Evaluation of metal seal criteria on spent fuel cask closures

Reliability of the gasket used for sealing the end closure of fuel casks and mating appurtenances of similar fluid containing piping is of prime importance in overall system evaluation. The degree of reliability will be dependent upon the gasket's ability to respond to relative displacements of the mating seal surfaces during both operational pressure and thermal cycles and superimposed mechanical shock loads that occur during maximum credible incidents. Basic sealing parameters for metal-to-metal gasketed joints which will result in leakage rates less than 1 x 10-6 cc/sec helium are summarized. The mode of achieving initial minimum seal interface loading to meet this leak rate criteria is evaluated with regard to the material properties of mating connectors and gaskets. The effects of seal geometry and mode of interface loading on the reusability of seals and seal surfaces to minimize replacement and repair is discussed. Economic considerations of manufacturing tolerances for both initial installation and rework operations are reviewed. Coating and plating effects on initial sealing, reusability and reliability are considered. Overall sealing criteria are summarized for various seal types providing a guideline for designers in gasket selection