Patent Number: 
Section: claims

1. A rupture disk for a device for protecting against overpressure inside an apparatus, the disk consisting of a part of generally circular form comprising two planar faces substantially parallel to one another, and two scores each located on a circumference, wherein the circumferences of the two scores are different from one another, the score located on the larger circumference being produced on one of the planar faces, called bottom face, whereas the score located on the smaller circumference is produced on the other of the planar faces, called top face, the score located on the top face further being configured to rupture at a first pressure P0 under a first gas whereas the score located on the bottom face being configured to rupture at a second pressure P1 different from P0 under a second gas. 2. The rupture disk as claimed in claim 1, one and/or the other of the scores being continuous over its circumference. 3. The rupture disk as claimed in claim 1, one and/or the other of the scores being discontinuous on its circumference. 4. The rupture disk as claimed in claim 1, wherein the circumferences of the two scores are concentric to one another. 5. The rupture disk as claimed in claim 1, wherein the circumferences of the two scores are centered on the center of the circular part. 6. The rupture disk as claimed in claim 1, wherein the part is made of a steel chosen from the ferritic, martensitic, ferrito-bainitic, bainitic, ferrito martensitic, ferrito-perlitic, and perlitic steels. 7. The rupture disk as claimed in claim 1, wherein the part has a thickness of 1 to 5 mm. 8. The rupture disk as claimed in claim 1, wherein the depth of the scores is less than or equal to a value corresponding to approximately 70% of the thickness of the part. 9. The rupture disk as claimed in claim 1, wherein the radius at the bottom of the scores is between 0.1 and 0.6 mm. 10. The rupture disk as claimed in claim 1, wherein the aperture angle of the scores is less than or equal to 50°. 11. An apparatus, intended to contain, in succession, two gases of different chemical nature, comprising:a wall in which an aperture is formed;a device for protecting the apparatus against overpressures comprising:a rupture disk as claimed in claim 1, the bottom face of which is in direct contact with the pressure contained in the apparatus,at least one bearing element, designed to press the disk against the wall with the scores of the disk over the aperture. 12. The apparatus as claimed in claim 11, wherein the protection device comprises:sealing means arranged between the periphery of the disk and the wall around the aperture,at least one holding element, called closing cap, bearing against the bearing element, and fixed by tightening to the apparatus so as to hold the bearing element and the rupture disk on the apparatus and ensure the seal at the level of the sealing means. 13. The apparatus as claimed in claim 12, wherein the closing cap and the apparatus is pierced respectively with tapped holes facing one another to house the screws for tightening the closing cap on the apparatus. 14. The apparatus as claimed in claim 11, wherein the bearing element is a ring whose bottom face bears against the top face of the disk and whose aperture is arranged facing the aperture of the wall. 15. The apparatus as claimed in claim 11, further comprising sealing means arranged between the periphery of the ring and the closing cap. 16. The apparatus as claimed in claim 15, the sealing means consisting of one or more O-ring seals. 17. A method comprising containing under pressure, two gases of different chemical nature, by the apparatus as claimed in claim 11. 18. The method as claimed in claim 17, wherein the apparatus is a hydrogen production and storage apparatus.