TOPICAL BAM CASK DESIGN EVALUATION USING DROP TESTS AND NUMERICAL CALCULATIONS: ACCIDENTAL CASK DROP WITHOUT IMPACT LIMITERS ONTO A STORAGE BUILDING FOUNDATION

In recent years BAM has been performing extensive design and drop test programmes to evaluate the mechanical safety of new transport and storage cask designs from national and international manufacturers like GNS (Gesellschaft für Nuklear-Service mbH), TN International (TNI) and Mitsubishi Heavy Industries (MHI). Although most test scenarios use IAEA test conditions for Type B transport packages, additional investigations are necessary to analyse typical accident scenarios with handling procedures inside storage facilities where casks are moved without impact limiters. Cask impacts without impact limiters on unyielding targets result in totally different mechanical reactions from those of relatively smooth impacts using impact limiters. During the licensing procedure of the new GNS CASTOR® HAW 28M design for vitrified high activity waste, BAM therefore decided to perform an additional drop test with a 1:2 scale test cask (CASTOR® HAW/TB2). In spite of a small drop height of only 0.3 meters, contact with the unyielding target of the BAM drop test facility, which conservatively covers any storage building foundation, causes considerable stresses to the cask structure with high stress and strain rates. This paper presents the evaluation strategy of BAM including drop test results and the development and qualification of appropriate finite element modeling to achieve sufficient accordance between test and calculation results. Further steps are mechanical analyses of reduced and full-scale cask designs to determine the most critically stressed areas of the structure, verify scaling factors and demonstrate safety with respect to cask integrity and tightness.