Jōyō (nuclear reactor)

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Experimental Fast Reactor Jōyō
Made based on National Land Image Information (Color Aerial Photographs), Ministry of Land, Infrastructure, Transport and Tourism

Jōyō (常陽) is a test sodium-cooled fast reactor located in Ōarai, Ibaraki, Japan, operated by the Japan Atomic Energy Agency. The name comes from the previous country name of the area around Ibaraki.

It was made with the purpose of doing tests on and advancing the development of that type of reactor, as an irradiation test facility for construction materials. It also does tests with the nuclear fuel as well as activation experiments.

The reactor has gone through 3 different core changes.

  • MK-I April 24, 1977 - January 1, 1982 (the power was 50-75 MWt)
  • MK-II November 22, 1982 - September 12, 1997. This core surpassed 50,000 hours of operating time with 100 MWt.
  • MK-III July 2, 2003–2007 (140-150 MWt).

The current core provides the neutron flux of 4×1015 cm−2s−1 for E>0.1 MeV.

After an incident in 2007, the reactor is suspended for repairing, recovery works were planned to be completed in 2014.

Following the closure of the unsuccessful follow-on fast breeder reactor Monju in 2016, a decision was made to continue research at Jōyō.[1]

See also[edit]


  1. ^ "Japan to continue fast reactor development without Monju". Nuclear Engineering International. 4 October 2016. Retrieved 29 December 2017.

External links[edit]

Coordinates: 36°16′05″N 140°33′15″E / 36.268039°N 140.554093°E / 36.268039; 140.554093