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.