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.

A containment building includes a wall made of a material of the concrete type that delimits a space and at least one viewing module, the viewing module including at least one window arranged in an opening in the wall, the window having a frame in which at least one optical unit that provides protection from high-energy and/or neutron radiation is placed, the frame being fitted in the opening, the viewing module also having a protective element that includes a sash bearing a pane and is arranged so as to close the opening at the face on the inside of the building, the viewing module thus including at least one interface between two surfaces. The containment building also includes at least one sealing system arranged at at least one interface.

A containment building includes a wall made of a material of the concrete type that delimits a space and at least one viewing module, the viewing module including at least one window arranged in an opening in the wall, the window having a frame in which at least one optical unit that provides protection from high-energy and/or neutron radiation is placed, the frame being fitted in the opening, the viewing module also having a protective element that includes a sash bearing a pane and is arranged so as to close the opening at the face on the inside of the building, the viewing module thus including at least one interface between two surfaces. The containment building also includes at least one sealing system arranged at at least one interface.

A plurality of different sized and shaped lightweight, shielded enclosures can be configured from a plurality of lightweight, shielded walls that attenuate one or more electromagnetic frequencies.

A plurality of different sized and shaped lightweight, shielded enclosures can be configured from a plurality of lightweight, shielded walls that attenuate one or more electromagnetic frequencies.

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.

A method of improving residual stress in a canister in which fuel assemblies are loaded includes, when the canister having a cylindrical canister shell and a canister lid welded to the upper opening of the canister shell is disposed in a cylindrical cask body, filling the space above and around an upper end portion of the canister in the cask body with fill water. Then, compressive stress is applied to a predetermined region of the upper end portion of the canister in the fill water. This makes it possible to readily apply compressive stress to the canister while shielding radioactive rays by the fill water.

A method of improving residual stress in a canister in which fuel assemblies are loaded includes, when the canister having a cylindrical canister shell and a canister lid welded to the upper opening of the canister shell is disposed in a cylindrical cask body, filling the space above and around an upper end portion of the canister in the cask body with fill water. Then, compressive stress is applied to a predetermined region of the upper end portion of the canister in the fill water. This makes it possible to readily apply compressive stress to the canister while shielding radioactive rays by the fill water.

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.

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.