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Nuclear Power and storage technologies for marine Propulsion and floating nuclear power plants

The International Energy Agency’s has found that the accelerating demand for electricity – due to a growing global population and rising levels of affluence – is on course to outpace the growth of renewable energy and increase reliance on fossil fuels.


The International Maritime Organization has adopted mandatory measures to reduce emissions of greenhouse gases from international shipping, under their pollution prevention treaty (MARPOL) using their Energy Efficiency Design Index (EEDI) mandatory for new ships, and their Ship Energy Efficiency Management Plan (SEEMP).  The IMO is targeting a reduction in the carbon intensity of international shipping by at least 40% by 2030 compared with 2008 levels, and by 70% by 2050. The IMO took this action in support of the United Nations Sustainable Development Goal 13, to take urgent action to combat climate change and its impacts.


The International Shipping Industry shares about 90% of the global trade in goods, with more than 53,000 merchant ships currently operating in the oceans. They account for over 6% of the global oil use, or about 5 billion barrels per year. The IMO is considering a range of long-term zero-carbon fuel solutions, such as ammonia and hydrogen, but it’s nuclear that provides the most promise with respect to fuel cost and performance. The presence of hundreds, if not thousands of hydrocarbon burning vessels in the Arctic region would lead to substantial ice loss independent from concerns regarding anthropogenic CO2 emissions.


IMO is considering small nuclear reactors, similar to those that have made our Nuclear Navy so successful. Just like the Navy, the big shipping fleets have very large ships that require a hug amount of fossil fuel. The United States Navy alone has over a hundred nuclear reactors that power 86 submarines and aircraft carriers, producing electricity, heat and propulsion.


Nuclear power can achieve these higher speeds for much lower costs than fossil-fueled powered vessels. Based on the low cost of fuel, the economics of nuclear powered ships will tend towards higher speeds such as 20 knots for bulk carriers, or 30 knots for container ships. Besides fuel savings, nuclear powered ships go about 50% faster than oil-fired ships of the same size. For the shipping industry, the increased number of runs per year, and the increased profits, appear to more than offset the increased operational costs of nuclear, according to an analysis by researchers at Penn State.


The steady decline of polar sea ice over the last few decades has led to predictions that the North Polar regions will be open to regular marine traffic by at least the middle of the century (sooner if specially constructed ice-breaking vessels are built). This has generated a lot of excitement in maritime industry circles as it provides shorter distances compared to current trade routes, alternatives to the Panama and Suez canals, and represents a new frontier for exploration and development. However, there are challenges and environmental aspects that must be considered. The use of natural gas is not a silver bullet for this issue because the lubricating oil in the cylinders of diesel engines will be burned and also produce soot (Femenia, 2008). It does not take a lot of soot to increase the heat retention of ice. Nuclear power is the
only way to avoid this potential environmental damage while still remaining economical.


Another aspect of utilizing nuclear power for transarctic vessels is the disproportionately lower fuel cost of nuclear fuel compared to liquefied natural gas and fuel oil, allowing for higher powers and operating speeds. There is a considerable amount of extra power needed to break through several feet of ice. Because the transarctic ships will be susceptible to bad weather that can delay their voyages, higher open-ocean speeds will be needed to make up the lost time. Nuclear power can achieve these speeds much more cheaply due to its lower fuel costs.


Hazards of Nuclear Power for Ships

Nuclear power has its own safety and environmental considerations. These are mostly tied to worst case scenarios where some part of the reactor is compromised, leading to the release of radioactive materials into the environment. Our current experience with “meltdowns” is not an inherent feature of nuclear power, but of fundamental reactor design. It is possible to design reactors so the release of radioactive materials in the worst types of accidents are minimized and even prevented.


Safety considerations with nuclear powered commercial ships are primarily focused on reactor design and safety systems. Key topics are safety of the reactor during accident situations and what happens to the reactor if the vessel sinks. Meltdowns and radioactive emissions can be averted through proven reactor designs. Current practices for protecting the engine spaces during cargo fires will likely suffice for marine
reactors, especially since nuclear reactors do not contain flammable hydrocarbons. Recovery of the cores may have to be factored into the
design and arrangement of the reactors aboard vessels, but the world’s marine salvage industry has proven itself up to such a task


There is existing IMO legislation for nuclear-powered ships. Chapter VIII of the International Convention for the Safety of Life at Sea 1974 gives basic requirements for nuclear-powered ships that are particularly concerned with radiation hazards. This set of rules refers to a detailed and comprehensive Code of Safety for nuclear merchant ships, which the IMO Assembly adopted in 1981. It would have to be updated to reflect new technologies, but it should overall cover them.


Annual radiation doses to Navy personnel have averaged only 0.005 rem/year (5 mrem/year; 0.05 mSv/year), a thousand times less than the federal 5 rem/year allowed for radworkers. Normal background radiation in the United States varies from 100 mrem/year to over 1,000 mrem/year. The Nuclear Navy has logged over 5,400 reactor years of accident-free operations and travelled over 130 million miles on nuclear energy, enough to circle the earth 3,500 times.


Modular Molten Salt Nuclear Power

Several navies around the world operate scaled-down versions of nuclear power stations aboard ships and submarines to provide propulsion and ancillary power. The onboard nuclear reactors are cooled by high-pressure water and many (including the U.S. Navy’s reactors) require weapons-grade uranium for fuel. While such propulsion technology is suitable for a naval vessel, it has zero application in commercial civilian ship propulsion.

New developments in nuclear technology are based on an old idea involving the molten salt reactor, which can operate free from high pressure water and offer greater long-term operational safety while being suitable for mass production, reducing capital cost.


The technology uses solid non-weapons grade uranium fuel mixed into a chloride salt that melts at 750 degrees F in a pressure-free reactor. Any mixture that should ever leak out of the reactor would cool and solidify, free from any explosion. For maritime propulsion, the technology is comparable to a battery that holds sufficient charge to provide up to 25 years of propulsion at variable power settings. The carbon-free propulsion system saves many years of expense on fuel oil for transoceanic propulsion, providing the maritime industry with an economic and environmental case for its use.


The modular molten salt reactor delivers up to 100 MW of thermal energy at sufficient temperature to generate steam to activate turbines, which drive electrical generators. Unlike earlier nuclear technology that has to operate continually at constant power output, the molten salt reactor can rapidly adjust its power output and adapt to external demand. A single module could deliver between 4,000 and 26,000 horsepower in either propulsive or stationary floating generator station applications.


Ship Propulsion

The generating system would run on steam power and used seawater to cool the condensers when required when operating at elevated levels of output, with potential for organic Rankine-cycle engines to convert a portion of the exhaust heat to useable power. Many vessel operators reduce sailing speed to 12 knots to save fuel and reduce engine exhaust emissions, while others sail their ships at 18 to 24 knots. A trio of modular molten salt nuclear reactors connected to steam power conversion could provide sufficient power to sail the largest bulk carriers and the largest container ships economically at elevated speed. Slower ships could use a single molten salt reactor as a primary source of propulsion, perhaps with a back-up piston or turbine engine.


Molten salt nuclear technology has the potential to reuse spent fuel from older nuclear power stations. It can do so at a very high level of safety, eliminating high-pressure water from the reactor while the molten salt material contains the radiation. Reusing reprocessed spent fuel offers a long-term cost advantage in terms of the expense of hydrocarbon oil fuel. As the fuel approaches expiration, much of it is recyclable via reprocessing while non-recyclable material would be cast in concrete and stored until full expiration after a period of about 100 years.


The modern modular molten salt nuclear reactor has potential to fulfill multiple applications in the maritime sector, including propulsion and floating power generation. It has the potential to power a commercial vessel for the entirety of its normal lifespan without refueling.


Korean collaboration to research marine SMR

The Korea Atomic Energy Research Institute (KAERI) and shipbuilder Samsung Heavy Industries have announced plans to work together on the development of a molten salt reactor (MSR) for marine propulsion and floating nuclear power plants. Samsung Heavy Industries is also carrying out R&D into using ammonia and hydrogen to power ships in efforts to find alternative, low-emission propulsion options.


A cooperation agreement signed by the two organizations in  June 2021 at Samsung Heavy Industries’ Geoje Shipyard includes is aimed at joint research on MSR technology. This will include the design of an “offshore-based” small modular reactor, element technology/equipment development and performance verification, business model development and economic evaluation of offshore nuclear products.  “MSR is a carbon-free energy source that can efficiently respond to climate change issues and is a next-generation technology that meets the vision of Samsung Heavy Industries,” the company’s president, Jin-taek Jeong, said.


The development of marine transport ships based on MSR technology “can be a game changer in international logistics. MSR is a carbon-free energy source that can efficiently respond to climate change issues,” KAERI President Won-seok Park added. Shipping is seen as a ‘hard-to-abate’ sector for decarbonisation. The International Maritime Organisation aims to cut greenhouse gas emissions from international shipping by at least 50% by 2050 compared to 2008, and eventually to eliminate them completely.


South Korea’s Kepco Engineering & Construction Company and Daewoo Shipbuilding & Marine Engineering last year signed a Memorandum of Understanding to cooperate on the development of floating nuclear power plants. Russia’s first floating nuclear power plant, Akademik Lomonosov, started providing electricity in December 2019 to the isolated grid of the Chaun-Bilibino energy centre in Pevek, in the Chukotka region of Russia’s Far East. China National Nuclear Corporation and China General Nuclear have also announced plans to construct demonstration small modular offshore multi-purpose reactors.



Nuclear energy storage

One of the obstacles to total green energy reliance is that many sources of carbon-neutral energy, such as solar and wind power, are unpredictable and intermittent. A possible solution is to build energy storage facilities that can charge up while excess energy is being generated, then discharge when demand overtakes supply.  Battery-based grid-storage facilities using a range of battery types have already been built for this reason, but there is still a need to develop an economical, safe, and long-term solution.


There is a critical need to find efficient, cost-effective thermal energy storage solutions to maximize the use of domestic solar and nuclear energy resources. Most utility-scale solar power plants only run at about 25% of their capacity because they can’t generate power at night–thermal energy storage makes it possible to increase this capacity to up to 60-75%. Similarly, nuclear power plants produce a constant output of power–thermal energy storage could help increase this output during times of critical peak demand. Cost-effective thermal energy storage would enable increased use of domestic energy resources like solar and nuclear–strengthening the nation’s energy security.


Researchers are developing Energy storage systems encompassing four main categories: electrical, mechanical, thermal, and chemical. Examples in the electric category include superconducting magnetic energy storage and capacitors.  Pumped hydroelectric power, compressed air, and flywheels represent mechanical storage mechanisms.  Batteries are the most common type of chemical storage, and ice is the most common form of thermal storage.


Over the past 10 years, a small number of companies have developed small-scale nuclear reactors with output comparable to large commercial ships. Toshiba has developed an installation of 10MW output, Hyperion focused on developing an installation of 25MW and NuScale has developed an installation of 60MW. While nuclear fuel is costly, the group supported by Gates has focused on developing a nuclear reactor capable of using spent nuclear fuel rods as the main energy source.


An initiative by former Microsoft CEO Bill Gates offers the possibility of adapting evolving nuclear technology to future commercial maritime propulsion. His research team seeks to combine an improved version of thermal storage technology pioneered by the solar thermal power industry with a 345MW liquid sodium cooled reactor. That combination offers future propulsive possibility to the maritime sector.  The sheer amount of spent nuclear fuel rods internationally enhances the commercial and social attractiveness of re-using spent fuel rods.


The development of thermal storage technology enhances the operation and cost-effectiveness of nuclear power stations. During off-peak periods and during rare emergency shut-downs, a large portion of heat produced by a nuclear reactor may be transferred into heat-of-fusion thermal storage at constant temperature. There may be scope to develop thermal storage technology for mobile operation aboard a vessel and to source thermal energy from a large shore or offshore-based stationary large-scale thermal storage installation built adjacent to a nuclear power station. Mobile thermal storage may also allow for development of commercial nuclear ship propulsion.


Evidence from the natural world indicates that thermal storage material has incredible useable life expectancy. Water has solidified and melted billions of times over the earth’s history. High temperature thermal storage material capable of producing steam can also offer thousands to millions of repeated cycles solidifying during cooling and melting during reheating. Nuclear reactors operate optimally with highest reliability when maintained at constant temperature, which access to thermal energy storage would encourage. Access to thermal storage would enhance the operation of even a small nuclear reactor adapted to mobile operation in maritime propulsion.


Onboard heat-of-fusion technology that produces steam to drive an engine can offer ships a few hundred miles of operational range. The technology could be installed into a tug that would push and navigate a barge. Alternatively, the heat-of-fusion vessel could be a power generator to be towed by a large ship to which it provides electrical power to activate ship-mounted electric motors that drive propellers (azipods). The towed vessel could also include a small nuclear generator that would provide propulsive electric power to the main ship and offer trans-ocean sailing range.


Future nuclear power would include the Gates-inspired 345MW reactor designed to operate on spent nuclear fuel rods as well as radiation-free fusion thermal power currently being researched. Access to thermal storage technology would enhance the economics of nuclear fission and radiation-free fusion technologies, as well as 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. Research in underway involving thorium based reactor technology with potential to reprocess thorium for repeated use to maintain reactor thermal energy production.


The combination of coastal nuclear power with grid-scale thermal storage would allow thermal rechargeable tugs and vessels to operate comparatively short-sea shipping service, between ports where thermal energy storage is also available. Coastal short-sea shipping is cost-competitive in terms of moving bulk cargo and includes both domestic shipping and international ship transportation. Most short-sea shipping operations involving thermal energy storage would combine a large tug pushing and navigating a large barge. International trans-oceanic shipping involving the operation of a nuclear reactor would be restricted to routes where navies could assure ships security from piracy.


Several companies internationally are involved in the research and development of small-scale nuclear power capable of providing propulsive power to a single ship or a small convoy of ships. The development of thermal energy storage technology that is compatible to nuclear power enhances the long-term operation and long-term cost competitiveness of small –scale nuclear power


Transportation terminals

Many advances are occurring in electric battery storage technology applied to the transportation sector. This includes short-sea maritime, commercial roadway, railway and even short-haul airline propulsion. There are many locations internationally where maritime ports are located within close proximity to airports, both of which connect directly or indirectly to road and railway transportation. Future battery-electric propulsion provides opportunity to install modular molten salt reactor technology at major transportation terminals to provide energy recharge for a variety of short-sea maritime vessels, commuter aircraft, trucks, buses and even railway technology powered by any of batteries, overhead cable or third rail.


At some locations, there may be scope to use floating technology to carry several modular reactors, the result of seasonal peak traffic at some major transportation terminals. Floating technology could move internationally to spend a few weeks to a few months at locations requiring peak seasonal electric power. Land based modular reactors located next to the ocean would provide base-load power throughout the year. Modular reactors would be able to generate hydrogen for mainly aircraft propulsion, with hydrogen also being made available to some forms of maritime, railway and road vehicle propulsion.


Danish company plans to fit ships with small nuclear reactors to send energy to developing countries

Although nuclear energy has been used onboard seaborne vessels for decades to power submarines and “icebreaker” tankers, Seaborg’s design would be one of the first examples of a commercially available nuclear barge used to provide electricity to the mainland.


Floating barges fitted with advanced nuclear reactors could begin powering developing nations by the mid-2020s, according to a Danish startup company. Seaborg Technologies believes it can make cheap nuclear electricity a viable alternative to fossil fuels across the developing world as soon as 2025. Its seaborne “mini-nukes” have been designed for countries that lack the energy grid infrastructure to develop utility-scale renewable energy projects, many of which go on to use gas, diesel and coal plants instead.


The ships are fitted with one or more small nuclear reactors, which can generate electricity and transmit the power to the mainland. The first ship of this kind began supplying heat and electricity to the Russian port of Pevek on the East Siberian Sea in December 2019. Troels Schönfeldt, the chief executive of Seaborg, said the company’s 100-megawatt compact molten salt reactor would take two years to build and would generate electricity that would be cheaper than coal-fired power.


Chris Gadomski, a nuclear analyst at Bloomberg New Energy Finance, said: “The concept of a floating nuclear power plant has been around for a long time, and makes a lot of sense. But there are concerns.” There was inherent risk involved with nuclear reactor technologies and floating power plants, so combining to two could raise serious questions for investors and governments, he said. “In places like the Philippines and Indonesia it makes a lot of sense. But it wasn’t so long ago that the Philippines was the site of a major tsunami, and I don’t know how you would hedge against a risk like that,” he added.


Jan Haverkamp, from Greenpeace, said floating reactors were “a recipe for disaster” including “all of the flaws and risks of larger land-based nuclear power stations”. “On top of that, they face extra risks from the unpredictability of operation in coastal areas and transport – particularly in a loaded state – over the high seas. Think storms, think tsunamis,” he said. Schönfeldt said the advanced reactor was designed to be as safe as possible in a worst-case scenario accident, with a system causing the radioactive material to form a solid rock outside of the reactor core so it cannot disperse into the air or sea as a catastrophically harmful gas or liquid.





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