The scope of nuclear civil vessels includes the following three types of vessels:

  1. Nuclear Merchant Ships;
  2. Nuclear Icebreakers; and
  3. Nuclear Cruise Ships.

This chapter is dedicated to Nuclear Merchant Ships.


A nuclear merchant ship, which is, powered by a nuclear reactor, is a civilian commercial ship that transports cargo and passengers.  There have been only the following four nuclear merchant ships ever built by four different countries in the world:

1.1      The USA Nuclear Merchant Ship – NS Savannah:

The world’s first nuclear powered merchant ship, the NS Savannah (Figure 10/1), is owned and maintained by the Maritime Administration and is licensed and regulated by the United States Nuclear Regulatory Commission.


Administration was charged with the responsibility for promoting the development and maintenance of an adequate, well-balanced United States merchant marine, sufficient to carry the nation’s domestic waterborne foreign commerce, and capable of serving as a naval and military auxiliary in time of war or natural emergency. The Maritime Administration also seeks to ensure that the United States maintains adequate shipbuilding and repair services, efficient ports, effective inter-modal water and land transportation systems, and reserve shipping capacity for use in time of national emergency.

The Maritime Administration an agency of the US Department of Transportation which was organized as a part of the Department of Commerce until 1983. The Maritime Administration has an excellent reputation for constructing, owning, operating, and maintaining merchant ships since its inception in 1916.

In this capacity the Maritime Administration was acutely aware of the fact that the merchant ship industry was faced with the following two major challenges in the 1950s:

  • Large passenger liners were phenomenal oil burners, consuming 50 tons per hour at high speed which represented a significant operating cost;
  • Fast cargo ships, like those used to transport perishable items were not as large or powerful, but they could consume 10-20 tons per hour which was not only expensive from the current standards but these ships were also limited to short trips because of the fact that these ships didn’t have enough fuelling space on board to support longer trips.


Based on the extensive research on the subject and from a strategic point of view, the Maritime Administration was convinced that powering merchant ships with nuclear energy is the answer to overcoming those shortfalls and prospering in the future as:

  • The cost of nuclear fuel was significantly less than bunker fuel; and
  • The ability of nuclear powered ships to use concentrated nuclear fuel will allow fuel supplies to last for many years.

President Dwight D. Eisenhower in his speech before the Associated Press in New York, on April 25, 1955, announced plans for a nuclear powered merchant ship. The ship would be, based on specifications developed by the Atomic Energy Commission and the Maritime Administration that he would submit to Congress.

The success of the USA Navy in 1955 with the USS Nautilus (CCN571), the world’ first nuclear submarine was a testimony to the hypothesis of nuclear engines for civilian ships as a natural extension to the nuclear submarine. This was indeed a mammoth encouragement for the Maritime Administration, to proceed with the plans to deploy nuclear reactors for powering commercial vessels.

Authorization to build the ship was, given by Congress on July 30, 1956 through public law 848 Chapter 792.

The N.S. Savannah was, designed by George G. Sharp, Inc. of New York and was, built by the New York Shipbuilding Corporation of Camden, New Jersey. The Babcock and Wilcox Company of Lynchburg, Virginia, as prime contractor for the power plant designed and built the 74 maximum power thermal megawatt pressurized water reactor. The world’s first nuclear ship Savannah was, commissioned in 1962.

Savannah was, designed to carry 9,400 tons of cargo, 60 first class passengers and 124 crew.  It was capable of cruising at 21 knots and traveling 336,000 miles on a single fuel load.

Savannah is a nuclear merchant ship of combined passenger and cargo design. Savannah was equipped with 30 air-conditioned staterooms, each with an individual bath, a dining facility that could seat 100 passengers, and a lounge that could double as a movie theatre, a veranda, a swimming pool and a library. Savannah was, designed to be visually impressive. The hull was, streamlined to look more like a luxury yacht than a bulk cargo vessel. Savannah steamed in excess of 450,000 nautical miles; called at more than 70 foreign and domestic ports and was, visited by more than 1.5 million people.

The core objectives of the Savannah program were to:

  • Demonstrate to the world the peaceful use of atomic power;
  • Demonstrate the feasibility of nuclear powered merchant ships;
  • Establish international recognition and acceptance of peaceful nuclear power; and
  • Establish an infrastructure in the marine industry to support operations by nuclear powered merchant ships.

The characteristics of Savannah include the following:

  • Savannah met all the objectives including the technical feasibility of nuclear propulsion for merchant ships but it was not, expected to be commercially competitive. However, financial pressures due to the Vietnam War and the implementation of the Merchant Marine Act of 1970 programs led to the decision to decommission Savannah in 1971.

1.2     The Japanese Nuclear Cargo Ship – NS Mutsu:

The first Japanese nuclear powered merchant ship, Mutsu, was, put to sea for the experimental voyage in 1974 at 800 km east of cape Shiriya in Aomori. Mutsu was, built as a prototype commercial ship for transporting special cargos and training crew.


Through the shipbuilders’ Association of Japan, the hull was, commissioned to Ishikawajima-Harima Heavy Industries Co. Ltd. and the reactor to Mitsubishi Atomic Power Industries, Inc. Ishikawajima-Harima Heavy Industries started construction of the hull at its Second Tokyo Factory on November 17, 1968. The hull of Mutsu was, launched on June 12. It was, delivered, to registered port of Ohminato, at Mutsu Bay on July 13, 1970.

The reactor was, completed on August 25, 1972 and nuclear fuel was loaded on September 4, 1972. The officials announced the test run of the ship where the reactor was to be, operated at low output. The local fishermen and inhabitants protested against this experiment and as a result, the test was postponed. After several negotiations, the government, the Japan Ship Development Agency and the local community agreed to test the ship away in the outer sea.


On August 26, 1974, the ship left the port of Ohminto. On August 28, the ship’s reactor attained criticality for the first time in the testing area 800 km east of cape Shiriya in Aomori.

At around 17:00 on September 1, the alarm went off as it detected an increase in radiation when its crew brought the reactor up to 1.4 percent of full capacity. The reactor was, shut down before contamination became serious.

Mutsu underwent lengthy repairs from 1978 to 1982 at the port of Sasebo.

Mutsu was, completed in February 1991, after number of experiments and thorough overhaul in the Sekinehama Mooring port, its mother port since 1983. It was designed to travel 82,000 km (Circles the earth twice) with the reactor using 42.g of uranium-235 as fuel (5,000 t if petroleum). After accomplishing the objective, Mutsu was, decommissioned in 1992.

1.3 The Russian Nuclear Cargo Ship – Sevmorput:

The name of the vessel, Sevmorput (Figure 10/4), is a Russian abbreviation of Severny Morskoy Put, i.e. the Northern Sea Route. It is a nuclear powered cargo ship with icebreaking ability, which is still operating under nuclear power. It was built at Kerch ship building plant in period from June 1, 1982 to December 31, 1988 with the objective mainly to serve northern Siberian ports.


The project was designed based on joint decision of the Ministry of Marine Fleet and Ministry of Ship Building N C-13/01360 dated May 30, 1978, according to the specifications. It is classified as a Lash-Carrier hauling lighters and container cargo. 

The body of the vessel was designed and built with the ice reinforcement “ULA” category according to the requirements of the Register Rules of the USSR, 1981. It has been operating with respect of domestic and international rules, conventions, and norms, including:

  • IMO Code on Safety of Nuclear Powered Freight Vessels;
  • International Convention on Safety of Nuclear Powered Freight Vessels;
  • Norms of radiation safety;
  • Rules of nuclear safety; and
  • Main sanitary regulations.

Since the commissioning of Sevmorput in December 31, 1988, it has made 302,000 miles, carried more than 1.5 million tons of cargo. It is a 61,900 tonne 260 m long, LASH-carrier (taking lighters to ports with shallow water) and container ship with ice-breaking bow. It is powered by the same KLT-40 reactor as used in larger icebreakers, delivering 32.5 propeller MW from the 135 MWt reactor and it needed refueling only once to 2003.


The purpose of the ship was to transport:

  • LASH type lighters in the specially provided cells in the bilge and on the main deck, loaded and unloaded by ship lighter cranes; and
  • International ISO standard containers in the bilge and on the main deck without special rearrangement of the ship.

Load/unload is carried out by coastal means. Limited lots can be loaded and unloaded with container add-ons of the lighter crane. Total number of lighters to be taken aboard 74 of 300 tons each or 1,328 of 20ft containers.

Here are the characteristics of Sevmorput:

  • Owned and operated by the Murmansk Shipping Company, Sevmorput serves along the Northeast Passage for which she is equipped with an icebreaking bow. Sevmorput is capable of breaking ice up to 1 meter thick (1.2 meters according to this source); and
  • As of August 2007 Sevmorput was, being, converted into the world’s first nuclear-powered oil drilling vessel. The conversion was expected to take only 18 months.

1.4     The German Nuclear Cargo Ship – Otto Hahn:

The German-built 15,000 tonne Otto Hahn cargo ship (Figure 10/7) and research facility sailed some 650,000 nautical miles on 126 voyages in 10 years without any technical problems. It had a 36 MWt reactor delivering 8 MW to the propeller.


Planning of a German-built trade and research vessel to test the feasibility of nuclear power in civil service began in 1960. Otto Hahn’s keel was, designed in 1963 by Howaldtswerke Deutsche Werft AG of Kiel. It was commissioned in 1964 and named in honour of Otto Hahn, the German chemist and Noble prizewinner who was credited with the discovery of nuclear fission of uranium in 1938. The first captain of the Otto Hahn was Heinrich Lehmann-Willenbrock, a famous German U-Boat ace of World War II.

In 1968, the ship’s 38-megawatt nuclear reactor was, taken critical and sea trials began. In October of that year, NS Otto Hahn was, certified for commercial freight transport and research.

Otto Hahn was, designed to carry passengers and ore; it made her first port call in Safi Morocco loading a cargo of phosphate ores in 1970. In 1972, after four years of operation, her reactor was, refueled.

The Otto Hahn was, deactivated in 1979 and between 1979 and 1982; her nuclear propulsion equipment was removed and replaced with standard marine diesels. In 1983, the Otto Hahn was recommissioned as the contained ship MS Trophy and leased into commercial marine service. The ship was subsequently renamed MS Norasia Susan (1983), MS Norasia Helga (1985), MS Hua Kang He (1989), MS Anais (1998), and MS Madre (1999).

Her last owner, from 2006, was the Liberian-based Domine Maritime Corporation, under the management of Alon Maritime Corporation of Athens, Greece. The ship was, scrapped at Alang, India in 2009.

Here is a graph, which illustrates the characteristics of Otto Hahn:


1.5     The Future of Nuclear Merchant Ships:

Environmental concerns and long term economic advantages are raising the possibility of nuclear energy being used as the main means of propulsion on cargo ships; the \international Maritime Organization’s ( IMO) increasing thrust on controlling emissions from ships is making technocrats reconsider various business models that will make the idea palatable. Marine and energy consultants BMT Group and Enterprises Shipping and Trading have joined with start-up small reactor firm Hyperion and the Lloyd’s Register. They will “investigate the practical maritime applications for small modular reactors,” says World Nuclear News, a service supported by the World Nuclear Association and one that covers nuclear power developments.

“We will see nuclear ships on specific trade routes sooner than many people currently anticipate,” it quotes Lloyd’s Register CEO Richard Sadler as saying. Lloyd’s Register has now reportedly redrafted its rules for nuclear ships and submitted the draft to its technical committee. Vince Jenkins of the organization says, however, “National maritime regulators have little nuclear capability, so land based nuclear regulators will be needed in support. Our nuclear powered ship rules have suggested a framework which may allow nuclear powered shipping to operate”.

There are some issues, the main one being the lack of acceptability of nuclear power driven merchant ships by Port States. The technical requirements of radiation shielding, crew training and the cost of setting up a nuclear plant on a ship- with additional grounding, collision, fire and such risks- will undoubtedly be other major factors that will have to be considered, even though fuel savings will make the cost worthwhile in the long term. Another advantage: there would also be no need of slow steaming to save on fuel or to control emissions, as is the case today.

The Industry is already reported to be toying with various commercial models using nuclear power and making initial evaluations. It is possible, for example, that two countries agree to use a specific nuclear powered vessel for a port-to-port service. On bulk carriers that are part of a ‘moving pipeline’, fewer and faster ships, thus defraying initial capital costs somewhat, could move large volumes.

Another interesting variation of this is the ‘Supertug’ concept, where a nuclear powered tug attaches itself to a conventional ship for the sea voyage, thus saving on fuel costs and making the passage emission free. It then stays in international waters while the ship steams in on her diesel engines into the port, reattaching itself again for the return voyage.

Analysts say that a luxury liner-which has the power demand curve of a small town would be an ideal ship to use nuclear systems with conventional diesel generators being used for back up and to handle ‘peak load’. However, this is unlikely to happen in a hurry, given the stiff resistance that will probably be faced from passengers and ports both.

These are early days and the debate on the possibility of nuclear powered merchant ships- a controversial idea, to be sure- is just beginning. One cannot help thinking that this road is likely to be a rough one. Perhaps some countries will promote these ships on their domestic routes first, hopefully after stringent regulation.

The bottomline is that the current research into the viability of nuclear merchant ships is considering the technical feasibility, public attitudes, commercial prospects and regulatory requirements and while it may not result in immediate developments, there is a certain amount of optimism that a nuclear powered merchant ship might be considered feasible.


  1. Nuclear Ship Savannah,      Public Information Meeting;
  2. AAE: Nuclear Power for      Commercial Ships;
  3. World Nuclear      Association: Nuclear-Powered Ships;
  4. Wikipedia: Nuclear Marine      Propulsion;
  5. Radiation Leaks from Mutsu;
  6. Sevmorput: Nuclear Container      Ship; and
  7. Wikipedia: Otto Hahn.
  • This chapter was published on “Inuitech – Intuitech Technologies for Sustainability” on January 18, 2011; and
  • This chapter was updated on 12 June 2020.

Chapter 11