Georgia Power now says its 1,100 MW Vogtle Unit 3 nuclear generating facility is now expected to reach initial criticality during February and to be in service in April, a delay from the company’s previous projections .

A filing made January 11 with the U.S. Securities and Exchange Commission blamed the latest delay on vibrations associated with certain piping in the cooling system. The vibrations were detected during the unit’s start-up and pre-operational testing. The plant’s licensee, Southern Nuclear Operating Co., is working to address the vibrations.

The filing said that extending the in-service date beyond the first quarter is estimated to result in additional base capital costs for Georgia Power of up to $15 million pre-tax per month, as well as related allowance for funds used during construction and any additional related construction, support resources, or testing costs.

It said the projected Unit 3 schedule largely depends on the progress of start-up, final component, and pre-operational testing, “which may be impacted by equipment or other operational failures.” The utility said a further update would be provided as part of Southern Company’s February earnings report.

The two AP1000s under construction at Vogtle near Waynesboro are the first new nuclear units to be built in the U.S. in more than three decades. Construction of Vogtle 3 began in March 2013 and unit 4 in November of that year. Southern Nuclear and Georgia Power, both units of Southern Company, took over managing the construction project in 2017 following Westinghouse’s Chapter 11 bankruptcy.

Vogtle Unit 4 is expected to begin hot functional testing by the end of the first quarter.

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