|Fig. 1:The world's first floating nuclear power plant, the United States' MH-1A, on the Sturgis. Source: Wikimedia Commons|
Floating nuclear power stations are low-capacity cogeneration plants that produce a modest amount of heat and power from nuclear fission. Compact reactors and their associated safety, power generation, and cooling systems are placed on barges and towed out to semi-permanent offshore sites. These barges may or may not be self-contained, possibly relying additional oil or coal for propulsion, and can be reused for many years, although occasional nuclear fuel replacement is needed. 
The choice to build floating nuclear power plants, rather than the more standard land-based plants, is driven by economic incentives and geographic considerations.
Floating nuclear power plants provide energy to remote and isolated regions that are otherwise unserviced or expensive to operate, including hard-to-reach coastal towns and offshore fossil fuel facilities. Sergei Kiriyenko, head of Russia's state nuclear agency Rosatom, said, "The floating nuclear power plants make a genuine leap forward from building and running costly electric power lines and maintaining electric power stations". 
One obstacle for land plants is acquiring a large plot of open space for construction and operation, usually ranging from several hundred to several thousand acres per site. Finding this much free land near a population center is not always possible and often very expensive. Additionally, public opposition to nuclear power plants close to residential areas is historically strong, as demonstrated by the NIMBY or "not in my backyard" movement. Offshore plants there provide a solution for finding an available site and resolving NIMBY opposition. 
Manufacturing and operation advantages also support the case for floating nuclear power plants. All land plants must be customized, engineered to be site-specific according to geographic, ecological, and population needs. In contrast, sea-bound power plants can be standardized and mass-produced, reducing engineering and construction costs. Logistical and scientific arguments can also be made in favor of floating plants' efficiency, namely that water for coolant is abundant and close to a reactor floating in water.
|Fig. 2: Scale models of Rosatom's fleet of floating nuclear power plants, including the Akademik Lomonosov. Source: Wikimedia Commons|
Marine-based nuclear power plants possess additional safety and environmental concerns beyond those of traditional land-based plants.
The major safety concerns for floating plants center around the risks of a nuclear accident and subsequent radioactive contamination. When there is meltdown and primary containment has been breached, nuclear fuel may leach from the reactor's core into the surrounding environment. On land, the fuel's high heat would melt the surrounding earth to create a sort of insulation chamber. Contamination by the radioactive fuel would be localized to the region around the plant. If a meltdown were to occur over the ocean, widespread water contamination is likely. For example, the poisonous reactor core could melt through the floating barge into water below or boat damage could cause the plant to capsize. Oceanic contamination would be a global problem, rather than a local one.  Security and protection also is limited on the open seas, leaving the reactors vulnerable to terrorism and harsh environmental conditions, such as tsunamis.
Long-term placement of a floating nuclear facility will likely impact surrounding marine geography and ecology. Anticipated environmental problems include altered sediment deposition patterns in the waters adjacent to the plants, causing abnormal siltation and erosion to shores, deltas, and beaches. The plant's cooling system may also affect the growth and delicate balance of natural flora and fauna by flushing out large amounts of heated water, which alters gas solubility and bacterial growth. Accessory equipment presents similar challenges. For example, large breakwaters could develop into artificial reefs and miles of underwater powerlines may disturb the seabed. 
In 1963, the Martin Marietta Corporation constructed the first floating nuclear power plant, the MH-1A, for the United States Army. Engineers placed a pressurized water reactor and containment vessel in a converted Liberty ship, the Sturgis, as a cost- and time-saving measure. The MH-1A supplied 10 MW power in the Panama Canal Zone from 1968 to 1975, ultimately retiring due to high operating costs and the discontinuation of the Army's nuclear reactor program. 
In 1972, Westinghouse Electric Company and the shipbuilder Tenneco formed the joint operation Offshore Power Systems Corporation (OPS), based in Jacksonville, FL. OPS planned to build nuclear plants on towable barges and station them several miles off the U.S. coast in the Atlantic Ocean, protected by concrete breakwaters. Public Service Electric and Gas Company (PSE&G) hoped to generate electricity with these offshore reactors, but never constructed any due to delays in federal approval, decreased economic incentives as a result of the 1973 oil crisis, and public opinion in the wake of the Three Mile Island accident. 
The Russian state atomic energy agency Rosatom launched the self-contained floating nuclear heat-and-power plant Akademik Lomonosov on June 30, 2010 at St. Petersburg's Baltic shipyard. The world's first mass-produced floating reactor, the Akademik Lomonosov is Rosatom's inaugural marine vessel, although the agency has about a seven similar ships planned for future construction.  The low-capacity plant contains two 150 MW(t) and 38.5 MW(e) KLT-40S nuclear reactors that have an estimated lifespan of 40 years and can power a city of 200,000 people.  Refueling will occur every 3-4 years, where spent nuclear fuel will remain on board until 4-6 sets of spent cores have accumulated, at which time scheduled maintenance will occur.  The Akademik Lomonosov aims to provide power to distant and isolated regions, as well as to offshore oil and natural gas sites in the far north of Russia and Artic seas.  While the floating nuclear plant was placed in category 2 for radioactive danger and meets SP ATES-03 requirements, critics cite Soviet nuclear history--the Chernobyl INES Level 7 disaster and sinking of the nuclear-powered submarine Kursk--as cause for concern over safety. 
© Claire Durkin. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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