Small-Scale Nuclear Power for Commercial Ship Propulsion

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.   

Introduction

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. 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.

Thermal Storage Technology

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. 

Combined Thermal Recharge

While a stationary nuclear power station would provide recharge energy to a large-scale stationary thermal storage installation, there would likely be scope to modify the technology to include thermal recharging from mobile nuclear reactors installed in a towed vessel that provides propulsive electrical power to a large ship. Onboard stored battery electric power could provide short-distance low-speed sailing to the large ship, with the option of the ship towing a local battery-electric or thermal-electric vessel able to provide propulsive electric power to the ship’s propellers. Such ships would sail between ports that have nearby coastal thermal storage technology.

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.

Maritime routes

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.

Security reasons would prevent sailing nuclear powered commercial vessels via the southern region of the Red Sea, leaving trans-North Atlantic routes between Europe and North America, trans-Pacific routes between the Americas and Australia as well as between the America’s and East Asia. Future nuclear-powered trans-Pacific commercial shipping would likely involve transshipment operations at any of the Philippines, Taiwan or Chinese ports located east of Hong Kong. With big ships requiring over 80MW of main engine power, a ships carrying a 345MW nuclear reactor could sail in a convoy of 4 to 5-ships to which it supplies propulsive electrical power.

Conclusions

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. The initiative of former Microsoft CEO Bill Gates involves both the development of suitable thermal storage technology as well as methods by which to generate electric power from energy contained in the abundance of spent nuclear fuel rods.

While nuclear power is controversial, small-scale nuclear power combined with thermal storage technology offers a future propulsion option to the maritime industry.

Harry Valentine is a regular contributor to The Maritime Executive Magazine.