Maintaining leak-free vessel seals at French PWRs

Applications for the Helicoflex gasket have been found in both nuclear and non-nuclear plants, uranium enrichment facilities, and experimental fusion reactors. All 900, 1300 and 1500 MWe units in France as well as all Framatome-built units outside France use this same gasket design - close to 1600 seals installed in all. They have provided excellent leaktight sealing; indeed, no leaks have been observed at any of the reactor vessels equipped with these gaskets. The gasket features a spring, which acts as an elastic core, and an outer metallic lining, which gives it the necessary plasticity. In the case of PWR vessels, Inconel X-750 is used for the spring, and Inconel 600 plus silver for the lining. This choice was made after an extensive R and D programme conducted by the CEA on behalf of Framatome for EdF. (author)