For many people, if not the majority, nuclear power has been linked with negative circumstances. The accidents in Chernobyl and Fukushima have made the public fear of the potential consequences of a nuclear failure.
But, is it that dangerous? And if not, how can we use this energy source, in order to achieve decarbonization, especially in shipping?
How can nuclear power help shipping?
The discussion regarding nuclear power and ships is not new. In fact, the first nuclear power plant started operations more than half a century ago, in 1955, with the US Navy. Since then, about 700 reactors have been operational at sea, while today there are around 100.
By using nuclear power, ships can be sure that they will be using a zero-emission solution, as it does not emit any SOx, NOx, CO2 or particulates.
As Lloyd’s Register explains, nuclear power is millions of times more power-dense than fossil fuels, as well as alternative fuels, such as methanol, ammonia and hydrogen. In practical terms, this means that by using such a technology, shipping can achieve IMO’s 2050 greenhouse gas (GHG) reduction ambition, as it will replace fossil fuels.
Another fact that shipping should keep in mind, is that this energy source is currently excluded from the Energy Efficiency Design Index (EEDI). This means that there are no barriers for vessels using this technology.
Ferries can be especially benefitted by using nuclear power. This is because of two main factors. Firstly, ferries will be zero-emission ships, as they will not have to bunker while they embark or disembark passengers. Secondly, they will not have the need to use shoreside power to cut their emissions, while it might as well be possible to even supply power from the vessel to shoreside, thus gaining a further revenue source.
What is more, ships with nuclear power have much fewer refilling needs. This makes them able to travel long distances with a single time energy production, thus making the voyage faster.
This is especially visible in nuclear military ships, such as submarines, which have the ability to survive underwater for whole months, without needing to resurface for refueling.
In addition, nuclear energy provides a better power to weight ratio. This means that ships using the technology will have better weight carrying capacity, and travel long distances faster, even if they have more load.
What are the barriers to nuclear energy uptake?
Despite the environmental benefits that nuclear power has, it is not widespread. A significant factor for this, is the public perception and acceptance, which raise important barriers in adopting this technology.
The problems however, are more practical as well. According to a paper by the International Atomic Energy Agency (IAEA), the main issue is radioactive waste disposal and accidental release of radioactivity. Writing a paper on this matter, C. Roberts (IAEA) highlighted that the International Atomic Energy Agency had already conducted a study of problems regarding the disposal of wastes into the sea, while another expert group considered the way that the techniques of oceanographic radiation monitoring could be standardized, in order to establish uniform regulations. Namely, nuclear reactions produce enormous energy, which if controlled incorrectly, could lead to disaster. In fact, even a seemingly minor fault, could be able to cause accidents with massive implications globally. As far as nuclear ships are concerned, a contamination of water bodies with nuclear fuel is possible, something that can affect both marine and human life.
Moreover, a special problem derives from sea motion, and generally external forces acting on a marine reactor during rough sea. For this case, a research from Japan, presented by I. Uchida, discovered that in heaving and pitching conditions the smallest acceleration effect was near midship.
In addition, issues with the reactor shielding are more important for marine units than for land based plants. This is not only due to potential collisions, but also because of the fact that the operating personnel of a vessel could be near the reactor even in their leisure hours. For this reason, researchers have stated the opinion that it would be wise to follow the recommendations of the International Commission on Radiological Protection (ICRP) for the maximum permissible radiation doses. In fact, all crew of a nuclear ship could be regarded as "radiation workers", for whom ICRP allows a maximum dose of 5 rems per year.
As for passengers on such vessels, they must not be exposed to more than half a rem per year. However, this would not lead to significant problems, as the passenger accommodation is normally located away from the machine rooms. This means that it is virtually impossible to gather as much as half a rem on one trip that lasts no more than four months.
Are any operational nuclear ships today?
As we said before, nuclear technology is not something new. In fact, nuclear reactors have been powering submarines for more than 60 years. Today, mostly naval ships are powered by nuclear energy.
The first nuclear submarine was the USS Nautilus, which was put to sea in 1955. Today, the US Navy has over 80 ships that are powered from nuclear source, including aircraft carriers and submarines, a report by the Federation of American Scientists informs.
In addition, Russia also has a nuclear-powered fleet, consisting from icebreakers. These ships are designed to sail through ice with nuclear reactors on board.
What is more, 2018 marked a milestone for nuclear energy on ships. Namely, the world’s first floating nuclear power plant, the "Akademik Lomonosov", started its voyage on Saturday, 28 of April 2018, from St. Petersburg.
The vessel will be the first of a fleet of floating nuclear power stations to be stationed in the Russian Arctic.
However, nuclear ships had their failures as well. Specifically, 50 years ago the world's first nuclear-fueled cargo-passenger ship, NS Savannah, sailed from the US to Europe on a publicity tour. The journey aimed to convince the public to welcome this technology. But it didn't go as planned.
The problem was that the ship was designed to store a volume of radioactive waste that was quickly exceeded. As a matter of fact, just in its first year, 115,000 gallons of low-level waste was released into the sea. To address this, the storage space increased, but again small volumes of waste continued to be released.
Nuclear energy is without a doubt a carbon-free and thus environmental-friendly solution. The history has shown that it can provide many benefits, but a potential failure could be catastrophic. For this reason, a proper planning and the correct safety measures must be undertaken, in order to reduce this danger to the minimum.