According to this report, French steel will be used to build UK nuclear submarines:
But did you know that French steel used to build nuclear reactor vessels around the world apparently is fatally flawed? You can read about it here:
My dad used to work for Lincoln Electric Company. They originally used US produced steel in their products, but eventually switched to French steel to save money. He claimed it was scrap and that so much of it had to be discarded that the final cost was higher than if Lincoln had just continued to use the original US material.
Producing high quality steel for large forgings is an art as well as a science, one that many (apparently including France) no longer can master.
I would NEVER go to sea in a French made sub, let alone submerge the thing. NO WAY. And I've been at test depth on some real clunkers.