Patent Number: 
Section: claims

1. A spent nuclear fuel rod canister, comprising:a submersible pressure vessel comprising a casing that defines an interior cavity, the casing comprising a corrosion resistant and heat conductive material;a rack enclosed within the interior cavity and configured to support one or more spent nuclear fuel rods;a riser that defines a fluid pathway between a top portion of the interior cavity and a bottom portion of the interior cavity;an annulus defined between the riser and the casing; anda heat exchanger attached to the casing of the pressure vessel,the heat exchanger comprising at least one conduit that is at least partially disposed exterior to the casing,the at least one conduit comprising an interior volume flowpath that is in fluid communication with the interior cavity of the pressure vessel,the at least one conduit comprisinga first conduit comprising an end of the interior volume flowpath that includes an opening located in the riser anda second conduit comprising an end of the interior volume flowpath that includes an opening located in the annulus. 2. The spent nuclear fuel rod canister of claim 1, further comprising:a first hemispherical enclosure coupled to the casing at a top end of the casing, the first hemispherical enclosure comprising a radiussed interior surface that defines a top portion of the interior cavity; anda second hemispherical enclosure coupled to the casing at a bottom end of the casing, the second hemispherical enclosure comprising a radiussed interior surface that defines a bottom portion of the interior cavity. 3. The spent nuclear fuel rod canister of claim 1, further comprising a fuel basket positioned in the interior cavity within the riser and near the bottom portion of the interior cavity. 4. The spent nuclear fuel rod canister of claim 3, wherein the fuel basket comprises:a perforated support plate adjacent a bottom surface of the rack, the fluid pathway fluidly coupled to the bottom portion of the interior cavity through the perforated support plate. 5. The spent nuclear fuel rod canister of claim 1, wherein the at least one conduit further comprises a third conduit comprising another end of the interior volume flowpath that includes an opening located in the annulus. 6. The spent nuclear fuel rod canister of claim 1, wherein the casing is configured to permit radiation from the one or more spent nuclear fuel rods therethrough. 7. The spent nuclear fuel rod canister of claim 2, wherein the end of the first conduit is positioned below a liquid level of a coolant that at least partially fills the interior cavity of the casing. 8. The spent nuclear fuel rod canister of claim 7, further comprising a fuel basket positioned in the interior cavity within the riser and near the bottom portion of the interior cavity. 9. The spent nuclear fuel rod canister of claim 8, wherein the fuel basket comprises:a perforated support plate adjacent a bottom surface of the rack, the fluid pathway fluidly coupled to the bottom portion of the interior cavity through the perforated support plate. 10. The spent nuclear fuel rod canister of claim 9, wherein the at least one conduit further comprises a third conduit comprising another end of the interior volume flowpath that includes an opening located in the annulus. 11. A method of dissipating decay heat generated by a spent nuclear fuel rod, the method comprising:loading at least one spent nuclear fuel rod into a rack positioned within an interior cavity of a spent nuclear fuel rod canister, the canister comprising:a submersible pressure vessel comprising a casing that defines an interior cavity that is at least partially filled with a fluid coolant,the casing comprising a corrosion resistant and heat conductive material,a rack enclosed within the interior cavity and configured to support one or more spent nuclear fuel rods, anda heat exchanger attached to the casing of the pressure vessel,the heat exchanger comprising at least one conduit that is at least partially disposed exterior to the casing,the at least one conduit comprising an interior volume flowpath that is in fluid communication with the interior cavity of the pressure vessel,the at least one conduit comprisinga first conduit comprising an end of the interior volume flowpath that includes an opening located in a riser that defines a fluid pathway between a top portion of the interior cavity and a bottom portion of the interior cavity anda second conduit comprising an end of the interior volume flowpath that includes an opening located in an annulus defined between the riser and the casing;submerging the spent nuclear fuel rod canister in a heat transfer fluid contained in a spent fuel pool;transferring decay heat from the spent nuclear fuel rod to the fluid coolant;circulating the heated fluid coolant through the riser and into the end of the first conduit;transferring the decay heat from the heated fluid coolant, through the casing, and to the heat transfer fluid in the spent fuel pool; andcirculating the fluid coolant from the end of the second conduit to and through the annulus. 12. The method of claim 11, wherein the fluid coolant is circulated through natural circulation. 13. The method of claim 11, further comprising exposing the casing of the spent fuel canister to ambient air. 14. The method of claim 13, further comprising:based on the exposure to ambient air, phase changing a portion of the fluid coolant from a liquid to a gas in the spent nuclear fuel rod canister; andphase changing the gas back to a liquid condensate on an interior surface of the casing based at least in part on heat transfer between the gas and the ambient air. 15. The method of claim 11, wherein transferring the decay heat from the heated fluid coolant, through the casing, and to the heat transfer fluid in the spent fuel pool comprises:convectively transferring the decay heat from the heated fluid coolant to the casing; andconvectively transferring the decay heat from the casing to the heat transfer fluid. 16. The method of claim 11, wherein a rate at which heat is transferred from the spent fuel rod is at least as great as a rate at which the spent nuclear fuel rod produces decay heat. 17. The method of claim 11, wherein the casing is configured to permit radiation from the at least one spent nuclear fuel rod therethrough. 18. The method of claim 11, wherein the at least one conduit further comprises a third conduit comprising another end of the interior volume flowpath that includes an opening located in the annulus. 19. The method of claim 18, further comprising circulating the fluid coolant from the end of the third conduit to and through the annulus. 20. The method of claim 19, wherein the fluid coolant is simultaneously circulated from the ends of the second and third conduits to the annulus.