May 21 (Reuters) - U.S. energy company Southern Co has delayed the startup of the third reactor at its Vogtle nuclear plant in Georgia to the first quarter of 2022, from December 2021, due to problems found during testing, according to analysts and local media.
Analysts at Mizuho Group said Friday that Southern interrupted "hot functional testing" due to vibration of the plant's pressurizer.
The Atlanta Journal-Constitution reported that the company told state regulators about the delay earlier this week.
Officials at Southern were not immediately available for comment.
Southern, which only last month announced Unit 3's delay from its regulatory-approved November 2021 in-service date to December 2021, has said it remains on track to put the fourth reactor at Vogtle into service between August 2022 and its regulatory-approved November 2022 in-service date.
The two units at Vogtle are the only big nuclear reactors under construction in the United States.
When Georgia utility regulators approved the Vogtle expansion in 2009, the two 1,117-megawatt Westinghouse AP1000 reactors were expected to cost about $14 billion and enter service in 2016 and 2017.
But some analysts estimate costs have ballooned to more than $25 billion due to delays related to the nuclear accident at Japan's Fukushima plant in 2011 and the 2017 bankruptcy of Westinghouse, the project's former lead contractor.
Delays and cost overruns in building reactors could make it difficult for new nuclear facilities to play much of a role in the Biden administration's plan to get all of the nation's power from non-carbon-emitting sources like nuclear and renewables by 2035.
Southern has estimated the capital cost for its 47.5% share of the new Vogtle reactors would be about $8.8 billion. Southern has already spent about $7.6 billion as of March 31.
In addition, the company has estimated its construction financing costs at around $3 billion.
(Reporting by Scott DiSavino; Editing by Susan Fenton)