By: Stefan Anton, John Zhai

Publisher: Proceedings of the 18th International Symposium on the Packaging and Transportation of Radioactive Materials

Year: 2016

Abstract: Holtec International developed a dual purpose (storage and transport) spent fuel cask, HI-STAR 180, for use in Switzerland. After initial licensing by the USNRC, the cask is being licensed in Switzerland by the Swiss Regulatory Authority ENSI. The storage regulations in Switzerland require consideration of an aircraft impact, which is defined in the regulation as a force-time history. The requirement was satisfied through a two-phase 1:3.78 scale physical test program carried out at the US Army Aberdeen Proving Grounds (APG) in Maryland, USA.

The first phase of the program consisted of devising and benchmarking a synthetic missile that would emulate the specified force-time curve in a reasonably bounding manner. This phase resulted in a successful design of a missile by testing it against a roller mounted “rigid” wall. The evaluation of the impact from the synthetic missile demonstrated that the missile comfortably bounds the impulse of the aircraft crash event.
In the second phase of this program, a heavily instrumented test cask was impacted by the calibrated missile accelerated along the rail by a rocket-propelled sled. The missile successfully hit the test cask at the most vulnerable location identified in advance through numeric simulations. The impact was bounding in terms of missile weight, velocity, impact force and duration.

The test was confirmed to be successful by the measurements during and after the impact with the following conclusions:

  • The post-impact helium leak test showed the leak rate to be three orders of magnitude less than the permissible value.
  • The axial stresses in the enclosure lid bolts remained in the elastic range.
  • There is no measurable permanent ovalization of the cask’s flange.
  • Numerical predication using LS-DYNA reasonably matches the measured data of key safety-related cask responses.

The aircraft crash physical test program conclusively demonstrates that the HI-STAR 180 cask can withstand the postulated aircraft crash event with ample margin. In a broader sense, the comparison of the test data with the LS-DYNA simulation of the test indicates the ability of LS-DYNA to predict the consequence of an aircraft strike on a metal cask.

Citation: Anton, S. & Zhai, J. “Aircraft Impact Test on the HI-STAR 180 Dual Purpose Cask.” Proceedings of the 18th International Symposium on the Packaging and Transportation of Radioactive Materials, 2016.