Systems and methods for storing spent nuclear fuel

1. A method of storing radioactive materials, the method comprising:

a) positioning a system comprising a shell forming a cavity and having an open top, and at least one inlet ventilation duct extending from an inlet to an outlet at a bottom portion of the cavity in a below grade hole so that the inlet of the inlet ventilation duct is above grade and the outlet of the inlet ventilation duct into the cavity is below grade;

b) introducing engineered fill into the hole to circumferentially surround the shell;

c) lowering a canister containing radioactive materials through the open top of the shell into the cavity; and

d) subsequent to the canister being lowered into the cavity, placing a removable lid on the shell;

wherein the shell is formed of steel and the inlet ventilation duct is seal joined to the shell and a bottom plate attached to the shell to form a self-supporting unitary structure.

2. The method of claim 1 wherein the system further comprises at least one outlet ventilation duct forming, a passageway from a to portion of the cavity to an ambient atmosphere.

3. The method of claim 2 wherein the lid comprises at least one outlet ventilation duct forming, a passageway from a top portion of the cavity to an ambient atmosphere.

4. The method of claim 1 wherein the system further comprises a concrete body circumferentially surrounding the shell, the engineered fill circumferentially surrounding the concrete body.

5. The method of claim 1 wherein step c) further comprises supporting the canister in the cavity so that an inlet air plenum exists between a floor of the cavity and a bottom surface of the canister and an outlet air plenum exists between a bottom surface of the lid and a top surface of the canister.

6. The method of claim 1 wherein the cavity extends along a longitudinal axis and has a transverse cross-sectional area that can accommodate no more than one of the canister.

7. A method of storing radioactive materials, the method comprising:

a) providing a system comprising a structure having a metal shell forming a cavity and having an open top, the cavity having a top portion and a bottom portion, at least one inlet ventilation duct thrilling a passageway from an ambient air inlet to an outlet at the bottom portion of the cavity, and at least one outlet ventilation duct forming a passageway from the top portion of the cavity to ambient air;

b) lowering a canister loaded with radioactive materials through the open top of the structure into the cavity until a bottom surface of the canister is lower than a top of the outlet of the at least one inlet ventilation duct;

c) supporting the canister in the cavity in a position where the bottom surface of the canister is lower than the top of the outlet of the at least one inlet ventilation duct, wherein the inlet ventilation duct is shaped so that a line of sight does not, exist to the canister from the ambient air inlet through the at least one inlet ventilation duct; and

d) placing a removable lid atop of the structure;

wherein the inlet ventilation duct is seal joined to the shell and a bottom plate attached to the shell to form a self-supporting unitary structure.

8. The method of claim 7 wherein the lid comprises the at least one outlet ventilation duct.

9. The method of claim 7 wherein step a comprises positioning the system in a below grade hole so that at least a major portion of the structure and the cavity is located below grade, the outlet of the at least one inlet ventilation duct is located below grade, and the inlet of the at least one inlet ventilation duct is above grade.

10. The method of claim 7 wherein the structure is a metal shell and the system further comprises a concrete body surrounding the metal shell.

11. The method of claim 7 wherein the cavity extends along a longitudinal axis and has a transverse cross-sectional area that can accommodate no more than one of the canister.

12. The method of claim 7 wherein step c) further comprises supporting the canister in the cavity so that an inlet air plenum exists between a floor of the cavity and a bottom surface of the canister and an outlet air plenum exists between a bottom surface of the lid and a top surface of the canister.