Transportation and storage cask for spent nuclear fuels

#The present invention relates to containers used for transportation and short term storage of spent nuclear fuel.

#As the nuclear utility industry matures, there is an ever-increasing need for additional storage space to safely contain spent nuclear fuel. One method that has been developed in recent years for storage of spent nuclear fuels is dry storage in horizontal storage modules, which are shielded bunkers in which containerized spent fuel is stored and monitored for definite periods of time. One conventional technique for horizontal modular dry storage of spent nuclear fuel rods is disclosed in U.S. Pat. No. 4,780,269 to Fischer et al.

#A basic procedure for dry storage of spent nuclear fuel is to position a dry shielded canister into a shielded transfer cask. The canister and cask are filled with deionized water, which is then lowered into a pool containing the spent nuclear fuel. Spent fuel assemblies are then placed into the canister, and a shielded end plug is positioned to close the canister. The canister and cask are then removed from the pool, and the cask and canister are drained and dried. The exterior of the cask is decontaminated, followed by closure of the cask with a closure plate. The closed transportation cask is then lowered onto a transport trailer and secured by tie-downs.

#The present invention and its attendant advantages will be more readily understood in view of the following description, when read in conjunction with the accompanying drawings, in which:

#FIG. 1 provides an isometric view of a cask constructed in accordance with the present invention, with a portion of the cask cut away to show a dry shielded canister for containment of spent nuclear fuel installed therewithin, and with a shield plug for a tie-down key way shown exploded from the cask;

#FIG. 2 provides a cross-sectional view of the cask of FIG. 1, excluding the internal dry shielded canister, taken along a plane intersecting the longitudinal axis of the cask as indicated by line 2--2 in FIG. 1, with an access aperture closure plate and top closure plate shown exploded from the cask;

#A preferred embodiment of a cask 10 for transportation and short-term storage of spent nuclear fuel is shown in FIG. 1. The cask 10 includes a body 12 constructed from a tubular structural shell 14 having an upper shell portion 16 and a lower shell portion 18. The lower shell portion 18 is sealed by a bottom closure plate 20 that has a central access aperture 22 that is sealed with an access cover plate 24. The upper shell portion 16 is sealed with a top closure plate 26. The exterior of the structural shell 14 is shielded with a neutron absorbing shield jacket 28. Two diametrically opposed upper trunnions 30 (only one shown) are secured within upper trunnion mounting sleeves 32 to the exterior of the upper shell portion 16. Two lower trunnions 34 are secured in diametric opposition to the lower shell portion 18 within lower trunnion mounting sleeves 36.

#As used herein throughout, "bottom" and "lower" refer to the end of the cask 10 and its components closest in proximity to the bottom closure plate 20, while the words "top" and "upper" refer to the opposite end proximate the top closure plate 26. A dry storage canister 38 for spent nuclear fuel is shown installed within the interior cavity 40 of the cask 10. The construction of the dry storage canister 38 is fully described in a U.S. patent application filed on Oct. 8, 1993, in the name of inventors R. A. Lehnert, R. D. Quinn, S. E. Sisley, and B. D. Thomas, entitled CONTAINERS FOR TRANSPORTATION AND STORAGE OF SPENT NUCLEAR FUEL, the disclosure of which is hereby expressly incorporated by reference.

#A plurality of lugs 42 are secured to the structural shell 14 and to the annular ends of the shield jacket 28 about the circumference of the cask 10, on both the lower and upper (not shown) ends of the shield jacket 28. The purpose of the lugs 42 is to enable mating of the cask 10 with impact limiters during transport. Impact limiters and transportation skids suitable for use in transporting the cask 10 are fully disclosed in a United States patent application filed on Oct. 8, 1993 in the name of inventors R. A. Johnson, I. D. McInnes, R. D. Quinn, and C. J. Temus, entitled IMPACT LIMITER FOR SPENT NUCLEAR FUEL TRANSPORTATION CASK, the disclosure of which is hereby expressly incorporated by reference.