How Do Floating Nuclear Power Plants Work?

An innovative solution to our energy problem or a floating hunk of health hazard?
John Loeffler

Nuclear power has been the subject of considerable controversy for many decades now, but few nuclear power plants raise as many protests as those designed to float offshore or in the nearby waterways of small cities in hard-to-reach places.

Floating nuclear reactors are starting to see major interest in the Russian Federation, as well as areas of northern Europe, who see them as key energy resources for future development in the Arctic, as climate change continues to melt sea ice and glaciers in the northern latitudes.

Underneath those melting glaciers is a wealth of natural resources that have never even been seen — much less mined — by humans, but a problem remains: How do we build up the infrastructure necessary to exploit these resources. That's where floating nuclear power plants come in.

How do you build a floating nuclear reactor?

How Do Floating Nuclear Power Plants Work?
Nuclear engineers load the nuclear reactor into Rosenergoatom first floating nuclear power plant, the Akademik Lomonosov Source: Rosenergoatom

First off, a floating nuclear reactor isn't quite as simple as sticking a nuclear reactor on a boat and calling it a day, but it's also not that much more complicated either.

Special ships need to be built to house the reactors, but the idea of a nuclear reactor on a boat is not a new concept in the least. Military submarines and arctic icebreakers are powered by nuclear reactors already, so the idea isn't so much about adding a nuclear reactor to a ship, but more about making the nuclear reactor the whole point of the ship.

This obviously requires different design choices to accommodate the safety equipment as well as the nuclear reactors themselves. But probably the most important element is making it safe from extreme weather events or tsunamis that could sink the ship or otherwise damage it and release radioactive fallout or waste.

Such a circumstance happened in Chernobyl, Ukraine, in 1986, and more recently in Fukushima, Japan, when a 49-feet-tall (15 meters) tall tsunami in 2011 disabled the power supply and reactor cooling for three of the Fukushima Daiichi nuclear power plant's reactors. Of course, these were ground-based reactors.

How a ship handles those challenges and others, like storing the highly radioactive spent nuclear fuel rods used by the reactor, remain important and open questions.

How Do Floating Nuclear Power Plants Work?
Source: Nicolai Gontar/Greenpeace

The Akademik Lomonosov, Russia's first floating nuclear power plant, completed in 2018, is a form of pressurized water reactor that generates heated, high-pressure water which transfers its thermal energy to lower pressure water in a secondary system which also generates steam.

Similar to the nuclear reactors on ships, the issue of radioactive waste is a huge challenge, since it is in the form of radioactive liquid. As a pressurized water reactor, there is also the issue of a potential accident leading to the explosive dispersal of radioactive material into the atmosphere.

Denmark's Seaborg Technologies believes the solution to this is to use a molten salt reactor in its floating nuclear reactor design. Here, fluoride salts mixed with nuclear fuel forms a liquid above 932 °F (500 °C), letting it flow into and out of a reactor.

Unlike pressurized water reactors, if the reactor chamber is breached somehow — during an accident brought on by a natural disaster, for example — the molten salt doesn't violently explode into steam. Instead, when molten salt is exposed to air, it hardens into a rock, much like lava, which not only contains the radioactive material but also makes handling as disposal much easier.

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Molten salt reactors come with their own containment challenges though, especially around corrosion. Hot salts are notoriously corrosive in maritime environments like gas-powered turbines on ships, so building a nuclear reactor with them will require special shielding that can withstand the kind of corrosion that even stainless steel can't withstand.

Why build a floating nuclear reactor?

What's the point of a floating nuclear reactor though? Primarily, a floating nuclear reactor is used to provide substantial power for industrial and residential use in remote locations.

The Akademik Lomonosov, for instance, is in use powering the northern Russian town of Pevek, as well as powering a desalinization plant in the region. Russia has also approved five additional floating nuclear power plants to operate along its northern arctic coastline.

In addition to providing electricity to some of Russia's most isolated communities, these power plants will also provide the power necessary to push development even further north into more pristine, unspoiled arctic areas now being exposed by receding sea ice and glaciers.

Outside of Russia, a floating nuclear reactor could be used to help power regions of the world where electricity is scarce or non-existent, as well as help power disaster-hit regions as they recover.

The United States operated a floating nuclear power plant in the Panama Canal in the 1960s and early 1970s, though that was not nearly as ambitious as what others, like Seaborg Technologies and Russia's Rosenergoatom, propose.

Seaborg Technologies Plan For Floating Nuclear Power Plants
Seaborg Technologies design for floating nuclear power plants. Source: Seaborg Technologies/Facebook

Seaborg Technologies hopes to eventually produce hundreds of floating nuclear power plants every year, claiming that these reactors will offset 33,600,000 tons of carbon dioxide, at a minimum, over the life of the reactor when compared to a similarly-sized coal power plant.

"The world needs energy, but we also need to decarbonize," said Troels Schönfeldt, Seaborg co-founder and CEO. "With a highly competitive product, using existing production capacity, we can deploy hundreds of reactors every year — we are geared for global impact,"

That decarbonization goal is a vital one, without question, and even some otherwise pro-environment policy advocates say that decarbonizing the economy to combat climate is impossible without increased nuclear energy production.

As others point out though, building safe nuclear power takes a great deal of time — something we are pretty much out of when it comes to averting climate change — so putting our climate hopes in nuclear power to save us may be effectively moot.

What are the limitations of floating nuclear reactors?

Starting with the obvious, floating nuclear reactors can only be used where there is sufficient water for them to float, so either in the open ocean or in sufficiently wide waterways like large rivers.

If more isolated interior regions aren't connected to the same power grid as the coastal region that a floating nuclear power plant is connected to, then it won't be much help to them.

This would be especially frustrating if the purpose of a floating nuclear power plant was to provide energy to a disaster-hit region, where disruptions in the power grid must be expected — if a local grid even existed in the first place.

In 2017, Hurricane Maria devastated the US territory of Puerto Rico, knocking out power for months in some areas of the island. The problem here wasn't so much that a power plant had been knocked offline for this entire time, but that Maria had torn down powerlines all across the island. 

Power was only officially restored to all of Puerto Rico's residents in March 2019, almost two full years after Maria had struck the island. This kind of infrastructure challenge isn't something that a floating nuclear power plant could have fixed, and their utility in other disaster areas would be likewise limited.

What are the risks associated with floating nuclear reactors?

The biggest issue on the horizon for floating nuclear power plants is the same one that confronts any nuclear power plant: What are the risks associated with it?

Proponents of nuclear power are quick to point out that nuclear power actually has a fantastic safety record, considering how many nuclear power plants there are in service around the world. And there is definitely something to be said for this, in context.

There are only 443 currently operating nuclear reactors in the world right now, so when assessing the risk of a nuclear accident, you have to consider the size of the sample pool you are considering. If you flip a coin once and it lands on heads, you cannot use that to say coin flips never come up tails.

There have been 190 nuclear power plants decommissioned around the world as of April 2021, with the total number of commercial nuclear power plants that are currently operable at around 449. There have been a number of major high-profile nuclear accidents, including the 1957 Kyshtym Nuclear Disaster, Three Mile Island, Chernobyl, and Fukushima.

After the Fukushima disaster, researchers analyzed all past core-melt accidents and estimated a failure rate of 1 per 3704 reactor (operation) years. The results also suggested that there are likely to be more severe nuclear accidents than have been expected.

Princeton University nuclear expert Harold A. Feiveson wrote that although nuclear power plants have become very reliable, “Even if the chance of a severe accident were, say, one in a million per reactor year, a future nuclear capacity of 1,000 reactors worldwide would be faced with a 1 percent chance of such an accident each 10-year period – low perhaps, but not negligible considering the consequences” 

And the consequences of that accident are as outsized as the nuclear power plant's benefits are when it's functioning properly. Nuclear power is an unquestionably high-risk-high-reward proposition, even when the absolute number of nuclear accidents remains small.

The Chernobyl 'Sarcophagus' Housing The Nuclear Reactor That Melted Down In 1986
The Chernobyl 'Sarcophagus' that contains the nuclear reactor that melted down in 1986 Source: Petr Pavlicek/IAEA/Flickr

As environmental activist group Greenpeace points out, a nuclear accident in the Arctic from a floating nuclear power plant would be potentially catastrophic.

"Nuclear reactors bobbing around the Arctic Ocean will pose a shockingly obvious threat to a fragile environment which is already under enormous pressure from climate change," said Jan Haverkamp, nuclear expert for Greenpeace Central and Eastern Europe, in response to the completed construction of the Akademik Lomonosov in 2018.

Deputy director of Rosenergoatom, Sergey Zavylov, told the BBC in 2010 that "these [floating nuclear power stations] have very good potential, creating the conditions for exploring the Arctic shelf and setting up drilling platforms to extract oil and gas. Work in the Arctic is very complicated and dangerous and we should ensure there's a reliable energy supply."

"We can guarantee the safety of our units one hundred percent," Zavylov added, "all risks are absolutely ruled out."

As for extreme weather events and tsunamis, floating nuclear power plant proponents insist that these vessels will withstand these events, but not only has that yet to be demonstrated, it doesn't seem at all likely that they could guarantee this, at least not the ones we've seen produced already.

"The floating nuclear power plants will typically be put to use near coastlines and shallow water. Contrary to claims regarding safety, the flat-bottomed hull and the [Akademik Lomonosov]’s lack of self-propulsion makes it particularly vulnerable to tsunamis and cyclones," Greenpeace's Haverkamp said.

It's important to remember that hurricanes and tsunamis out in open seas can be dangerous, but they are far less so than along coastlines, where the displaced water runs into often-populated coastal areas, leading to massive storm surges and worse. Any floating nuclear power plant will be just as vulnerable to these forces as any other large vessel along a coastline.

While this might not be a major concern in northern Russia, several nations in Africa, South America, and Asia have expressed interest in floating nuclear power plants in the past, and interest is only likely to grow as Russia and others start mass producing them.

At least, until there are accidents, and there will certainly be accidents when you produce a substantial number of these floating nuclear power plants. Flip that proverbial coin a thousand times and the true risk of these floating nuclear power plants will come into much sharper focus than it is now.

Ultimately, the actual risk that floating nuclear power plants pose is not known since we simply don't have enough of a sample size to definitively measure it, though that's actually a good thing. Having lots of data points of past nuclear accidents and what caused them isn't the kind of thing anybody wants to see, but for most of us, that might be out of our hands.

As the rush to exploit the Arctic heats up in the coming decades, powering the drilling and mining operations in the Arctic, and providing electricity and clean water to those work them, is going to be an increasing priority for those nations with claims on Arctic resources.

As drinking water becomes more scarce in the Global South, desalinization plants are going to be essential to keeping an unfathomable number of people alive, and so even with the risks of nuclear accidents, the risks of dying of thirst are going to be much more immediate for many.

Mass-produced floating nuclear power plants may very well be the wave of the future, whether we like it or not.

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