by James Ashworth
The nuclear debate polarises opinion. There are good reasons to be fearful, but just as many, if not more, to be positive. Nuclear power is an essential component of the energy mix, and this extends to merchant shipping.
When you ask educated, professional groups whether they believe we should become more reliant on nuclear power, 30-40 percent are positive. When you ask the same group if they would be prepared to take their family on holiday on a nuclear powered cruise ship, the number drops to below 10 percent.
Perception and fear of the unknown is still a huge issue in the nuclear debate. The recent crisis at Fukushima Daiichi has done much to reverse a slow thawing of opinion, leaving politicians scrambling for nuclear abolition to appease voters, often with scant regard for the energy needs of their economies.
However, perceptions and attitudes to risk change. Early motor cars were preceded by a man walking with a red flag to warn people. Even though road traffic fatalities continue in high numbers, the man and the flag are long gone.
The maritime conundrum
The maritime sector is heavily regulated. The burden of compliance with the IMO MARPOL Annex VI regulations on emissions bears down on owners and operators. The number of Emission Control Areas (ECAs) and Sulphur Emission Control Areas (SECAs) is set to grow, imposing heavy penalties on non-compliant vessels. This adds cost, but with vessel oversupply in many areas and a faltering economic recovery, the outlook for charter rates, and thus earnings, remains uncertain.
SECAs and ECAs in the Baltic and North Sea, and plentiful North Sea gas have triggered an emergent market for small LNG-bunkered vessels that meet emissions legislation, both current and planned. Others are now reconsidering their options. Gas is plentiful, with reserves offering an estimated 250 years' supply. However, the question is "who blinks first?" Ship-owners will not convert to LNG until there are sufficient LNG bunker ports in the right locations. Ports will be hesitant to provide LNG infrastructure until a guaranteed market is there.
Nuclear propulsion meets these challenges in one stroke. There are effectively zero emissions, and with refuelling intervals up to ten years, minimal port dependency. Nuclear also offers an increasingly competitive cost profile as fossil fuels become more expensive and potential economies of scale kick in. Nuclear propulsion deserves another, more serious look.
It is a tragedy that the nuclear industry was born out of warfare, from the Second World War and through the Cold War. What was good for the military was not necessarily good for the world, from the choice of uranium as the preferred fuel to limitations of use in the transport sector.
The world's first nuclear surface vessel was 'Lenin', a 20,000DWT Soviet icebreaker commissioned in 1959. She remained in service for 30 years to 1989 and was only retired because the hull was worn thin from ice friction. She initially had three 90 megawatt thermal (MWt) OK-150 reactors, providing steam for turbines, which generated electricity to deliver 34MW at the propellers. The original reactors were badly damaged during refuelling in 1965 and 1967 and replaced in 1970 by two 171MWt OK-900 reactors.
The first nuclear-propelled merchant ship was the USA's passenger/cargo vessel 'Savannah'. Commissioned in 1955 by President Eisenhower, she entered service in 1962 and could travel 300,000 miles (483,000 km) without refuelling. She sailed over 450,000 miles in her five years of merchant service (1965-70) requiring a crew of more than 100 mariners.
Arguably the most successful nuclear merchant ship was Germany's 'Otto Hahn'. As a cargo ship and research facility, she was launched in 1964 and refuelled in 1972. She sailed 650,000 nautical miles, spanning 126 voyages. For economic reasons, diesel propulsion was installed in 1979, but her ten years sailing under nuclear propulsion saw no technical problems.
Japan's entry into nuclear merchant shipping was a less fortunate affair. 'Mutsu' entered service in 1970, powered by a 36MWt reactor. However, she was dogged by technical and political problems and never properly entered service. After removal of the reactor in 1995, she was rebuilt to become the ocean observation vessel 'Mirai'.
Today, the only commercial nuclear vessels in operation are Russian icebreakers, frequently offering Arctic cruise holidays. All others are military vessels, mostly submarines.
To date, the maritime nuclear propulsion unit of choice has been the Pressurised Water Reactor (PWR). Water is heated to 315°C and pressurised up to 155 bar via a nuclear fission process within fuel rods in a strong reactor containment structure. Temperature is regulated by the insertion of boron or cadmium steel control rods that absorb neutrons and reduce fission. The pressurised water then heats a secondary independent water circuit, generating steam that drives a turbine, which can be coupled to the prop shaft or used to generate electricity.
PWRs are very stable due to their tendency to produce less power as temperatures increase. Water in the secondary loop is separate and not contaminated by radioactive materials. The control rods are held by electromagnets and fail-safe falling by gravity when current is lost. Full insertion safely shuts down the primary nuclear reaction. However, the post shutdown period of one to three years requires cooling. It is this cooling that failed at Fukushima, causing high temperatures to separate water into hydrogen and oxygen, causing explosions.
High pressures in the primary water circuit require robust containment and this adds to build and operating costs. The reactor pressure vessel is typically manufactured from ductile steel but, as the plant is operated, neutron flux from the reactor causes this steel to become less ductile, potentially limiting service life.
Various new nuclear technologies are being developed, some of which might be applicable to propulsion. One example is a uranium nitride nuclear battery, currently being developed by Hyperion at Los Alamos Laboratories in the USA. Intended for captive power generation in remote locations, the battery has an output of 75MWt or 25MWe, measures 1.5 by 2.5 metres, and weighs around 50 tonnes. With a sealed core and ten-year service life, such units would be easy to remove and replace. However, the battery is fuelled by uranium – and there are alternatives.
Why uranium?
Today's nuclear industry grew out of the Cold War, whose antagonists required plutonium (derived from uranium) for their nuclear arsenals. This is unfortunate, as there is a much better option if you do not want to make bombs.
Thorium can generate significantly larger amounts of energy than uranium, can be used in existing reactors, does not require conversion or enrichment, cannot be used as bomb material, is inherently incapable of causing a meltdown, and produces waste material that can be recycled as fuel. Spent thorium fuel is radiotoxic for decades rather than millennia.
Thorium exists as a by-product of the extraction of rare earths from monazite sands, found in greater abundance and higher concentrations than uranium, making it much less expensive and environmentally unobtrusive to mine. The primary locations of thorium reserves are Australia (25 percent), India (24.9 percent), Norway (14.6 percent), the USA (13.7 percent) and Canada (9 percent), improving supply security over that of uranium.
Research is underway to commercialise thorium fuels, and some challenges lie ahead. The USA added research funding for a destroyer-sized thorium reactor in 2010, and India is developing a 300MW prototype of a thorium-based advanced heavy water reactor (AHWR), expected to be fully operational this year, after which five more reactors will be constructed. India plans to meet 30 percent of electricity demand through thorium-based reactors by 2050.
No technology will succeed without meeting minimum economic criteria. Nuclear endeavours in transportation have always been military or experimental in nature, bringing a legacy of high capital and operating costs. In the age of cheap energy, it never made commercial sense. But cheap energy is increasingly becoming distant history. Has the tide turned for nuclear?
In exploring this question, the naval architects CR Cushing and Co considered a recently built 15,000TEU container vessel with 32-knot service speed. The study compared the costs for nuclear propulsion against a conventional system, assuming a plant life of 40 years and an interest rate of 10 percent.
Annualised capital costs for nuclear totalled US$38.36 million, against US$10.23 million for conventional. Operating costs such as security, insurance, personnel, M&R and reactor disposal, came to US$16.2 million for nuclear, compared with US$2 million. Therefore, when capital and operating costs are added up, nuclear propulsion was found to be US$42.34 million more expensive than conventional propulsion.
However, factoring in fuel costs at current prices, the picture changes dramatically. For the same operations, the annual fuel cost for nuclear was US$6.75 million, while conventional came in at US$112 million. Nuclear propulsion saved US$105.25 million on fuel.
Therefore, with all costs integrated, a 15,000TEU container vessel with a 32-knot service speed is almost US$63 million cheaper to run nuclear than with diesel propulsion. And why stop at 32 knots? Service speeds of 50 knots are entirely feasible with little or no fuel cost penalty.
With such savings on offer, convenience and political expediency will inevitably overcome contemporary perceptions. This point is not lost on Lloyd's Register, who commissioned a research programme into Merchant Nuclear Propulsion in 2007, with other stakeholders including Hyperion Power Generation, BMT and Greek shipping conglomerate Enterprises Shipping and Trading. Babcock International entered the frame with a nuclear LNG carrier proposal in 2010.
Since the 1950s around 700 marine reactors have been in service, accumulating more than 12,000 reactor years. There have been hundreds of accidents involving nuclear vessels, some of which have sunk. There has never been any recorded leakage from a sunken nuclear reactor. Sea water provides cooling, preventing hydrogen explosions. Today, there are around 140 vessels powered by 180 small nuclear reactors.
There are challenges. The anti-nuclear lobby is vocal and plays increasingly on the apprehensions of politicians and their electorates. Security challenges are important but quantifiable. The threat should a reactor be stolen is overstated, particularly with modular reactors. Issues around waste disposal are negligible.
Some new port infrastructure will be required, particularly for refuelling or the swap of nuclear reactors but little else. Staff competency is a challenge but can be met, and with high levels of automation and a reduced maintenance burden, fewer staff will be required.
Probably the biggest threat comes to vested interests in the status quo. Maintenance reduction associated with nuclear propulsion will undermine a significant global industry in maritime maintenance. Heavy fuel oil burned in ships engines is a significant outlet for oil refinery residues and supports a large marine bunker service sector. With no other obvious use for residues, both LNG and nuclear present problems for oil refiners. The emergent MARPOL legislation on emissions will increasingly segment the shipping population into "compliant" and "non-compliant" vessels biasing charter markets.
What are the opportunities?
Current thinking sees the most likely merchant applications in container vessels, oil tankers, LNG carriers, fast ferries and cruise ships. With virtually zero emissions, nuclear vessels meet all current and predicted environmental legislation. Increasing fossil fuel costs and possible reduced availability enhance the savings and security offered by the nuclear option. Savings are further enhanced as nuclear take-up provides economies of scale. Smaller nuclear propulsion units and removal of bunker tanks provide more space for passengers or cargo, improving vessel yields. Fast operating speeds mean that fewer ships can provide equivalent services. Charter rates, especially for perishable goods, could carry a premium.
Piracy is frequently cited as a negative factor, but high operating speeds offer a deterrent to boarding. The practice of "cold ironing", where vessels switch to shore power while docked can be turned on its head with nuclear ships: surplus generation capacity could be fed into the grid of the port state, perhaps adding a revenue stream for ship-owners and operators.
Changes in the energy map bring challenges. While hydrocarbon costs increase, public perceptions of nuclear power are mixed, driven by Three Mile Island, Chernobyl and Fukushima. The challenges cannot be underestimated, but nuclear power is fundamentally safe, clean and increasingly affordable. This heralds an exciting future for engineers and naval architects.
What does a 20,000TEU container ship with a 50-knot service speed look like? What final drive system should be used? How do the economics stack up? All these and other questions need to be answered and the time for this is now.
James Ashworth is a Singapore-based chartered engineer and consultant with a background in both marine and mechanical engineering. He is the chairman of the Joint Branch of The Royal Institution of Naval Architects and The Institute of Marine Engineering, Science and Technology (Singapore).