Floating Nuclear Power
Nuclear power is a controversial but necessary part of our existing grid structure. Many nuclear power reactors are nearing retirement, but there are very few new reactors under construction to replace them. This is primarily due to time and cost to construct a new plant. Floating nuclear power may be a viable, and safer, alternative. In this post we’ll look into the history of floating nuclear power as well as its advantages and disadvantages.
Nuke Plant Social Security
Nuclear power makes up a tenth of the total generating capacity in the United States. As of December 1, 2016 there were 99 operating nuclear reactors at 61 nuclear power plants in the United States, responsible for over 99,000 megawatts (MW) of power generation . The rated capacity of all these reactors ranges from 500 megawatts to almost 4 gigawatts (GW), with an average of 1.2 GW .
U.S. nuclear power plants are getting old and there aren’t enough new builds in the pipeline to replace those that age-out. Operating lifetimes for many of these plants was only intended to be 40 years, or 60 years if the plant applies for an extension , but the average age is now 36. As shown in the graph, over 20 reactors will retire in the next twelve years, which accounts for roughly 24 GW of capacity that needs to be replaced. The decade after shows even more retirements.
Why so Few Nuke Plants?
New plants take a while to build: the average time from construction permit issuance to operating permit issuance is almost ten years. That’s ten years that investors must wait for returns. Over the last thirty years there have only been nine new operating licenses issued and currently there are only two reactors under construction in the United States, both in Georgia.
There are a number of reasons why fewer nuke plants being are being built today than in decades past. A main reason is cost. Each nuclear power plant is bespoke. Each project requires new designs, new contractors, new impact assessments, new tooling, and new training for technicians. Since each new plant is a unique design it’s very hard for developers to drive down costs and improve economies of scale.
Another reason fewer nukes are being built is because people simply just don’t like them as much as they used to. According to recent polls, roughly half of Americans oppose nuclear power (a majority according to one recent Gallup poll ) and would prefer not to have it in their community. Ironically, most survey respondents agree that nuclear power is safe, but apparently not safe enough to have near their own home.
Our grid will need a significant amount of new capacity in the next decade, and even more in the decades that follow. Much of it could be met by renewable energy: 2016 saw nearly 15 GW of renewable energy capacity additions in the U.S. . However, with the current administration and expiring tax incentives and credits, it is likely we’ll see a reduction in such large-scale renewable deployments in the near future. If we want to have any hope of meeting emission reduction targets nuclear power needs to be part of the solution. Since there is so much contention around nuke plants on shore, perhaps we should consider another option: floating nuclear power.
Floating Nuclear Power
Floating nuclear power is different from traditional nuclear power plants in two ways. First, a floating nuclear reactor generally has a smaller capacity. Instead of thousands of megawatts seen in conventional plants on shore, the small modular reactors (SMRs) of floating nuke plants are typically around 300 MW or less. Second, the reactor is floating at sea, and thus mobile, but delivering power to shore. Of course the U.S. Navy has nuclear reactors on many of their vessels, but the distinction is that these vessels don’t contribute to the power grid on shore.
The Beginnings of Floating Nuclear Power
Offshore floating nuclear power is not a new concept. The United State’s first foray into floating nukes was actuallyled by the U.S. Army. Constructed in 1967, the USS Sturgis MH-1A was a 10 megawatt floating nuke plant. It was a converted Liberty Ship that was originally intended to supply power in combat zones or remote areas. Although the vessel was never in a combat zone, it did supply power to the pumps in the locks of the Panama Canal Zone from 1968 to 1975. The Sturgis was defueled in 1977 and is currently being decommissioned in Galveston, TX.
The Public Service Electric and Gas Company, an electric utility in New Jersey, also considered floating offshore nuclear power in the 1960s and 70s. With help from Westinghouse, they proposed a 2.3 gigawatt dual reactor to sit atop a 400 foot long barge. The barge would be anchored about 12 miles offshore of Atlantic City NJ and send power back to shore. The project faced numerous set-backs from the beginning and was ultimately abandoned in 1978 before any design hit the water . After these two attempts, there was a floating nuclear lull; but recently there have been new developments abroad.
Floating Nuclear Power Abroad
In Russia, the Baltiysky Zavod shipyard is nearing completion of the Akademik Lomonosov, the country’s first floating nuclear plant. The Lomonosov contains two naval propulsion reactors with a combined 70 megawatt capacity that have been repurposed for delivering power to shore. Ironically, the Lomonosov lacks its own propulsion and must be towed to location. It is claimed the plant will be operational by 2019 and it looks to be on schedule. The construction and install cost is reportedly $480 million, or about $6.90 per watt, slightly more than the average conventional plant .
China is also showing interest in floating nukes. Recently, the State-owned China National Nuclear Power Company announced they will construct a 60 megawatt, modular, multifunction, floating reactor by 2020. Three years is an aggressive schedule when compared to the thirteen years Russia has been building the Lomonosov. It is reported that China’s floating nuclear power plant will cost $150 million  or $2.50 per watt, half of a traditional plant . If Russia’s similar sized plant cost more than three times as much and took four times as long to build, it makes one wonder where China is making cuts.
Although there have not been any new floating nuke plants in the U.S. since the Sturgis, that does not mean there aren’t groups researching the idea. There is one such group at MIT. Instead of a ship or barge housing the reactor, this group proposes to use a spar buoy design. Spar buoys are like icebergs: the majority of the structure is submerged beneath the water. With all the weight down low, spar buoys have very good stability against wind, waves, and currents. This makes them an ideal platform for ocean measurements, subsea drilling, or even floating offshore wind turbines.
Nearly three-quarters of the roughly 75 meters of the MIT group’s spar design would be submerged. Inside the bottom of the spar would be the reactor. This strategic placement ensures that it is always surrounded by pressurized emergency cooling water, which drastically reduces the risk of overheating. Since a spar buoy of this size has such a deep draft, this type of design is best suited for offshore locations in waters that have depths greater than 100 meters. There are no cost estimates for this 300 megawatt  design since it is still conceptual, but the designers are confident that through economies of scale their design will be significantly less than conventional nuke plants.
Floating Nukes: Good or Bad?
Nuclear power is a controversial subject. It’s emission free, on-demand energy with a low variable cost. It has reliably contributed almost twenty percent of electrical generation in the United States and it accounts for nearly two-thirds of non-greenhouse-gas-emitting generators . On the other-hand, storing spent fuel is an environmental time bomb and a large radiation leakage from a reactor is a terrifying scenario. Let’s investigate the relative advantages and disadvantages of floating nuclear power.
The Bright Side of Floating Nuclear Power
From a design standpoint, a floating nuclear power plant that works in the Atlantic Ocean will also work in the Indian or Pacific Ocean. By contrast, a nuclear power plant built in Maryland would not fare so well if it was moved to California. This is to say that floating nuclear power plants would be less site specific in their designs and thus easier to standardize. After the first couple iterations, cost and construction time would fall rapidly.
Floating nukes are mobile. They can be moved whenever and wherever they are needed most. This would be extremely useful in the aftermath of natural disasters such as the one facing Puerto Rico, providing much needed power generation without the need for fossil fuel resupply.
A floating plant would have the advantage of reduced siting costs, as ‘land’ at sea is generally cheaper than land on shore. If the selected site loses favorability at any point, a floating plant is easily moved to a new location. This last point would also make decommissioning more straightforward. Instead of bringing in expensive clean-up crews, the floating plant could simply be towed to one of the U.S. Navy’s nuclear decommissioning sites that are already equipped and trained for proper disposal.
Damage from seismic events and overheating of the reactor are constant threats to conventional nuclear power plants. Offshore, seismic events like earthquakes and tsunamis are barely noticeable due to the ocean depth; a tsunami becomes dangerous only as it approaches the shallow water near the coast.
Most importantly, the risk of overheating a thermal nuclear reactor is drastically reduced due to the unlimited supply of emergency cooling water from the surrounding sea. The threat of radiation leakage is therefore also reduced.
The Dark Side of Floating Nuclear Power
Of course there are some potential downsides to a nuclear power plant. Floating nuke plants will need to contend with rough seas and storms. These events can put enormous strains on ships and platforms and a single material defect could have catastrophic consequences. One could argue that since these power plants are mobile they can get out of the way of storms, but this is easy in theory and hard in practice.
If a reactor leaked at sea, the repercussions would be far-reaching and nearly impossible to contain. The same ocean currents that provide useful cooling could also deliver leaked radiation far and wide; for example, after the Fukishima disaster radiation leakage was detected as far away as California. However, due to the ocean’s immense volume the radiation concentration was extremely dilute. The radiation levels detected in California a year after the disaster were 500 times less than the U.S. Government’s standard for safe drinking water . That said, a radiation leak at sea would an environmental disaster and dilution is not a solution.
Thermal pollution is another potential hazard. It is less apparent than floating trash or oil slicks, but it can be just as damaging. As we know thermal reactors emit a large amount of heat that needs to be absorbed by a cooling fluid. This cooling fluid also needs be cooled so that it can be reused over and over again, and for a floating nuclear power plant the most economical cooling source would be the ocean.
If there is sufficient flow of hot water being discharged into the sea, it can actually increase the temperature of the ocean in that immediate area. This is well documented . For sea creatures, even a fraction of a degree temperature change can be deadly and lead to changes in the ocean water chemistry. Thermal pollution would be more of a problem for floating nuke plants close to shore in shallow water, but less so for designs in deep water with better circulation.
Nuclear power, although controversial, is needed on the grid for the time being. How much nuke power is needed is a more nuanced question. One thing is for sure, the U.S. is not building anywhere near enough nuke plants to replace the number retiring, and this discrepancy is only going to get worse. Floating nuclear power may be a viable alternative to conventional nuclear power plants as they are potentially faster to build, cheaper, and less susceptible to overheating. Before we start deploying any nuke plants in the sea we need to be absolutely certain that our designs are robust and that every single precaution is taken to protect the environment.
 Stauffer, Nancy W. June 24, 2015. “A new look for nuclear power.” MIT Energy Initiative. http://news.mit.edu/2015/new-look-floating-nuclear-power-0624
 Chandler, David. April 16, 2014. “Floating nuclear plants could ride out tsunamis”. Nuclear Science & Engineering at MIT. http://web.mit.edu/nse/news/spotlights/2014/buongiorno-floating-nuclear-plant.html
 Lin, Jeffery; Singer, P.W. August 18, 2017. “These are China’s plans for floating nuclear reactors”. Popular Science. https://www.popsci.com/china-floating-nuclear-reactors#page-3
 U.S. Energy Information Agency. https://www.eia.gov/tools/faqs/faq.php?id=104&t=3
 U.S. Department of Energy, Office of Nuclear Energy. Nuclear Reactor Technologies. https://www.energy.gov/ne/nuclear-reactor-technologies
 Wellock, Thomas. “Floating Nuclear Power Plants: A Technical Solution to a Land-based Problem”. United States Nuclear Regulatory Commission. September 24, 2013. https://public-blog.nrc-gateway.gov/2013/09/24/floating-nuclear-power-plants-a-technical-solution-to-a-land-based-problem-part-i-2/
 Farley, Robert. “Navy’s record unblemished” June 9th, 2008. Politifact. http://www.politifact.com/truth-o-meter/statements/2008/jun/09/john-mccain/navys-record-unblemished/
 The United States Naval Nuclear Propulsion Program. March 2013. U.S. Department of Energy and U.S. Department of the Navy. https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=7&cad=rja&uact=8&ved=0ahUKEwiss5TYwbrXAhUCbiYKHRmrCSsQFghSMAY&url=https%3A%2F%2Fnnsa.energy.gov%2Fsites%2Fdefault%2Ffiles%2Fnnsa%2F04-14-inlinefiles%2F2014-04-09%25202013_Naval_Nuclear_Propulsion_Program.pdf&usg=AOvVaw3vGd6LnSPWSEqHMWieVdJU
 World Nuclear Association. “Nuclear Power in the USA”. October 2017. http://www.world-nuclear.org/information-library/country-profiles/countries-t-z/usa-nuclear-power.aspx
 Schlissel, David; Biewald, Bruce. Synapse Energy Economics, Inc. “Nuclear Power Plant Construction Costs”. July 2008. https://www.synapse-energy.com/sites/default/files/SynapsePaper.2008-07.0.Nuclear-Plant-Construction-Costs.A0022_0.pdf
 Ferris, Robert. “U.S. watches as Fukushima continues to leak radiation”. CNBC. March 2016. https://www.cnbc.com/2016/03/10/us-watches-as-fukushima-continues-to-leak-radiation.html
 M. A Zoran, R. S. Savastru, D. M. Savastru, S. I. Miclos, M. N. Tautan, L. V. Baschir, “Thermal pollution assessment in nuclear power plant environment by satellite remote sensing data”, Proc. SPIE 8531, Remote Sensing for Agriculture, Ecosystems, and Hydrology XIV, 853120 (19 October 2012); doi: 10.1117/12.974402; http://dx.doi.org/10.1117/12.974402
 California State Lands Commission. “Resolution by the California State Lands Commission Regarding Once-Through Cooling in California Power Plants”. April 2006. http://www.energy.ca.gov/siting/documents/2006-04-13_SLC_PROPOSED_COOLING.PDF
 U.S. Energy Information Administration. “Today in Energy” https://www.eia.gov/todayinenergy/detail.php?id=29492
 Gallup News. “For First Time, Majority in U.S. Oppose Nuclear Energy”. http://news.gallup.com/poll/190064/first-time-majority-oppose-nuclear-energy.aspx?g_source=Politics&g_medium=newsfeed&g_campaign=tiles
 Novak, Matt. “The American Plan to Build Nuclear Power Plants in the Ocean” February 26, 2013. Smithsonian.com. https://www.smithsonianmag.com/history/the-american-plan-to-build-nuclear-power-plants-in-the-ocean-27801262/