High-density subterranean storage system for nuclear fuel and radioactive waste

Abstract

An underground ventilated system for storing nuclear waste materials. The system includes a storage module having an outer shell defining an internal cavity and an inner shell. A majority of the height of the outer shell may be disposed below grade. The outer shell may include a hermetically sealed bottom. First and second canisters are positioned in lower and upper portions within the cavity respectively in vertically stacked relationship. A centering and spacing ring assembly is interspersed between the first and second canisters to transfer the weight of the upper second canister to the lower first canister. The assembly may include centering lugs which laterally restrain the first and second canisters in case of a seismic event. A natural convection driven ventilated air system cools the canisters to remove residual decay heat to the atmosphere. In one non-limiting embodiment, the shells are made of steel.

What is claimed is: 
     
         1 . A system for vertically-stacked storage of nuclear waste canisters comprising:
 an elongated outer shell defining a vertical axis and an internal cavity;   a first canister positioned in the cavity in a lower position;   a second canister vertically stacked above the first canister in an upper position, the first and second canisters being concentrically aligned with the vertical axis;   a centering and spacing ring assembly interspersed between the first and second canisters; and   a removable top lid mounted on top of the outer shell covering the cavity.   
     
     
         2 . The system of  claim 1 , wherein the centering and spacing ring assembly is arranged and operable to transfer weight of the second canister to the first canister. 
     
     
         3 . The system of  claim 1 , further comprising an elongated inner shell disposed in the cavity and concentrically aligned with the outer shell. 
     
     
         4 . The system according to  claim 1 , wherein the centering and spacing ring assembly includes a plurality of radially extending centering lugs spaced circumferentially apart around the ring. 
     
     
         5 . The system of  claim 4 , wherein the inner shell has a vertical height coextensive with a vertical height of the outer shell. 
     
     
         6 . The system of  claim 5 , wherein the lugs of the centering and spacing ring assembly are engageable with the inner shell. 
     
     
         7 . The system of  claim 6 , wherein the centering and spacing ring assembly has a castellated surface. 
     
     
         8 . The system of  claim 7 , wherein the castellated surface includes a plurality of alternating arcuate raised segments and arcuate recessed segments. 
     
     
         9 . The system according to  claim 1 , further comprising a top centering and spacing ring assembly engaged with a top of the second canister. 
     
     
         10 . The system according to  claim 9 , further comprising a bottom centering and spacing ring assembly engaged with a bottom of the first canister. 
     
     
         11 . The system of  claim 1 , further comprising a bottom plate hermetically sealed to the outer shell forming an impermeable moisture barrier. 
     
     
         12 . The system of  claim 11 , further comprising a concrete top pad surround a top of the outer shell and a concrete base pad engaging the bottom plate on outer shell. 
     
     
         13 . The system of  claim 12 , further comprising soil filled adjacent to the outer shell and extending between the top pad and the base pad. 
     
     
         14 . The system according to  claim 3 , wherein the outer and inner shells are formed of steel.