Page 34: of Maritime Reporter Magazine (November 2026)

NUCLEAR PROPULSION n 2023 the International Maritime Organization against correlated failures. One point is easy to miss: (IMO) set a goal of net-zero greenhouse gas emissions what matters is net propulsion power, not the reactor’s from international shipping by around 2050. LNG, thermal rating. Emergency systems, pumps, ventilation, methanol, ammonia and hydrogen each solve part of hotel loads and low-power operation all take their share.

I the problem and create another. Nuclear propulsion Large container ships, tankers and bulkers need tens to offers a different trade: fuel so energy-dense that a ship hundreds of megawatts, which may mean several mod- can sail for years without bunkering, with no combustion ules, and reliability must then be judged for the whole emissions at the point of use. ship rather than reactor by reactor.

Nuclear ships are not new. Four civil vessels proved the concept decades ago. What is new is the Small Modular PROOF FROM THE FIRST NUCLEAR

Reactor (SMR), and the fact that classi? cation societies are MERCHANT SHIPS now approving ship designs built around it. Our study asks Four civil ships supply the real-world evidence. The whether SMR propulsion is a realistic option for merchant US-built NS Savannah, with a 74–76 MW thermal PWR shipping. The short answer: promising for selected high- and about 16.4 MW at the shaft, logged roughly 450,000 utilization ships, but not a universal replacement, and the nautical miles on a single refueling. Germany’s Otto barriers are as much institutional as technical. Hahn, with an integrated 38 MW reactor, covered around 650,000. Japan’s Mutsu (36 MW) developed automatic

MORE THAN A REACTOR load-following and showed stable response in 1991 sea tri-

A nuclear ship takes its thrust from heat released by als. The Soviet icebreaker Lenin, commissioned in 1959, ? ssion. In a pressurized water reactor (PWR), the coolant began with three reactors totalling 270 MW thermal and is held at high pressure so it does not boil while carrying was later upgraded to about 342 MW.

heat from the fuel. But a marine installation is far more Together they show that turning nuclear heat into ship than a reactor and a steam generator. As Fig. 1 shows, propulsion works. They also carry a warning: Savannah’s heat passes through a steam cycle or intermediate heat retirement showed that technical success does not guaran- exchanger to a turbine-generator, then through a high- tee commercial viability.

voltage switchboard to the propulsion motors, with waste heat rejected to the sea. WHICH REACTOR?

Electric transmission gives designers freedom, includ- PWRs have the strongest marine record, but a reactor ing multiple shafts and ? exible power allocation, but it in a protected central hull section competes with cargo adds conversion equipment and demands redundancy space. Advanced concepts promise more. Molten salt re-

Credit: Authors

Figure 1: SMR propulsion chain, from reactor module to propeller, with shielding, emergency decay-heat removal and cooling supporting the plant. 34 Maritime Reporter & Engineering News • November 2026

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