AND RADIOACTIVE WASTE

CROSS-REFE ENCE TO RELATED APPLICATIONS

[0001 I The present application claims the benefit of United States Provisional Patent Application Serial No. US 61/750,986 filed January 10. 2013, which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTIO

[0002] The present invention relates to spent nuclear fuel and radioactive waste storage systems, and more particularly to such a system suitable for consolidated interim waste storage.

BACKGROUND OF THE INVENTION

[0003] Used or spent nuclear fuel and radioactive waste materials are presently stored on an interim basis "on site" at commissioned and some decommissioned nuclear generating plants until the federal government provides a central permanent repository. For example, spent nuclear fuel is stored in the reactor fuel pool after removal from the core where it continues to generate decay heat. The fuel can be transferred after a period of cooling in l¾e poo! to canisters which are placed in dry storage casks (i.e. overpaeks) typically constructed of concrete, steel and iron, etc. to provide containment and radiation shielding. The casks are stored on site at the generating plant.

[0004] The concept of using consolidated, interim storage (CIS) is intended to provide geographically distributed off-site storage facilities for spent nuclear fuel and radioactive wastes (collectively "waste") gathered from a number of individual generating plant sites, thereby providing greater control over the widely dispersed waste stockpiles. The waste materials would initially be transported to the CIS facility from the generating plants for a period of time, with the eventual goal of a final mo ve to a permanent unclear waste repository when available. Such so called independent spent fuel storage installations (ISFSI) are facilities designed for the interim storage of spent nuclear fuel comprising solid, reactor- related, greater than Class C waste, in addition to other related radioactive materials. Each ISFSI facility would typically maintain an inventor of a multitude of waste canisters containing spent nuclear fuel and/or radioactive waste materials.

SUMMARY OF THE INVENTION

[0005] The present disclosure provides a below-ground used or spent nuclear fuel storage system designed for the compact dr storage of a large number of used fuel canisters in a

- i - small land area. In a noa-Iimiting exemplary embodiment, two or more elongated canisters may be stored in vertically oriented and slacked relationship in each of a plurality of underground vertical ventilated storage modules which, provide an overpack. The storage modules may be diametrically sized to fit a single canister therein at a given elevation, as further described herein. The collecti ve array of storage modules defines an independent spent fuel storage installation (ISFS1) facility suitable for CIS that may include any number and arrangement of modules.

[0006] The canisters may contain both radioactive used nuclear fuel and/or non-fuel waste materials in some embodiments. In one embodiment, the canisters may be Mulii-Purpose Canisters (MFCs) available from Holt.ee International of Marl ton, ew Jersey.

(ΘΘ07 The underground storage system is intended to provide vantshingly low site boundary radiation dose levels and safety during catastrophic events. As an underground system, the system takes ad vantage of the surrounding soil or subgrade to provide shielding, physical protection, and a low center of gravity for a stable storage installation. Each vertical storage module prov ides storage of canisters in a vertical configuration insi de a cylindrical cavity located entirely below the top-of-grade in the storage facility. The vertical modules may each be generally comprised of a. cavity enclosure container formed by an outer shell, an inner divider shell, and a top closure lid in addition to various interfacing structures and features, as further described herein.

[0008] The canister storage system is further configured to provide passive heat removal from the canisters via natural convection during storage in the modules, thereby rejecting the used fuel's decay heat emitted to the ambient air above the module. Radiation emitted from the used nuclear fuel is substantially contained within the soil fill in which the modules are disposed and canisters stored.

|O009| Advantageously, stacking two canisters in each vertical ventilated storage module according to the present disclosure ultimately cuts the required storage area in half. For example, a 14 acre ISFSI for CIS can store 4,000 canisters containing more than 50,000 tons of uranium. This significantly reduces siting requirements. The radiation released to the environment .from such a CIS facility storing used fuel may be .negligible.

[0010] According to one exemplary embodiment a system for vertically-slacked storage of nuclear waste canisters includes an elongated outer shell defining a vertical axis and an internal cavity; a first canister positioned in the cavity in a lower position; a second canister vertically stacked above the first canister in an upper position, the .first and second canisters being concentrically aligned with the vertical axis; a centering and spacing ring assembly interspersed between fixe first and second canisters; and a removable top lid mounted on top of the outer shell covering the cavity . The centering and spacing ring assembly is arranged and operable to transfer weight of the second canister to the first canister.

(0611] According to another embodiment, a storage module for vertically-stacked storage of nuclear waste canisters includes an elongated outer shell defining a vertical axis and an internal cavity; an elongated inner shell disposed in the internal cavity; a first annular space formed between the inner and outer shells, the first annular spacing defining a vertical downcomer ventilation shaft operable to convey ambient cooling air downwards to the cavity; a first canister positioned in the cavity in a lower position; a second canister vertically stacked above the first canister in an upper position, the first and second canisters being concentrically aligned with the vertical axis; a middle centering and spacing ring assembly interspersed between the first and second canisters, the middle centering and spacing ring- assembly operable to transfer weigh of the second canister to the first canist er; a second annular space formed between the first and second canisters and the inner shell, the second annular space defining a vertical riser ventilation shaft operable to convey cooling air upwards across outer surfaces of the canisters; and a removable top lid mounted on top of the outer shell covering the cavity, the top ltd being i fluid communication with the riser ventilation shaft and configured to form an airflow pathway to atmosphere through the lid. |0612] According to another embodiment, an underground storage module for vertically- stacked storage of nuclear waste canisters includes an elongated vertical outer shell defining vertical axis and an internal cavity, the outer shell having a top and a hermeticall sealed bottom, the outer shell being disposed below grade for a majority of its height; a. common inlet air plenum disposed a the top of the otster shell, the air plenum arranged to draw ambient cooling air through, a pluralit of air inlets in fluid communication with the air plenum; an annular-shaped vertical downcomer ventilation shaft arranged to convey the cooling air from the inlet air plenum downwards along the outer shell to a bottom of the cavity; a first canister positioned in the cavit in a lower position; a second canister vertically stacked above the first canister in an. upper position, the first and second canisters being concentrically aligned with the vertical axis; an elongated inner shell disposed inside the outer shell and cavity; an annular-shaped vertical, riser ventilation shaft formed, between, the inner shell and the canisters, the riser ventilation shaft being in fluid communication with the downcomer ventilation shaft near the bottom of the outer shell and arranged to convey cooling air upwards across outer sidewall surfaces of the canisters for removing decay heat; and a removable top lid mounted on top of the outer shell covering the cavity, the top ltd in fluid comtnunicalioe with the riser ventilation shaft and configured to form an airflow pathway to atmosphere through the lid from the riser ventilation shaft.

BRIEF DESCRIPTION OF THE DRA WINGS

[0013) The features of the exemplary embodiments of the present invention will be described with reference to the following drawings, where like elements are labeled similarly, and in which:

[0014] FIG. 1 is a perspective vie w of an iSFSI facility for consolidated interim storage of spent nuclear fuel and waste materials utilizing an array of underground storage modules each capable of holding at least two canisters according to an. embodiment of the present invention;

[0015) FIG. 2 is a three-dimensional cross-sectional view of a fully insialied storage module of FIG. 1 showing one nuclear waste canister in a lower position in the module;

[0016] FIG. 2A is a detailed view from FIG. 2;

[0017 J FIG. 3 is a three-dimensional cross-sectional view of a fully installed storage module showing two vertically stacked canisters positioned, in the module;

(0018) FIG. 3A is a detailed view from FIG. 3;

ίθθί')] FIG. 4 is a three-dimensional cross -sectional view of a storage module with concrete top pad alone without soil or bottom concrete base pad;

[00201 IG- 4A is a detailed view from FIG. 4;

[00211 FIG. 4B is a detailed view from FIG. 4;

[0022] FIG. 4C is a detailed view from FIG. 4;

[0023] FIG. 5 is an airflow diagram showing the storage module and natural convection ventilation system, showing the cooling air flow paths through the module;

[0024) FIG. 6 is a three-dimensional cross -sectional vie of a fully insialied empty storage module before lacement of the canisters and removable to ha: and

[0025) FIG, 6A is a detailed view from FIG. 6.

[Θ026] All drawings are schematic and not necessarily to scale. Parts given, a reference numerical designation in one figure may be considered to be the same parts where they appear in other figures without a numerical designation for brevity unless specifically labeled with a different part number and described herein. References herein to a .figure number (e.g. FIG. 1 } shall be construed to be a reference to all subpart figures in the group (e.g. FIGS. 1. A, I B, etc.) unless otherwise indicated. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The features and benefits of the invention are illustrated and described herein by reference to exemplary embodiments. This description of exemplary embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. Accordingly, the disclosure expressly should not be limited to such exemplary embodiments illustrating some possible non-limitinj combination of features that may exist alone or is other combinations of features.

[0028] In the description of embodiments disclosed herein, any reference to direction or orientation is merely intended for convenience of description and is not intended in any way to limit the scope of the present invention. Relative terms such as "lower," "upper," "horizontal," "vertical,", "above " "below," "up," "down," "top" and "bottom" as well as derivative thereof (e.g., "horizontaliy," "downwardly," "upwardly," etc.) should be construes to refer to the orientation as then described or as shown in. the drawing under discussion. These relative terms are for convenience of description only and do not require that the apparatus he constructed or operated in a particular orientation. Terms such as '"attached," "affixed," '"connected," '"coupled," "interconnected," and similar refer to a relationship wherei structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movabie or rigid attachments or relationships, unless expressl described otherwise.

10029] PIG. 1 depicts an ISFSi facility forming a high-density subterranean Consolidated Interim S torage (CI S) sy s tem 100 comprising an array of underground vertical ventilated storage modules i 1.0, in one embodiment, each storage module 1 10 houses at least two sealed canisters containing spent nuclear fuel and/or radioactive waste materials. The storag modules 1 1 are arranged in. a tightly packed configuration to mmimtee spatial site requirements. The storage modules 1 10 are spaced apart by a grid of orthogonally intersecting ais!es 102 formed of concrete slabs 104 to provide access for commercially- available motorized wheeled equipment operable to move and lift (i.e. .raise/lower) the canisters for insertion into and removal from the modules. Such equipment is well known to those skilled in the art without further elaboration. The low exposed vertical profile of the storage modules 11.0 (as further described herein) allows the equipment to move over modules in a single row to the desired module for inserting or removing canisters.

[Θ03Θ1 Each storage module 1 10 may include an associated concrete top pad 1 12 which is positioned and disposed between the aisles 102 of slabs 104. The top pads 112 may form a contiguous structure with slabs 104 to provide radiation shielding. The top pads i 12 may be square-shaped n top plan view in one non-limiting example; however, other suitable polygonal and non-polygonal configurations (e.g. circular) may be used.

}0§31| FIG. 2 is a cross-sectional view of a single storage module 1 0 from FIG. 1. With additional .reference to FIGS. 6 and 6A, storage module 1 10 is vertically elongated and includes a vertically-extending outer shell 120 defining an. internal cavity 122 and an inner shell 130. in one embodiment, outer and inner shells 120, 130 are eyhndricaify and complementary shaped, albeit di ensioually different. The outer shell 120 provides an impermeable barrier against leakage of ground water through the earthen soil S 00. into the storag module 1 10. Outer shell has an open top 121 and a closed bottom formed by bottom plate 123 at the bottom end of the shell. Bottom plate 123 may be substantially flat and is preferably seal welded to outer shell 120 in one embodiment to hermetically seal the bottom of the shell thereby forming an impermeable barrier to ingress of external ground water. Accordingly, ail portions of storage module 1 10 below- grade are sealed against the ingress of moisture or water from the environment transmitted through the soil.

[0032 J The bottom plate 1.23 o f outer shell 120 may be positioned, on and supported by a concrete base pad 106. The area adjacent the outer shell 120 between the top pad 1 12 and base pad 106 is filled with fill or soil "S", thereby forming a cross-sectional composite structure of upper and lower concrete caps with soil disposed therebetween, A majority of the height of the outer and inner shells 120, 130 is disposed below grade as shown in FIGS. 2 and 6 The top portion of outer shell 120 is surrounded, by the top pad 1 I 2 and embedded therein so that virtually none or only a small projection of the top end 121 of the outer shell protrudes above the concrete pad. Substantially the entire height of the outer shell. 120 is therefore embedded in soil and/or concrete in the embodiment being described.

j¾033j It will be appreciated that in some embodiments, a monolithic concrete base pad 1 6 may extend beneath a pluralit or cluster of individual storage modules 110 in lieu of individually poured pads. Similarly, a monolithic top pad 1 12 may be used to surround and extend between a phmiltty or cluster of individual storage modules 1 1 in lien of individually poured pads.

[Θ034 j It will be appreciated that although the cross-sectional shape of the outer and inner shells 120, 130 may be cylindrical in the illustrated embodiment, the shells can have other suitable polygonal and non-poiygonai shapes, including without limitation rectangular, conical, hexagonal, or irregularly shaped, in some embodiments, the outer and inner shells 120, 1.30 need not be concentrically aligned with each other. (Θ035) Outer and inner shells 120, 130 and bottom piate 123 are made of metal such as steel in exemplary non-limiting embodiments. Outer shell 120, which provides a barrier between the soil S in which the outer shell is embedded, is preferabl made of a corrosion, resistant metal such as without limitation coated steel stainless stee etc,

[0036! embodiment, inner shell 1 30 has an open top 13 1 and open bottom .132 .reference FIGS. 6 and 6.4). The open top 13 1 allow insertion of canisters 140 into the storage module 1 10, as further described herein. Inner shell 130 may be coaxially and concentrically aligned with outer shell 120 about a vertical axis VA defined by storage module 1 10. Outer and inner shell 120, 130 have vertical heights that are substantially coextensive. The bottom. 132 of inner shell .130 may rest on top of the bottom plate 123 of the outer shell 120 n one arrangement. The outer and inner shells 120, 130 have a sufficient height or depth suitable to allow at least two canisters 1 0 to be stored in a vertically stacked configuration or relationship. In other embodiments, the outer and inner shells 1.20, 130 may have heights or depths suitable for holding three or more vertically stacked canisters 140. [Θ037] inner shell 130 has a smaller diameter than outer shell 1.20. inner shell 1 30 is radially spaced apart inwards from the outer shell 120 and acts to divide the cavity 1 20 into an outer annular space 124 and an inner portion configured and dimensioned to hold canisters 140, The outer annular space 124 extends Irom the top 121 to bottom plate 123 of outer shell 120. }0038 The outer annular space 124 defines an annular-shaped vertical downeomer ventilation shaft 125 for introducing outside ambient, cooling air into cavity 1.22 of storage module 1 10 to remove decay heat emitted from the spent nuclear fuel or radioactive waste material contained in canisters 140. To complete a . natural convection heat removal airflow- circuit, a second inner annular space 133 is defined between the outer cylindrical shell sidewa.ll 141 of canister 140 and inner shell 1 30 which i s radially spaced apart outwards from the canister. The second inner annular space 133 extends from the bottom 132 to top 131 of inner shell 130 and defines an annular-shaped vertical riser ventilation shaft 134 for removing heated cooling air from storage module 110. The inner shell 130 serves to separate the downeomer ventilation air from the up-flowing air heated by contact with the canister (see, e.g. airflow diagram of FIG. 5).

]0039j The downeomer ventilation shaft 125 is ffuidly (i.e. airflow) separated and isolated from riser ventilation shaft 134 by inner shell 130 for substantially the entire vertical height of storage module 1 10 along shells 120, 1 30 except near the bottom of the storage module. The downeomer and riser ventilation shafts 125, .134 respectively are in fluid communication through a plurality of ci.rcum.feren.tia.ily arranged and spaced apart airflow openings 135 formed at the bottom end of the inner shell 130 near the bottom 132, The bottom end of shell 130 may have a castellated configuration in one embodiment with the openings 1 5 having a generally square or rectangular shaped configuration. Other suitable shaptxl airflow openings may be used however.

}OO4 | In one embodiment, the inner "di ider" shell .130 is insulated being provided with an insulation layer 150 to minimize heat exchange between the incoming cooling (downcomer ventilation shaft 1:25) and outgoing heated (riser ventilation shaft 134) ventilation air in contact with the inner shells inner and outer surfaces, respectively (see, e.g. FIGS. 4 and 5, and best shown in detail in FIG. 4B). This keeps the ambient cooling air drawn into the storage .module i 10 by natural convention as cold as possible until it encounters the hotter outer shell sidewal! 141 of the canisters 140 to maximize cooling efficiency. In one embodiment, the insulation layer 150 is disposed on the outer surface of inner shell .130 between the inner shell and outer shell 120 in the downcomer ventilation shaft 1.25 to preven damage which could potentially occur from inserting and removing canisters from the storage module 110. Any suitable type of insulating material may be used, including without limitation separately ^" formed and applied pliable, semi-rigid, and rigid insulating materials and sprayed on types (e.g. hardening foams). The insulation 26 is preferably chosen so that it is water and radiation resistant without substantial degradation. Some examples of suitable forms of insulation include, without limitation, blankets of alumina-silica, fire clay (Kaowool Blanket), oxides of alumina and silica (Kaowool. S Blanket), alumina-sihca-zirconia fiber (Cerab!anket), and aiumina-silica-chromia (Cerachrome Blanket). The desired thickness of the of insulation layer 150 will be dictated by such considerations such as the heat load (e.g. temperature differential between ambient air and canister external temperatures), the

thickness of the shells, and the type of insulation used (e.g. K. factor), in some embodiments, the insulation may have a representative non-limiting thickness in a range of about 1/2 to 6 inches for example.

(1)041 j Canisters 140 stored in storage module 1 10 may be any type of canister, including without limitation Maid-Purpose Canisters (MFCs) available from Holtec International of Marl ton. New jersey. As shown in FIG, 5, canisters .140 have a generally hollow cylindrical shell sidewal! 141 including a top .142 with removable and scalable lids 144 for msertmg spent nuclear fuel and/or radioactive waste materials and an opposing bottom 1.43, The interior of canisters 140 may include racks or grids to contain and support spent fuel rods and waste materials. [ΘΘ42 i F 3S. 4 and 4A show the construction of the upper portion of storage module 1 10 and top pad \ 12 in greater detail The tops 1 2.1 and 131 of outer and inner shells 120, 130 respectively penetrate top pad J .12, thereby providing external above grade access to downcomer ventilation shaft 125, riser ventilation shaft 134, and cavity 122 of storage

.module 1 1 for inserting and removing canisters 140. The top pad 1 12, which may be formed of concrete in one preferred embodiment, extends at least partially beyond the diameter of outer shelf 120 as shown, in this non-limiting example, the top pad 1 12 may- have a square shape (in top plan view) as previously described. The perimeter of the top pad 1 .12 would be adjoined by the access aisles 1 2 formed betwee adjacent storage modules 1 10.

[0043] With continuing reference to FIGS. 4 and 4A, to pad i 12 includes one or more air inlets .160 which are in fluid communication with annular-shaped downcomer ventilation shaft 125 to introduce cooling ambient, ventilation air into the storage module 1 10. A common recessed air plenum 161 covered by a removable cover plate 2 may be formed in top pad 1 12 around outer shell 120 to tluidly connect the air inlets to the ventilation shaft 125. Air plenum .161 further .tluidly interconnects the air inlets 160 to each other. ^" The air plenum 161 is formed by a recessed, portion of top pad 1 12 and has a bottom surface 1 6 spaced vertically below the higher top surface i B at peripheral portions of the pad 1 12, as shown. Air plenum 161 may have a complementary shape to top pad .1 .12 (e.g. square in this embodiment), or a different shape.

[Θΰ44| The a ir inlets 1 0 may be formed in one embodiment, from short sections of pipe attached directly to and removable as a unit with the cover plate 162 (both of which preferably are formed of metal) by any suitable means (e.g. fasteners, welding, etc.). Cover plate 1 2 includes apertures 1.67 which flnidiy communication with short pipe sections. The air inlet 160 pipe sections include lateral airflow openings 1 4 cut into the sides of the pipe and the open free end is covered b a weather cap 163 t prevent the direct ingress of rain and/or debris. The top end of shell .1 0 may include a plurality of ci.rcumferentially spaced apart airflow openings 1 5 which are in fluid communication with air plenum 1 1 to allow ambient ventilation air to flow through the air inlets 1 0 into the plenum and. in turn down into the downcomer ventilation shaft 125 through the openings 1 5.

J 0O4S] The anibteut ventilation cooling air is admitted through a plurality of air inlets 160 in the top pad 1 12 that are arranged to be non-preferential with respect to the horizontal direction of the wind to maximum cooling of the canisters in storage module 1 1 . In one non-limiting embodiment, four air inlets 160 may be provided with, one inlet being positioned at each of the four comers of the iop pad 1 12 to ensure each quadrant of die storage module 1 10 via the downcomer ventilation shaft 125 receives an equal amount of ambient cooling ventilation air. The air plenum 161 advantageously serves to Anther distribute the ventilation air uniformly to all portions of the downcomer ventilation shaft 125.

}0046| li will be appreciated that other suitable configurations and numbers of air inlets 160 and configurations of air plenum 16 Ϊ may be provided depending on the configuration of top pad 1 12 used and other factors.

[Θ047] The heated ventilation air exits riser ventilation shaft. 134 from storage module 1 1 0 through a central airflow passageway 201 in the top lid 200 shown in FIGS. , 4A, and 5. Top lid 200 is a removable cover that closes storage module 1 10 and is positioned over the tops 121 and 131 of outer and inner shells 120, 130, respectively,

}0648| The top lid 200 is a massive stepped-shaped circular shielded structure in one embodiment equipped with a diametrically enlarged upper portion. 202 and smaller cylindrical bottom protrusion 203 extending downwards therefrom. The upper portion 202 has a larger diameter than the diameter of the outer shell 120 forming an annular shaped peripheral portion (in top plan view) overhanging the outer shell, in some embodiments, upper portion 202 is configured and dimensioned to close off both the open tops 121 , 131 of the outer and inner shells 1 0, 130. This effectively seals off the top of vertical downcomer ventilation shaft 1 5 to prevent inlet cooling ventilation air entering from air plenum 161 via airflow openings 165 at the top of outer shell 12 from, bypassing the shaft 125 and entering the riser ventilation shaft ! 34 at the top of the storage module 11 . I some embodiments, a top seal plate may be used to seal the top of vertical downcomer ventilation shaft 125 in addition to top lid 200,

[0949] An annular gasket 250 formed of a suitable material may be provided between the underside of the upper portion 202 of top lid 200 and the inner top 13 1 of the inner shell 130 providing a sealed lid-to-inner shell interface (see FIG. 4 A).

f uSO] The bottom protrusion 203 has a diamete smaller than the inner shell 130 and forms a plug that is inserted at least partially into the inner shell into cavity 122 to keep the lid 200 from sliding in a lateral direction excessively during a seismic event (e.g. earthquake}. The annular gap G formed between th bottom protrusio 203 and inner surface of inner she ll 130 forms a continuation of vertical riser ventilation shaft 134 as best shown in FIGS. 4A and 5. j0w51 In some embodiments, the top lid 150 may be a substantially hollow metal structure filled with a radiation absorbing material shielding such as concrete. The metal exoskeleton of top lid 150 can be constructed of a wide variety of materials, including without limitation various steel, stainless steel, aluminum, aluminum-alloys, and other metals, In some embodiments, the lid may be constructed of a single piece of material, such as concrete or steel for example,

(0052] With continuing reference to FIGS. 4, 4A, and 5, upper portion 202 of top iid 200 is annular shaped which defines the centra! airflow passageway 20.1 to eject heated ventilation air from vertical riser ventilation shaft .134 to the ambient environment. To complete th s airflow circuit, the bottom protrusion 203 of lid 200 mciodes a plurality of radially extending air passages 205 which are in fluid communication with the annular-shaped riser ventilation shaft 134 and central airflow passageway 201 in the upper portion 202 of the lid. An air outlet 21 extending upwards from top lid 200 ma be mechanically thereto and Oukli coupled to central airflow passageway 201 to help vent heated ventilation air away from storage module 1.10. The air outlet 210 may be .formed in one embodiment from a short section of pipe attached to the upper portion 202 of top lid 200 by any suitable means (e.g. fasteners, welding, etc). The air outlet pipe sections include lateral atrilow openings 21 1 cut into the sides of the pipe and the open free end is co v ered by a weather cap 212 to prevent the direct ingress of rain, and/or debris.

10653] In one embodiment, top lid 200 may include four intersecting rigging plates 204 useable to raiser and lower the iid into position on storage module 1 10 (see, e.g. FIGS. 4 and 4A). The plates 204 may be welded to the metal exoskeleton. plates of the lid 200. The plates 204 ma extend from the bo ttom of bottom protrusion 203 to the top of upper portion 202, aud m some embodiments have center extension sections 206 which extend radially inwards into central airflow passageway 20! and protrude upwards therefrom. Extension section of rigging plates 204 may therefore extend vertically upwards into and be covered by air outlet 2 S O when storage module 1 1 is in use. Extension sections 206 are configured for grappling by rigging and hoisting equipment (e.g. holes, clips, etc.) to facilitate manipulating and maneuvering the top lid 200. Other suitable configurations and arrangements for rigging lid 200 are possible.

[0054] FIG. 5 is an airflow diagram showing the cooling ventilation air path through storage module 110 created by the features described above. As shown by the directional airflow arrows in this figure, the cooling ventilation, air will travel in a generally U-shaped airflow path through the storage module i 10 t remove and dissipate decay heat emitted from the canisters 140 by the spent nuclear fuel and/or radioactive waste stored therein. Airflow circulation is created by natural convection induced by the decay heat liberated. [005S| In operation, ambient cooling air is first drawn into air plenum 161 through each of the individual air inlets 160 and is mixed together. The inlet air circulates around and through the plenum. It should be noted that the air lenum 161 prevents ambient air flowing from the air inlets 160 directly into the annular vertical downcomer ventilation shaft 125. Advantageously, this mitigates the effects of preferential wind direction which otherwise .might adversely affect the amounts of cooling ventilating airflow reaching certain portions of the storage module 110 and canisters 1 0 t erein. Without the plenum and its airflow balancing effects, certain areas of the canisters 140 may be starved of cooling air while other portions receive cooling resulting in differential cooling of the canisters shell si.dewal.is 141 . This would reduce the natural convection cooling efficiency.

|0f ⁾ 56 With continuing reference to FIG, 5, the cooling ventilation air leaves the air plenum 1 1 through the airflow openings 165 and enters the vertical downcomer ventilation shaft 125. The air flows downwards in the downcomer ventilation shaft .125 towards the bottom of the storage module 1 10, The cooling ventilation air travels through the plurality of airflow openings 135 formed at the bottom end of the inner shell. 130 near its bottom 132 (see also FIGS. 4 and 4C) and enters the bottom of cavity 122 and the annular vertical riser ventilation shaft 134.

JOuS?! The cooling air reverses direction and flows upward through the riser ventilation shaft 134 contacting the exposed outer circumferential surfaces of the first the bottom and then the top canister 140 in storage module 1 10 to draw away decay heat via convection. As the ventilation air flows vertically upward along the canisters 140 i the riser ventilation, shaft 1 34, the air becomes progressively heated.

J 0058] The now heated ventilation air flows to and eventually reaches the top of the storage module 11 at the top of cavity ί 22 in the vertical riser ventilation shaft 134. The air flow changes direction and flows radially inwards through the radial air passages 205 in top lid .200 and is recombined in the central airflow passageway 201 in the upper portion 202 o the lid. The ventilation air then changes direction again and flows vertically upward entering air outlet 210 from which it is exhausted to atmosphere completing the ventilation airflow cycle.

[ΘΘ59) The support and placement of the multiple canisters 140 in storage module 1 10 will now further described.

|0 6fl| Referring to FIGS. 4 and 4C, the bottom or lower canister 140 (shown in, e.g. FIGS. 2 and 3) is horizontally supported and laterally restrained by a cireumferen ally spaced apart series of suitably shaped centering lugs 300. Lugs 300 are oriented and extend in a radial direction from the vertical axis VA of the storage module 1 .10. When placed in the storage module 1.10, the lower canister 140 rests on bottom plaie 123 welded to the outer shell 120 and transfers dead load (weight) of both the lower and top or upper canisters 140 housed in the storage module 11 to the concrete base pad 106. The canister 140 is positioned laterally adjacent to and inside die ring of radial lugs 300 as seen in FIG . 2. The lugs 300 are located proximate to the shell sidewall 141 of the canister 140 and positioned to ully engage die canister in die event of a lateral shift: in position of the canister caused by a seismic event. This would stabilize the canister 1 0 and prevent excessive horizontal movement to protect the canister and its corneals. Any suitable number of iugs 300 may be provided.

[00611 Lugs 300 may be formed from generally flat steel plate in one embodiment and extend both, upwards and inwards from the outer shell 120 towards the vertical axis VA (see, e.g. FIG, 6A). As shown, the lugs 300 may have a substantially greater radial width and axial height than thickness T (thickness being measured perpendicular to the width and height in a circumferential direction along the outer shell 120). At least a portion of the innermost axial edge 301 of lugs 300 is preferably straight or flat and arranged parallel to the shell sidewall 141 of canister 140 and vertical axis VA to prevent puncturing the canister in case of seismic event. The lug 300 includes an angled edge 302 which adjoins the axial edge 301 that is angled downwards and inwards as shown in FIG. 6A. When the lower canister 140 is initially lowered into storage module 1 10, this angled edge 302 helps blindly guide and center the bottom 143 of the cani ster towards the centerline or vertical axis VA so thai the can ister becomes properly seated on the bottom plate 123 or ring 31 i f provided.

[0062 j Centering and spacing lugs 300 may be attached, to the outer shell 120 and/or inner shell 1 0 and are essentially not vertical load bearing structural members. In one exemplary arrangement, lugs 30 ma be directly attached to the shell 120 (e.g. welded) through slots 136 formed through inner shel l 130 at the location of each lug 300. The slots may be closed at the top and open at the bottom adjacent boitom 132 of the inner shell 130 to allow the inner shell to slide over the lugs when initially inserted into the outer shell 120 during fabrication. The bottom ends of the inner shell 130 may then rest on the fiat boitom plate 123 affixed to the outer shell. 120.

[Θ063) In one embodiment shown in FIGS. 6 and 6A, a interlacing centering and spacing bottom ring 310 may be provided for some specific canister designs to engage the bottom 143 of the canister. Ring 310 is disposed inside the lugs 300 and may be fixedly attached thereto (e.g. welded) or a separate element in various embodiments. In the latter separate or loose construction, the ring 310 may have peripheral notches configured to engage the lugs 300 for preventing the ring from rotating in relation to the lugs and outer shell 120. On other

- S 3 - embodiments, me ring 300 fits loosely inside lugs 300 without notches. The ring 300 rests on bottom plate 123 of outer shell .120 in abutting contact for transferring dead load (weight) of the canister 140 to the concrete base pad 106 , Ring 310 is preferably made of metal, such, as a suitable steel,

[0064! some embodiments, the top surface 31 . of ring 310 may be castellated including a plurality of alternating arcuate raised segments 312 and arcuate recessed segments 314 having a complementary configuration to match and engage similarly configured features on the bottom 143 of a lower canister 140, The segments 31.2, 314 may extend radially from the inside to the outside of the ring 300 as best shown in FIG. 6A. Segments 312, 314 have a circumferentially measured arc width greater tha the corresponding width of th e lugs 300, and preferably may have a width at least coextensive with the radial depth of the segments (.measured from the center of the ring outwards). The bottom surface 313 of ring 310 may be substantially flat.

[Θ065] Referring to FIGS. 2, 2A, and 5, the lower and upper canisters 1 0 are horizontally supported and laterally restrained against the inner shell 130 by a centering and spacing middle ring 320. Ring 320 may be configured and constructed similarly to bottom, support, ring 310 described above and shown in FIGS, 6 and 6A. In one embodiment, middle ring 320 may be a composite structure formed of an upper ring 320A and lower ring 320B each shaped similarly to bottom ring 310. The two rings 320A, 320B may be attached together (e.g. welded) in back-to-back relationship with flat bottoms 1 in contact and exposed surfaces 31 1 with the raised and recessed segments 312, 314 facing axially outwards as best shown in FIG. 2A.

[Θ066] It will be appreciated that in some embodiments, the upward and downward feeing exposed top surfaces 311. of the middle ring 310 may be substantially at without raised/recessed segments 312, 31 depending on the canister design used. f different configuration lower and upper canisters 140 are to be accommodated in the storage module 110, one of the rings 31 OA. or 310B may be castellated (i.e. raised/recessed segments 312, 314) and the other may be flat on both surfaces. Accordingly, any combination may

advantageously be used depending on the canister types to be stored in the storage module 1 10.

[0067] Referring to FIGS. 2, 2A _« and 5, centering and spacing middle ring 320 assembly further includes radially extending centering lugs 322 arranged in a circumferentially spaced pattern around the ring similarly to the bottom lugs 300 and ring 3 10 assembly already described. In one construction, the centering lugs 322 are welded around the perimeter of middle ring 320 and made integral therewith; both, of which preferably are both made of suitable metal such as steel The lugs 322 may not be fixedly attached to tbe inner shell 1 0 of storage module 1 S O such that the middle ring-lug assembly 320/322 is removable as a. unit from the storage module with the canisters 140. This allows the first lower canister 1 0 to be first positioned it.) the bottom half of the storage module i 10, die middle ring-lug assembly 320/322 then lowered and placed on top of the lower canister, and then the second upper canister 3 0 lowered and positioned into the top half of the storage module 1 10 to engage the middle ring-lug assembly 320/322. The middle ring-lug assembly 320/322 may alternatively be lowered into the inner shell 130 with the lower canister simultaneously allowing the ring- lug assembly to be placed on top of the lower canister before being lowered into the inner shell together in one step.

}0668| FIG. 2 shows the lower canister 140 in position within the storage module .1 10 and ready for receiving the upper canister 140. The middle ring-lug assembly 320/322 is in position. The centering lugs 322 may have a similar side profile as lugs 3 J 0 already described including angled edges 302 to help guide and center the bottom .1 3 of the upper canister 140 when lowered into storage module 1 10 on top of the lower canister (see also FIG. 2A). ^' Both the upper and lower portions of htgs 322 may include angled edges 302 as shown which helps center and properly position the middle ring-lug assembly 320/322 on the top 142 of the lower canister 140 when the assembly is iowered into place in the storage module 1 10. Accordingly, in one embodiment the upper and lower portions of lugs 322 are mirror linages .

[Θ069] it will be appreciated that middle ring-lug assembly 320/322 in conjunction with the lower canister 140 supports the upper canister 140 a shown in FIGS. 3 and 3A,

Advantageously, from a structural standpoint, (he middle ring 320 transfers and distributes the weight of the upper canister to the inherently stronger and stiiier cylindrical sidewa!ls of the shell sidewall 14.1 of the lower canister instead, of onto the central portion of the structurally weaker canister lid. This enhances the load bear ing capability of the lower canister for supporting the weight of the upper canister.

[ΘΘ7Θ) The middle ring-lug assembly 320/322 also laterally restrains the bottom end 143 of the upper canister 1.40. Accordingly, the centering lugs 322 are configured, dimensioned, and positioned to engage both the top .142 of the lower canister 140 and the bottom 143 of the upper canister 140, Significantly, the middle nng-lug assembly 320/322 further serves to maintain the inner annular space 133 and vertieai riser ventilation shaft 134 formed between, the canisters 1.40 and inner shell 130 by providing proper horizontal aligned of the canisters

- 35 - along the vertical axis VA of the storage module 1 10. The .middle ring-lug assembly 320/322 also provides some vertical spacing between the top 142 of the lower canister 140 and bottom of the upper canister 140 to permit cooling ventilation air to flow in the small space between, the two canisters to enhance cooling the canisters.

}0071| Referring to FIGS. 3 and 3A, a to ring-l g assembly 330/332 is also provided to laterally support and restrain the top 1 2 of the upper canister 140 against the inner shell 130. This assembly is comprised of a single support ring 330 having the arcuate raised/recessed segments 31.2, 314 facing downwards towards the upper canister. The plurality of cen tering lugs 332 are welded to the perimeter of ring 33 in a similar manner to the middle ring 320 as already described. Preferably, the lugs 332 are not. fixedly attached to the inner shell 130 like the middle centering lugs 322 to allow the top ring-lug assembly 330/332 to be removable in the same manner from the storage module 1 10. In some embodiments, both the top and bottom: surfaces 311 , 313 of the to ring 330 may be substantiall flat instead of castellated. The centering lugs 332 may be configured similarly to lugs 310 or 322 already described.

[Θ072 ] It should be noted that the centering lugs 300, 322, and 332 laterally restrain, and horizontally support the lower and upper canisters 140 inside storage module ί 10 during a seismic event (e.g. earthquake) against excessive movement, la addition, these lugs also maintain the inner annular space 133 along the entire height of the module to preserv e the inner annular space 133 between the sidewalls of the canister shells .1 0 and inner shell 130 of the storage module 1 10 thereby protecting the integrity of the vertical riser ventilation shaft 134 for proper ventilated cooling of the canisters.

[Θ073] It should be noted that the support rings 31 , 320, and 330 with undulatin top surfaces 31 1 having raised and recessed segments 312, 3 14 may be used with both canisters 140 having plain, (i.e. flat) top and bottom, ends, or with specially configured ends as described herein with complementary configured ends as the rings to provide an anti-rotation feature. In other possible embodiments, the rings 310, 320, 330 may be substantially flat on both the top surface 311 and opposing bottom surface 313.

[0074] In some alternative constructions, the middle and top lugs 322, 332 may be attached (welded) to the inner shell 130 of the storage module 1 10 and rings 320, 330 may be separate and removable elements,

J00?S| FIGS, 3 and 3 A show storage module 1 it) with both lower and upper canisters 140 in position and top lid 200 in place after insertion of the canisters. The lower and upper canisters 140 are concentrically aligned with the verticai axis VA of the storage module 1.1.0, In one embodiment, the diameter of the inner shell 130 and diameter of the internal cavity 122 are only wide enough to accommodate a single canister 140 at each elev ation of the storage module i 10 so that, two canisters will not tit in side-by-side relationship in the storage module. The canisters .140 undergo cooling by natural convection via the ventilated cooling air system described above and shown by the directional airflow arrows in FIG. 5. It stands noting thai the upper canister .140 does not directly contact the lower canister, but instead bears on middle ring-lug assembly 320/322 which, vertically separates and spaces the two canisters. The dead load or weight of the upper canister is transferred through the middle ring-lug assembly 320/322 to the lower canisier which bears the weight of the upper canister. j O076j it will be appreciated that the number of vertically stacked canisters in each storage module 1 10 may be limited by the load carrying capacity of the canisters themsel ves since each canister in the stack transmits and bears the weight of the canisters above; the iowermost canister 140 in the stack bearing the entire dead weight of the whole canister stack.

Accordingly, a vertically deeper (higher) storage module 1 10 and internal cavity 122 with additional canisters can be deployed if the structural strength of the iowermost canister 140 and the support foundation were accordingly strengthened to support greater than two canisters.

10677] According to the present invention, it bears noting that the top and bottom canisters 140 can be of different diameters and heights within a range of limits which fit within the storage module 1 10. The centering and spacing rings 310, 320, 330 with lugs 300, 322, 332 as described herein can be customized to provide the necessary adaptation for varying canister diameters and different end type features. Accordingly, the storage modules 1 10 disclosed herein are highly customizable to accept numerous types and sizes of canisters irom a number of different canister suppliers or sources.

[Θβ78] While the foregoing description and drawings represent exemplary embodiments of the present disclosure, it will be understood that various additions, modifications and

substitutions may be made therein without departing from the spirit and scope and range of equivalents of the accompanying claims. In particular, it. will be clear to those skilled in the art that the present invention may be embodied in other forms, structures, arrangements, proportions, sizes, and with other elements, materials, and components, without departing from, the spirit or essential characteristics thereof. In. addition, numerous variations in the methods processes described herein may be made within the scope of the present disclosure. One skilled in the art will further appreciate that the embodiments may be used with man modifications of structure, arrangement, proportions, sizes, materials, and components and otherwise, used in the practice of the disclosure, which are particularly adapted to specific

- Π - environments and operative requirements without departing from the principles described herein. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive. The appended claims should be construed broadly, to include other variants and embodiments of the disclosure, which may be made by those skilled in the art without departing from the scope and range of equivalents.