Seismic Anchorage of Dry Storage Casks

摘要

Dry storage casks (DSCs) store spent fuel rods from nuclear power plants. The performance objectives for DSCs include preservation of cask assembly geometric arrangement and fuel rod and canister integrity. DSCs are typically unanchored, but units located in moderate to high seismic regions may slide and/or tip over, damaging the cask and internal contents. This research focuses on the benefits of seismic anchorage of DSCs. Two types of anchorage are investigated: (a) conventional bolt details with steel chairs using designs adopted from anchoring liquid storage tanks, and (b) stretch length bolt details with steel chairs, which were found to perform very well during the 2010 Maule, Chile earthquake. In the first phase of the study, single anchor tests are performed using both conventional and stretch length bolts under monotonic and cyclic shear. The stretch length considered is equivalent to eight bar diameters. Two thicknesses are considered for the plates of the steel chair: (i) 12.7 mm and (ii) 6.4 mm. In the second phase, a 1:2.5 scaled DSC is tested under quasi-static horizontal cyclic loads applied at the center of gravity of the DSC; a steel clamp ring with stretch length bolts is utilized in the test. The experimental results are presented and compared for conventional and stretch length bolt details, as well as the scaled DSC in terms of load, displacement, and hysteretic energy capacity. It is shown that stretch length bolt anchorage details provide superior seismic performance in terms of displacement capacity before failure compared to conventional bolt anchorage details.