The AP1000 is a nuclear power plant designed and sold by Westinghouse Electric Company. The plant is a pressurized water reactor with improved use of passive nuclear safety and many design features intended to lower its capital cost and improve its economics. The design traces its history to the System 80 design, which was produced in various locations around the world. Further development of the System 80 initially led to the AP600 concept, with a smaller 600 to 700 MWe output, but this saw limited interest. In order to compete with other designs that were scaling up in size in order to improve capital costs, the design re-emerged as the AP1000 and found a number of design wins at this larger size. Six AP1000s are currently in operation or under construction. Four are located at two sites in China, two at Sanmen Nuclear Power Station and two at Haiyang Nuclear Power Plant. Two are under construction at the Vogtle Electric Generating Plant in the US. , all four Chinese reactors were completed and connected to the grid. Construction at Vogtle has suffered numerous delays and Unit 3 is now expected to be completed in 2022. Cost overruns at Vogtle and V.C. Summer led to Westinghouse's bankruptcy in 2017. Construction of the two reactors at the Virgil C. Summer Nuclear Generating Station was cancelled in 2017 following Westinghouse's bankruptcy. As of July 2021, China is the sole operator of this reactor design and currently developing more advanced versions and owns their patent rights. The first AP1000 began operations in China at Sanmen, where Unit 1 became the first AP1000 to achieve criticality in June 2018, and was connected to the grid the next month. Further builds in China will be based on the modified CAP1000 and CAP1400 designs. History Previous work The AP1000 design traces its history to two previous designs, the AP600 and the System 80. The System 80 design was created by Combustion Engineering and featured a two-loop cooling system with a single steam generator paired with two reactor coolant pumps in each loop that makes it simpler and less expensive than systems which pair a single reactor coolant pump with a steam generator in each of two, three, or four loops. Three completed reactors in the US and another four in South Korea made it the most successful Generation II+ design. ABB Group bought Combustion Engineering in 1990