First sea trial of the nuclear attack submarine De Grasse

On February 24, the nuclear-powered attack submarine (SSN) De Grasse made its first sea trial, just 18 months after the Tourville.

It is the first step of a several-month sea testing campaign in the English Channel and the Atlantic. Staff from TechnicAtome and Naval Group are participating jointly, under the command of the French Navy.

The sea testing campaign follows on from the initial startup of the nuclear power plant on December 12 and will validate the performance of the propulsion system—comprising the power plant, the main engine, and the electrical system—up to full power. It will also confirm that the vessel’s systems (navigation, diving, combat systems, etc.) are fully operational prior to the submarine’s scheduled delivery to the Navy.

The De Grasse is the fourth SSN submarine in the Barracuda class, following the Suffren, the Duguay-Trouin, and the Tourville, which respectively entered active service in June 2022, April 2024, and July 2025.