do we know how expensive (per unit energy) 
    US Navy reactors are? It doesn't matter how safe 
    they are if they are twice as expensive as 
    renewables (plus storage / power-to-gas).

Renewables (and fusion, although that's arguably a renewable) are obviously the end goal but until they can fill 100% of our energy needs the real cost comparison needs to be "the cost of nuclear" versus "the cost of fossil fuel plus the cost of the damage done by fossil fuels."