Mutsu (ship)

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For the battleship, see Japanese battleship Mutsu.
Career (Japan)
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
Launched: 12 June 1970
Delivered Ōminato, 13 July 1970
Completed: 4 September 1972 (fuel loaded)
Decommissioned: 1992
General characteristics
Class and 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.[citation needed]

Nuclear propulsion tests[edit]

The reactor was completed on 25 August 1972, and fuel was loaded on 4 September.[2] When officials announced that the first test run was to be run at the pier in Ōminato, local protests forced them to reconsider.[2] Eventually it was decided to test the ship in the open ocean, 800 kilometres (430 nmi) east of Cape Shiriya.[2] The ship departed Ōminato on 26 August 1974, and the reactor attained criticality on 28 August.[2]

Radiation accident[edit]

As the crew brought the reactor up to 1.4% of capacity at 5pm on 1 September 1974,[2] there was a minor leak of neutrons and gamma rays[1] from the reactor shielding.[2] Westinghouse had reviewed the design and warned of this possibility, but no changes were made to the design.[2] 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.[2]

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.[2] Following an overhaul, the Mutsu was completed in February 1991.[2] She then completed her original design objective of travelling 82,000 kilometres (51,000 mi) in testing, and was decommissioned in 1992.[2] Over 25 years the programme had cost more than 120 billion yen (about US$ 1.2 billion).[2]

RV Mirai[edit]

The reactor was removed in 1995. After decontamination, the Mutsu was rebuilt as the ocean observation vessel Mirai.[1][3]

See also[edit]

Notes and references[edit]

  1. ^ a b c d OECD Nuclear Energy Agency (2001), Investing in Trust: Nuclear Regulators and the Public : Workshop Proceedings, Paris, France, 29 November - 1 December 2000, OECD Publishing, p. 30, ISBN 978-92-64-19314-7 
  2. ^ a b c d e f g h i j k l Nakao, Masayuki, Radiation Leaks from Nuclear Power Ship "Mutsu" (PDF), Japan Science and Technology Agency (JST)  Good overview of the construction, leak, and lessons learnt.
  3. ^