2006–present
On June 19, 2006, NRG Energy filed a letter of intent with the NRC to build two 1,358-MWe advanced boiling water reactors (ABWRs) at the South Texas Nuclear Project site.[14] South Texas Nuclear 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 an application with the NRC to build two Toshiba ABWRs at the South Texas Nuclear Project site.[14] It was the first application for a nuclear reactor submitted to the NRC since 1979. The proposed expansion would generate an additional 2700 MW of electrical generating capacity, which would double the capacity of the site.[15] 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 had informed CPS Energy that the cost would be "substantially greater," possibly up to $4 billion more. As a result of the escalating cost estimates for units 3 and 4,[16] 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 (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 500 MW of generation capacity). The agreement was made conditional upon STNP securing construction loan guarantees from the United States Department of Energy.[17][18][19]
On 19 April 2011, NRG announced in a conference call with shareholders, that they had decided to abandon the permitting process on the two new units due to the ongoing expense of planning and slow permitting process. Anti-nuclear campaigners alleged that the financial situation of new partner TEPCO, combined with the ongoing Fukushima nuclear accident were also key factors in the decision.[20] NRG has written off its investment of $331 million in the project.[21]
Despite the April 2011 NRG announcement of the reactor's cancellation, the NRC continued the combined licensing process for the new reactors in October 2011.[22] It was unclear at the time why the reactor license application was proceeding. During early 2015 some pre-construction activities were performed on site and initial NRC documents listed the original targeted commercial operational dates as March 2015 for unit 3 and a year later for the other unit.[23] On February 9, 2016, the NRC approved the combined license.[24] Due to market conditions, no construction events occurred at that time. The two planned units do not currently have a planned construction date.[25]
On February 15, 2021, during a major power outage that impacted much of the state of Texas, an automatic reactor trip shut South Texas Nuclear Generation Station Unit 1 due to low steam generator levels. According to a Nuclear Regulatory Commission report, the low steam generator levels were due to loss of feedwater pumps 11 and 13. However, Unit 2 and both units at the Comanche Peak Nuclear Power Plant remained online during the power outage.[26]
