Ventilated storage system and method enabling triangular storage arrangement of casks containing hazardous radioactive material

Abstract

To provide a ventilated storage system and method that enable a space efficient storage of a cask including a dangerous nuclear matter.SOLUTION: Each of a plurality of dry storage casks has a plurality of air inlets at a bottom part or in the vicinity of the bottom part, and has a ventilated overpack that includes a plurality of air outlets at a top or in the vicinity of the top. Thus, each thereof enables ambient air to flow through the plurality of air inlets, and flow out from the plurality of air outlets through the overpack, and ventilates and cools the dangerous nuclear matter. In a storage pad into which each of the plurality of dry storage casks is seated, a plurality of air channels is present that supplies air to the plurality of air inlets located at the bottom part of the plurality of dry storage casks. The storage pad facilitates getting the plurality of dry storage casks more closer to each other, and enables achieving a triangle array excellent in space efficiency.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] [Priority claim] This application claims priority to and benefit of Application No. 63 / 526,787, filed July 14, 2023, Attorney Docket No. 61404-8200, which is incorporated herein by reference in its entirety. [Technical field] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate generally to the storage of hazardous radioactive materials, and more particularly to the dry storage of hazardous radioactive materials, such as casks including, but not limited to, spent nuclear fuel. [Background technology]

[0002] In commercial nuclear power plants, spent nuclear fuel has often been stored within nuclear power plants in deep reservoirs called spent fuel pools. When these spent fuel pools reach their spent fuel capacity limits, or when a nuclear power plant undergoes complete removal of spent fuel from the spent fuel pools at the end of its facility's life, the fuel may be transferred to metal canisters with final closure lids that are welded shut or sealed with mechanical devices at the plant following the loading of spent fuel or radioactive waste. The sealed canisters are then placed into ventilated storage overpacks (typically constructed of layers of steel and concrete) that act as enclosures providing mechanical protection, passive heat removal, and additional radiation shielding for the inner metal canisters containing radioactive material.

[0003] The ventilated storage overpack containing the welded or bolted metal canister in which the radioactive material is stored is then placed in a designated secure location outside the nuclear plant structure, typically on a site under the owner's control, to ensure that appropriate control and monitoring is exercised in connection with the ventilated storage overpack containing the metal canister.

[0004] U.S. Patent No. 11,676,736, incorporated herein by reference, describes the use of a ventilated metal storage overpack (VMSO) with a ventilation inlet at the bottom and a ventilation outlet at the lid to allow cooling by ambient air passing through the cask through the ventilated overpack. Due to the extremely restrictive space limitations of many storage facilities, the VMSO was designed to allow hazardous radioactive material to be stored in less space by using small-diameter overpacks made of metal rather than concrete. Summary of the Invention

[0005] The present disclosure provides embodiments of ventilated storage systems and methods that enable the implementation of more space-efficient, i.e., compact, triangular storage arrangements for storing spent nuclear fuel casks.

[0006] This embodiment is particularly useful and preferred in connection with the use of the VMSO described above, but may be limited to this type of ventilated overpack or this type of cask. The disclosed embodiments can be used in connection with any cask that uses ambient air for cooling and has an air inlet located at or near the bottom and an air outlet located at or near the top.

[0007] The triangular storage arrangement reduces the area required to store multiple canisters of radioactive waste. By not having lateral inlets and outlets for convective airflow, casks can be effectively placed very close together (within a few inches) on the storage pad. This alternative design, with its complex design of the storage pad integrated as part of the storage system, uniquely optimizes storage capacity for extremely limited area requirements.

[0008] Other embodiments, systems, devices, methods, features, and advantages of the present invention will be apparent to one of ordinary skill in the art upon examination of the following figures and detailed description, all of which are intended to be included within this disclosure, be within the scope of this disclosure, and be protected by the accompanying claims. [Brief explanation of the drawings]

[0009] Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure.

[0010] [Figure 1] FIG. 1 is a perspective view of a storage pad of the present disclosure in which casks are arranged in a compact triangular storage array, showing ambient air entering through inlets located on the sides of the storage pad and exiting through air outlets located at the top of the casks storing hazardous radioactive material.

[0011] [Figure 2] FIG. 2 is a cross-sectional view showing the flow of ambient air through the air passage pads and into the cask.

[0012] [Figure 3] FIG. 3 is a perspective view showing the connection between the ventilation holes in the cask and the airflow outlets in the pad.

[0013] [Figure 4] FIG. 4 is a perspective view illustrating the use of a storage pad with a VMSO as described and shown in U.S. Pat. No. 11,676,736 and a modular portable cask transfer facility as described and shown in U.S. Pat. No. 10,614,925.

[0014] [Figure 5] FIG. 5 is a top view of the triangular array.

[0015] [Figure 6] FIG. 6 is a side view of the triangular arrangement. DETAILED DESCRIPTION OF THE INVENTION

[0016] As shown in Figures 1-3, to enable airflow through the ventilated metal storage overpack 11 (VMSO), the pad 13 on which the storage cask 11 sits provides connections for the airflow source. As used herein, a "VMSO" refers to any cask that uses ambient air for cooling and has an airflow inlet located at or near the bottom and an airflow outlet located at or near the top. Incorporating airflow inlet paths into and along the storage pad 13 on which the VMSO 11 is installed allows for the densification of the storage array 15 into a compact triangular arrangement, as shown by the arrows in Figures 1 and 2, and also eliminates any radiation spillage typically associated with exposed airflow inlets.

[0017] In a preferred embodiment, the VMSO 11 is configured as described in U.S. Patent No. 11,676,736. In this regard, the VMSO 11 has a sidewall with an inner metal layer and one or more sets of alternating layers. Each set includes a neutron-absorbing layer adjacent to another metal layer, such that the neutron-absorbing layer and the metal layer alternate across the sidewall. The neutron-absorbing layer is designed to absorb neutron particles emitted by radioactive nuclear waste, and the metal layer is designed to absorb gamma particles emitted by radioactive materials. Additionally, for ventilation and cooling, each VMSO 11 is equipped with four air inlets at its bottom and four air outlets near its top.

[0018] By incorporating straight and cross flow air supply plenums, or channels, a single air chamber is developed with the bottom of the VMSO 11 integrated together, where the air inlets located at the bottom of the VMSO 11 are connected to the developed air chamber, thereby allowing the VMSOs 11 to be substantially close together, as shown in the triangular array 15.

[0019] In a preferred embodiment, the pad 13 has a multi-layer structure, as shown in FIG. 1 , including a top layer 13a having a plurality of circular receptacles 17, a middle layer 13b underlying and supporting the top layer 13a and having air flow passages 18 and peripheral airflow inlets 22, and a bottom layer 13c underlying and supporting the middle layer 13b. Preferably, but not by way of limitation, each of the layers 13a, 13b, and 13c is rectangular. Each receptacle 17 has a bottom support surface and circular vertical sidewalls. The receptacles 17 receive and support a respective cask 11. The receptacles 17 arrange the casks 11 in a compact triangular array 15, and the bottom support surface includes the pad's airflow outlets 19. In a preferred embodiment, but not by way of limitation, each receptacle 17 is shown with two airflow outlets 19a, 19b, while each VMSO 11 is shown with four underlying airflow inlets, but not by way of limitation.

[0020] Specific advantages of this unique approach of incorporating an airflow inlet plenum into the storage pad 13 include, but are not limited to, a reduced area requirement for locating storage casks 11 and simplified airflow inlet inspections required by regulatory requirements during storage. Instead of having to inspect four airflow inlets on each storage cask 11, inspections need only inspect the peripheral airflow inlets 22 on the side of the storage pad 13. With regard to the temperature monitoring equipment required, the centralized VMSO outlet may require only a single monitoring device, such as that used with modern storage casks 11 deployed in a typical single-unit storage configuration.

[0021] An additional distinct benefit of this unique triangular storage arrangement is the inherent improved seismic performance of the tightly packed spent fuel storage system, whose integrated performance may provide greater stability during anticipated seismic activity and reduce the need for seismic restraints typically required for spent fuel storage systems in high seismic regions of the world.

[0022] By utilizing axial airflow, VMSO11 and integrated storage pads, the present invention primarily optimizes the areal density of the spent fuel storage system, and also provides improved monitoring, seismic performance, and operational performance of the storage system, reducing both occupational and off-site radiation exposure.

[0023] As shown in Figures 4-6, the storage envelope reduction can also be integrated with a modular portable cask transfer facility 21, as described and shown in U.S. Patent No. 10,614,925, which is incorporated herein by reference. This approach allows for either canister transfer or direct-loaded VMSO placement at the pad 13.

[0024] The triangular array and its supporting plenum or flow channel may be configured to allow for an initial deployment to be installed, and then expanded as needed by adding additional portions of the triangular array as the need for any number of additional nuclear material storage locations is recognized.

[0025] Finally, it should be emphasized that the above-described embodiments of the present invention, particularly any "preferred" embodiments, are merely possible, non-limiting examples of implementations set forth for a clear understanding of the principles of the present invention. Many variations and modifications can be made to the above-described embodiments of the present invention without substantially departing from the spirit and principles of the present invention. All such modifications and variations are intended to be included herein within the scope of this disclosure and the present invention.

[0026] As an example of a variant, if the cask 11 has a side air inlet, the air outlet associated with the pad can be designed to supply air to the cask 11 horizontally.

Claims

1. 1. A ventilated storage system for efficiently storing hazardous nuclear material, comprising: a plurality of dry storage casks containing the hazardous nuclear material, each having a ventilated overpack with a plurality of air inlets at its bottom and a plurality of air outlets at its top, wherein ambient air flows into the plurality of air inlets, passes through the ventilated overpack and flows out of the plurality of air outlets to cool the hazardous nuclear material; a storage pad on which the plurality of dry storage casks rest, the storage pad having a plurality of air channels supplying air to the plurality of air inlets located at the bottom of the plurality of dry storage casks; 1. A ventilated storage system comprising:

2. The plurality of dry storage casks are arranged in a triangular array when viewed from above.

10. The ventilated storage system of claim 1.

3. The storage pad comprises: a top portion supporting the plurality of dry storage casks; The bottom and a plurality of peripheral sides extending between said top and said bottom; the plurality of air flow paths have a plurality of air flow inlets located on the plurality of peripheral sides of the storage pad, the plurality of air flow paths extending horizontally through the storage pad and extending vertically through the storage pad to a plurality of air flow outlets below the plurality of dry storage casks; 10. The ventilated storage system of claim 1.

4. the storage pad comprises a plurality of circular receptacles having a bottom support surface and a circular vertical sidewall, the plurality of circular receptacles receiving and supporting each dry storage cask, the plurality of circular receptacles arranging the plurality of dry storage casks in a triangular array, and the bottom support surface comprising the plurality of air flow outlets of the storage pad; 4. The ventilated storage system of claim 3.

5. The storage pad comprises three layers, including a top layer having the plurality of circular receptacles, a middle layer located below the top layer, supporting the top layer, and forming a ventilation air chamber, the middle layer having the plurality of air channels and the plurality of air inlets, and a bottom layer located below the middle layer and supporting the middle layer.

5. The ventilated storage system of claim 4.

6. the plurality of air inlets on the plurality of peripheral sides of the storage pad are fewer in number than the plurality of air inlets on the plurality of dry storage casks; 4. The ventilated storage system of claim 3.

7. A storage pad on which a plurality of dry storage casks may reside, the storage pad having a plurality of air channels supplying ambient air to a plurality of air inlets located at the bottom of the plurality of dry storage casks.

8. The method further comprises a plurality of dry storage casks containing hazardous nuclear material and residing on said storage pad, each dry storage cask having a ventilated overpack with a plurality of air inlets at its bottom and a plurality of air outlets at its top, wherein ambient air flows into said plurality of air inlets, passes through said ventilated overpack and out of said plurality of air outlets to cool said hazardous nuclear material.

8. The storage pad of claim 7.

9. The plurality of dry storage casks are arranged in a triangular array when viewed from above.

9. The storage pad of claim 8.

10. 10. The storage pad of claim 8, wherein the ventilated overpack is primarily made of metal and is concrete-free.

11. The storage pad comprises: a top portion supporting the plurality of dry storage casks; The bottom and a plurality of peripheral sides extending between said top and bottom portions; the plurality of air flow paths have a plurality of air flow inlets located on the plurality of peripheral sides of the storage pad, the plurality of air flow paths extending horizontally through the storage pad and extending vertically through the storage pad to a plurality of air flow outlets below where the plurality of dry storage casks will be located; 8. The storage pad of claim 7.

12. the storage pad comprises a plurality of circular receptacles having a bottom support surface and a circular vertical sidewall, the plurality of circular receptacles receiving and supporting each dry storage cask, the plurality of circular receptacles being designed to arrange the plurality of dry storage casks in a triangular array, and the bottom support surface comprising the plurality of air flow outlets of the storage pad; 12. The storage pad of claim 11.

13. the air conditioner includes three layers, including a top layer having the plurality of circular receptacles, a middle layer located below the top layer and supporting the top layer, the middle layer having the plurality of air channels and the plurality of air inlets, and a bottom layer located below the middle layer and supporting the middle layer.

13. The storage pad of claim 12.

14. the plurality of air inlets on the plurality of peripheral sides of the storage pad are substantially fewer in number than the plurality of air inlets on the plurality of dry storage casks; 12. The storage pad of claim 11.

15. 1. A ventilated storage system for efficiently storing hazardous nuclear material, comprising: a plurality of dry storage casks containing the hazardous nuclear material, each having a ventilated overpack with a plurality of air inlets at its bottom and a plurality of air outlets at its top, wherein ambient air flows into the plurality of air inlets, passes through the ventilated overpack and flows out of the plurality of air outlets to cool the hazardous nuclear material; a storage pad on which the plurality of dry storage casks rest, the storage pad having a plurality of air channels supplying air to the plurality of air inlets located at the bottom of the plurality of dry storage casks; the plurality of dry storage casks are arranged in a triangular array when viewed from above; The storage pad a top portion supporting the plurality of dry storage casks; The bottom and a plurality of peripheral sides extending between said top and bottom portions; the plurality of air flow passages extend horizontally through the storage pad and vertically through the storage pad to a plurality of air flow outlets below the plurality of dry storage casks; Ventilated storage system.

16. the storage pad comprises a plurality of circular receptacles having a bottom support surface and a circular vertical sidewall, the plurality of circular receptacles receiving and supporting each dry storage cask, the plurality of circular receptacles arranging the plurality of dry storage casks in a triangular array, and the bottom support surface comprising the plurality of air flow outlets of the storage pad; 16. The ventilated storage system of claim 15.

17. the storage pad comprises three layers, including a top layer having the plurality of circular receptacles; a middle layer located below the top layer, supporting the top layer, and having the plurality of air channels and the plurality of air inlets; and a lower layer located below the middle layer, supporting the middle layer.

17. The ventilated storage system of claim 16.

18. the plurality of air inlets on the plurality of peripheral sides of the storage pad are fewer in number than the plurality of air inlets on the plurality of dry storage casks; 16. The ventilated storage system of claim 15.

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