Plant owner Georgia Power said the successful completion of testing was another critical milestone along the path to bringing online the first new nuclear units in the US for more than 30 years.
The two Westinghouse Generation III+ AP1000 plants at Vogtle are the only two commercial reactor units under construction in the US.
During cold hydrostatic testing the reactor coolant system was filled with water and pressurised above normal operating conditions, then lowered to normal design pressure while inspections took place to verify systems met design standards. This included checking that welds, joint pipes and other components did not leak under pressure.
Chris Womack, chief executive officer and chairman of Georgia Power, said: “These units are a long-term investment for our state and essential to building the future of energy for Georgia.”
In October, Georgia Power began loading fuel into the reactor core of Vogtle-3 with the unit expected to enter service in the first quarter of 2023.
The in-service date for Vogtle-3 when the project was approved in 2012 was 2016, but the project has seen a number of delays and cost overruns.
Southern Company, which owns Georgia Power, announced in July that it had increased its cost estimate for Georgia Power’s share of the two-unit Vogtle project.