Toshiba 4S

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The Toshiba 4S (Ultra super safe, Small and Simple) is a micro sodium reactor design.

General description

Cross-sectional image of the 4S design

The plant design is offered by a partnership that includes Toshiba and the Central Research Institute of Electric Power Industry (CRIEPI) of Japan.[1]

The technical specifications of the 4S reactor are unique in the nuclear industry.[2] The actual reactor would be located in a sealed, cylindrical vault 30 m (98 ft) underground, while the building above ground would be 22×16×11 m (72×52.5×36 ft) in size. This power plant is designed to provide 10 megawatts of electrical power with a 50 MW version available in the future.[3]

The 4S is a fast neutron sodium reactor. It uses neutron reflector panels around the perimeter to maintain neutron density. These reflector panels replace complicated control rods, yet keep the ability to shut down the nuclear reaction in case of an emergency. Additionally, the Toshiba 4S utilizes liquid sodium as a coolant, allowing the reactor to operate 200 degrees hotter than if it used water.[clarification needed] Although water would readily boil at these temperatures, sodium remains a liquid; the sodium coolant therefore exerts very low pressure on the reactor vessel even at extremely high temperatures.[citation needed]

The Toshiba 4S Nuclear Battery was proposed as the power source for the Galena Nuclear Power Plant in Alaska, but the project was abandoned and Toshiba did not proceed with an application for certification of the design.[4]

See also


  1. ^ Central Research Institute of Electric Power Industry
  2. ^ "Here Come the Japanese Nuclear Reactors". November 5, 2009. New Energy and Fuel. Accessed 3 May 2018.
  3. ^ "Plans for 'small' reactors nudge waste-disposal concerns to fore". Japan Times.
  4. ^ Molly Rettig, "Why nuclear energy is on hold for Alaska", Fairbanks Daily Newsminer, Jan 23, 2011. Accessed 3 May 2018.

External links

  • IAEA Advanced Reactors Information System: 4S
  • NRC overview Official information from Nuclear Regulatory Commission
  • Atomic Insights article information about the reactor, its specifications, and engineering aspects and challenges.
  • ROE: Technical details about the 4S planned for Galena, Alaska.
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