History and present of floating nuclear power plants

In around two years, Russia's first floating power plant, Akademik Lomonosov, is due to enter operation. The vessel with two reactors is being completed, while the necessary infrastructure for mooring the plant is being built in the town of Pevek in Chukotka. Let us therefore look at the history and present of these facilities.

The first floating nuclear power plant

The first floating nuclear power plant, MH-1A, was built in the United States in the 1960s and operated aboard the Sturgis, a vessel named after General Samuel D. Sturgis Jr. The vessel had no engines of its own, as it was expected to remain moored most of the time. It was transported by tugboat. A pressurised water reactor using low-enriched uranium containing 4 to 7% uranium-235 isotope was installed in a converted Liberty ship. The floating power plant was the result of a programme to develop small, compact mobile reactors for producing electricity and heat in relatively inaccessible areas.

Development of the reactor was launched by Martin Marietta in 1961, while physical construction itself began in 1963. It took place at Fort Belvoir, where work on compact small reactors was under way. The first fission chain reaction occurred on 24 January 1967. The plant then supplied electricity to Fort Belvoir in test mode for a further 11 months.

After the tests were completed, it was moved to the Panama Canal Zone, where it supplied 10 MW of electricity on Gatun Lake. The plant operated there from October 1968 until 1975, supplying electricity for the needs of the Panama Canal Zone. It helped ensure optimal water management at a time when water was scarce in the canal and the lakes used by it. During this period, the fuel in the reactor core was replaced five times.

In 1975, the military reactor development programme ended, and MH-1A, as a unique development prototype, had excessively high operating costs. At the same time, the Panama Canal Zone had acquired sufficient onshore electricity generation capacity. Its operational deployment therefore ended, and the MH-1A plant was decommissioned in 1976. At the turn of 1976 and 1977, it was moved back to the United States. The spent fuel was removed there. The plant was partially decontaminated and placed in a condition in which it could await final disposal. Full dismantling of both the reactor and the vessel then began in 2014 and was due to be completed in 2018. Once all contaminated components have been removed, the remaining parts will be processed in the same way as other retired vessels.

Akademik Lomonosov floating power plant

A second attempt to put floating nuclear power plants into practical use is now under way. A floating power plant that is intended to be the first in a series of such facilities is being completed in Russia. They are intended to help supply electricity and heat to remote and difficult-to-access areas where other sources are difficult to build. These are mainly areas of Siberia, especially the Far North and the Far East. Nearly two-thirds of Russia's territory lies in the permafrost zone, where it is very difficult to locate energy facilities, transmission systems or pipelines. The floating units are intended to supply local settlements and drilling rigs. Another potential use for the plants is in isolated locations lacking drinking water, where they could be used to desalinate large volumes of seawater.

Development of the floating power plant began at the start of the 21st century. The first unit, named Akademik Lomonosov, began construction in 2007 at the Sevmash shipyard in Severodvinsk, Arkhangelsk Oblast. In 2008, however, construction of the vessel was moved to the Baltic Shipyard in St Petersburg. Further vessels are also expected to be built there. Construction of the second is due to begin in 2019.

The plant has two KLT-40S reactors. Each can provide 150 MW of thermal output and 35 MWe of electrical output, or produce 240 000 m³ of water per day through desalination. This is a variant of the pressurised water reactor used on Russian icebreakers and the container ship Sevmorput. Icebreakers and the container vessel use the KLT-40M and KLT-40 variants, with very highly enriched uranium-235 isotope, either 30-40% or even 90%. The Akademik Lomonosov plant uses fuel with low enrichment of 14%. Overall, the floating power plant is expected to operate for 35 to 40 years. Fuel will be replaced every seven years. For refuelling, the vessel must be towed to its home facility, where the necessary inspection, maintenance and replenishment of supplies will also be carried out. Floating power plants could therefore be swapped at a given location.

Later modifications are also expected to use other reactors, smaller or larger as needed. The vessel itself is 140 m long, 30 m wide and has a displacement of 21 000 tonnes. The floating nuclear power plant is designed to withstand tsunamis and other natural disasters. The nuclear facility meets all requirements of the International Atomic Energy Agency. It is currently being commissioned and its basic mechanisms and equipment are being tested.

The Akademik Lomonosov vessel is a reference and test unit. Further units will be built based on experience from its construction and operation. Only serial production will ensure the required parameters, especially economic ones. The overall economics of the project will depend on the number of units produced, which is why Rosatom is seeking customers to purchase them abroad as well.

The first unit will be located in the town of Pevek in Chaun District in the Chukotka Autonomous Okrug. Construction has already begun there on auxiliary facilities for mooring the floating power plant and the connections needed to transmit electricity and heat ashore. Akademik Lomonosov will replace the capacity of the Bilibino nuclear power plant and Chaun thermal power plant, which currently supply the area with energy. Both plants are nearing the end of their service lives and must be shut down in the coming years.

The Bilibino nuclear power plant was built at the turn of the 1960s and 1970s in the town of Bilibino and comprises four small EGP-6 units. These are graphite-moderated, light-water-cooled reactors, each providing 12 MWe of electrical output. The reactors are also designed to supply heat, making their thermal output of 62 MW important. Depending on demand, the plant can focus more on supplying either electricity or heat. They were commissioned successively between 1974 and 1976. Their gradual shutdown is planned between 2019 and 2021. The plant currently supplies nearly 80% of electricity in the Chaun-Bilibino power grid. Its replacement is to be provided by the Akademik Lomonosov floating power plant, which is due to enter operation in 2019.

China joins in

China in particular is following developments in this field in Russia with considerable interest. China would like to use mobile nuclear power plants to supply drilling rigs in offshore oil and gas extraction areas along its coast. It had considered a possible purchase of, or cooperation on, Russian designs. Recently, however, it has begun work on its own project, and construction of a demonstration Chinese floating power plant was launched at the end of November; it is due to be completed in 2020. CNG has begun manufacturing the ACPR50S reactor, while conceptual and design work has already been completed. The safety parameters of this reactor, based on passive principles, have already received a positive assessment from the International Atomic Energy Agency. The reactor is expected to have thermal output of 200 MW and electrical output of 60 MWe. The competing company CNNC is also developing a floating nuclear power plant, using the ACP100S reactor design with electrical output of 100 MWe. Both of the aforementioned small modular reactors are pressurised water reactors and are also planned for use on land. The two state-owned companies recently signed cooperation agreements in this field.

It is clear that a turning point is under way in the production of small modular reactors for use in floating nuclear power plants. The success of the new attempt to deploy them will depend mainly on how well they perform in operation and how many find applications. The development of these facilities could also represent a breakthrough in the use of small modular reactors more generally.

Cover photo: Concept of the appearance of a future floating nuclear power plant proposed by Chinese company CGN (Source: CGN)