Unit 1 and 2, rated 1.3 GWe each, and based on Westinghouse design,[1] were ordered following the Messmer Plan and deliver full power since 1987.

In charge Areva proved unable to managed this project (just like Olkiluoto 3), leading to the ultimate demise of the company.

[15] The next day the Italian power company Enel announced it was relinquishing its 12.5% stake in the project, and five future EPRs.

[18] In April 2015, Areva informed the French nuclear regulator, Autorité de sûreté nucléaire (ASN), that anomalies had been detected in the reactor vessel steel, causing "lower than expected mechanical toughness values".

[19][20] Segolene Royal, Minister of Ecology, Sustainable Development and Energy in the Second Valls Government, asked the producer for further details and possible consequences.

[21] Various safety problems have been raised, including weakness in the steel used in the reactor[22] together with heterogeneity of the steel alloy forged high integrity components used in the reactor pressure vessel,[23] that have also been shown to be present in Japanese-sourced components that have entered the French nuclear equipment supply chain.

[27] In September 2015, EDF announced that the estimated costs had escalated to €10.5 billion, and the start-up of the reactor was delayed to the fourth quarter of 2018.

[29] In February 2017, renewed delays in the construction of the EPR-reactors at Taishan Nuclear Power Plant prompted EDF to state that Flamanville 3 remains on schedule to start operations by the end of 2018, assuming it receives regulator approval.

[8][9] In July 2020, the French Cour des Comptes finalised an eighteen-month in-depth analysis of the project, concluding that the total estimated cost reaches up to €19.1 billion.

[7] In the same month, France's energy minister Barbara Pompili noted the high costs and delays, calling the project "a mess".

[38] In December 2022, EDF announced a further delay of at least six months with an estimated cost increase of €500 million due to more work to establish a new process for the stress relieving heat treatment of some welds close to sensitive equipment.

[39][40] On 3 September 2024, the reactor started test operation, but the following day it shut down automatically, possibly due to a configuration error.