HERMIT (an acronym for Holtec Earthquake Response Mitigator) is a device that was developed and perfected by Holtec to enable cask loading operations to be carried out without physically typing down the cask to protect against earthquakes. HERMIT reduces occupational dose in dry storage implementation and reduces the loading cost. HERMIT is typically used to stabilize the cask when it is undergoing decontamination and prepping operations in the pool deck region. In plants featuring elevated fuel pools, the Design Basis Earthquake in the pool deck region may be quite significant due to elevation effects.

For sites with high free-field earthquake characteristics, HERMIT is also used to isolate the transfer cask/storage overpack stack from the seismic inputs. HERMIT was first deployed at the Columbia Generating Station in 2002. Since then, numerous U.S. plants have elected to make use of this ingenious product of Holtec’s R&D to reduce site construction costs and total radiation dose to the loading crew.


TitleYearPatent No.Status
Seismic Cask Stabilization Device2005US 6,848,223 B2Granted