South Texas Nuclear Generating Station

South Texas Project Electric Generating Station
Industry	Nuclear power generation
Founded	1971
Founder	Houston Lighting & Power Co., cities of Austin and San Antonio, Central Power and Light Co.
Headquarters	Bay City, Texas, United States
Area served	Texas, United States
Products	Electricity generation (nuclear power)
Owner	Constellation Energy (44%), CPS Energy (40%), Austin Energy (16%)
Parent	STP Nuclear Operating Company (STPNOC)

Adapted from the English Wikipedia article South Texas Nuclear Generating Station, available under CC BY-SA 4.0Updated 7 August 2025

The South Texas Project Electric Generating Station (STP, STPEGS) is a nuclear power complex situated southwest of Bay City, Texas, United States. Positioned on a site to the west of the Colorado River and approximately southwest of Houston, STP consists of two Westinghouse Pressurized Water Reactor units. The facility utilizes a reservoir for cooling purposes, thereby eliminating the need for conventional cooling towers.

1971–1994

On December 6, 1971, Houston Lighting & Power Co. (HL&P), along with the cities of Austin and San Antonio and Central Power and Light Co. (CPL), initiated a feasibility study to develop a jointly owned nuclear power plant. The initial cost projection was $974 million (equivalent to roughly $4.9 billion in 2015 dollars).

By mid-1973, HL&P and CPL had selected Bay City as the preferred location, with San Antonio joining as a partner shortly thereafter. Brown and Root was contracted as both architect and construction manager. In November 1973, Austin voters narrowly approved their city's participation, with further referendums held to confirm continued involvement.

Construction permits were granted by the Atomic Energy Commission (now the Nuclear Regulatory Commission) in December 1975, allowing immediate commencement of construction. By 1978, the project encountered delays extending two years and significant budget overruns. HL&P responded by replacing management late that year to address these challenges. The 1979 Three Mile Island accident further affected the nuclear industry, leading to revised budgets and timelines. Brown and Root's completion forecast shifted to June 1989, with estimated costs ranging from $4.4 billion to $4.8 billion. Due to inadequate progress, Brown and Root was dismissed as architect/engineer in September 1981 and replaced by Bechtel Corporation; Ebasco Constructors assumed construction responsibilities in February 1982 following Brown and Root’s withdrawal.

In November 1981, Austin authorized the sale of its 16% ownership share but was unable to find buyers.

Unit 1 achieved initial criticality on March 8, 1988, commencing commercial operation on August 25; Unit 2 reached initial criticality on March 12, 1989, entering commercial service on June 19.

Both units were temporarily shut down in February 1993 to repair issues with steam-driven auxiliary feedwater pumps; operations resumed by May 1994.

The completion of STNP is particularly notable given that many nuclear projects initiated during this period were canceled following the Three Mile Island incident.

2006–present

On June 19, 2006, NRG Energy submitted a letter of intent to the NRC proposing construction of two advanced boiling water reactors (ABWRs), each rated at 1,358 MWe, at the South Texas Nuclear Project site. Initial plans did not include partners CPS Energy or Austin Energy.

NRG Energy filed the first U.S. nuclear reactor application since 1979 on September 24, 2007, seeking approval to build two Toshiba ABWRs at South Texas. This expansion would potentially double the site's generating capacity by adding approximately 2,700 MW. Construction costs were initially estimated at $10 billion but were expected to rise to $13 billion after financing costs, according to CPS Energy's interim general manager.

By October 2009, Toshiba informed CPS Energy that expenses could escalate by up to $4 billion. As a result, CPS Energy reduced its ownership share from 50% to 7.625% in 2010 after investing $370 million. This reduction threatened the viability of the expansion project.

In October 2010, Tokyo Electric Power Company (TEPCO) agreed to acquire an initial 9.2375% stake in the expansion from Nuclear Innovation North America—a joint venture between Toshiba and NRG—for $125 million, with an option for additional ownership contingent upon securing U.S. Department of Energy loan guarantees.

On April 19, 2011, NRG announced its withdrawal from the permitting process due to escalating costs and slow regulatory approvals; TEPCO's financial difficulties following the Fukushima disaster also influenced this decision. NRG recorded a $331 million write-off on its investment.

Despite NRG’s withdrawal, licensing efforts continued under NRC oversight as of October 2011. Some preliminary construction activities took place by early 2015 with targeted commercial operation dates set for March 2015 for one unit and one year later for another. The NRC granted combined license approval on February 9, 2016; however, no construction has commenced due to prevailing market conditions and no scheduled start date has been established.

During the Texas power crisis on February 15, 2021, Unit 1 at South Texas Nuclear Generation Station underwent an automatic shutdown triggered by low steam generator levels caused by feedwater pump failures. Units 2 and those at Comanche Peak Nuclear Power Plant remained operational throughout this event.

Electricity generation

Annual output (MWh) from South Texas Project Electric Generating Station

Year

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Total

2001

1,886,321

1,525,367

1,023,965

1,693,902

1,749,601

1,803,826

1,862,368

1,861,391

1,784,413

948,097

1,821,433

1,879,914

19,840,598

2002

1,877,631

1,694,952

1,874,294

1,802,364

1,853,569

1,651,816

1,804,722

1,863,231

1,809,080

961,912

648,839

1,207,192

19,049,602

2003

993,000

858,234

1,167,859

906,020

926,323

897,961

924,414

1,550,300

1,826,511

1,901,587

1,835,032

1,901,300

15,688,541

2004

1,794,208

1,783,984

1,866,066

967,940

1,898,881

1,833,986

1,888,035

1,886,885

1,832,462

1,898,705

1,846,256

1,874,559

21,371,967

2005

1,910,104

1 , 425 , 909

1 , 145 , 000

1 , 347 , 849

1 , 899 , 476

1 , 827 , 979

1 , 882 , 165

1 , 865 , 460

1793 , 374

961 , 783

1812 , 505

1917 , 689

19 ,789 ,293

-

2006

1918 ,500

1734 ,226

1916 ,180

1848 ,924

1902 ,066

1835 ,603

1894 ,140

1889 ,118

1754 ,581

949 ,107

1751 ,295

1974 ,529

21 ,368 ,269

-

2007

1978 ,523

1769 ,752

1631 ,719

1020 ,990

1997 ,207

1913 ,083

1974 ,291

1945 ,127

1911 ,186

1994 ,784

1951 ,698

2020 ,923

22 ,109 ,283

-

2008

2027 ,749

1894 ,252

1857 ,380

1059 ,644

1996 ,808

1911 ,071

1970 ,008

1968 ,743

1883 ,018

1091 ,075 </.small>

<.small>1804 ,680 </.small>

.<.small>.2028 ,.321.</.smal l. .>

21 ,.492 ,.749

2009

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1985 whistleblower incident

In 1985, Ronald J. Goldstein, a supervisor employed by EBASCO—one of the principal contractors for the South Texas nuclear facilities—raised safety concerns through SAFETEAM, an internal compliance initiative jointly managed by EBASCO and Houston Lighting. His report highlighted issues such as breaches of safety protocols, omission of mandatory safety documentation, and quality control deficiencies that compromised plant safety.

Although SAFETEAM was presented as an autonomous channel for reporting safety matters, employees were not made aware that submissions to this program lacked legal safeguards. After Goldstein submitted his complaint, he was terminated and subsequently initiated legal action invoking federal nuclear whistleblower protection laws.

The U.S. Department of Labor determined that Goldstein’s disclosures were protected and declared his termination unlawful; this ruling was affirmed by Labor Secretary Lynn Martin. Nevertheless, the Fifth Circuit Court of Appeals reversed this verdict, concluding that private internal programs did not confer whistleblower protections. This case prompted Congress to revise federal nuclear whistleblower legislation to safeguard reports made through internal mechanisms and to prohibit retaliatory actions.

Ownership

The South Texas Project Electric Generating Station (STPEGS) is managed by the STP Nuclear Operating Company (STPNOC). Ownership stakes are held by Constellation Energy (44%), the municipal utility CPS Energy of San Antonio (40%), and Austin Energy (16%).

Nearby population

The Nuclear Regulatory Commission (NRC) delineates two emergency planning zones around nuclear power plants: a 10-mile radius plume exposure pathway zone addressing airborne radioactive hazards, and a 50-mile ingestion pathway zone concerning contaminated food and water sources.

According to 2010 data, the population residing within 50 miles of the facility totaled 254,049—a growth of 10.2% since 2000—while the population within the 10-mile zone decreased by 2.4% to 5,651 individuals. Cities located within a 50-mile radius include Lake Jackson (approximately 40 miles distant) and Bay City.

Seismic hazard

Based on a 2010 assessment by the NRC, the estimated annual probability of an earthquake intense enough to inflict core damage at the South Texas site is approximately 1 in 158,730.

Reactor specifications

The South Texas Generating Station operates two Westinghouse four-loop pressurized water reactors (PWRs). Plans to add Units 3 and 4, designed as Advanced Boiling Water Reactors (ABWRs), were ultimately abandoned.

Reactor unit	Reactor type	Capacity (MW)		Construction start date	Grid connection date	Commercial operation date	License expiration date
Reactor unit	Reactor type	Net	Gross	Construction start date	Grid connection date	Commercial operation date	License expiration date
South Texas-1	Westinghouse four-loop PWR	1280	1354	22 December 1975	30 March 1988	25 August 1988	20 August 2047
South Texas-2	Westinghouse four-loop PWR	1280	1354	22 December 1975	11 April 1989	19 June 1989	15 December 2048
South Texas-3 (cancelled)	ABWR	1350	1400	License terminated (2018)
South Texas-4 (cancelled)	ABWR	1350	1400	License terminated (2018)

Sources

"Milestones". South Texas Project Nuclear Operating Company. Accessed July 14, 2005.
"CenterPoint Energy Historical Timeline". CenterPoint Energy. Accessed July 14, 2005.

External links

Energy Information Administration