• David Armes

Nuclear reactors, ready for maritime?

Shipping emits about 3.5% of the world’s CO2, 9% of sulphur oxides, and 18-30% of nitrogen oxides. There’s a big push to decarbonize and reduce or eliminate emissions by 2050, less than 30 years away. Most of the airtime is dedicated to renewable energy in the form of hydrogen and ammonia along with assisting technologies like wind and batteries. Today we’re going to take a look at an energy source with no emissions, more power, and could only need refueling once every quarter of a century: nuclear.

We talked about a Bill Gates backed, micro reactor that could work for maritime propulsion in September of 2020 (video below). The 345MW sodium cooled reactor could be on one ship that travels with a small fleet, powering all of the vessels with a single reactor. Today, we’re going to take a wider lens to nuclear energy and its potential in shipping from large upfront costs to increased speed of large vessels that could cut down shipping time by 50%.

Video from U.S. Department of Energy on YouTube.


Nuclear is usually thought of as “expensive” due to large upfront costs from build-out and fuel. These builds look at the lifetime cost of operation, including refueling (if necessary) and disposal of spent fuel. Current fossil fuel engines also look at upfront costs as well as continued fueling, but leave out the emissions component of the equation. The emissions released into the atmosphere have a cost that if assigned a value and included in the OPEX - or captured and disposed of - raises the cost of operation of fossil fuel vessels. The larger continued operating costs make the initially larger upfront cost of nuclear more competitive. It’s hard to pinpoint this amount currently, as nuclear has yet to be adopted at any scale.


Nuclear reactors aren’t produced in any meaningful quantity; normally, they are one-off developments for specific situations. Small modular reactors (SMRs) are being designed to operate in the 10-100s of megawatts range, which are well suited for many large shipping vessels. Molten salt reactors (MSRs), a newer, safer type of nuclear reactor, could prove to be on par with the cost of zero-emission fuels, which would make them more desirable. They also require refueling every 3-30 years, depending on the design and type of fuel used. According to Lloyd’s Register, TerraPower and CorePower are developing MSRs that would fuel ships for 25-30 years, on par with the lifetime of the entire ship. This means that they would need no refueling after the initial build. Thus, removing the logistics of traditional fuels and the even more difficult logistics of newer fuels like hydrogen and ammonia. It also frees up space on vessels for additional cargo as reactors are small and do not require the volume of storage of a traditional bunker fuel.

Schematic of a molten salt reactor

“Fig. 1. Schematic representation of a typical MSR.” Image from Science Direct.

Past nuclear power

Some of the concern around nuclear reactors stems from the older style pressurized water reactors, or PWRs. According to The Maritime Executive, “Nuclear incidents, such as Fukushima (Japan), Three Mile Island (United States), and Chernobyl (USSR – Russia), and the stockpile of semi-spent nuclear fuel rods have elicited much public opposition to expanding nuclear power.” Other reactor designs now exist, like helium gas cooled reactors, but they suffer from similar weaknesses. High pressure water and gas reactors that have a structural failure can be catastrophic. Liquid metal cooling is a new technology that uses metal that stays liquid from 98 degrees to 800 degrees Celsius, removing the pressure component that is subject to failure. The molten salt reactor is an even more promising solution where nuclear material is added to molten salt that is liquid above 400 degrees Celsuis and is solid below that. Molten salt provides the pressure elimination benefit as well as the safety that in a rupture of the reactor, the temperature would drop, hardening the salt. Methods are also being developed to use semi-spent nuclear material in these types of reactors, meaning reuse of the “spent” nuclear material that is currently stored for thousands of years.

Public perception of nuclear power

Getting energy from an atom is different than getting it from batteries or traditional fuel. Accidents like Three Mile Island, Chernobyl, and Fukushima generated a lot of bad press for nuclear energy. The good news is that perception is changing. According to Nuclear Newswire, people are becoming more informed, and subsequently have a more favorable opinion toward nuclear power. Of people who feel very well informed on the topic, approximately 85% strongly or somewhat favor nuclear energy. Perception is still shifting, as just a couple of years ago, the notion of nuclear powered containerships seemed unrealistic, but now it’s regularly brought up at maritime conferences. As of right now, it’s almost impossible to pass through the Suez Canal in a nuclear powered vessel. However, when nuclear powered vessels become a reality, the next step will be updating regulations.

Chart of the public opinion on nuclear energy

Public opinion of nuclear energy (2019). Image from Nuclear Newswire.

Energy production

Any source of energy production and storage has a conversion efficiency, which means that producing, storing, and retrieving energy causes some loss of energy. According to The Maritime Executive, green hydrogen production, producing hydrogen from electricity, has a conversion efficiency of about 65 to 75 percent. Fuel cells convert that energy at around 55 to 65 percent. Thus, leaving the entire process around 45 to 50 percent efficient, meaning about half the originally produced energy is used in the end process. A nuclear power plant producing electricity through transmission lines, then gets converted into hydrogen that powers a ship has a total process efficiency of 18 percent. Any form of power production, conversion, and retrieval has losses. Direct nuclear power eliminates these losses in efficiency by using the produced power right where it’s needed. Small nuclear reactors can power a ship without any transformational loss in efficiency. It also reduces the land needed for biomass production for biofuels or renewable energy capture, storage, and conversion, freeing up that land for other purposes (i.e., food).

Extra power and efficiency brings up another topic; since ships aren’t running at full speed and capacity 24/7, how can the extra energy be captured and used later? Nuclear power stations use thermal storage technology to save energy at off-peak times or if the plant has to be shut down. Mobile thermal storage is still in the idea stage, but could also be used on commercial vessels to save up power when in port to use during peak load at full speed. Nuclear reactors operate best at a constant temperature. Therefore, storing some of the excess energy would help keep them running at peak efficiency.

Render of a small scale nuclear reactor

CORE-POWER render of nuclear reactor. Image from Splash247.


Speaking of speed...in addition to the possibility of no emissions and no refueling, nuclear power could produce enough thrust to potentially speed up vessels. In some cases, vessels could increase speed on the open water by 50%, cutting a three-week containership journey from China to the U.S. down to only two weeks, according to Hackaday. The increase in speed would also make this technology more appealing as it reduces the time cost of shipping goods across the world. From our article on Navy ships, we noted that many civilian vessels, such as containerships, travel at speeds of around 10 knots while aircraft carriers, which are powered by nuclear reactors, travel at speeds of faster than 30 knots or 3 times as fast!

In the near future, nuclear reactors on ships could be a common sight: “mobile nuclear technologies that include the 60MW NuScale reactor, the 25MW Hyperion reactor, and 10MW Toshiba reactor that could all be adapted to civilian commercial maritime propulsion”, according to The Maritime Executive. Radiation-free fusion thermal power is also being researched. The age of Pressurized Water Reactors (PWRs) is passing, and newer, safer, more efficient technologies like Molten Salt Reactors (MSRs) are almost here. This new age of nuclear power could bring zero emissions, no refueling for the life of the ship, and faster transit speeds. As with most technology, as small-scale nuclear scales up, costs will decrease. If nuclear is close to being competitive now, imagine how prices would drop with 10 or 20 years of additional innovation. There are big changes on the horizon for shipping, and nuclear power could be the optimal solution to the problem of decarbonizing and speeding up shipping.

Happy Fun Fact Friday!












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