Systems and methods for passive cooling of geothermal furnaces

Abstract

Passive safety systems cool the reactor using the surrounding ground as a heat sink. The coolant flow path loops around the reactor and then potentially through the containment building into the surrounding ground. Active components may not be used in the exemplary embodiment safety system, which may be powered entirely by gravity-based natural circulation. The coolant loop is airtight and may be filled with any coolant, such as water, air, nitrogen, noble gases, refrigerants, or any other fill with desired heat transfer properties. Coolant loops may use coolant fins and / or jackets with secondary coolant. The coolant loop may be buried at any fixed or variable depth, and the reactor and containment vessel may also be buried underground. [Selected figure] Figure 2

Description

[Technical field]

[0001] Systems and methods for passive cooling of geothermal furnaces [Background technology]

[0002] FIG. 1 is a profile cross-section of a related art liquid metal reactor as described in U.S. Patent No. 5,405,602, incorporated herein by reference in its entirety. As seen in FIG. 1, an annular or circular concrete silo 8, potentially underground, houses an annular containment vessel 2, which in turn houses a nuclear reactor 1, potentially all aligned concentrically. The reactor 1 includes a reactor core 12 immersed in a liquid metal coolant, such as liquid sodium. The space between the reactor 1 and the containment vessel 2, shown as gap 3, may be filled with an inert gas, such as argon. The reactor 1 and containment vessel 2 are suspended vertically downward from an upper frame 16. The concrete silo 8 may support the upper frame 16 by seismic isolators 18 to maintain the structural integrity of the reactor 1 and containment vessel 2 during an earthquake and to allow for isolated movement between those structures and the surrounding silo 8.

[0003] The reactor 1 is controlled by neutron absorbing control rods 15 that are selectively inserted or withdrawn from the core 12. The reactor 1 may be shut down completely to respond to an emergency condition or to perform routine maintenance by inserting control rods 15 into the fissionable fuel core 12 to deprive it of needed fission-producing neutrons. However, residual decay heat continues to be generated from the core 12, which decreases exponentially with time. This heat must be dissipated from the shut down reactor 1. The thermal capacity of the liquid metal coolant and the adjacent reactor structure helps to dissipate the residual heat. For example, heat may be transferred by thermal radiation from the reactor 1 to the containment vessel 2. Heat from the containment vessel 2 may also be radiated outwardly therefrom to a concrete silo 8 spaced apart therefrom.

[0004] A system for removing this attenuating heat vents, or otherwise removes heat from the reactor 1 and surrounds the structure to a heat sink such as the environment. One such system may be a reactor vessel auxiliary cooling system (RVACS) as shown in FIG. 1. The heat collecting cylinder 5 is concentrically disposed between the containment vessel 2 and the silo 8, defining a hot air riser 4 between the containment vessel 2 and the inner surface of the heat collecting cylinder 5. The heat collecting cylinder 5 may further define a cold air downcomer 7 between the silo 8 and the outer surface of the heat collecting cylinder 5. Heat may be transferred from the containment vessel 2 to the air in the hot air riser 4. The inner surface of the heat collecting cylinder 5 may receive thermal radiation from the containment vessel 2, from which heat is transferred by natural convection to the rising air for the updraft, which removes the heat via the air outlet 9. Heating the air in the upcomer 4 by the two surrounding hot surfaces induces a natural air draft in the system, where atmospheric air enters above ground level through the air inlet 6. Air from inlet 6 is directed to cold air downcomer 7 and then to the bottom of the concrete silo 8 where it swirls and enters hot air riser 4. The hot air is directed to air outlet 9 above ground level.

[0005] Similar related passive reactor coolant systems are described in U.S. Patent No. 5,190,720, issued March 2, 1993 to Hansvedt et al., and U.S. Patent No. 8,873,697, issued October 28, 2014 to Horie et al. Commonly owned U.S. Patent Application Serial No. 15 / 785,548, filed August 17, 2017, and incorporated herein by reference in its entirety. Hamdhan et al., "Determinism of Thermal Conductivity of Coarse and Fine Sand Soils," Proceedings of World Geothermal Congress 2010, Bali, Indonesia, April 25, 2010, is incorporated herein in its entirety. U.S. Patent Publication No. 2012 / 0255706 (published October 11, 2012) to Tadayon et al. U.S. Patent No. 4,485,1183 issued July 25, 1989 to Hanpei; Wiggs et al., U.S. Patent No. 5,816,314 (issued October 6, 1989); U.S. Patent No. 7,179,697 issued November 17, 2009 to McCaughan; China Patent Publication No. 102032716, published on April 27, 2011; U.S. Patent No. 7,480,937 issued May 9, 2003 to McNair; U.S. Patent No. 6,814,866 issued May 9, 2004 to Potts; U.S. Patent No. 5,223,210 to Hans Bedd, issued May 29, 1993, It is incorporated herein by reference in its entirety. Summary of the Invention [Means for solving the problem]

[0006] Exemplary embodiments include a passive safety system and a reactor including the same. The safety system of the exemplary embodiment removes unwanted heat from the reactor vessel with a coolant flow path that passes through the surrounding ground as a heat sink. The coolant flow path may be split into downcomers and upcomers that loop around the reactor and then potentially through a containment building into the surrounding ground. Any type of reactor may be used, including light water, gas-cooled, or prismatic reactors that use molten metal or molten salt as the primary heat exchange fluid, which do not need to operate during cooling by the passive cooling system of the exemplary embodiment. In fact, no active components may be used in the safety system of the exemplary embodiment, which may be completely powered by gravity-based natural circulation. A passive damper system may operate without power in the coolant loop to open the conduits at a threshold temperature.

[0007] The coolant loop is airtight and can be filled with water, air, nitrogen, rare gases, Medium Can be filled with any desired coolant The ground may be in direct contact with the loop. Gray limestone, soft gray sandy clay, gray slightly SiltyThe coolant loop may include a filler such as gravel, gravel, or any other filler with the desired heat transfer properties. To enhance heat transfer and expand the ground volume available to absorb heat, the coolant loop may be jacketed with coolant fins and / or a secondary coolant. The coolant loop may be buried at any constant or variable depth, and the reactor and containment vessel may also be buried in the earth. Exemplary embodiments will become more apparent from a detailed description of the accompanying drawings, in which like elements are given by way of example only and therefore not by way of limiting the terms to which they are attached. [Brief description of the drawings]

[0008] [Figure 1] 1 is a profile schematic of a conventional reactor vessel auxiliary cooling system (RVACS). [Diagram 2] 1 is a schematic diagram of an exemplary embodiment nuclear power plant. [Diagram 3] FIG. 3 is a schematic diagram of an exemplary embodiment geothermal coolant loop for the nuclear power plant of FIG. [Figure 4] FIG. 4 is a cross-sectional view of a cooling loop pipe that can be used in the geothermal coolant loop of the exemplary embodiment of FIG. [Diagram 5] 4 is a graph illustrating the liquid and vapor phases of coolant available in the coolant loop of an exemplary embodiment by temperature. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Since this is a patent document, broad rules of construction should generally be applied when reading it. Everything described and shown in this specification is an example of the subject matter included in the claims appended below. Any specific structural and functional details disclosed herein are merely for the purpose of explaining how to make and use the examples. Several different embodiments and methods not specifically disclosed herein may fall within the scope of the claims. Thus, the claims may be embodied in many alternative forms and should not be interpreted as being limited to only the examples described herein.

[0010] It will be understood that the ordinal numbers of first, second, etc. are for describing various elements. In this specification, these elements should not be limited to any order by these terms. These terms are used only to distinguish one element from another element. When there are multiple second or higher orders, there must simply be a greater number of elements without any difference or other relationship. For example, a first element can be called a second element, and similarly, a second element can be called a first element, without departing from the scope of the exemplary embodiment or method.

[0011] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items unless expressly stated that only a single item, subgroup of items, or all items are present. It indicates the inclusion of all other elements belonging to the same group of the above items in any signal(s) and / or combination(s) and also indicates the inclusion of all other elements in a plurality.

[0012] When elements are referred to as being "connected," it will be understood to be "coupled," "coupled," "attached," "fixed," etc. Another element may be directly connected to the other element, or there may be intervening elements. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present in the other element. Other words used to describe the relationship between elements should be interpreted in a similar manner (e.g., "between" vs. "directly between," "adjacent" vs. "directly adjacent," etc.). Similarly, terms such as "communicatively connected" include all permutations of information exchange and routing between two electronic devices, including intermediate devices, networks, etc. that are wirelessly connected.

[0013] As used herein, the singular forms "a", "an" and "the" are intended to include both the singular and the plural unless expressly indicated otherwise. Indefinite articles such as "a", "an" introduce or refer to both previously introduced and otherwise terminology, while definite articles such as "the" refer to the same previously introduced terminology. Thus, "a", "an" modify an item previously introduced or recognized as new, while the definite article modifies the very same item previously introduced. It will be understood that the terms "comprising" and "including" specify the presence of stated features, characteristics, steps, operations, elements, and / or components, but do not in themselves preclude the presence or addition of one or more other features, characteristics, steps, operations, elements, ingredients and / or groups thereof.

[0014] The structures and operations described below may occur in a different order than that depicted and / or illustrated in the figures. For example, two operations and / or figures shown in succession may in fact be performed simultaneously, or sometimes in the reverse order, depending on the functionality / operations involved. Similarly, individual operations within the exemplary methods described below may be performed individually or sequentially to provide a loop or other sequence of operations apart from the single operation described below. Any embodiment or method having the features and functions described below, in any workable combination, should be presumed to fall within the scope of the exemplary embodiments.

[0015] As used herein, the term "underground", with respect to a nuclear power plant, includes any location below the ground, horizon, or natural earth surface, but not directly above without digging, excavation, or other surface removal. This refers to a position where it is impossible to make contact. For example, these terms include burying the element with soil covering the element, placing the element in a container or structure underground, and building a bank around the element to keep it buried.

[0016] The inventors have recognized that while above ground chimneys and associated passive coolant systems such as RVACS utilizing fluid media can dissipate tens of megawatts of thermal decay heat in some reactor designs, this may not be necessary for smaller reactors, particularly liquid metal cooling based reactors such as the Prismatic Reactor. The inventors have recognized that smaller reactors generating up to 20 megawatts of thermal decay heat in shutdown conditions can be adequately cooled by a solid media heat sink including soil.

[0017] The inventors further recognized that related art RVACS with their large ground-based cooling structures represent additional mishap vectors resulting from aircraft collisions, weather, and attacks facilitated by their accessible location. To overcome these newly recognized problems, as well as others, the inventors have developed the exemplary embodiments and methods described below to address these and other problems recognized by the inventors with unique solutions enabled by the exemplary embodiments.

[0018] The present invention is a geothermal reactor cooling system, a reactor containing the same, and a method for using the same in a nuclear reactor. In contrast to the present invention, the several exemplary embodiments and exemplary methods described below illustrate only a few of the various different configurations that may be used with and / or in conjunction with the present invention. As shown in Figure 2, the exemplary embodiment plant includes a nuclear reactor 100 with a core 101 located entirely underground. In the prismatic reactor example, a primary coolant loop containing a liquid metal such as a sodium or salt heat exchange coolant may potentially be embedded within a confined containment structure 110 having a base mat structure 111. Only an intermediate or non-primary heat exchange loop 105 may be located above the power turbine and generator 106.

[0019] Loss or damage to the intermediate heat exchange loop 105, turbine, and generator 106, and even operation of the reactor and plant component operating control room 160, generally does not pose a risk to the reactor 100, which uses an underground self-contained primary coolant. For example, the reactor shown in Figure 2 may be substantially identical to other prismatic reactors as described in the incorporated literature, except that the RVACS is entirely underground and is replaced with a geothermal attenuation heat removal loop 120 in the example embodiment.

[0020] As shown in FIG. 2, the geothermal coolant loop 120 of the RVACS-like embodiment can flow directly around the reactor vessel or its conductive structures to absorb heat from the reactor. In the example of a shutdown Prism Reactor, the upward flowing conduit 120A can absorb up to 20 megawatts of heat from the shutdown reactor, and 1-2 megawatts of heat for a Prism 10 reactor design. The upward flowing conduit 120A may run the height of the reactor 100, potentially several meters, and around the circumference of the reactor 100. The upward flowing conduit 120A can take the form of a heat pipe that is additively manufactured to the reactor vessel itself, allowing maximum heat transfer between the reactor 100 and the upward flowing conduit 120A. This height and heat absorbed along the reactor 100 can drive natural convection within the conduit 120, with hot fluid being driven upward in the loop due to density gradients.

[0021] The upward conduit 120A is structure 110 and the reactor support structure may be drained into an underground geothermal cooling loop 120 that may be buried several feet into soil or other surface media, including all soil and media types disclosed in the incorporated Hamdohan documents. Burial depth D may be, for example, 1-20 feet, or any depth sufficient to provide sufficient thermal capacity while protecting loop 120 from surface damage and also minimizes construction costs. Alternatively, depth D may be hundreds or thousands of feet deep to take advantage of deeper geothermal heat sinks. Cooling loop 120 may deepen through length with various burial depths d and d' as shown in FIG. 2, thereby enhancing natural circulation to have a gravity gradient in the direction of the cooler temperature. And it should be understood that loop 120 may alternatively be of the same or consistent depth where d=d'.

[0022] Loop 120 may flow through a cold trap 150 and / or a stop control 151 that may regulate and control the flow through loop 120. For example, cold trap 150 may condense vapor that accumulates in loop 120, and stop control 151 may include a damper or other flow restrictor that limits or allows flow through loop 120 depending on the needs of the heat sink.

[0023] Loop 120B includes a downward conduit 120B to return the cooled coolant in loop 120 to reactor 101. As shown in FIG. 2, after passing through ground 20 and transferring heat thereto, conduit 120 flows downward to the reactor containment structure 110 and the supporting structure to form a loop with upper conduit 120A. Again, with the cooled fluid in lower conduit 120B, this can drive natural circulation in loop 120. In this manner, natural convection can occur within conduit 120 to aid in the transfer of heat from reactor 100, with the heat sink of the soil cooler vertically above the elevated reactor heat source. In this manner, the geothermal heat sink system of the exemplary embodiment can be largely passive and automatic, transferring heat from the reactor at the decay heat generation rate without any pumps, fans, etc. 。

[0024] Of course, conditionals and active components may be used in the exemplary embodiment. For example, a damper system from the incorporated sinus document may passively close the conduit 120 during normal operation to avoid loss of heat that can be used for energy generation. Alternatively, a meltable plug may be used in the conduit 120 to open it when, for example, a temperature associated with requiring emergency or shutdown cooling is reached. Alternatively, for example, the conduit 120 may be plugged or insulated during normal operation, but freeze or contain heavy non-condensable gases that are forced out of the conduit as the reactor 100 and coolant approach emergency temperatures. Active blowers, coolant injectors and other systems may optionally be used to drive additional convection as needed.

[0025] As shown in Figure 3, multiple loops 120 may be used with upper conduit 120A flowing into loop 120. Based on the heat capacity set forth in the incorporated Hamdohan document and the expected geothermal heat of around 55 degrees Fahrenheit due to geothermal effects, loop 120 may be effective in dissipating decay heat. Due to the effects of geothermal dissipation, the surrounding soil may become hotter and hotter than the reactor and containment areas. structure 110 having a perimeter of several hundred feet can act indefinitely as a heat sink for, say, 20 megawatts of heat.

[0026] As shown in Figures 4A-4C, the conduit 120 may generally be surrounded by ground 20 or other heat sink medium surrounding the conduit 120. The conduit 120 may take on several different configurations depending on the desired heat exchange characteristics. For example, the conduit 120 may be a thin highly thermally conductive material tube as shown in Figure 4A that may carry a coolant 122. Similarly, as shown in Figure 4B, one or more cooling fins 121 may extend into the surrounding ground 20 to further aid in heat transfer and cooling. As shown in Figure 4C, the conduit 120 may be surrounded by an additional jacket or external conduit 120, such as a pipe-in-pipe design with a secondary coolant 122 B, such as water or another heat sink, surrounding the primary conduit 120 with the primary coolant 122 A. Additionally, the conduit 120 may be divided into several smaller channels, such as a heat exchanger design. The conduit 120 may be of any size, shape, configuration, and length based on the desired heat sink capacity and the known thermal properties of the surrounding ground.

[0027] The fluid coolant 122 flowing through the conduit 120 can be any fluid capable of carrying the expected attenuated heat load while flowing by natural convection. For example, air, nitrogen, helium, refrigerant, water, and others can all be used in the underground coolant loop, as well as any other fluids as shown in FIG. 5, which shows the liquid phase range (with subsequent gas phase) of some potential coolant fluids. Similarly, the type of soil or fill in the ground surrounding the loop can be based on soils that are naturally available on-site or purposely configured for thermal conductivity. For example, finer sandy clays with higher thermal conductivity and heat capacity can be used to bury the conduit if the natural crushed material does not have the desired heat transfer properties. The thermosiphon effect can be maximized by using the available uplift gain in the conduit, complemented by the separation of vapor and liquid legs by the sintered wick design to maximize the liquid return rate of the coolant 122.

[0028] Because the reactor and geothermal coolant conduits of the exemplary embodiments may be cooled underground and passively, the risk of above ground damage such as weather events, collisions, explosions, malfunctions, etc. is reduced or eliminated due to the lack of accessibility provided by the conduits to both the reactor and its emergency coolant systems. Of course, conduit integrity and functionality monitoring may also be employed by maintaining and measuring pressurization within the conduits to detect leaks, heat setting the conduits with flexible connections and potentially shock absorbers or snubbers, installing regulation grade leak seals around containment penetrations, etc.

[0029] Thus, while exemplary embodiments and methods are described, those skilled in the art will understand that the exemplary embodiments may be modified and substituted through routine experimentation while still falling within the scope of the following claims. For example, while a complete underground reactor with an above-ground turbine and generator is shown, other upper and lower combinations of any of the elements may be used simply through appropriate positioning of the exemplary embodiments and fall within the scope of the claims. Such variations should not be considered as a departure from the scope of these claims.

Claims

1. A reaction vessel (100), a divided flow path (120A, 120B) surrounding the reaction vessel (100) and including a coolant downcomer (120B) and a coolant riser (120A) between the coolant downcomer (120B) and the reaction vessel (100); a closed coolant loop (120) connected to the coolant downcomer (120B) and the coolant upcomer (120A) above the divided flow paths (120A, 120B), buried in the ground (20) to a depth of at least 1 meter and in direct contact with the soil; the coolant downcomer (120B) and the coolant riser (120A) are in fluid communication at a bottom of the divided flow passages (120A, 120B), and the closed coolant loop (120) allows fluid to flow from the coolant riser (120A), through the closed coolant loop (120) to the coolant downcomer (120B); A passive safety system for removing decay heat from nuclear power systems.

2. a containment structure (110) surrounding the reaction vessel (100); the containment structure (110) and the reaction vessel (100) are below ground (20), a primary heat exchange fluid passes through the reaction vessel (100), the primary heat exchange fluid being a molten metal, a molten salt, or a gas; The system of claim 1 .

3. 2. The system of claim 1, wherein the coolant riser (120A) and the coolant downcomer (120B) are in direct fluid communication only at the bottom of the split flow path (120A, 120B), and the fluid flows through the coolant loop (120), the coolant downcomer (120B), and the coolant riser (120A) to cool the reaction vessel (100) without any working parts.

4. 2. The system of claim 1, wherein the coolant riser (120A), the coolant downcomer (120B), and the coolant loop (120) are fluid-tight and filled with at least one of water, air, nitrogen, a noble gas, and a refrigerant.

5. 10. The system of claim 1, wherein the soil comprises at least one of gray limestone, soft gray sandy clay, and gray slightly silty gravel.

6. The system of claim 1 , wherein the coolant loop (120) includes a plurality of heat transfer fins (121) extending from an outer surface thereof into the earth (20).

7. burying a closed coolant conduit (120) at a depth of at least one meter below the ground (20) outside the containment structure (110) of the nuclear reactor (100) and in direct contact with the soil, outside the containment structure (110) of the nuclear reactor (100); a coolant riser pipe (120A) and a coolant downcomer pipe (120B) in the containment structure (110) such that fluid flows from the coolant riser pipe (120A), through the closed coolant conduit (120) to the coolant downcomer pipe (120B).

8. 8. The method of claim 7, wherein the soil comprises at least one of gray limestone, soft gray sandy clay, and gray slightly silty gravel, and the coolant conduit (120) is fluid tight and filled with at least one of water, air, nitrogen, a noble gas, and a refrigerant.

9. The method of claim 7 , wherein a primary heat exchange fluid passes through a vessel of the nuclear reactor (100), the primary heat exchange fluid being a molten metal, a molten salt, or a gas.

10. 2. The system of claim 1, wherein the closed coolant loop (120) includes an inner conduit (120), an outer conduit (120'), and a secondary coolant (122B) between the inner conduit (120) and the outer conduit (120').

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