Mutsu (nuclear ship)

History
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.^[2]

Nuclear propulsion tests

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

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

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

Mutsu Science Museum

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.^[2]

See also

• NS Otto Hahn (Germany)
• NS Savannah (USA)
• NS Sevmorput (Russia)
• Mutsu, Aomori

Notes and references

1. 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. http://www.iaea.org/inis/collection/NCLCollectionStore/_Public/27/029/27029493.pdf
3. 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.
4. "MIRAI < Research Vessels and Vehicles < Research Vessels, Facilities and Equipment < About JAMSTEC < JAMSTEC". Jamstec.go.jp. Retrieved 2016-07-17.
5. "むつ科学技術館のホームページへようこそ！！". Jmsfmml.or.jp. Retrieved 2016-07-17.