Patent Number: 044951418
Section: claims

1. A tagging gas releasing element for insertion within a nuclear fuel rod, said tagging gas releasing element consisting essentially of an inorganic solid material having a tagging gas composed of at least one rare gas selected from the group consisting of helium, xenon, neon and krypton adsorbed on the surface region thereof so as to detect failure in a nuclear fuel rod, said tagging gas being released from said element and into the interior of said fuel rod by means of desorption under the high temperature operation conditions of a nuclear reactor so as to tag each fuel rod and detect failure of the fuel rod when the tagging gas leaks therefrom, said inorganic solid material containing the tagging gas being the sole source of the tagging gas. 2. A tagging gas releasing element according to claim 1, wherein the inorganic solid material is a metal containing a tagging gas injected and entrained into the surface region thereof. 3. A tagging gas releasing element according to claim 2, wherein the metal is in the form of a thin film. 4. A tagging gas releasing element according to claim 3, wherein the thin metal film is formed on the surface of a solid carrier. 5. A tagging gas releasing element according to claim 3, wherein a number of thin metal films into which the tagging gas is injected and entrained into the surface region thereof are closely laminated to one another to form a multi-layer structure. 6. A tagging gas releasing element according to claim 3, wherein the thin metal film into which the tagging gas is injected forms a coating on the surface of a nuclear fuel pellet. 7. A tagging gas releasing element according to claim 3, wherein the thin metal film, in the outer surface of which the tagging gas is injected, is wrapped around the peripheral face of a nuclear fuel pellet. 8. A tagging gas releasing element according to claim 2, wherein the metal is selected from the group consisting of titanium, aluminum, zirconium, nickel, stainless steel and alloys thereof. 9. A tagging gas releasing element according to claim 1, wherein the inorganic solid material is a heat-resistant porous material in which the tagging gas is adsorbed. 10. A tagging gas releasing element according to claim 9, wherein the heat-resistant material is a heat-resistant porous granular material and the tagging gas is adsorbed in said porous granular material. 11. A tagging gas releasing element according to claim 10, wherein the tagging gas-adsorbed porous granular material is filled in a capsule comprising a cylinder composed of a hardly fusible metal and porous walls of the same metal disposed on both ends of said cylinder. 12. A tagging gas releasing element according to claim 1, wherein the tagging gas is a mixture of stable isotopes of at least one member selected from a group consisting of xenon and krypton. 13. A tagging gas releasing element according to claims 2 or 5 in which the tagging gas is injected and entrained onto the surface of said inorganic solid material by the ion injection method. 14. In a nuclear fuel rod composed of a cladding tube containing nuclear fuel pellets and a tagging gas composed of at least one rare gas selected from the group consisting of helium, xenon, neon and krypton, the improvement in which the tagging gas is entirely adsorbed onto the surface region of the tagging gas release element inserted into the cladding tube, said element composed of an inorganic solid material such that the tagging gas is released from said element by desorption under the high temperature operation conditions of a nuclear reactor to tag each fuel rod and detect failure of the fuel rod when the tagging gas leaks from the fuel rod. 15. The improvement according to claim 14 in which the inorganic solid material is a metal containing the tagging gas injected into the surface region of said metal. 16. The improvement according to claim 15 wherein the inorganic solid material is composed of a number of thin metal films formed on the surface of a solid carrier and in which a plurality of carrier and film combinations are closely laminated to one another to form a multi-layer structure. 17. The improvement according to claims 15 or 16 in which the tagging gas is injected into the surface of said metal or metal films by the ion injection method. 18. A fuel rod comprising a cladding tube and a fuel pellet material loaded in the cladding tube, characterized in that a metal foil having a tag gas injected therein for detecting breakage of the cladding tube is further loaded in the cladding tube, the metal foil being loaded in the cladding tube on the end portion in the form of circular foils, said foils each having a diameter smaller than the inner diameter of the cladding tube. 19. The fuel rod according to claim 18, wherein the metal foil is formed of a metal selected from the group consisting of aluminum, an aluminum alloy, zirconium, a zirconium alloy and stainless steel. 20. The fuel rod according to claim 18, wherein said tag gas is injected into a surface region of the metal foil. 21. The fuel rod according to claim 18, wherein said tag gas-injected metal foil is loaded in a plenum of the cladding tube. 22. A nuclear fuel rod, which comprises: a cladding tube, filled with a tag gas and sealed at both ends; and a plurality of nuclear fuel pellets piled one atop another in the cladding tube, wherein an adsorbent carrying a tag gas for detecting a nuclear fuel rod failure is received in the inner space of the cladding tube above the nuclear fuel pellet pile whereby said gas is released from said adsorbent when the temperature thereof increases. 23. The nuclear rod according to claim 22, wherein the adsorbent is active carbon. 24. The nuclear rod according to claim 22, wherein the adsorbent is received in a container. 25. The nuclear rod according to claim 24, wherein the container is formed of a hardly fusible metal container which is perforated at the top. 26. The nuclear rod according to claim 22 wherein the tag gas is at least one member selected from the group consisting of helium, xenon and krypton. 27. The fuel rod according to claim 19, wherein said tag gas-injected metal foil is loaded in a plenum of the cladding tube. 28. The fuel rod according to claim 20, wherein said tag gas-injected metal foil is loaded in a plenum of the cladding tube.