Ongoing research into small-scale conversion of nuclear energy has greatly increased safety with the development of sodium-cooled reactors and nuclear technology for molten salt. While the technology is potentially feasible, the need to negotiate internationally through multiple channels and ports remains.
introduction
The history of nuclear propulsion dates back to the mid-1950s when the United States developed the Nautilus submarine. In late 1959, the Soviet Union responded to the challenge of nuclear propulsion by shooting down the icebreaker Lenin. Since then, all nuclear-powered ocean-going vessels have been linked, directly or indirectly, to a national military or navy. Recent advances in nuclear technology offer opportunities for commercial propulsion applications.
Environmental concerns about greenhouse gas emissions from the maritime sector have led research and development into a variety of alternative fuels and marine propulsion technologies. While alternative fuels like LPG and methanol help run internal combustion engines, other fuels like hydrogen and recycled ammonia help run fuel cells that generate electricity. Some new generation versions of small nuclear power plants solve the problem of cooling reactors with high pressure water or high pressure helium gas. The widespread acceptance of nuclear-powered merchant ships depends on providing the population with the greater safety of modern nuclear technology.
Nuclear Concerns
Nuclear incidents such as Fukushima (Japan), Three Mile Island (USA) and Chernobyl (USSR – Russia) and the supply of half-used nuclear fuel rods have generated much public opposition to the expansion of nuclear energy. While conventional nuclear reactors are cooled with water, helium gas pumped under high pressure cools some modern high-temperature reactors. Structural failures in water-cooled or gas-cooled high pressure reactors have catastrophic effects. Recent developments solve the pressure problem by cooling the reactor with a liquid metal that melts just below 210 ° F (98 ° C) and remains liquid at 1470 ° F (800 ° C) at atmospheric pressure.
Another unique nuclear technology involves the addition of nuclear material to molten salt, which also addresses concerns about cooling nuclear reactors with high pressure steam or gas. Molten salt core material becomes a liquid at about 750 ° F (400 ° C) and is solid below that temperature. Some evolving nuclear technology, including variations on molten salt, is capable of reprocessing half-used nuclear fuel. Any breakage of the nuclear reactor with molten salt would result in a drop in temperature and solidification of the molten salt nuclear fuel, increasing its safety and suitability for commercial marine propulsion.
Energy conversion efficiency
The production of green hydrogen requires electrical energy to achieve electrolysis, which splits hydrogen from oxygen with a conversion efficiency of 65 to 75 percent. Solid oxide fuel cells convert hydrogen into electrical energy with an efficiency of 55 to 65 percent, with the overall efficiency of the energy conversion from electricity back to electricity being around 45 to 50 percent. A nuclear power plant can generate electrical energy with 36 percent efficiency from the fuel rod to the transmission line, which results in a maximum overall efficiency of 18 percent from the power plant to hydrogen and fuel cells to the ship’s propeller. Nuclear energy can be used indirectly to produce ammonia as well as methanol, with losses in energy conversion efficiency.
The direct nuclear power generation on board a ship bypasses the efficiency losses in the production of hydrogen, ammonia or methanol. While inferior waste heat from land-based nuclear power plants can contribute to methanol production, energy is required to grow and harvest the crops needed for methanol production. The direct use of nuclear energy for commercial ship propulsion enables arable land to be used for food production to feed the human population, rather than growing crops to produce biofuels. Over the life of a ship, there is the potential for a nuclear powered ship to be inexpensive to compete with other carbon-free technologies.
Ports and Suez Canal
Public pressure and security concerns have led many coastal cities internationally to ban nuclear-powered ships from entering ports. The Suez Canal Authority is currently advising against driving nuclear-powered ships through the Suez Canal. Only in very rare cases and with the kind permission of intergovernmental negotiations has the Suez Canal Authority allowed a nuclear-powered ship to pass through the Canal. The impending breakdown on board a nuclear power plant while driving through the canal would lead to a closure of the canal and massive loss of income for the canal authority.
Tugs
The Suez Canal Authority allows tugs to pass through the canal. When a smaller ship, like a tugboat, is towing a large ship through the canal, there is usually advance notice and negotiation. Occasionally a large ship has towed a much smaller ship through the Canal, and such a precedent provides a possible basis for future discussions and negotiations with the Suez Canal Authority. One future possibility would be for a small ship to generate electricity while being pulled by a much larger ship that pulls a tow cable that also carries accompanying power cables.
A molten salt nuclear reactor could be deactivated before a nuclear powered ship arrives at the Suez Canal entrances, and a towed electric generator ship would be attached to each deactivated nuclear ship via towing cables and connecting cables to provide propulsion power and navigational controls to the large ship. The electrical energy from the small tug would keep the propulsion and navigation controls for the large ship. Although such an operation is technically possible, it has never been driven through the Suez Canal and would require a directive from the Suez Canal Authority.
Battery power on board
Battery technology has the potential to maintain low-speed propulsion and ship navigation along the 120-mile length of the Suez Canal. The same batteries would provide short range propulsion and navigational controls when nuclear powered merchant ships arrive and depart from ports that require the deactivation of molten salt reactors on board each nuclear merchant ship. Alternatively, port-based battery ships would be connected via tow cables and interconnected power cables to provide propulsion and navigation to large nuclear-powered merchant ships arriving and departing with the molten salt reactors deactivated.
Multi-nation port authorities and the Suez Canal Authority would need to consider the future possibility of nuclear-powered merchant ships arriving in port and requesting passage through the Suez Canal. Both the port authorities and the Suez Canal Authority would need to reassure themselves of the relative safety of molten salt nuclear technology compared to previous nuclear technology. All authorities would likely face public pressure to maintain safety in the ports and along the Suez Canal. Shipping companies considering future nuclear powered super container ships must negotiate internationally with the Suez Canal Authority and the port authorities.
Conclusions
In South Korea, plans are underway to develop a commercial ship powered by a molten salt nuclear reactor. It is one of the technological options as the international shipping industry moves to low-carbon, zero-emission propulsion. There will likely be future talks with the Suez Canal Authority regarding nuclear powered merchant ships that need to be transported between the Mediterranean and the Red Sea, as well as future talks with international port authorities.
The opinions expressed here are those of the author and not necessarily those of The Maritime Executive.
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