CN116829274A

CN116829274A - High density underground storage system for nuclear fuel and radioactive waste

Info

Publication number: CN116829274A
Application number: CN202180088668.4A
Authority: CN
Inventors: 克里希纳·P·辛格
Original assignee: Holtec International Inc
Current assignee: Holtec International Inc
Priority date: 2020-11-25
Filing date: 2021-11-16
Publication date: 2023-09-29

Abstract

An underground passive ventilated nuclear waste storage system includes an array of cavity-enclosing containers, each cavity-enclosing container including a cavity containing a nuclear waste canister containing heat-generating radioactive waste. Each container includes at least one pair of air inlets, each air inlet being directly fluidly coupled to a separate vertical cooling air supply housing spaced from the container. The feeder housing, which is in fluid communication with ambient air, operates to draw in ventilation air that flows to the container by a natural convection thermosiphon effect driven by heat emitted from the tank heating the container cavity. The containers are arranged in a plurality of parallel rows in a continuously spaced apart manner. The containers in each row are fluidly isolated from the containers in the other rows. The containers within each row are further fluidly isolated from other containers within the row when the ventilation system is in operation. These containers are part of a reinforced temporary storage facility for radioactive waste.

Description

High density underground storage system for nuclear fuel and radioactive waste

Cross Reference to Related Applications

The present application claims the benefit of U.S. provisional patent application No. 63/118,350, filed on 25 months of 11 in 2020, and U.S. provisional patent application No. 63/123,706, filed on 10 months of 12 in 2020; which is incorporated by reference in its entirety.

Technical Field

The present invention relates to spent nuclear fuel and radioactive waste storage systems and, more particularly, to a system suitable for consolidated temporary waste storage.

Background

Currently, spent or spent nuclear fuel and radioactive waste are temporarily stored "on site" in nuclear power plants that have been placed in service and some retired until the federal government provides a central permanent warehouse. For example, spent Nuclear Fuel (SNF) is withdrawn from the core and stored in a reactor fuel pool and continues to generate decay heat. After cooling in the tank for a period of time, the fuel may be transferred to a nuclear canister placed in a thick-walled external container (e.g., a dry storage module or cask typically made of concrete, steel, iron, etc.) to provide sealing and radiation shielding. These drums are stored on site in the power station.

The concept of using consolidated temporary storage (CIS) aims to provide geographically distributed off-site storage facilities for spent nuclear fuel and other high level nuclear radioactive waste collected from multiple independent electric sites, thereby better controlling widely dispersed waste reserves. The waste is stored in a sealed nuclear waste tank, such as a multi-purpose tank (MPC) available from Hall-Tek International company, carmden, N.J. The canister typically includes an elongated cylindrical stainless steel shell, a base plate, and a lid that is sealed to the shell to form a bounded boundary for a stored fuel assembly disposed in the canister. A fuel basket disposed within the canister has a rectilinear honeycomb structure defining a plurality of open prismatic cells, each cell housing a nuclear fuel assembly. The fuel assembly includes a plurality of nuclear fuel rods or "cladding" containing uranium fuel balls that, when removed from the nuclear reactor, continue to release significant amounts of decay heat.

Nuclear waste tanks may initially be transported from a power station to a CIS facility for a period of time with the ultimate goal of ultimately being transferred to a permanent nuclear waste warehouse at the time of government supply. Such so-called stand alone spent fuel storage facilities (ISFSI) are facilities designed for temporary storage of spent nuclear fuel, including solid, reactor-related, greater than class C waste materials, and other related radioactive materials. Each ISFSI facility typically maintains a list of a large number of canisters containing spent nuclear fuel and/or radioactive waste.

Some ISFSIs include a plurality of storage modules that store nuclear waste underground and are ventilated with natural ambient cooling air. However, such existing underground nuclear waste storage systems do not meet all of the current requirements of ISFSI in all situations. For example, the modules may be fluidly coupled to an available ambient cooling air source and/or to each other in a manner that deprives some of the modules of ventilation air needed to optimally cool the radioactive waste in each module.

There is a need for improvements in such underground ventilated nuclear waste storage systems.

Disclosure of Invention

One aspect of the present invention provides an underground natural draft and passive cooled radioactive nuclear waste storage system designed for underground storage of fuel. The system comprises a plurality of modules, such as CECs (cavity closed containers), which can be arranged in an upright position on an underground concrete foundation pad, which is located below the surface soil and/or engineering filler of the final clean floor of the storage site. Thus, most of the height of the underground CEC is preferably below the ground, thereby forming a low profile to prevent potential intentional or unintentional projectile impact (projectile impact). In one embodiment, CECs in an array may be arranged in a single column linear pattern spaced apart to form a nuclear waste storage row extending horizontally along a common longitudinal axis. A plurality of CECs in parallel linear rows may be provided in a CIS facility forming an ISFSI facility.

In one embodiment, each CEC defines an internal cavity configured diametrically in a cross-sectional area for housing a single cylindrical Spent Nuclear Fuel (SNF) canister. The canister contains the SNF assemblies and/or other high level radioactive waste as previously described herein, which continue to release significant amounts of heat that needs to be dissipated in order to preserve the structural integrity of the fuel assembly or other waste. In certain other embodiments contemplated, multiple cans may be stacked vertically on top of one another in a single CEC, such as disclosed in commonly owned U.S. patent 9,852,822, which is incorporated herein by reference. In this case, the CEC may be diametrically arranged in the cross-sectional area to fix the individual tanks at a single height at upper and lower positions within the CEC.

In a preferred but non-limiting embodiment, a passive ambient air ventilation system without fan or blower assist is used to cool the CEC and internal tanks to circulate cooling air through the CEC. When the air in the annular space is heated by the tank, the heat emitted by the tank drives fluidly a convective natural thermosiphon effect to draw ambient air through the CEC cavity in the annular space between the CEC and the tank. In other possible embodiments, fans/blowers may be provided if desired, but are less preferred because an interruption in the power to the CIS site would interfere with the ability to adequately cool the CEC and the radionuclide and/or other waste contained therein.

In a preferred but non-limiting embodiment, each CEC includes a minimum of two air inlets. In one embodiment two air inlets are provided. The air inlet is directly fluidly coupled to at least one direct source of cooling air via laterally and horizontally extending flow conduits (i.e., there is no intervening CEC in the airflow channel defined by the flow conduits between the source of cooling air and the air inlet of the CEC). Furthermore, each CEC is not fluidly coupled to any other CEC (i.e., shell-to-shell) via a flow conduit in a direct manner. This advantageously minimizes fluid air flow interactions between adjacent CECs that result in an air pressure imbalance where those CECs containing radioactive waste emit more heat than other CECs that disproportionately absorb a greater amount of available ventilation air in the system than other CECs that partially lack sufficient cooling air.

In some embodiments, the cooling air source may be one or more vertically elongated and tubular/hollow ambient cooling air supply housings. The air feeder housing may have a smaller outer diameter than the CEC, allowing the CECs to be spaced as closely as possible to save available nuclear waste storage space at the CIS facility within each row of CECs. Each air feeder housing is in fluid communication with the ambient atmosphere at the top and is operable to draw cooling air downwardly into the housing by a natural convection thermosiphon effect driven by heat emitted from the nuclear waste canister within the CEC. Air flows through the flow conduit and into the CEC, is warmed by the radioactive waste in the canister, and is then vented back to atmosphere through the top of the CEC, which may be above ground to define an air outlet.

In some embodiments disclosed herein, a pair of air inlets of a CEC may each be directly fluidly coupled to a single separate and independent cooling air supply housing via a flow conduit. In other embodiments disclosed herein, CEC is directly fluidly connected to a pair of air supply housings via a flow conduit. In another embodiment disclosed herein, a high airflow capacity system is provided for nuclear waste to still emit very high levels of heat conductively through the nuclear waste tank wall, wherein each CEC is fluidly coupled to two (i.e., four) pairs of cooling air supply housings. In all of these embodiments, each air inlet of the CEC is arranged via a separate dedicated single flow conduit rather than a shared manifold or manifold-type flow conduit that may prevent each CEC from receiving the required cooling air volume/flow in some cases as in some past approaches.

In any of the above three possible cooling air supply arrangements of CECs and cooling air feeder enclosures, providing at least two separate air inlets for each CEC and directly fluidly coupling to one or more feeder enclosures advantageously improves the ability of the natural ventilation system to adequately cool each CEC to the necessary extent to protect the structural integrity of the SNF assemblies and/or other high level nuclear waste stored within the CEC tank. Because ambient cooling air flowing from one or both of the cooling air supply housings to each CEC does not first pass through any upstream intermediate CEC (such as is used in some existing systems), the flow of ambient cooling air directly supplied to the CEC to naturally vent its interior space or cavity and cool the SNF tank is not reduced. This prevents situations in existing ventilation systems where a vertically oriented CEC or a storage enclosure at the end of a plurality of fluidly serially interconnected CECs cannot receive sufficient cooling air. This is because the upstream CEC absorbs a disproportionate share of the available cooling air supply flowing through the ventilation system. By coupling each CEC directly to at least one cooling air supply housing according to the present disclosure, the amount of cooling air required to adequately cool the tanks in each CEC by the thermosiphon fluid flow effect is ensured regardless of the level of decay heat generated by the radioactive waste in each CEC. Thus also avoiding an imbalance in air pressure between CECs due to different levels of decay heat.

In a nuclear waste storage system, such as a CIS facility with a passive ambient air ventilation system according to the present disclosure, in which a plurality of parallel linear rows of CECs are provided, any CEC in one row may be directly or indirectly fluidly coupled to any other CEC or cooling air supply housing in an adjacent row (i.e., via an intermediate CEC or flow conduit). This prevents fluidic interactions between CECs in adjacent rows that could lead to pressure and flow imbalances, resulting in cooling of some CECs in proportion to others as previously described. Furthermore, it is worth noting that the use of multiple parallel rows of CECs that are not fluidly interconnected advantageously simplifies the extension of existing CIS facilities, as it is not necessary to partially search for previous rows of CECs to create new fluid couplings with existing embedded CECs.

The collective array of CECs according to the present disclosure may form part of an independent spent fuel storage facility (ISFSI) adapted for a CIS system that may include any suitable number of CECs as desired. CEC may be part of a CIS system, such as HI-stop UMAX (hall tak international underground highest security storage module), which is a subsurface Vertical Ventilation Module (VVM) dry spent fuel storage system designed to be fully compatible with all currently certified multi-purpose tanks (MPC). Each HI-stop UMAX vertical ventilation module provides vertically configured MPC storage within a cylindrical cavity that is located entirely below the top-of-ground level top of the ISFSI. VVM is stacked like above ground, consisting of CEC; according to the present disclosure, each VVM includes a removable top closure cap.

The nuclear canister useful in the present CEC may contain both radioactive Spent Nuclear Fuel (SNF) and/or non-fuel radioactive waste, which may be a stainless steel multi-purpose canister (MPC) available from hall-tag international company of camden, new jersey. Other tanks may be used.

Current underground nuclear waste storage systems aim to provide extremely low site boundary radiation dose levels and safety during catastrophic events. As an underground system, the system provides radiation shielding, physical protection, and low center of gravity with surrounding soil/engineered fill or foundations to achieve stable storage installations.

According to one aspect, an underground passive ventilated nuclear waste storage system includes: a horizontal longitudinal axis; an underground concrete foundation mat; a vertically elongated first cavity-closing container located on the base pad and the longitudinal axis, the cavity-closing container defining a vertical centerline axis and comprising a first air inlet, a second air inlet, an air outlet, and an interior cavity; the cavity of the first cavity-closing container is configured to house a nuclear waste canister containing exothermic radioactive nuclear waste; a vertically elongated first cooling air supply housing in fluid communication with ambient atmosphere and operable to intake ambient air, the first cooling air supply housing being directly fluidly coupled to the first air inlet of the first cavity-closing container via a first flow conduit; a vertically elongated second cooling air supply housing is in fluid communication with the surrounding atmosphere and is operable to draw in ambient air, the second cooling air supply housing being directly fluidly coupled to the second air inlet of the first cavity-closing container via a second flow conduit. In one embodiment, the first cavity-closing container is not directly fluidly coupled to any other cavity-closing container.

According to another aspect, an underground passive ventilated nuclear waste storage system includes: a horizontal longitudinal axis; an underground concrete foundation mat; a vertically elongated first cavity-closing container located on the base pad and the longitudinal axis; a vertically elongated second cavity-closing container located on the base pad and the longitudinal axis, the second cavity-closing container being spaced apart from the first cavity-closing container; the first and second cavity-closing containers each defining a vertical centerline axis and including a first air inlet, a second air inlet, an air outlet, and an interior cavity; a nuclear waste tank located in each of the inner cavities of the first cavity-closing container and the second cavity-closing container, the tank emitting heat; a vertically elongated cooling air supply housing disposed on a longitudinal axis between the first cavity-enclosing container and the second cavity-enclosing container, the cooling air supply housing being in fluid communication with the ambient atmosphere and operable to draw in ambient air; the cooling air supply housing is directly fluidly coupled to the first air inlet of the first cavity-closing container via a first flow conduit; the cooling air supply housing is directly fluidly coupled to the first air inlet of the second cavity-closing container by a second flow conduit; wherein the first cavity-closing container is not directly fluidly coupled to any other cavity-closing container and the second cavity-closing container is not directly fluidly coupled to any other cavity-closing container.

According to another aspect, a reinforced temporary storage facility for nuclear waste comprises: a plurality of elongated cavity containment vessels, each elongated cavity containment vessel being established on the underground foundation pad and extending vertically upward from the underground foundation pad to the concrete roof pad; an engineered fill disposed between the base pad and the top pad; the cavity-closing receptacles are arranged in an array comprising a plurality of longitudinally extending and parallel linear rows of cavity-closing receptacles, each row defining a longitudinal axis, and each cavity-closing receptacle being arranged on a longitudinal axis; a plurality of vertically elongated cooling air feeder housings disposed in each row on a respective longitudinal axis, one cooling air feeder housing interposed between and directly fluidly coupled to a pair of cavity-enclosing containers located on opposite sides of the cooling air feeder housing, each cooling air feeder housing in fluid communication with the ambient atmosphere; the one cooling air supply housing being operable to draw in ambient air and distribute the air directly to each pair of cavity-enclosing containers; wherein the cavity-closing containers in each row are fluidly isolated from the cavity-closing containers in any other row.

According to another aspect, an underground passive ventilated nuclear waste storage device for reinforcing a temporary storage facility, the device comprising: a vertically elongated cavity-closing container supported on the underground foundation mat and extending vertically upward therefrom to the concrete roof mat; an engineered fill disposed between the base pad and the top pad; a nuclear canister located in the interior cavity of the cavity-closing vessel, the canister emitting decay heat that heats air in an annular space formed between the cavity-closing vessel and the canister; a vertically elongated hollow cooling air supply housing disposed on a side of the cavity-enclosing container, the cooling air supply housing being in fluid communication with the ambient atmosphere and operable to draw in ambient air; the cooling air feeder housing is directly fluidly coupled to the lower portion of the cavity via a first flow conduit through a first air inlet of the cavity-closing container; the cooling air feeder housing is also fluidly coupled directly to the lower portion of the cavity through a second air inlet of the cavity-closing container via a second flow conduit; the first flow conduit and the second flow conduit are fluidly coupled to a lower portion of the cooling air supply housing; wherein a cooling air flow passage is defined wherein ambient cooling air is drawn into the cooling air supply housing, flows through the first flow conduit and the second flow conduit to the lower portion of the cavity-enclosing container, flows upwardly in the annular space and is heated by the canister, and is exhausted back to atmosphere from an air outlet at the top of the cavity-enclosing container.

Drawings

Features of exemplary embodiments of the present invention will be described with reference to the following drawings, in which like elements are labeled similarly, and in which:

FIG. 1 is a perspective view of an ISFSI facility including a first embodiment of a nuclear waste storage system according to the present disclosure for the consolidated temporary storage of spent nuclear fuel and other highly radioactive nuclear waste;

FIG. 2 is a top view thereof;

fig. 3 is a perspective view of one of the nuclear waste storage banks of the ISFSI facility of fig. 1 and 2.

Fig. 4 is a first cross-sectional view of a second embodiment of the nuclear waste storage system showing a cavity-closing container (CEC) and its cooling air supply housing;

fig. 5 is a second cross-sectional view of a CEC alone.

Fig. 6 is a top view of a plurality of CEC arrangements of the second embodiment.

Fig. 7 is a perspective view of one nuclear waste storage row according to the second embodiment.

Fig. 8 is a top perspective view of the first embodiment of the nuclear waste storage system of fig. 1-3, showing one of the modular nuclear waste storage units including CEC; a pair of directly fluidly coupled cooling air supply housings are all mounted on a common support plate;

fig. 9 is a bottom perspective view thereof.

Fig. 10 is a first side view thereof.

Fig. 11 is a second side view thereof.

Fig. 12 is a front view thereof.

FIG. 13 is a top view thereof with the cap in place on the CEC;

FIG. 14 is a top view thereof with the top cover removed to show the internal cavity of the CEC;

FIG. 15 is a top plan view thereof with the top air intake housing removed from the pair of cooling air supply housings to show the array of radiation attenuator plates therein;

fig. 16 is a top perspective view thereof.

FIG. 17 is a cutaway perspective view thereof showing a modular nuclear waste storage unit mounted on an underground concrete foundation mat, a concrete roof mat and an engineered fill therebetween;

fig. 18 is a side sectional view thereof.

FIG. 19 is a side cross-sectional view showing a plurality of CEC and cooling air supply housings; in a portion of the nuclear waste storage row of fig. 3.

Fig. 20 is a top view of a third embodiment of a nuclear waste storage system according to the present disclosure, showing a pair of CEC and cooling air supply housings.

All of the figures are schematic and not necessarily drawn to scale. Components given a reference number in one figure may be considered as the same components that they appear in other figures without a reference number for brevity, unless specifically labeled with a different part number and described herein. Unless otherwise indicated, references herein to an entire reference numeral including multiple figures with the same reference numeral but different letter suffixes should be interpreted as a general reference to all figures sharing the same entire reference numeral.

Detailed Description

The features and benefits of the present invention are illustrated and described herein with reference to exemplary ("exemplary") embodiments. The description of the exemplary embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. Thus, the disclosure should not be expressly limited to the exemplary embodiments, which illustrate some possible non-limiting combinations of features that may be present alone or in other combinations of features.

In the description of the embodiments disclosed herein, any reference to direction or orientation is for descriptive convenience only and is not intended to limit the scope of the invention in any way. Terms such as "lower," "upper," "horizontal," "vertical," "above," "below," "upward," "downward," "top" and "bottom" and the like as well as derivatives thereof (e.g., "horizontally," "downwardly," "upwardly," etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These related terms are only for convenience of description and do not require that the apparatus be constructed or operated in a particular orientation. Unless specifically stated otherwise, terms such as "attached," "fixed," "connected," "coupled," "interconnected," and the like refer to a relationship wherein structures are directly or indirectly secured or connected together by intervening structures, as well as both movable or rigid attachments or relationships.

As used throughout, any range disclosed herein is used as a shorthand for describing each and every value that is within the range. Any value within a range may be selected as the end of the range. In addition, all references to prior patents or patent applications cited herein are incorporated by reference in their entirety. If a definition in this disclosure conflicts with a definition of a cited reference, the present disclosure controls.

Fig. 1 and 2 depict top views of ISFSI facilities including a passively cooled underground ruggedized temporary storage (CIS) system 100 according to the present disclosure. In accordance with the present disclosure, the system 100 includes an array of underground vertically ventilated Cavity Enclosed Containers (CECs) 110, wherein each CEC is equipped with a nuclear waste canister 150 containing radioactive nuclear waste, and a vertically elongated cooling air supply housing 130 interspersed between and fluidly coupled to the CECs. As further described herein, the CEC and air feeder housing are configured to form an integral component of an unpowered natural convection ventilation system that operates by a thermosiphon effect to cool nuclear waste stored in each CEC.

Fig. 4 and 5 depict one embodiment of CEC 110 and cooling air supply housing 130 of a nuclear waste storage system according to the present disclosure in more detail. CEC 110 and cooling air supply housing 130 are built upon and supported by a thick and horizontally extending underground foundation pad 101, which foundation pad 101 is located below the cleaned top surface or ground "G" of original soil "S" at the CIS system site. In one embodiment, the base pad 101 may be made of reinforced concrete; however, in other embodiments, other materials, such as compacted gravel, may be used so long as a stable and sturdy base is provided to support the CEC and air supply housing. In the case of concrete shown in the illustrated embodiment, the CEC and air feeder housing may be rigidly anchored to the foundation pad via a plurality of anchor members 103, such as solid J-shaped fasteners (threaded or otherwise), or other suitable types of anchors commonly used to fasten structures to concrete. Preferably, the base pad 101 has a suitable thickness and a sufficiently strong structure to withstand the presumed seismic event and maintain secure support for the CEC 110 and containment of its nuclear waste contents.

A horizontally and longitudinally extending concrete roof pad 102 is formed on top of an engineered fill 140 described below, the engineered fill 140 being placed after the base pad 101 is poured. Thus, the roof pad 102 protrudes upward from the cleaned ground G of the surrounding raw soil S and rises above the ground G. The top pad is vertically spaced from the underlying ground base pad 101. The roof pad defines an upwardly facing top surface 102a above the ground to prevent water accumulation from the surrounding raw soil S due to rainfall from entering CEC 110. The top surface 102a is substantially parallel to the upwardly facing top surface 101a of the base pad 101 (the term "substantially" contemplates minor variations in the height of the surfaces 101a, 102a and the depressions and/or contours formed therein for various purposes). Top pad 102 preferably extends at least one CEC outside diameter beyond peripheral CEC 110. Preferably, the progressively sloped topography of the native soil S around the roof pad facilitates drainage of rainwater from the CEC.

The vertical gap or space formed between the base and top pads 101, 102, including the open horizontal/lateral space between adjacent CECs 110 and the cooling air supply housing 130, is filled with a suitable "engineered fill" 104 to provide lateral radiation shielding for the nuclear waste stored within the CEC110, as well as complete lateral structural support for the CEC and the cooling air supply housing 130. Any suitable engineered filler may be used, such as, but not limited to, a flowable CLSM (controlled low strength material), which is a self-compacting cement filler material commonly used in industry as backfill to replace conventional compacted soil fillers. If further enhancement of the radiation dose blocking capability of the CIS system is desired, plain concrete can also be used as the inter CEC and base-to-top pad gap filler material. Other types of filler materials that provide radiation shielding and lateral support of the CEC and air supply housing may be used.

With continued general reference to fig. 4 and 5, each CEC 110 includes a vertically elongated metal housing body 111 defining a vertical centerline axis VC1 and extending between a top end 112 and a bottom end 113 of the body. As shown, an upper portion 111a of the housing body defining the top end 112 may be embedded in the concrete top pad 102, including between the top surface 102a and the bottom surface 102b of the top pad 102. In some embodiments shown in fig. 4-5 and 17-19, the top end 112 of CEC housing body 111 may terminate at top surface 102a of the top pad. In either case, in a preferred non-limiting embodiment, the body 111 of the CEC 110 may be cylindrical with a circular cross-sectional shape; however, other non-polygons and polygon-forming features may be used in certain other acceptable embodiments. The housing body 111 of each CEC 110 defines a vertically extending interior cavity 120 extending between the ends 112, 113 configured for receiving a cylindrical canister 150. As previously described, the canister 150 defines an interior space that houses spent fuel assemblies and/or other highly radioactive waste materials from the nuclear reactor.

The nuclear canister 150 stored in the CEC 110 includes a vertically elongated hollow cylindrical housing 151, a top closure plate 152 and a bottom closure plate 153. The top and bottom closure plates are seal welded to the top and bottom ends of the housing 151 to form a hermetically sealed boundary for nuclear waste stored in the tank. In a preferred embodiment, the can 150 (i.e., the housing and the closure plate) may be formed of stainless steel for corrosion resistance. The height H3 of the tank 150 is less than the height H2 of the CEC housing body 111 such that the top of the tank is vertically and downwardly spaced from the bottom of the concrete roof pad 102 (see, e.g., fig. 3). This helps to ensure that no lateral radiation flows outwardly from CEC 110 at the top and provides impact protection against incident projectiles (e.g., missiles, etc.). Canister 150 may be any type of nuclear waste/SNF canister including, but not limited to, a multi-purpose canister (MPC) available from Hall-Tek International company, carmden, N.J.

CEC 110 also includes a substrate 114 hermetically welded to bottom end 113 of housing body 111. A plurality of metallic radial support lugs 124 are welded to base plate 114 and/or on the inner surface of CEC housing 111 at the bottom of cavity 120 in a circumferentially spaced apart manner. The lugs are formed of a suitable metal (e.g., stainless steel or other metal) and are used to support and lift the canister 150 above the substrate. This creates an open space between the top of the baseplate 114 and the bottom closure plate 153 of the canister 150 to allow cooling ventilation air to circulate under the canister to remove heat from the bottom of the canister from nuclear waste stored in the canister.

In one embodiment, support ledge 124 may be generally L-shaped with a horizontal portion 124a welded to base plate 114 and an integral adjoining vertical portion 124b welded to the inner surface of CEC housing body 111. The vertical portions 124b each define a radially extending lower seismic constraining member that engages the sides of the tank 150 to keep it centered within the cavity 120 of the CEC 110, particularly during a seismic event (e.g., an earthquake). A plurality of radially extending upper seismic restraining members 123b project inwardly from the shell body 111 in the cavity 120 to center the upper portion of the tank 150. The restriction members 123b may be formed of circumferentially spaced metal plates or lugs welded to the inner surface of the CEC housing main body 111.

When canister 150 is positioned in cavity 120 of CEC 110, a vented annular space 121 is formed therebetween that extends the entire height of the canister. The vent annulus is in fluid communication with the cooling air supply housing 130 at the bottom via a flow conduit 160 and an air outlet chamber 152 formed inside the CEC cavity 120 above the canister.

The housing main body 111 and the base plate 114 of each CEC 110 may be formed of a suitable metal, such as stainless steel, for corrosion resistance.

The top end 112 of CEC 110 is closed by a removable radiation-protective thick cover 115 removably mounted on top of CEC housing 111. The cover may have a composite metal and concrete construction including an outer shell 115a and an inner concrete liner 115b formed of steel (e.g., stainless steel). This robust construction not only provides radiation shielding, but also provides additional protection against projectile impact. In one configuration, the cap 115 includes a cylindrical circular upper portion 116a and an adjoining cylindrical circular lower portion 116b, the outer diameter D4 of the lower portion 116b being smaller than the outer diameter D3 of the upper portion. An annular stepped shoulder 116c is formed between the upper and lower portions of the cover. In some embodiments, the diameter D3 and/or D4 may be greater than the outer diameter D2 of CEC housing body 111.

As shown (see, e.g., fig. 4-5), the lower portion 116b of the cap 115 is insertably positioned within a corresponding upwardly opening circular recess 117 formed in the top surface 102a of the top pad 102 about the top end 112 of each CEC 110. The diameter D5 of the recess 117 is larger than the outer diameter D2 of the CEC housing main body 111. In one embodiment, the upper portion 111a of CEC 110 (i.e., housing body 111) may include an enlarged diameter top cylindrical portion 111b having the same diameter D5 as recess 117 and in effect defining the recess in the embodiment shown in fig. 14 and 16. The lid is raised slightly and half-opened in its recess to the top pad 102 to form an air outlet 118, thereby forming a vent channel between the lid and the CEC 110 for return of the raised ventilation air from the CEC cavity 120 to the ambient atmosphere. The air outlet 118 is configured to form a circuitous multi-angle passage such that there is no direct line of sight from the cavity 120 to the atmosphere for radiation escape (i.e., radiation flow). As shown in fig. 2, for this purpose, in one embodiment, the outlet 118 may have a double L-shaped configuration; however, other circuitous shaped channels may be used.

In some embodiments, as shown in fig. 16-18, the top 111b of CEC housing body 111 may also include a flat radially protruding annular base flange 111c. The base flange is configured to engage and rest on the top surface 102a of the concrete roof pad 102.

Each cooling air supply housing 130 is a tubular hollow structure comprising a metallic vertical elongated body 131 defining a vertical centerline axis VC2 and a bottom closure plate 132 welded to a bottom end 134 of the housing. The vertical centerlines VC2 and VC1 of CEC 110 are parallel to each other. In a preferred, non-limiting embodiment, the body 131 may be cylindrical with a circular cross-sectional shape; however, other non-polygons and polygon-forming features may be used in certain other acceptable embodiments. The body 131 of each feeder housing defines an open vertical air channel 133 extending between the bottom end 134 and the top end 135 of the housing 130 for drawing ambient cooling air downwardly through the housing. In some embodiments, the top end of the housing 130 may terminate at the top surface 102a of the concrete roof pad 102. As shown, a perforated air intake housing 136 is coupled to the top end 135 of the housing 130, which protrudes vertically upward from the top pad 102. In one embodiment, the housing 136 may be formed from a cylindrical shell perforated to form a plurality of lateral openings extending 360 degrees in the circumferential direction for drawing air laterally into the feeder housing 130. A circular cap 137 closes the top of the air inlet housing 136 to prevent rain water ingress. The air feeder housing 130, the bottom closure plate 132, the air intake housing 136, and the cap 137 may be made of metal such as stainless steel to prevent corrosion. Other shapes of caps and air intake housings may be used in other embodiments.

In order to cause as little as possible of the rising air exiting the top of cavity 120 of CEC110 that has been heated by canister 150 to be drawn back into intake housing 136 of cooling air feeder housing 130, in some embodiments, each feeder housing is preferably spaced from housing body 101 of an adjacent CEC a sufficient lateral/horizontal distance, such as at least one outer diameter D1 of the feeder housing.

With continued reference to fig. 4 and 5, the height H1 of the cooling air supply housing 130 is at least the same as the height H2 of the CEC housing body 111. As one non-limiting example, H2 and H1 may be approximately 227 inches (576.6 centimeters). In one embodiment, housing 130 may have a height H1 (measured between bottom end 134 and top end 135) that is slightly greater than height H2 of CEC housing body 111 (measured between bottom and top ends 113, 112 of the body including upper portion 111 a).

The overall height H3 of the canister 150 (including the top and bottom closure plates 152, 153) is less than the height H2 of the CEC housing body 111, thereby forming an air outlet chamber 154 between the bottom of the CEC cap 115 and the top closure plate 152 of the canister. The top of the tank defined by the top closure plate 152 terminates below the concrete roof pad 102 of the CIS system, which may be within the vertical extent of the engineered fill 140. This helps prevent "sky light" radiation from flowing to the surrounding environment.

Referring to fig. 1 and 2, in one embodiment, the cavity-closing containers 110 and the cooling air supply housing 130 may be arranged in a closely-packed array to minimize space floor requirements at the CIS facility. The array includes a plurality of longitudinally extending and parallel linear nuclear waste storage rows R, each row R including a plurality of CECs 110 and cooling air supply housings 130. For ease of illustration, the arrays in FIGS. 1 and 2 show only five rows R; however, it is recognized that more or fewer rows of CECs and air supply housings may of course be provided as desired. Each row defines a respective horizontally extending longitudinal axis LA. The geometric center of each CEC intersecting its vertical centerline axis VC1 intersects the corresponding longitudinal axis LA in each row such that CEC110 may be considered to lie on the longitudinal axis. For ease of reference, the transverse axis TA may be defined as oriented perpendicular to the longitudinal axis LA in each row extending back and forth between rows R in the array (see, e.g., fig. 2).

The nuclear waste storage rows R of CECs 110 are spaced apart and parallel to each other to form a longitudinally extending channel AI that provides a channel for commercially available motorized wheel or track-driven lifting equipment (such as, but not limited to, drum crawlers or other equipment that transports, maneuvers and raises/lowers the canister 150 to insert and remove CECs 110 from CECs 110). The device may span a row of CECs 110 and wheels or tracks run in the channels AI on each side of the row. Such devices are well known to those skilled in the art and need not be described in further detail. The low exposed vertical profile of CEC110 (as further described herein) allows devices to be moved over CEC modules in a single row to a desired CEC to insert or remove cans.

Fig. 4-7 illustrate a first possible embodiment and arrangement of CEC 110 and cooling air supply housing 130. In this embodiment, each CEC 110 in each row R is directly fluidly coupled to a pair of cooling air supply housings 130 by a horizontally/laterally extending flow conduit 160; as shown, each feeder housing 130 is located on opposite lateral sides of CEC along longitudinal axis LA. From another perspective, each air supply housing 130 may be considered to be centrally located between a pair of CECs. Thus, each CEC includes a pair of air inlets 125 on opposite sides forming an opening that extends through the body 111 of CEC 110 to the interior cavity 120. Accordingly, an air inlet 125 is formed in and through the lower portion 111d of the CEC (i.e., the housing body 111) to introduce cooling air into the bottom of the CEC cavity 120 and the vent annular space 121. In a preferred but non-limiting embodiment, as shown, the air inlets 125 are each configured and arranged to introduce cooling ventilation air tangentially into the cavity 120 of each CEC 110. The introduction of cooling air in such a tangential manner that flows circumferentially around the inner surface of the CEC to rapidly fill the CEC cavity and vent advantageously results in a smaller pressure drop than the radial and vertical introduction of air at the canister shell 151.

The flow duct 160 includes a horizontally extending metal tubing portion that spans between the cooling air supply housing 130 and their respective CECs 110. The flow conduits fluidly couple each CEC air inlet 125 "directly" to a respective air feeder housing 130, which means that cooling air is transferred from the feeder housing to the respective CEC without passing through any other CEC or feeder housing en route. As previously described herein, this arrangement advantageously maximizes the amount of cooling air received by each CEC110 commensurate with the different levels of heat emitted by the tanks in each CEC. Thus, the CEC does not lack any cooling air flow required for upstream CEC. Because CECs and their nuclear waste contents are passively and convectively cooled by a natural thermosiphon effect as previously described herein, the present cooling device arrangement avoids pressure imbalance in the cooling air ventilation system that may adversely affect proper cooling of each CEC. Providing two air inlets 125 for each CEC110 and a separate source of cooling air (i.e., feeder housing 130) for each inlet further ensures that each CEC is cooled to remove heat generated in its cavity to the greatest extent possible.

For the same foregoing reasons, it is further noted that there is no interconnecting flow conduit between any CEC or cooling air supply housing 130 located in one row and any other row R in order to ensure that each CEC 110 receives a desired amount of cooling air based on the particular thermal load generated by the nuclear canister 150 therein. Thus, each nuclear waste storage row R is fluidly isolated from each of the other rows.

Although perhaps less obvious from the figures, it is also worth noting that when the ambient air cooled ventilation system is in operation (i.e., the nuclear canister 150 disposed in the CEC thereby creating an active airflow through the ventilation system via the thermosiphon effect described previously herein), each CEC 110 in a single row R is fluidly isolated from adjacent CECs as well as from each other CEC in the same row. For example, referring to FIG. 4, ambient cooling air will be drawn downwardly in the centrally located air supply housing 130 and then flow laterally outwardly to each of the two CECs 110 illustrated via the flow conduits 160 (see directional air flow arrows). When the air in the CEC cavity 120 is heated by the canister 150, cool air enters the bottom of the CEC and flows vertically upward (see, e.g., fig. 2). Thus, given the direction of flow through the nuclear waste storage system components, it is not possible for air to flow from one CEC 110 back through the centrally located air supply housing 130 and into the remaining CECs. Thus, CECs are effectively fluidly isolated from each other.

As previously described, the flow conduit 160 may comprise a metal tubing portion, such as stainless steel of suitable diameter. In a preferred but non-limiting embodiment, the flow conduits are configured such that there is no line of sight between each cooling air supply housing 130 and the respective pair of cavity-closing containers 110 fluidly coupled thereto to prevent radiant flow. This is accompanied by ensuring that there is no straight line of sight through the feeder housing 130 between any CECs 110 in row R. In one configuration, the flow conduits 160 may each include an angled transverse portion 162 oriented transverse to the longitudinal axis LA and an adjoining longitudinal portion 161 oriented parallel to the longitudinal axis. A welded miter joint 163 (see, e.g., fig. 6) may be formed between the lateral and longitudinal portions. An oblique angle is formed between the two parts of the flow conduit. In other possible embodiments, curved pipe bends may be used instead of mitered portions of straight pipes to prevent straight line of sight.

Because each cooling air supply housing 130 need only be sized in diameter to supply cooling air to a pair of CECs 110, the diameter of the supply housing can be minimized to allow the CECs in each row to be closely spaced. This advantageously allows more CECs and nuclear waste to be stacked into each row R. Accordingly, in a preferred but non-limiting embodiment, the outer diameter D1 of the feeder housing 130 may be smaller than the outer diameter D2 of the CEC 110. As one non-limiting example, D1 may be about 30 inches (76.2 cm) and D2 may be about 84 inches (213.4 cm). For size matching, the diameter of the flow conduit 60 may be smaller than D1 or D2; in one embodiment, for example, but not limited to, about 24 inches (61 cm). Other diameter sizes may be used in other embodiments and are not limiting of the invention.

To summarize the operation of the nuclear waste storage system and the ambient cooling air ventilation system, a nuclear waste tank 150 containing radioactive waste (e.g., SNF fuel assemblies and/or other highly radioactive waste removed from the reactor) is loaded into CEC 110. A cap 115 is then placed over the CEC to enclose the CEC and its internal cavity.

With the canister positioned inside the CEC and the lid in place, the air in the vented annular space 121 between the canister and the housing 111 of each CEC 110 is heated by the canister. The heated air rises, collects in an air outlet chamber 154 above the canister in the cavity 120 of the CEC, and exits the CEC back to the atmosphere through an air outlet 118 formed through the cap 115 of the CEC (see directional air flow arrows in FIGS. 4-5 and 18).

The upward convective flow of air within the cavity 120 of each CEC 110 creates a negative pressure that draws ambient air downward into the cooling air supply housing 130 by a known thermosiphon effect or mechanism. CEC draws air from the bottom of the air supply housing into the lower portion of its interior cavity 120 and the vent annulus 121 through the flow conduit 160 to complete the vent air flow circuit. Notably, such natural air flow is devoid of the assistance of electric fans or blowers, thereby avoiding the operational costs associated with power consumption, but it is important to ensure continuous cooling of CEC 110 in the event of power interruption to prevent CEC overheating and to protect the containment of nuclear waste.

Fig. 20 depicts an alternative second embodiment and arrangement of a nuclear waste storage system and corresponding ventilation system. In this embodiment, each CEC 110 is fluidly coupled to only a single cooling air supply housing 130 by a pair of angled/curved flow conduits 160 to prevent the flow of radiation as previously described herein. The CEC comprises two air inlets 125, which air inlets 125 are also arranged to introduce ventilation air tangentially into the internal cavity of the CEC. The bifurcated ventilation air supply effectively forms a curtain of cooling air around the nuclear waste tank 150 within the CEC with a minimum flow resistance to maximize the airflow for cooling the radioactive waste. This alternative embodiment may be suitable where certain canisters 150 still emit extremely high levels of thermal energy (heat), which must be dissipated to preserve the structural integrity of the canisters and the nuclear waste therein. The pairs of fluidly isolated CECs 110 and cooling air supply housings 130 in fig. 20 may be arranged in a row R of a CIS facility. CEC 110 and air supply housing 130 are arranged on a longitudinal axis LA of each row R that may be provided in a CEC array.

Notably, some CIS facilities may combine CECs 110 and air feeder housings 130 of some rows of nuclear waste cans for high thermal energy emissions according to the arrangement shown in fig. 20, and CECs and air feeder housings of some other rows of nuclear waste cans for lower thermal energy emissions according to the arrangement shown in fig. 4-7. In still other embodiments, two different arrangements of CECs and air supply housings may be mixed in a single row R. Thus, many variations are possible depending on the particular nuclear waste storage needs and the level of thermal energy emitted by the tank 150.

Fig. 1-3 and 8-19 depict yet a third alternative embodiment and arrangement of a nuclear waste storage system and corresponding ventilation system. This is a high airflow capacity configuration of a passive cooled nuclear waste storage system with a thermosiphon driven ventilation system, suitable for emitting very high heat of radioactive nuclear waste, which must be dissipated by ambient cooling air to protect the radioactive waste (e.g., SNF fuel assemblies, etc.) within the nuclear waste tank 150. The cooling air requirements of these high heat load CECs may even exceed the higher airflow capacity provided by CECs in fig. 20, as shown, with a dedicated pair of separate cooling air supply housings 130.

Accordingly, CEC 110 in this third embodiment of high airflow capacity may each be fluidly coupled to two pairs (i.e., four) of cooling air supply housings 130 (see, e.g., fig. 1-3 and 14) via air flow conduits 160. With continued general reference to fig. 1-3 and 8-19, as shown, one pair of feeder housings 130 may be located on one lateral side of the CEC while the remaining pair of feeder housings may be located on the opposite other lateral side. CEC includes four air inlets 125; each of which is fluidly coupled to one of the four cooling air feeder housings 130 by a flow conduit 160. The flow conduit 160 may be configured and arranged similarly to the previous embodiments of the ambient air ventilation system described previously herein to introduce ventilation air tangentially into the lower/bottom of the internal cavity 120 of the CEC 110 to achieve the same airflow benefits mentioned above.

It is noted that as shown in FIGS. 1-3, each CEC 110 in a single row R need not be connected to four cooling air supply housings 130. For example, one CEC 110 at one end of row R is shown fluidly coupled to only a pair of cooling air supply housings 130 because the thermal load of that CEC is less than that of the remaining other CECs depicted, requiring a higher ambient ventilation air flow or rate of row height (e.g., CFM-cubic feet per minute) to dissipate the higher thermal emissions of the tanks 150 stored therein. Thus, the passive cooling nuclear waste storage and ventilation system of the present invention provides considerable flexibility in configuration that can be tailored to accommodate the specific heat load dissipation requirements of different CECs.

With continued general reference to fig. 1-3 and 8-19, the construction and structural details of CEC 110 in the third embodiment and arrangement of a passive cooling nuclear waste storage system may be similar to the previously described embodiments, except that there is an additional cooling air inlet 125 for receiving two pairs of cooling air supply housings 130. Therefore, a description of the CEC structure including the cover 115 will not be repeated herein for the sake of brevity. Therefore, the numbers of features or parts of CECs in the third embodiment of the currently-shown nuclear waste storage system are the same as those in the drawings of the first and second embodiments.

However, in this high airflow embodiment shown in FIGS. 1-3 and 8-19, CEC 110 and cooling air supply housing 130 have been structurally integrated into a modular nuclear waste storage unit 200 (best seen in FIGS. 8-16) that is easy to transport and install. The modular unit 200 is a self-supporting and transportable assembly or structure that includes a common or common support plate 202 formed of a suitable strength and a suitable metallic material (e.g., stainless steel or other). The support plate 202 has a horizontally widened and flat body 201 configured to be mounted and anchored (e.g., by anchors 103) to the top surface of the subsurface concrete foundation pad 101, the anchors 103 being threaded fasteners or other types of anchoring/mounting devices. The single pair of cooling air supply housings 130 on one side of one CEC 110 and CEC are fixedly attached to a common or shared support plate 202, such as by welding. The support plate 202 may have any suitable configuration, such as a U-shaped hybrid polygonal-non-polygonal configuration in one non-limiting embodiment as shown.

To ensure that the vertically tall housing body 111 of the CEC 110 and the pair of cooling air supply housings 130 are structurally stable and supported for lifting and transport as a single self-supporting unit, a plurality of horizontally extending cross-support members 204 (e.g., appropriately shaped structural beams) are provided that structurally connect the CEC housing and the supply housing together in a rigid manner. In one embodiment (as variously shown in fig. 8-16), CECs 110 in each modular nuclear waste storage unit 200 are structurally connected and laterally supported to each of a pair of cooling air supply housings 130 by a plurality of vertically spaced cross-support members 204. In the non-limiting illustrated embodiment, three cross-support members are shown to connect each of the lower, middle and upper portions 111d, 111e, 111a of the CEC to each of the two feeder housings 130. More or fewer cross-support members 204 may be used. The pair of cooling air supply housings 130 are similarly connected together in structure and laterally supported by vertically spaced cross-support members 204, which cross-support members 204 may be of the same type or a different type than the cross-support structural members connecting CEC 110 to each cooler air supply housing 130. In one non-limiting embodiment, a W-beam may be used to cross-support structural members 204; however, other suitable types/shapes of structural members may be used.

The modular nuclear waste storage unit 200 advantageously allows the unit to be manufactured under controlled shop conditions in a manufacturing facility and then transported to an installation site (e.g., a consolidated temporary storage facility). Since CEC 110 and a pair of cooling air supply housings 130 are said to have been palletized on a common support plate 201, installation only requires plumbing connections with flow conduits 160 at the site of installation. This enables a modular nuclear waste storage unit to be quickly installed and deployed.

To install the modular nuclear waste storage unit 200 in the manner shown in fig. 3, for example, at a CIS site or facility, the installation process or method includes casting the concrete base pad 101, and then positioning and installing the first storage unit 200 on the base pad when cured and hardened. Next, the second storage units 200 are positioned and mounted on the base pad adjacent to the first storage units in a longitudinally spaced apart manner along the row R. The first storage unit can now be piped. Then, each of the four cooling air supply housings 130 is directly fluidly coupled to the CEC 110 of the first storage unit via a separate flow conduit 160. The tubing connection between the CEC and the feeder housing 160 may be welded, or preferably a bolted tubing flange-type connection, which may be more convenient to manufacture than a welded connection. The flange-type connection is suitable for these conditions of use, since the air flowing in the flow conduit 160 during operation of the ventilation system is at most slightly negative (sub-atmospheric). The next additional third, fourth, etc. nuclear waste storage units 200 may then be added and installed in a similar manner. Once all units are mounted to the base pad 101 and fluidly coupled to their respective cooling air feeder housing 130, a flowable engineered fill 140 may be installed on top of the base pad and around the feeder housing of CEC and CIS facilities to fill the void between the devices for lateral support and radiation attenuation/blocking, as shown in fig. 17-19 (note that the engineered fill is not shown in fig. 3 for clarity).

Next, a concrete roof pad 102 may be formed on top of the engineered fill. The modular nuclear waste storage unit 200 is now ready to receive a nuclear waste canister 150 in each cavity 120. In some embodiments disclosed in U.S. patent 9,852,822, which is incorporated herein by reference, a pair of cans 150 can be vertically stacked in each CEC 110 and supported therein in the manner described. Notably, CEC 110 maintains a cross-sectional area that is sufficient to maintain only a single canister at a single elevation (i.e., without side-by-side canister placement), whether it maintains a single or two vertically stacked canisters 150.

Notably, in a preferred but non-limiting embodiment, the aforementioned CEC 110 of the plurality of modular nuclear waste storage units 200 is preferably located on the longitudinal axis LA of the storage row R (i.e., the vertical centerline axis VC1 intersects the longitudinal axis LA). This is similar to the previous two embodiments of the nuclear waste storage system 100 shown in fig. 4-7 and 20. In the present embodiment shown in fig. 1-3, the first and second cooling air supply housings 130 of the first pair of supply housings may be perpendicular to the longitudinal axis LA and laterally spaced apart on opposite sides of the longitudinal axis LA. The first and second feeder housings are located on a first lateral side of the first CEC 110. The third and fourth cooling air supply housings of the second pair of supply housings may similarly be laterally spaced apart in the same manner and located on a second lateral side of the first CEC 110 opposite the first lateral side.

The first, second, third and fourth cooling air supply housings 130 are preferably directly fluidly coupled to the first CEC via separate metal flow conduits 160, as shown in FIG. 3 (see also various FIGS. 8-19). Thus, there is no intermediate CEC or cooling air housing. The flow conduit 160 may be formed from a pipe section as previously described herein.

In the present third embodiment, the flow conduits 160 may each include a horizontally extending straight conduit portion fluidly connecting a lower portion of the cavity 120 of the first CEC 110 to a lower portion of each of the cooling air supply housings 130. Each straight conduit portion flow conduit 160 defines a horizontal centerline axis Hc that is at an acute angle A1 to the longitudinal axis LA (see, e.g., fig. 14). This angular arrangement of the cooling air supply housing 130 relative to the longitudinal axis is sufficient to ensure that there is no line of sight between a first CEC 110 and the next adjacent CEC mounted on a different support plate 201. In certain embodiments, angle A1 may be between about 10 degrees and 20 degrees, including 10 degrees and 20 degrees.

As also shown in fig. 14, the cooling air supply housings 130 in each pair on opposite lateral sides of the depicted CEC 110 are located on opposite sides of the longitudinal axis LA. The geometric vertical center line VC2 of each feeder housing falls on a horizontal reference line R1 that makes an acute angle A2 with the longitudinal axis LA of the nuclear waste storage row R. In one embodiment, as shown, angle A2 may be about 30 degrees (+/-5 degrees). Notably, the angular arrangement of the flow conduits 160 and the cooling air supply housing 130 at angles A1 and A2, respectively, relative to the longitudinal axis LA advantageously helps to allow for a tighter spacing between CEC 110 and the supply housing in each row. This allows more CECs to be closely stacked into each row R.

Referring to fig. 15-19, in some embodiments, each cooling air supply housing 130 may include an array 170 of vertically elongated radiation attenuator plates 171. The plates 171 may be flat and structurally coupled together (e.g., welded by clips/brackets, etc.) and arranged in an orthogonal grid as shown. The plates 171 are disposed in the vertical air channels 133 of the cooling air supply housing 130 and form vertically extending grid openings therebetween through which ventilation air is drawn downwardly through the housing. The attenuator plate 171 may extend vertically for cooling a majority H1 of the air feeder housing. In one embodiment, the attenuator plate extends vertically from the top end 135 of the housing downward toward the bottom end 134 and terminates at a point just above and near the top of the flow conduit 160 so as not to interfere with the flow of ventilation air from the housing 130 to the CEC 110. In one embodiment, the attenuator plate 171 may be formed of steel; however, other suitable materials may be used, including boron-containing materials and metals. The attenuator plate 171 advantageously helps to prevent radiation from flowing to the surrounding environment around the nuclear waste storage system.

In operation, the ambient cooling air ventilation system of this high air flow embodiment shown in FIGS. 1-3 and 8-19 operates and follows the same general path as the previously described embodiments. As shown, each air inlet 125 is configured and arranged to introduce cooling ventilation air tangentially into the cavity 120 of each CEC 110. Ambient ventilation air is drawn downwardly from and through the attenuator plates 171 within each cooling air supply housing 130 and between them, and then flows horizontally/laterally through the flow ducts 160 to the CECs 110 to cool the tanks 150 in each CEC via the convective natural thermosiphon effect as previously described.

In the present embodiment of FIGS. 1-3 and 8-19, an alternative air outlet 220 is shown that is formed directly through the lid 215, rather than between the perimeter of the lid and the upper portion 111a of CEC 110 and top pad 102 as in the previous FIG. 4-7 embodiment described herein, the lid 115. In this embodiment, the air outlet 220 forms a circuitous multi-angle passage internally through the cover that terminates in an exhaust housing 216 mounted to the top surface of the cover (see, e.g., fig. 18 and directional airflow arrows). To accommodate this interior air outlet 220 passage, the configuration of the cover 215 is slightly different from the cover 115 previously described herein.

The vent housing 216 of the cap 215 of the present invention comprises a perforated cylindrical metal shell that protrudes vertically upward from the top surface of the cap 215 as shown. In one embodiment, the housing 216 includes a plurality of lateral openings extending 360 degrees in a circumferential direction for venting air laterally outwardly therefrom back to the surrounding environment. A circular cap 217 surrounds the top of the vent housing 216 to prevent rain water ingress. The vent housing 216 and cap 217 may be formed of a metal such as stainless steel to prevent corrosion. Other shapes of caps and air intake housings may be used in other embodiments.

The cap 215 may have a composite metal and concrete construction and shape similar to the previous cap 115 in fig. 4-7, including an outer shell 215a and an inner concrete liner 215b formed of steel, such as stainless steel. This robust construction not only provides radiation shielding, but also provides protection against projectile impact. In one configuration, similar to the previous cap 115, the cap 215 includes a circular upper portion 218a and an adjoining circular lower portion 218b, the circular lower portion 218b having an outer diameter that is less than the outer diameter of the upper portion. The cap 215 effectively seals the upwardly opening recess 117, the recess 117 being formed in the top surface 102a of the top pad 102 around the top end 112 of each CEC 110 by the upper enlarged diameter top cylindrical portion 111b of the CEC.

In a cooling operation, air rising upward within the vent annulus 121 between the heat generating canister 150 of the CEC 110 and the housing body 111 flows to the bottom of the lid 215 (see, e.g., FIG. 18 and directional airflow arrows). The air then flows radially outward, turning upward around the perimeter of the smaller diameter lower portion 218b of the cap within the air outlet 220. The air then flows radially inward and turns upward 90 degrees toward the discharge housing 216. The heated air is discharged laterally and radially from the housing 216 back into the ambient atmosphere through the perforations. The cooling cycle continues to operate by the thermosiphon effect as long as the nuclear waste tank 150 continues to emit heat generated by the internal nuclear waste.

While the foregoing description and drawings represent exemplary embodiments of the present disclosure, it should be understood that various additions, modifications and substitutions may be made therein without departing from the spirit and scope of the 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. Furthermore, many variations on the methods/processes described herein are possible within the scope of the present disclosure. Those skilled in the art will also appreciate that many modifications may be made to the embodiments, in construction, arrangement, proportions, sizes, materials, and components and otherwise, used in the practice of the present disclosure, in order to be particularly adapted to specific environments and operative requirements without departing from the principles described herein. The presently disclosed embodiments are therefore considered in all respects to be 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.

Claims

1. An underground passive ventilated nuclear waste storage system comprising:

a horizontal longitudinal axis;

an underground concrete foundation mat;

a vertically elongated first cavity-closing container located on the base pad and the longitudinal axis, the cavity-closing container defining a vertical centerline axis and comprising a first air inlet, a second air inlet, an air outlet, and an interior cavity;

the cavity of the first cavity-closing container is configured to house a nuclear waste canister containing exothermic radioactive nuclear waste;

a vertically elongated first cooling air supply housing in fluid communication with ambient atmosphere and operable to intake ambient air, the first cooling air supply housing being directly fluidly coupled to the first air inlet of the first cavity-closing container via a first flow conduit;

a vertically elongated second cooling air supply housing in fluid communication with the ambient atmosphere and operable to intake ambient air, the second cooling air supply housing being directly fluidly coupled to the second air inlet of the first cavity enclosure via a second flow conduit.

2. The system of claim 1, wherein the first cavity-closing container is not directly fluidly coupled to any other cavity-closing container.

3. The system of claim 1 or 2, wherein the first cavity-closing container is structurally coupled to each of the first and second cooling air supply housings by a plurality of horizontally extending cross-support members that serve as lateral supports.

4. The system of claim 3, wherein the first and second cooling air supply housings are structurally coupled together by a plurality of horizontally extending cross-support members that serve as lateral supports.

5. The system of any of claims 1-4, wherein the first cavity-closing container and the first and second cooling air supply housings are fixedly mounted on a common support plate forming a self-supporting and transportable modular unit, the common support plate configured for anchoring to the concrete foundation pad.

6. The system of claim 1, wherein the first and second flow conduits each comprise a horizontally extending straight conduit portion fluidly coupling a lower portion of a cavity of the first cavity enclosure to a lower portion of each of the first and second cooling air supply housings.

7. The system of claim 6, wherein the first flow conduit and the second flow conduit are oriented at an acute angle to the longitudinal axis.

8. The system of claim 6 or 7, wherein the first and second air inlets of the first and second cavity-closing containers are configured to introduce cooling air tangentially into the interior cavities of the first and second cavity-closing containers, respectively.

9. The system of claim 1, wherein the first and second cooling air supply housings are spaced apart and located on a first lateral side of the first cavity-closing container.

10. The system of claim 9, further comprising third and fourth cooling air feeder housings spaced apart and located on a second lateral side of the first cavity-closing vessel opposite the first lateral side, the third and fourth cooling air feeder housings each being directly fluidly coupled to the first cavity-closing vessel by third and fourth flow conduits, respectively.

11. The system of claim 10, wherein the third and fourth cooling air supply housings are directly fluidly coupled to a second cavity-enclosing container by fifth and sixth flow conduits, respectively.

12. The system of claim 11, wherein a second cavity-closing container is located on the longitudinal axis, and the first, second, third, and fourth cooling air supply housings are not located on the longitudinal axis.

13. The system of claim 12, wherein the first and third cooling air supply housings are located on a first side of the longitudinal axis, the second and fourth cooling air supply housings are located on a second side of the longitudinal axis, the second side being opposite the first side of the longitudinal axis.

14. The system of claim 1, wherein the first and second cooling air feeder housings each comprise a vertical air channel containing a plurality of orthogonally intersecting radiation attenuator plates arranged in a vertically extending grid for use over a majority of the height of the first and second cooling air feeder housings.

15. The system of claim 1, further comprising a concrete roof pad defining a top surface, and an engineered fill disposed between the roof pad and the base pad, the roof pad being spaced apart from and arranged parallel to the base pad.

16. The system of claim 15, wherein each of the first and second cavity-closing containers comprises an upper portion embedded in the roof pad and a removable roof covering an interior cavity of the first cavity-closing container.

17. The system of claim 16, wherein the air outlet of the first cavity-closing container is formed by an air flow outlet channel extending between a top cover and an interior cavity of the first cavity-closing container.

18. The system of claim 16 or 17, wherein the top cover is partially disposed in an upwardly opening recess formed in the top pad.

19. The system of any of claims 15-18, wherein the first cavity-closing container comprises a body having a height extending upwardly from the base pad to the top pad, the first and second cooling air supply housings each having a height extending upwardly from the base pad to a top surface of the top pad.

20. The system of claim 19, wherein the heights of the first and second cooling air supply housings are each at least coextensive with the height of the body of the first cavity-closing container.

21. The system of claim 19 or 20, wherein the first and second cooling air supply housings each comprise a perforated intake housing disposed above a top surface of the top pad.

22. The system of any of claims 1-21, wherein the first cooling air supply housing, the second cooling air supply housing, and the first internal cavity-closing container are cylindrical, and wherein an outer diameter of each of the first cooling air supply housing, the second cooling air supply housing is smaller than an outer diameter of the first cavity-closing container.

23. The system of claim 1, wherein a cooling airflow channel is defined and configured wherein ambient cooling air is drawn vertically downward into the first and second cooling air supply housings, flows horizontally through the first and second flow conduits to the first cavity-closing container, rises vertically in the cavity of the first cavity-closing container, and is exhausted laterally back to atmosphere from the air outlets of the first and second cavity-closing containers, respectively.

24. The system of claim 23, wherein the cooling air flow is driven by a natural convection thermosiphon effect without blower or fan assistance.

25. The system of any of claims 1-24, wherein the first cooling air supply housing, the second cooling air supply housing, and the first cavity-closing container are made of stainless steel.

26. An underground passive ventilated nuclear waste storage system comprising:

a horizontal longitudinal axis;

an underground concrete foundation mat;

a vertically elongated first cavity-closing container located on the base pad and the longitudinal axis;

a vertically elongated second cavity-closing container located on the base pad and the longitudinal axis, the second cavity-closing container being spaced apart from the first cavity-closing container;

the first and second cavity-closing containers each defining a vertical centerline axis and including a first air inlet, a second air inlet, an air outlet, and an interior cavity;

a nuclear waste tank located in each of the internal cavities of the first and second cavity-closing containers, the tank emitting heat;

a vertically elongated cooling air supply housing disposed on the longitudinal axis between the first and second cavity-closing containers, the cooling air supply housing being in fluid communication with ambient atmosphere and operable to draw in ambient air;

The cooling air supply housing is directly fluidly coupled to the first air inlet of the first cavity-closing container via a first flow conduit;

the cooling air supply housing is directly fluidly coupled to the first air inlet of the second cavity-closing container via a second flow conduit;

wherein the first cavity-closing container is not directly fluidly coupled to any other cavity-closing container and the second cavity-closing container is not directly fluidly coupled to any other cavity-closing container.

27. The system of claim 26, wherein the cooling air supply housing is not directly fluidly coupled to any other cavity-closing container other than the first cavity-closing container and the second cavity-closing container.

28. The system of claim 26 or 27, wherein the first flow conduit is disposed without a straight line of sight between the first feeder housing and the first cavity-closing container, and the second flow conduit is disposed without a straight line of sight between the second feeder housing and the second cavity-closing container.

29. The system of any of claims 26-28, wherein the first air inlet and the second air inlet of the first and second cavity-closing containers are configured to introduce cooling air tangentially into the interior cavities of the first and second cavity-closing containers, respectively.

30. The system of claim 29, wherein the first flow conduit and the second flow conduit each comprise a first portion oriented transverse to the longitudinal axis and a second portion oriented parallel to the longitudinal axis.

31. The system of claim 30, wherein a welded miter joint is formed between the first and second portions.

32. The system of claim 26, wherein the second air inlet of the first cavity-closing container is directly fluidly coupled to a second cooling air supply housing disposed along the longitudinal axis via a third flow conduit, the second cooling air supply housing being in fluid communication with ambient atmosphere and operable to draw in ambient air.

33. The system of claim 32, wherein the second air inlet of the second cavity-closing container is directly fluidly coupled to a third cooling air supply housing disposed along the longitudinal axis via a fourth flow conduit, the third cooling air supply housing being in fluid communication with ambient atmosphere and operable to draw in ambient air.

34. The system of claim 26, further comprising a concrete roof pad defining a top surface, and an engineered fill disposed between the roof pad and a base pad, the roof pad being spaced apart from and disposed parallel to the base pad.

35. The system of claim 34, wherein the first and second cavity-closing containers each comprise an upper portion embedded in the roof pad and a removable roof covering the interior cavities of the first and second cavity-closing containers.

36. The system of claim 35, wherein the air outlets of the first and second closed-cavity containers are each formed by an air flow vent channel extending between the top caps of the first and second closed-cavity containers and the interior cavity.

37. The system of claim 35 or 36, wherein the caps are each partially disposed in an upwardly open recess formed in the top pad.

38. The system of any of claims 34-37, wherein each of the first and second cavity-closing containers comprises a cylindrical body housing having a height extending upwardly from the base pad to the top pad, and the first cooling air supply housing has a height extending upwardly from the base pad to a top surface of the top pad.

39. The system of claim 38, wherein the cooling air supply housing has a height that is greater than a height of a body housing of the first and second cavity-closing containers.

40. The system of claim 39, wherein the cooling air supply housing comprises a perforated inlet housing disposed above a top surface of the top pad.

41. The system of claim 26, wherein the cooling air supply housing and the first and second cavity-closing containers are cylindrical, and an outer diameter of the cooling air supply housing is smaller than an outer diameter of the first and second cavity-closing containers.

42. The system of claim 26, wherein a cooling airflow channel is defined, wherein ambient cooling air is drawn into the first cooling air supply housing, flows through the first and second flow conduits to each of the first and second cavity-closing containers, respectively, and is exhausted back to atmosphere from an air outlet in each of the first and second cavity-closing containers.

43. The system of claim 42, wherein the directed air movement in the air flow channel is configured to prevent exchange of cooling air between the first cavity-closed container and the second cavity-closed container through the first cooling air supply housing.

44. The system of claim 42 or 43, wherein the cooling air flow is driven by a natural convection thermosiphon effect without blower or fan assistance.

45. The system of any of claims 26-44, wherein the cooling air supply housing and the first and second cavity-closing containers are made of stainless steel.

46. A reinforced temporary storage facility for nuclear waste comprising:

a plurality of elongated cavity-closing receptacles each established on the underground foundation mat and extending vertically upward therefrom to the concrete roof mat;

an engineered fill disposed between the base pad and the top pad;

the cavity-closing receptacles are arranged in an array comprising a plurality of longitudinally extending and parallel linear rows of cavity-closing receptacles, each row defining a longitudinal axis and each of the cavity-closing receptacles being arranged on the longitudinal axis;

a plurality of vertically elongated cooling air feeder housings disposed in each row on a respective said longitudinal axis, one cooling air feeder housing interposed between and directly fluidly coupled to a pair of said cavity-enclosing containers on opposite sides of said cooling air feeder housing, said cooling air feeder housings each being in fluid communication with the ambient atmosphere;

The one cooling air supply housing being operable to draw in ambient air and distribute the air directly to each pair of cavity-enclosing containers;

wherein the cavity-closing containers in each row are fluidly isolated from the cavity-closing containers in any other row.

47. The facility of claim 46, wherein each cooling air supply housing is not fluidly coupled to any other cavity-closing container in any other row.

48. The facility of claim 47, wherein each cooling air supply housing is fluidly coupled only to its respective pair of cavity-closing receptacles on each side of the cooling air supply housing in a respective row.

49. The facility of any of claims 46-48, wherein the cooling air supply housing and the cavity-closing container are cylindrical, and an outer diameter of the cooling air supply housing is smaller than an outer diameter of the cavity-closing container.

50. The facility of claim 49, wherein each cooling air supply housing is directly fluidly coupled to its respective pair of cavity-closing containers by separate first and second flow conduits coupled between a lower portion of the cooling air supply housing and a lower portion of a cavity of its respective cavity-closing container.

51. A facility as in claim 50, wherein the flow conduits are configured such that there is no line of sight between each cooling air supply housing and its respective pair of cavity-enclosing containers to prevent radiation flow.

52. The facility of claim 50 or 51, wherein each cavity-closing vessel comprises a first air inlet and a second air inlet configured to introduce cooling air tangentially into an interior cavity of the cavity-closing vessel.

53. The facility of claim 52, wherein a first air inlet of each cavity-enclosure is directly fluidly coupled to a first one of the cooling air supply housings on a first side of the cavity-enclosure through the first flow conduit, and a second air inlet of each cavity-enclosure is directly fluidly coupled to a second one of the cooling air supply housings on a second side of the cavity-enclosure through the second flow conduit.

54. The apparatus of any of claims 26-53, wherein the cooling air supply housing and the first and second cavity-closing containers are cylindrical and made of stainless steel.

55. An underground passive ventilated nuclear waste storage device for reinforcing a temporary storage facility, the device comprising:

a vertically elongated cavity-closing container supported on the underground foundation mat and extending vertically upward therefrom to the concrete roof mat;

an engineered fill disposed between the base pad and the top pad;

a nuclear canister located in an interior cavity of the cavity-closing container, the canister emitting decay heat that heats air in an annular space formed between the cavity-closing container and the canister;

a vertically elongated hollow cooling air supply housing disposed laterally of the cavity-enclosing container, the cooling air supply housing being in fluid communication with ambient atmosphere and operable to draw in ambient air;

the cooling air supply housing is directly fluidly coupled to a lower portion of the cavity via a first flow conduit through a first air inlet of the cavity-closing container;

the cooling air supply housing is further fluidly coupled directly to a lower portion of the cavity via a second flow conduit through a second air inlet of the cavity-closing container;

the first and second flow conduits are fluidly coupled to a lower portion of the cooling air supply housing;

Wherein a cooling air flow passage is defined in which ambient cooling air is drawn into and cools the air feeder housing, flows through the first and second flow conduits to the lower portion of the cavity-enclosing container, flows upwardly in the annular space and is heated by the canister, and is discharged back to atmosphere from an air outlet at the top of the cavity-enclosing container.

56. The apparatus of claim 55, wherein the cavity-closing container is not directly fluidly coupled to any other cavity-closing container or cooling air supply housing.

57. The apparatus of claim 55 or 56, wherein the cooling air supply housing and the cavity-closing container are cylindrical and made of stainless steel, the cooling air supply housing having an outer diameter that is smaller than an outer diameter of the cavity-closing container.

58. The system of any of claims 55-57, wherein the first flow conduit is configured such that there is no line of sight between the cooling air supply housing and the cavity-enclosing container.

59. The system of any of claims 55-58, wherein the first air inlet and the second air inlet are configured to introduce air tangentially into a cavity of the cavity-enclosing container.

60. The system of claim 59, wherein the first flow conduit and the second flow conduit each comprise a first portion oriented transverse to a longitudinal axis extending between the cooling air supply housing and the cavity-closing container and a second portion oriented parallel to the longitudinal axis.

61. The system of claim 60, wherein a welded miter joint is formed between the first and second portions.

62. The system of claim 57, wherein the cavity-closing container has a height extending upwardly from the base pad to the top pad, the cooling air supply housing having a height extending upwardly from the base pad to a top surface of the top pad.

63. The system of claim 62, wherein the cooling air supply housing has a height that is greater than a height of the cavity-closing container.

64. The system of claim 55, wherein the cooling air supply housing comprises a perforated inlet housing projecting upwardly above a top surface of the top pad.

65. The device of any of claims 55-64, further comprising a removable cap covering the cavity of the cavity-enclosing container, and an air flow vent channel extending between the cap and the cavity of the cavity-enclosing container.