System for storing radioactive materials comprising: —a canister (4) containing radioactive waste; —a container (C), provided with a casing (1), a base (2) and a cover (3), and a passive helicoidal convection-based ventilation system provided with: lower air inlets (5); an area (6) of air circulation between the canister (4) and the inner surface of the container (C), and upper air outlets (7); the inlets (5) and outlets (7) have a decreasing variation of section in the direction of air circulation, are curved and facing an oblique direction with respect to the radial direction of the container, the air between said inlets (5) and outlets (7) describing an upward helicoidal path around the capsule or canister (4).

System for storing radioactive materials comprising: —a canister (4) containing radioactive waste; —a container (C), provided with a casing (1), a base (2) and a cover (3), and a passive helicoidal convection-based ventilation system provided with: lower air inlets (5); an area (6) of air circulation between the canister (4) and the inner surface of the container (C), and upper air outlets (7); the inlets (5) and outlets (7) have a decreasing variation of section in the direction of air circulation, are curved and facing an oblique direction with respect to the radial direction of the container, the air between said inlets (5) and outlets (7) describing an upward helicoidal path around the capsule or canister (4).

A separable multi-component cask for spent nuclear fuel transport and storage includes a vertically elongated outer cylinder having a neutron radiation shielding composition and a vertically elongated inner cylinder having a gamma radiation blocking composition. The inner cylinder includes a cavity configured to hold a spent nuclear fuel canister. The inner cylinder is detachably mounted and nested inside a cavity of the outer cylinder and is separable therefrom during spent fuel cask loading operations in a staged manner. An air ventilation annulus formed between the first and second cylinders forms a heat removal passage to remove heat emitted by the radioactive canister when placed inside the second cylinder. A pair of removably coupled mating top flanges on the inner and outer cylinders supports and suspends the inner cylinder in a cantilevered manner, thereby allowing the directly heated inner cylinder to thermally expand to a greater degree than the outer cylinder.

A separable multi-component cask for spent nuclear fuel transport and storage includes a vertically elongated outer cylinder having a neutron radiation shielding composition and a vertically elongated inner cylinder having a gamma radiation blocking composition. The inner cylinder includes a cavity configured to hold a spent nuclear fuel canister. The inner cylinder is detachably mounted and nested inside a cavity of the outer cylinder and is separable therefrom during spent fuel cask loading operations in a staged manner. An air ventilation annulus formed between the first and second cylinders forms a heat removal passage to remove heat emitted by the radioactive canister when placed inside the second cylinder. A pair of removably coupled mating top flanges on the inner and outer cylinders supports and suspends the inner cylinder in a cantilevered manner, thereby allowing the directly heated inner cylinder to thermally expand to a greater degree than the outer cylinder.

A system for externally cooling a cask containing heat-emitting spent nuclear fuel includes the cask comprising a radiation shielding body defining an internal cavity configured to hold a canister containing the spent nuclear fuel. A continuously annular cooling jacket extends circumferentially around an external surface of the cask body. The cooling jacket may have a double shell construction including an internal cavity for a cooling medium which provides an external heat sink for absorbing heat radiated from the external wall surface of the cask generated by the spent nuclear fuel. The heat emitted by the spent nuclear fuel is absorbed by the cooling medium in the cooling jacket, thereby in turn cooling the cask. In one embodiment, the cooling medium may be dry ice which undergoes sublimation by absorbing the heat to change from solid to gaseous phase directly. The jacket may be formed of multiple segments.

A system for externally cooling a cask containing heat-emitting spent nuclear fuel includes the cask comprising a radiation shielding body defining an internal cavity configured to hold a canister containing the spent nuclear fuel. A continuously annular cooling jacket extends circumferentially around an external surface of the cask body. The cooling jacket may have a double shell construction including an internal cavity for a cooling medium which provides an external heat sink for absorbing heat radiated from the external wall surface of the cask generated by the spent nuclear fuel. The heat emitted by the spent nuclear fuel is absorbed by the cooling medium in the cooling jacket, thereby in turn cooling the cask. In one embodiment, the cooling medium may be dry ice which undergoes sublimation by absorbing the heat to change from solid to gaseous phase directly. The jacket may be formed of multiple segments.

A nuclear fuel storage system includes an outer canister and fuel basket positioned therein. The basket is formed by orthogonally arranged and interlocked slotted plates which collectively define exterior side surfaces of the basket and a grid array of open cells each configured to hold a fuel assembly. At least some slotted plates comprise cantilevered plate extensions protruding laterally beyond the side surfaces of the basket to define various shaped peripheral gaps between the basket and canister. The plate extensions are configured to engage the shell of the canister. Vertically elongated reinforcement members are inserted in the peripheral gaps and fixedly coupled to the basket. Reinforcement members may comprise elongated reinforcement plates and/or tubular shimming members which may be fixedly coupled to the slotted plate extensions. The reinforcement members structurally strengthen the fuel basket. The plate extensions further act as fins to enhance heat dissipation from the basket.

Composition, manufactures, and methods of making and using them, illustratively a process including the steps of: changing density of a composition including a neutron absorbent, the absorbent having a neutron absorption cross section greater than or equal to Boron comprising at least 19.7% of Boron-10 isotope, and a thermal conductor having a thermal conductivity of at least 10% of coolant thermal conductivity at 100 degrees C. at sea level, combined into the particles that have a density of at least 0.9982 g/mL and not more than 2.0 g/ml, the altering carried out in association with nuclear fuel or nuclear waste in a cask that is not located in a nuclear reactor containment vessel, the cask being a nuclear fuel cask or a spent nuclear fuel cask, the changing carried out by relocating the composition by at least one of the sub steps comprising: (A) operating a hollow conduit connected to a reservoir to relocate at least some of the particles from a reservoir into the cask, and/or (B) altering a close pack formation of the particles by effectuating a change from a static coefficient of friction of the particles to a dynamic coefficient of friction of the particles, thereby redistributing the particles within the cask into an altered close pack formation, and/or (C) removing at least some of the particles from the cask into the reservoir.

Methods of placing sensors in structures may involve placing first particles including a first material of the structure on or above a support surface. Second particles including a second, different material may be dispersed among the first particles at least within a transition region of the structure proximate to a location where a sensor is to be supported by the structure. A sensor may be placed in the location. The first particles of the first material may be fused to one another and to the second particles of the second material to form the structure with the sensor supported by the structure.

A concrete cask enabling suppression of occurrence of stress corrosion cracking (SCC) in a lid welded part of a canister. The concrete cask includes: a metal canister accommodating spent fuel; a concrete container body for accommodating the canister inside the container body; a cooling passage provided between the external peripheral surface of the canister and the internal peripheral surface of the container body, and allowing air for cooling the external peripheral surface of the canister to pass; and a top space provided between the top surface part of the canister, and the inside of a lid of the container body. A baffle plate for suppressing introduction of air rising through the cooling passage to the top space is provided.