The South Texas Project Electric Generating Station (STPEGS, South Texas Project or STP), is a nuclear power station southwest of Bay City, Texas, United States. The STP occupies a 12,200 acre (49 km²) site on the Colorado River about 90 miles (145 km) southwest of Houston. It consists of two Westinghouse Pressurized Water Reactors and is cooled by a 7,000-acre (28 km²) reservoir, which eliminates the need for cooling towers.

South Texas Project Electric Generating Station was the first nuclear power plant in Texas, beginning operation in 1988. In 1996, the two South Texas units were two of the top 20 electricity-generating nuclear units worldwide.

STP is unique in its design of the safety systems for the reactors. Each unit has three, rather than the customary two, fully independent emergency core-cooling systems (ECCS) and associated support systems. However the addition of the third safety train was not fully recognized and credited by nuclear safety regulations during the plant licensing process. The third ECCS system provides significant real-risk reduction, and the utility undertook efforts to gain regulatory recognition of these features. These efforts led in part to the plant's engineering staff becoming early industry leaders in analytical risk modeling and real-time risk management during operations and maintenance activities.

Ownership

The South Texas Project Electric Generating Station reactors are operated by the STP Nuclear Operating Company (STPNOC). Ownership is divided among NRG Energy at 44 percent, San Antonio municipal utility CPS Energy at 40 percent and Austin Energy at 16 percent.

Future expansion of South Texas Nuclear Generating Station

On June 19, 2006 NRG Energy filed a Letter Of Intent with the Nuclear Regulatory Commission to build two 1,358-MWe Advanced Boiling Water Reactors (ABWRs) at the South Texas Project site. South Texas Project Partners CPS Energy and Austin Energy were not involved in the initial Letter of Intent and development plans.

On September 24, 2007, NRG Energy filed a full application with the NRC to build two Toshiba ABWRs at the South Texas Project site. This was the first full application to be submitted to the NRC since the year 1979. This proposed expansion of the South Texas Project will generate an additional 2,700 MW of electrical generating capacity, which will ultimately double the capacity of the current site. The total estimated cost of constructing the two reactors is $10 billion, or $13 billion with financing, according to Steve Bartley, interim general manager at CPS Energy.

In October 2009 main contractor, Toshiba, has informed CPS Energy that cost would be "substantially greater," possibly up to $4 billion more. As a result of the escalating cost estimates for units 3 and 4, in 2010 CPS Energy reached an agreement with NRG Energy to reduce CPS's stake in the new units from 50% to 7.625%. To that point, CPS Energy had invested $370 Million in the expanded plant. CPS Energy's withdrawal from the project put the expansion into jeopardy.

In October 2010, the South Texas Project announced that the Tokyo Electric Power Company, or TEPCO, had entered into an agreement with Nuclear Innovation North America (a joint venture between the reactor manufacturer, Toshiba, and plant partner NRG Energy) which was the largest of the two stakeholders in the proposed reactors, to purchase an initial 9.2375% stake in the expansion for $125 Million, and $30 Million for an option to purchase an additional stake in the new units for $125 Million more (resulting in approximately 18% ownership by TEPCO, or 500MW of generation capacity). The agreement was made conditional upon STP securing construction loan guarantees from the United States Department of Energy.