A natural passively cooled ventilated cask includes a cavity which holds a canister containing heat and radiation emitting spent nuclear fuel assemblies or other high level wastes. Ambient ventilation or cooling air is drawn inwards beneath the cask and vertically upwards into a lower portion of the cavity through air inlet ducts formed integrally with a bottom canister support structure coupled to the cask. The air heated by the canister flows upwards in the cavity and returns to atmosphere through air outlet ducts in the cask lid. Air circulation is driven via natural convective thermo-siphon flow. Structural standoff members elevate the bottom of the cask above a concrete base pad forming an air inlet plenum beneath the canister support structure. The lateral sidewall surface of the cask has no penetrations for the air inlets, which eliminates any streaming path for radiation emanating from the spent nuclear fuel.

In a canister horizontally installed and housed inside a concrete silo, at least two temperatures out of a temperature T.sub.B at a canister bottom portion to be one end portion in a lateral direction in a horizontally-installed attitude, a temperature T.sub.SB at a canister side surface lower portion located below a horizontal plane passing through a center of the canister, a temperature T.sub.T at a canister lid portion to be the other end portion in the lateral direction, and a temperature T.sub.ST at a canister side surface upper portion located above the horizontal plane passing through the center of the canister are monitored, and occurrence of leakage of an inert gas inside the canister is detected when there is a change in a temperature difference between the at least two temperatures.

In a canister horizontally installed and housed inside a concrete silo, at least two temperatures out of a temperature T.sub.B at a canister bottom portion to be one end portion in a lateral direction in a horizontally-installed attitude, a temperature T.sub.SB at a canister side surface lower portion located below a horizontal plane passing through a center of the canister, a temperature T.sub.T at a canister lid portion to be the other end portion in the lateral direction, and a temperature T.sub.ST at a canister side surface upper portion located above the horizontal plane passing through the center of the canister are monitored, and occurrence of leakage of an inert gas inside the canister is detected when there is a change in a temperature difference between the at least two temperatures.

A spent nuclear fuel storage facility. In one embodiment, the invention is directed to a storage facility including an array of storage containers. Each of the storage containers includes a body portion and a lid. The body portion has a storage cavity configured to hold a canister containing spent nuclear fuel. The lid, which may rest atop the body portion in a detachable manner, includes an inlet vent and an outlet vent. Each of the storage containers may be configured to draw air through the inlet vent and into the storage cavity where the air is warmed and passed through the outlet vent as heated air. The body portion of the storage containers may be positioned below grade and the lid of the storage containers may be positioned above grade.

A spent nuclear fuel storage facility. In one embodiment, the invention is directed to a storage facility including an array of storage containers. Each of the storage containers includes a body portion and a lid. The body portion has a storage cavity configured to hold a canister containing spent nuclear fuel. The lid, which may rest atop the body portion in a detachable manner, includes an inlet vent and an outlet vent. Each of the storage containers may be configured to draw air through the inlet vent and into the storage cavity where the air is warmed and passed through the outlet vent as heated air. The body portion of the storage containers may be positioned below grade and the lid of the storage containers may be positioned above grade.

Composition, manufactures, and processes of making and using them, consisting essentially of a neutron 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 water thermal conductivity at 100 degrees C. at sea level, combined such that the particles have a density of at least 0.9982 g/mL and not more than 2.0 g/ml. The composition can be located for release responsive to a loss of normal heat sink event and/or a loss of normal coolant event in a quantity sufficient, to palliate the loss of the normal heat sink event and/or the loss of normal coolant event.

Composition, manufactures, and processes of making and using them, consisting essentially of a neutron 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 water thermal conductivity at 100 degrees C. at sea level, combined such that the particles have a density of at least 0.9982 g/mL and not more than 2.0 g/ml. The composition can be located for release responsive to a loss of normal heat sink event and/or a loss of normal coolant event in a quantity sufficient, to palliate the loss of the normal heat sink event and/or the loss of normal coolant event.

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).

Basket for a transportation and storage cask for spent nuclear fuel from a pressurized water reactor, containing a base on which steel disks are fixed in height and aluminum disks are located between the steel disks equidistantly. Vertical clamping elements connect the steel and aluminum disks into a section cover. Two rows of apertures are made in the disks relative to their axis, two aperture in the inner row and eight in the outer row. The apertures comprise channels. Vertical clamping elements are located along the outer perimeter of the disks. The basket is made of one section and equipped with additional vertical disk clamping elements located in a circle between axes of the inner and outer rows of apertures in the disks The apertures and channels are round so that canisters for spent fuel assemblies can be placed therin. Grooves and hooks for canisters are provided in the base.