page_title: Fukushima Daiichi Nuclear Power Plant
section_title: The nuclear reactors
hierarchical_section_title: Fukushima Daiichi Nuclear Power Plant / The nuclear reactors
caption_attribution_description: English: Rough sketch of a typical Boiling water reactor (BWR) Mark I Concrete Containment with Steel Torus, as used in the BWR/1, BWR/2, BWR/3 and some BWR/4 model reactors. DW = Drywell WW = Wetwell SF = Spent fuel pool Deutsch: Schema eines Siedewasserreaktors (SWR) der Baulinie Mark I mit Sicherheitsbehälter aus Beton und torusförmiger Kondensationskammer aus Stahl, wie sie auch in Reaktoren der Baulinie SWR/1,SWR/2, SWR/3 und in einigen der Baulinie SWR/4 vorkommen. DW = Druckkammer WW = torusförmige Kondensationskammer SF = Abklingbecken Français&#160;: Diagrame/coupe d'un réacteur à eau bouillante (REB) typique de type Mark I à enceinte de confinement en béton avec tore d'acier sous-jacent, tel qu'utilisé dans les réacteurs de type REB/1, REB/2, REB/3 et certains REB/4. DW = enceinte sèche. WW = enceinte humide de "suppression de pression" de forme torique. SF = piscine de combustible usé.
context_page_description: Fukushima Daiichi Nuclear Power Plant is a disabled nuclear power plant in the town of Ōkuma in Fukushima Prefecture, Japan. Fukushima Daiichi was the first nuclear power plant to be built and run only by the Tokyo Electric Power Company.
  In March 2011 there were nuclear emergencies at the power plant and some other Japanese nuclear facilities, which raised questions about the future of nuclear power. Following the Fukushima nuclear disaster, the International Energy Agency halved its estimate of additional nuclear generating capacity to be built by 2035.
context_section_description: The nuclear reactors for units 1, 2, and 6 were supplied by General Electric, those for units 3 and 5 by Toshiba, and unit 4 by Hitachi. The architectural design for the General Electric's units was done by Ebasco. All of the building work was done by Kajima.  Since September 2010, unit 3 has been fueled by MOX fuel|mixed-oxide (MOX) fuel.  Units 1–5 had/have a Mark 1 type (light bulb shaped torus) containment structure, unit 6 has Mark 2 type (over/under) containment structure.
  Unit 1 is a 439 MW boiling water reactor (BWR3) constructed in July 1967. It started to commercially make electricity on March 26, 1971, and was planned to shutdown in March, 2011. It was damaged during the 2011 Sendai earthquake and tsunami.  The reactor had high atomic and earthquake safety levels when it was made, but it is now both old and out of date. No one knew such a bad earthquake could happen in Japan. Unit 1 was designed for a earthquake peak ground acceleration shaking motion of 0.18 g (1.74 m/s²) and a seismic response spectrum based on the 1952 Kern County earthquake.  All units were inspected after the 1978 Miyagi earthquake when the seismic ground acceleration was 0.125 g (1.22 m/s²) for 30 seconds, but no damage to the critical parts of the reactor was discovered.
caption: A panning type typical BWR Mark I Containment, as used in units 1 to 5.
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