Could cruise ships eventually run off nuclear power? This company is working on it

Nuclear-powered ships could be coming to the world of cruising — but with a twist.

Norwegian shipbuilder Ulstein this week unveiled a new concept for a cruise vessel that would run on electricity generated at sea using a nuclear reactor.

The twist is that the reactor wouldn't be located on the cruise ship itself, but on a separate service vessel. The service vessel would recharge electric batteries on the cruise ship every few days.

If the idea moves forward (something that will require both regulators as well as cruise lines to get on board), it will result in the arrival of what has long been something of a Holy Grail for the cruise industry – cruise vessels that are entirely emission-free.

Cruise ships have traditionally been powered with bunker oil, also known as heavy fuel oil, or another grade of oil called marine gasoil. Additionally, some ships in recent years have been designed to run on Liquefied Natural Gas, which is touted as a cleaner fuel than traditional marine-grade oils. However, using all such fuels results in emissions.

"Where you are going very long distances [with a cruise ship], you will never be able to be zero emissions with the fuel we have today," Ulstein senior naval architect Torill Muren told TPG on Tuesday at Seatrade Cruise Global, the cruise industry's annual meetup in Miami. "We want to start a discussion [about using nuclear power]."

Muren spoke one-on-one with TPG moments after Ulstein revealed the concept at the company's booth at Seatrade Cruise Global, which is taking place this week at the Miami Beach Convention Center.

The company unveiled an outline of its concept for both an all-electric cruise vessel and the nuclear power-generating service vessel that would keep the all-electric cruise vessel charged. It also showed off artist's renderings of what the two vessels would look like.

As depicted in the renderings, the cruise ship the line is proposing would be a small, hardy vessel of the sort that is used for expedition cruising — a type of cruising that involves traveling to hard-to-reach and often environmentally sensitive places such as Antarctica and the Arctic. It's a type of vessel that is a specialty for Ulstein.

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The company recently built two new expedition ships for Lindblad Expeditions that are considered among the most advanced expedition ships currently at sea.

Related: Is this the ultimate Antarctica cruise ship? Our take on Lindblad's new vessel

Muren said Ulstein's idea is that one service vessel with a small nuclear reactor could serve as a floating power station for up to four small, all-electric expedition ships sailing in a region such as Antarctica.

As Ulstein conceives it, the service ship would feature a rarely built type of nuclear reactor that uses a thorium molten salt mixture. Such reactors are considered safer than conventional nuclear reactors because they operate with fuel in a molten state. In the event of an emergency, the fuel would drain into a containment vessel and solidify, preventing the sort of uncontrolled nuclear meltdown that can happen with a more traditional uranium-fueled reactor.

Norway-based Ulstein is calling its concept for the service ship Ulstein Thor — a nod to the thorium fuel that will be used in the vessel's electricity-producing reactor that also evokes the power of the Norse god of the same name.

Muren told TPG the concept could become a reality within 10 years if the industry and politicians signed on to the idea.

She said rapid advancements in battery storage happening now could mean that electric batteries with a high-enough capacity to run a small cruise ship for many days will be available in "five or six years." Add in electricity generated by a thorium-fueled reactor, and there could be a revolution in how ships are powered, she suggested.

"A very small amount of thorium can power a ship for 25 years," Muren said.

The all-electric cruise vessel that Ulstein proposes would be about 328 feet long and carry up to 80 passengers and 80 crew. It would be built extra tough to operate in polar areas with ice (it would have a 1C ice class rating).

The power-generating service ship would also be built as a rescue ship that could aid vessels in distress in remote areas such as Antarctica, the company said.

"Thor enables replenishment of energy and supplies on site, while also boasting the technology to facilitate rescue operations, as well as conducting research tasks," the line said in a press release issued at the time of the announcement. "It is, in effect, a crucial piece of infrastructure to support sustainable and safer operations. Thor literally has the power to change our entire industry."

The service ship would have helicopter pads, firefighting equipment, rescue booms, workboats, autonomous surface vehicles and airborne drones, cranes, laboratories and a lecture lounge, the company said.

Muren noted that thorium has relatively low radioactivity and produces radioactive waste that is easier to manage than the radioactive waste from more traditional uranium reactors.

"Thorium is a much nicer substance, and it produces very little waste compared to uranium [used in other reactors]," she said. "With uranium, you have a lot of waste that you have to take care of for ... thousands of years. For thorium, it is a couple of hundred years."

Nuclear power plants have been used on military ships but almost never on passenger ships. A single nuclear-powered cargo vessel that also carried a small number of passengers, the NS Savannah, debuted in 1959 and operated for several years. It was built as a demonstration project with funding from the U.S. government.

Muren acknowledged that it could take some time to get cruise operators and political authorities comfortable with the idea of using nuclear power for cruise ship-related operations. However, she expects the cruise world will eventually embrace the idea of battery-run vessels charged with nuclear-generated energy.

"I think you will at some point see that we will go to batteries [for cruise ships], as we did with cars," she said. She added that it's important for the industry and authorities to begin talking about it now, even as the technology that could make it happen is still being developed.

"It's so important to start now, because the more we wait, the longer it will [take] before we are there," Muren said.

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