*Once per ~30 years[1], to be pedantic. The reasons are not simply refueling concerns, although that is a factor. The boats still need to refuel the humans onb

*Once per ~30 years[1], to be pedantic. The reasons are not simply refueling concerns, although that is a factor. The boats still need to refuel the humans onboard, ie. food supplies and occasionally munitions. The reactor powers the boat using less mass than a typical diesel-electric, is more quiet, and can remain underwater for an entire deployment if necessary - something that's simply not possible with other power generation methods. [1] https://en.wikipedia.org/wiki/Virginia-class_submarine#:~:text=Specifications,-Lead%20boat%20Virginia&text=Propulsion%3A%20S9G%20nuclear%20reactor%20delivering,fuel%20manufactured%20by%20BWX%20Technologies https://en.wikipedia.org/wiki/Virginia-class_submarine#:~:te....