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.