Techno-Economic and Decarbonisation Assessment of Small Modular Reactor Propulsion for Large Container Ships Under the IMO Net-Zero Framework

Nuclear propulsion has returned to the shipping decarbonisation debate, but its commercial case is settled by institutions rather than by reactors. We develop a reproducible stochastic model that endogenises the two-tier compliance mechanism of the IMO Net-Zero Framework, prices its surplus-unit market by scarcity, resolves port admission port by port along a real Asia-to-Europe rotation under SOLAS Chapter VIII, and budgets the reactor’s mass and volume. A 15,000 TEU container ship is compared over 25 years in five configurations, including a 2 × 30 MWe small modular reactor (SMR), with 31 correlated parameters run through 60,000 Monte Carlo trials, a Sobol’ decomposition, and validation against the IMO carbon-intensity reference line. At a 2030 delivery, the SMR abates 96.6% of life-cycle emissions, but its cost against the best conventional option is not a single number: it spans −1.13 to +17.75 USD per TEU-1000 nm across four admission pathways and 32.1 across the 16 to 22 kn speed envelope, against +6.88 on the middle pathway at 18.5 kn. Three institutional treatments decide the sign—admission as a timetable, the convention for counting a non-combustion plant’s energy, and the cost of capital charged for admission risk—and each outweighs the reactor. Separating the scenario layer from the parametric layer attributes 54% of the variance of the result to institutional scenarios and 46% to parameters, and a first-of-a-kind reactor is not competitive at any 2030 delivery. The findings characterise the conditions under which SMR propulsion becomes economically viable for this ship class, route and regulatory setting; they are not evidence of its competitiveness in international shipping as a whole.