Patent Number: 
Section: claims

1. A canister for final repository of spent fuel elements from a nuclear reactor comprising:an insert that contains said spent fuel elements;an inner copper casing that encloses said insert; andat least one outer casing that encloses said copper casing and that comprises a passive-film-forming metal or metal alloy, the passive film on the casing comprising an essentially oxidic film that is rich in one or more of the metals in the group of metals consisting of the metals zirconium, chromium and titanium. 2. A canister according to claim 1, wherein said essentially oxidic film essentially consists of one or more oxides of one or more of the metals that contain the group of metals consisting of the metals zirconium, chromium and titanium. 3. A canister according to claim 2, wherein said essentially oxidic film principally consists of one or more oxides of one or more of the metals that contain the group of metals that consist of the metals zirconium, chromium and titanium. 4. A canister according to claim 1, where the outer casing consists of cast, forged and/or rolled elements. 5. A canister according to claim 1, wherein the passive-film-forming metal or metal alloy is titanium or a titanium based alloy, which forms a titanium rich oxide, and wherein the outer casing has a material thickness in the range of 4-30 mm. 6. A canister according to claim 1, wherein the passive-film-forming metal or metal alloy is titanium or a titanium based alloy, which forms a titanium rich oxide, and wherein the outer casing has a material thickness in the range of 6-20 mm. 7. A canister according to claim 1, wherein the passive-film-forming metal or metal alloy is zirconium or a zirconium based alloy, which forms a zirconium rich oxide, and wherein the outer casing has a material thickness in the range of 3-20 mm. 8. A canister according to claim 1, wherein the passive-film-forming metal or metal alloy is a cobalt based or nickel based alloy that comprises at least 12% by weight of chromium. 9. A canister according to claim 1, wherein the passive-film-forming metal or metal alloy is a cobalt based or nickel based alloy that comprises at least 14% by weight of chromium. 10. A canister according to claim 8, wherein the outer casing has a material thickness in the range of 8-40 mm. 11. A canister according to claim 8, wherein the outer casing has a material thickness in the range of 10-30 mm. 12. A canister according to claim 1, wherein the passive-film-forming metal or metal alloy is stainless steel comprising at least 18% by weight of chromium, and wherein the outer casing has a material thickness in the range of 8-50 mm. 13. A canister according to claim 1, wherein the passive-film-forming metal or metal alloy is stainless steel comprising at least 18% by weight of chromium, and wherein the outer casing has a material thickness in the range of 10-40 mm. 14. A canister according to claim 12, wherein the stainless steel is an austenitic steel comprising at least 12% by weight of nickel. 15. A canister according to claim 12, wherein the stainless steel is a duplex steel with a nickel content in the range of 1.5-10% by weight of nickel. 16. A canister according to claim 12, wherein the stainless steel is a ferritic steel with a chromium content of at least 22% by weight of chromium. 17. A canister according to claim 12, wherein the passive-film-forming metal is alloyed with tungsten and/or molybdenum such that W+Mo>0.15% by weight. 18. A canister according to claim 1, wherein the inner copper casing has a material thickness of at least 25 mm. 19. A canister according to claim 1, wherein the insert is made of cast iron. 20. A canister according to claim 18, wherein the insert is made of cast iron with a chromium content of more than 13% by weight. 21. A canister according to claim 1, wherein the outer casing constitutes the outermost metal layer. 22. A canister for final repository of spent fuel elements from a nuclear reactor comprising:an insert constructed and arranged for containing spent fuel elements;an inner copper casing enclosing said insert; andat least one outer casing enclosing said copper casing, the outer casing being formed from at least one passive-film-forming metal or metal alloy selected from the group consisting of zirconium, chromium and titanium.