Aside from the real and perceived safety issues of nuclear propulsion, there is also the issue of operational availability.  US submarines and aircraft carriers spend a lot of their careers unavailable due to planned maintenance.  I wonder how much of that is due to the power plant?  New naval reactors are designed to last from 1&#x2F;2 to the entire life of the ship without refueling.  And at the end of that life, the entire reactor compartments are cut out, defueled, and stored in open-air trenches at the Hanford Reservation.[1]  Regardless of whether fission reactors are fueled with HEU, LEU, or Thorium, they leave a lot of long-term things that we been as-yet unable to muster the full technological and political means to deal with.<p>For the merchant ship application, it seems a reach to believe that the benefits of greenhouse gas reduction can be most efficiently achieved by replacing diesel engines with nuclear reactors.<p>[1]<a href="http:&#x2F;&#x2F;www.oregon.gov&#x2F;energy&#x2F;nucsaf&#x2F;docs&#x2F;naval_nuclear_reactor_fact_sheet.pdf?ga=t" rel="nofollow">http:&#x2F;&#x2F;www.oregon.gov&#x2F;energy&#x2F;nucsaf&#x2F;docs&#x2F;naval_nuclear_react...</a>