The casks won’t explode. After the reactor consumes the usable uranium fuel, the used fuel cells get stored in a cooling pool for not less than five years. Those cells qualifying for dry cask storage are arranged with 32 other bundles for the lowest flux distribution and power output. Cells qualifying for dry storage need to be below a thermal output and in the pool for at least 5 years.

They get transported to a separate area where they remain until there is another long term facility available for their receipt.

Over time dose rates will lower. The casks are air cooled.