND PROBLEMS OF ANALYTICAL PREDICTION

MOSAIK II-15 casks were designed for the transport of different types of radioactive waste, among others heavy scrap compacts and steel drums with conditioned radioactive material. According to the results of analytical predictions the mass of contents must be limited to specified values in order to avoid inadmissible strains of cask lid and lid bolts under IAEA test conditions, especially during drops flat onto the lid side impact limiter. Among others, high stresses were expected which are caused by interactions between free movable solid contents and the cask lid during the final phase of impact or the rebound of the package. Therefore, additional tests which have been performed with the package had two objectives: General check of the results of mechanical analyses, and, moreover, quantification of effects resulting from interactions between the package components that can be increased because of gaps between the containment components, the inner lead shielding and contents. The paper presents results of calculations and tests performed for two different package modifications: (1) cask with inner lead shielding loaded with close packed steel bars; small gaps between the package components, (2) cask without inner lead shielding loaded with a steel drum that was filled with steel scrap in a concrete matrix; large axial gap between the drum and cask lid.