Mutsu (ship)

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For the battleship, see Japanese battleship Mutsu.
Name: Mutsu
Namesake: City of Mutsu, Aomori
Operator: Japan Atomic Energy Research Institute
Builder: Second Tokyo Factory, Ishikawajima-Harima Hvy Ind
Laid down: 17 November 1968
  • 12 June 1970
  • Delivered Ōminato, 13 July 1970
Completed: 4 September 1972 (fuel loaded)
Decommissioned: 1992
General characteristics
Class & type: Mutsu
Type: Nuclear-powered freighter
Tonnage: 8240 tons
Length: 130 m (430 ft)
Beam: 19 m (62 ft)
Draught: 6.9 m (23 ft)
Depth: 13.2 m (43 ft)
Installed power: 36MW Mitsubishi PWR
Propulsion: steam turbine 10,000 hp (7.5 MW)
Speed: 32 km/h (17 kn)
Range: Nuclear
Crew: 80

Mutsu was Japan's first, and only nuclear-powered ship.[1] It was built as a nuclear merchant ship, one of four such vessels ever constructed, but never carried commercial cargo.[2]

Nuclear propulsion tests[edit]

The reactor was completed on 25 August 1972, and fuel was loaded on 4 September.[3] When officials announced that the first test run was to be run at the pier in Ōminato, local protests forced them to reconsider.[3] Eventually it was decided to test the ship in the open ocean, 800 kilometres (430 nmi) east of Cape Shiriya.[3] The ship departed Ōminato on 26 August 1974, and the reactor attained criticality on 28 August.[3]

Radiation accident[edit]

As the crew brought the reactor up to 1.4% of capacity at 5pm on 1 September 1974,[3] there was a minor leak of neutrons and gamma rays[1] from the reactor shielding.[3] Westinghouse had reviewed the design and warned of this possibility, but no changes were made to the design.[3] There was no significant radiation exposure, but it became a political issue, with local fisherman blocking her return to port for more than 50 days.[1] The government finally came to an agreement with the local government and fishermen; the Mutsu was allowed back to port on condition that it was to find a new home port, and the ship returned to Ōminato on 15 October.[3]

In Sasebo, between 1978 and 1982, various modifications were made to the reactor shield of the Mutsu, and its home port was moved to Sekinehama in 1983.[3] Following an overhaul, the Mutsu was completed in February 1991.[3] She then completed her original design objective of travelling 82,000 kilometres (51,000 mi) in testing, and was decommissioned in 1992.[3] Over 25 years the programme had cost more than 120 billion yen (about US$ 1.2 billion).[3]

RV Mirai[edit]

The reactor was removed in 1995. After decontamination, the Mutsu was rebuilt as the ocean observation vessel Mirai.[1][4]

Mutsu Science Museum[edit]

The reactor room, control room, bridge, bow, and propeller were converted into a museum and are open to the public at the Mutsu Science Museum.[5] Visitors can interact with the controls in the control room and view the reactor vessel through several viewing ports. Reactor room image 1 Reactor room image 2 Reactor vessel through viewing port image Control room image Bridge image

The nuclear material from the ship is stored across the street from the museum at a facility operated by the Japan Atomic Energy Agency.[6]

See also[edit]

Notes and references[edit]