Passive heat removal cask and method of use thereof

Abstract

The cask (100) shields materials and passively removes heat through a heat transfer path (150) from the depths of the cask to the exterior. The path may be nonlinear heat pipes and conductive rods to ensure radiation is always shielded by the cask. Dampers (160) may surround the ends of the heat transfer path to control heat loss from the cask. A jacket (110) of fluid or meltable material that conducts heat by convection may surround the stored material and ensure a uniform temperature within the cask, and the heat transfer path may absorb heat from the jacket. The cask can be used to safely store, transport, and dispose of any heat-generating or sensitive materials. Opening and closing the cask allows for simultaneous loading and unloading of materials at a constant operating temperature provided by heaters within the cask.

Description

[Background technology]

[0001] FIG. 1A shows a cross-sectional view of a related art transfer cask 10 used to store radioactive, heat-generating waste, such as spent nuclear fuel and irradiated waste. As shown in FIG. 1, the cask 10 includes an inner shield 11 and an outer shield 12, which form a central open space into which a fuel assembly 1 and a handling basket 2 can be inserted and stored. The inner shield 11 may be depleted uranium, which provides structural containment and shields against radiation emitted from the contents of the cask 10. The outer shield 12 may be a thicker boron carbide jacket that provides additional impact shielding, particularly against neutron irradiation. A retaining sleeve 14 at the top of the cavity within the shield 12 may align and position the fuel assembly 1 during insertion and storage, as well as allow for its indexing and removal. The cavity within the inner shield 11 may be backfilled with helium to avoid large pressure differentials across the cask 10 and to maintain chemical quiescence of the heat-generating contents. Drip pan 16 can catch liquids and solid debris that fall from the stored contents. Figure 1C is a cross-sectional view of related art cask 10 taken along elevation line h1, showing inner shield 11 as a ring surrounded by outer shield 12. A plurality of reinforcing partitions 15A, 15B, and 15C, which may be high-strength stainless steel, divide and reinforce the shields and form the exterior of cask 10.

[0002] The cavity 13 at the top of the cask 10 may be connected to a bistem assembly 20 at the top end of the cask 10. A dynamic pump and fluid recirculation system may be connected to the cavity 13 through the bistem assembly 20 to actively cool and transfer heat from the contents of the cask 10. As shown in the cross-sectional view at elevation line h2 in FIG. 1B, the bistem assembly 20 allows for handling of the cask 10, such as via a crane or other connection to the assembly 20. With appropriate environmental conditions and active cooling of the cask 10, energetic contents that generate large amounts of heat due to radiation can be stored and transported for long periods of time without damaging the cask 10 or irradiating the environment. U.S. Patent No. 6,223,499 to Loewen et al., published June 26, 2014, describes another related art cask for spent nuclear fuel with an active cooling system to similarly dissipate heat from the cask, and is incorporated herein in its entirety. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2014 / 0177775 Summary of the Invention [Means for solving the problem]

[0004] An exemplary embodiment of a cask passively removes heat that may be generated by its contents. The cask includes a shield surrounding the contents to prevent alpha, beta, gamma, or neutron radiation from escaping into the surrounding environment, and one or more heat transfer paths that facilitate the transfer of heat from the interior of the cask and shield to the exterior of the cask and ultimately to the environment or an external heat sink. The transfer paths may be any structure with sufficient high thermal convection, conduction, and / or radiation to prevent the interior temperature from reaching harmful levels, such as heat pipes and conductive rods. The heat transfer paths may be bent or may not extend in a straight line from the interior to the exterior of the cask, ensuring that radiation traveling along such a path impinges on the shield. Openable dampers may surround the ends of the heat transfer paths to control fluid convection around the heat transfer paths and ultimately limit heat loss from the cask. A jacket of fluid or meltable material that conducts heat by convection may surround the stored material and ensure a uniform temperature within the cask. Heat transfer channels and / or heating elements may be in communication with the jacket and may cool and / or heat the jacket as desired.

[0005] Example embodiment casks can be used to store, transport, and dispose of any sensitive or heat-generating material without thermal or radiation damage. This may include radioactive waste, irradiated elements, spent nuclear fuel, and fresh fuel. Opening and closing the cask allows for simultaneous loading and unloading of materials at constant operating temperatures provided by heaters within the cask. Passive heat removal from the cask allows for the placement and storage of multiple fuel assemblies and other highly radioactive structures in the cask without meltdown or loss of containment. [Brief explanation of the drawings]

[0006] [Figure 1A] FIG. 1A is a cross-sectional view of a related art fuel transport cask. [Figure 1B] FIG. 1B is a cross-sectional view of the cask of FIG. 1A. [Figure 1C] FIG. 1C is another cross-sectional view of the cask of FIG. 1A. [Figure 2A] FIG. 2A is a cross-sectional view illustrating the exterior configuration of a transportation cask according to an example embodiment. [Figure 2B] FIG. 2B is a detailed view of the heat transfer path of the cask of FIG. 2A. [Figure 2C] FIG. 2C is a cross-sectional view of the cask of FIG. 2A. DETAILED DESCRIPTION OF THE INVENTION

[0007] Exemplary embodiments will become more apparent from a detailed description of the accompanying drawings, in which like elements are represented by like reference numerals, which are provided for purposes of illustration only and therefore are not intended to limit the exemplary embodiments herein.

[0008] Because this is a patent document, general and broad rules of interpretation should be applied when reading it. Everything described in this document is an example of subject matter encompassed by the claims appended below. Specific structural and functional details disclosed herein are merely intended to illustrate how to make and use the examples. Several different embodiments and methods not specifically disclosed herein may fall within the scope of the claims. Accordingly, the claims may be embodied in many alternative forms and should not be interpreted as limited to only the examples set forth herein.

[0009] In this specification, modifiers such as "first," "second," and "another" may be used to describe various items, but the order or relationship of the modifiers does not limit the items they modify. These terms are used only to distinguish one element from another. The presence of "second" or higher ordinal numbers simply indicates that that number of elements must be present, not necessarily a difference or other relationship between the elements. For example, unless an order or difference is otherwise stated, a first element can be called a second element, and similarly, a second element can be called a first element. When listing items, the conjunction "and / or" includes all combinations of one or more of the associated listed items. The use of "etc." is defined as "et cetera," indicating the inclusion of all other elements belonging to the same group as the preceding item, in any one or more combinations of "and / or."

[0010] When an element is referred to as being "connected," "coupled," "mated," "attached," "secured," or the like, to another element, the element may be directly connected to the other element, or there may be intervening elements. Conversely, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements. Other terms expressing the relationship between elements should be interpreted similarly (e.g., "between" and "direct between," and "adjacent" and "direct adjacent," etc.). Similarly, terms such as "communicatively connected" include all variations of information exchange and routing between two devices, whether wirelessly connected or not, including intermediary devices, networks, etc.

[0011] As used herein, the singular forms "a," "an," and "the" are intended to include both the singular and the plural unless the language explicitly dictates otherwise. Indefinite articles such as "a" and "an" introduce or refer to any term they modify, whether previously introduced or not, and definite articles such as "the" refer to the same previously introduced term. As used herein, possessive words such as "comprises," "includes," "has," or "with" identify the presence of stated features, characteristics, steps, operations, elements, and / or components, but do not themselves exclude the presence or addition of one or more other features, characteristics, steps, operations, elements, components, and / or groups thereof. Rather, exclusive modifiers such as "only" or "singular" may exclude the presence or addition of a plurality or other subject matter in the modified word. As used herein, a "heat transport channel" refers to a solid structure that transports heat at a rate faster than surrounding materials without an external force or moving solid parts, and includes conductive rods and heat pipes.

[0012] The structures and operations described below may occur out of the order depicted in the figures. For example, two operations and / or figures shown in succession may in fact be performed simultaneously or in the reverse order depending on the functionality / acts involved. Similarly, individual operations within the exemplary methods described below may be performed repeatedly, either individually or sequentially, to provide a loop or other sequence of operations apart from the single operations described below. Any embodiment or method having the features and functions described below, in any workable combination, should be deemed to be within the scope of the exemplary embodiments.

[0013] The inventors have recognized this and have developed the exemplary embodiments and methods described below to address these and other problems they have recognized with unique solutions enabled by the exemplary embodiments.

[0014] In contrast to the present invention, the several exemplary embodiments and exemplary methods described below represent merely a subset of the various different configurations that may be used as and / or in connection with the present invention.

[0015] 2A is a cross-sectional view of an exemplary embodiment of a heat transfer cask 100 that employs a heat transfer path to passively remove heat from the cask contents. The cask 100 may have some similar configurations to the related art casks described above or shown in FIGS. 1A-1C, with added heat transfer elements, as described below, and structural and shielding elements formed of high-strength, non-reactive materials. The exemplary embodiment of the heat transfer cask 100 is robust and seals the integrity of the containment vessel, allowing it to be used to store, transport, and dispose of hazardous or sensitive materials, including radioactive and nuclear components, without risk of leakage, reaction, or damage when exposed to forces or harsh environments.

[0016] 2A, in the heat transfer cask 100 according to the exemplary embodiment, a heat transfer path 150 directly connects the inside of the cask 100 to or near the outside, transporting heat directly from the cask 100 without any solid moving parts. For example, a first end of the heat transfer path 150 may extend deep into the inner shield 11, or even into the shield, including a cavity that holds heat-generating material such as spent nuclear fuel 1. The opposite end of the heat transfer path 150 may pass through an outer portion, such as an outer damper 160, or even to the outside of the cask 10, for direct communication with the environment.

[0017] FIG. 2B is a detailed diagram of the heat transfer path 150 of FIG. 1A, illustrating the redirection of the path 150 to avoid a direct, straight path from the interior of the heat transfer cask 100 to the surrounding environment according to an exemplary embodiment. The path 150 may be fully shielded, differently shielded, or not necessarily shielded at all, so that a straight line from a radiation-producing storage element, such as spent fuel 1, to the outer cask 100 may provide an exposure path for dangerous or unwanted radiation to escape. To prevent or reduce such exposure outside the cask 10, the path 150 may be redirected, such as through a lateral jog in FIG. 2B through the surrounding outer shield 12, eliminating any straight path through the radiation shielding of the cask 100. The path 150 may curve, angle, bend, etc. in any number of different directions to prevent an escape route from the interior to the exterior of the cask 100. Additionally or alternatively, the flow channel 150 may incorporate shielding material or be shielded on both ends to further prevent radiation from escaping.

[0018] The heat transfer paths 150 facilitate the transfer of heat between the cask 100's interior and the exterior. For example, as shown in FIG. 2C, the heat transfer paths 150 may be solid, thermally conductive rods such as copper, iron, tungsten, aluminum, and / or conductive alloys such as aluminum nitride or silicon carbide. As shown in FIG. 2A, the heat transfer paths 150 may be heat pipes with internal paths that transfer heat by convection and conduction through evaporating and condensing coolant. Any number of heat transfer paths 150 necessary to remove the anticipated heat load may be used in exemplary embodiments. For example, heat transfer paths 150 of sufficient size and number, such as twenty 1 kW heat pipes, may be used to ensure that temperatures do not exceed or approach 650°C, based on the radioactivity of the objects placed in the cask 100. Heat transport passage 150, like other structural elements of cask 100, is formed of a material that is sufficiently strong to maintain the structural integrity of cask 100 while not undergoing substantial strength or material change or degradation when exposed to radiation, including stainless steel, aluminum alloys, nickel alloys, zirconium alloys, carbides, etc. In this manner, heat transport passage 150 may facilitate passively transferring heat away from cask 100 without external power or moving structures, while ensuring that cask 100 is robust and maintains containment against internal radioactive elements.

[0019] The heat transport cask 100 according to the example embodiment may include multiple dampers 160 in the cooling or peripheral portion of the heat transport path 150. For example, the dampers may form a skirt or ring around the periphery of the end of the cask 100, or may be located anywhere else around the heat transport path 150. The dampers 160 allow air flow and convection over the heat transport path 150 and may be opened manually or automatically to maximize heat transfer from the cask 100, or may be partially opened or closed to allow heating of the cask 100.

[0020] The heat transfer cask 100 of the exemplary embodiment may include a convection jacket or ring 110 that functions as a thermally conductive heat reservoir. For example, the ring 110 may be a 2-inch (approximately 5.08 centimeter) sodium ring that melts into a convective liquid at typical internal temperatures of the cask 100. The ring 110 may be directly or nearby connected to a heated or innermost portion of the heat transfer passage 150 to transfer heat to the passage 150 and then through the passage 150 to an outer portion, such as near the damper 160. The ring 110 may be located between the inner shield 11 and the outer shield 12 and may be thinner than that of a cask according to the related art to achieve the same outer diameter, or may be the same or larger size with a different outer diameter.

[0021] The internal cavity 160 formed by the shielding and internal structural partitions of the cask 100 according to the exemplary embodiment can be sized to accommodate any number of heat-producing materials, such as six fuel assemblies 1 for a liquid metal reactor, a light or heavy water reactor, a graphite-moderated reactor, or the like. The internal cavity need not be filled with helium; any inert fill material, including argon or nitrogen, can be used, taking into account the heat transfer capabilities of the cask 100. A central rod 105 may be used to pack the cavity 160, absorb radiation, and / or extend from the top of the cask 100 for handling purposes. For example, the central rod 105 may be boron carbide, which is both a neutron absorber and structurally integral with the rest of the cask 100, allowing for consistent handling at the end. This may limit the possibility of nuclear fission in the cavity 160, even when multiple nuclear fuel assemblies 1 are filled. 2C, the cavity 160 can be surrounded by the outer periphery of multiple heat transfer channels 150 in any order or thickness using structural partitions, similar to the shields 11 / 12 and ring 110. In this way, the cavity 160 can be uniformly and sufficiently cooled / heated by the channels 150 and ring 110.

[0022] Example embodiment heat transfer cask 100 may include immersion heating rods 120 for heating the contents of ring 110 and cavity 160 to a desired temperature. The immersion heating rods 120 may be similarly positioned relative to heat path 150 and operate in a largely opposite manner to supply heat to or generate heat in cask 100. For example, immersion heating rods 120 may be electrical resistance heaters with power connections 121 near the top end of cask 100 for heating the rods 120 and conducting heat to ring 110 and / or cavity 160. The rods 120, along with the heat path 150, may be staggered around the periphery of ring 110, as shown in FIG. 2C, to provide uniform heating and cooling. For example, if cask 100 is used to store and transport new fuel assemblies 1 for insertion into a liquid metal nuclear reactor, it may be desirable to bring the stored components to near operating temperatures exceeding 200°C by activating immersion heating rods 120. During such operation, damper 160 may be closed to prevent or reduce convection to the cold end of heat transfer path 150, so that heat is not lost from cask 100. Example embodiment heat transfer cask 100 may include end lids or seams to allow for insertion or removal of the contents of cavity 160 during this time; cask 100 may be maintained open and at operating temperature during all loading and unloading, as it is maintained at operating temperature by immersion heating rods 120.

[0023] Having thus described several exemplary embodiments and methods, those skilled in the art will recognize that variations in the examples may be made through routine experimentation and without further inventive effort. For example, while some exemplary systems utilize casks with annular shields, it will be understood that other cask configurations can be used in combination with the examples. Variations are not to be considered a departure from the spirit and scope of the exemplary embodiments, and all such modifications that would be apparent to those skilled in the art are intended to be included within the scope of the following claims.

Claims

1. A heat transfer cask (10) for storing nuclear material at temperatures below 650°C, a shield (11, 12) defining an internal cavity (160) and limiting the passage of ionizing radiation from said cavity to the environment surrounding said heat transfer cask; a heat transfer path (150) having a closed first end inside the shield and a closed second end outside the shield, thereby preventing fluid from exiting the heat transfer path (150); a convection jacket (110) surrounding the cavity, the convection jacket configured to uniformly distribute heat within the cavity, a heater (120) extending within the convection jacket; Equipped with The heat transfer cask (10) is formed in a shape that bends and passes between the first end and the second end of the heat transfer path (150) so as to pass through the shielding bodies (11, 12), and the heat transfer cask (10) is formed only from materials configured to maintain its chemical identity even when exposed to ionizing radiation from spent nuclear fuel.

2. The cask of claim 1 , wherein the transport path is at least one of a heat pipe and a solid conductive rod.

3. The cask of claim 1 , wherein the heat transport path includes a diversion through the shield to block the ionizing radiation.

4. 2. The cask of claim 1, further comprising nuclear material (1) contained within the cavity, the nuclear material being at least one of new nuclear fuel, spent nuclear fuel, a radioactive source, irradiated waste, and radioactively contaminated waste, the heat transport path being configured to transport heat outside the cask so that the cavity does not exceed 650°C, and the heat transport path including at least 20 1 kW heat pipes.

5. 2. The cask of claim 1, further comprising a damper housing (160) at an end of the cask, the heat transfer path extending into the damper housing, the damper housing being openable to enhance fluid convection around the heat transfer path and closeable to restrict fluid convection around the heat transfer path.

6. 2. The cask of claim 1, wherein the convection jacket contains only metallic sodium configured to melt and circulate to uniformly distribute heat within the cavity, and the heat transfer path has an end within the convection jacket.

7. A heat transfer cask (10) for storing nuclear material at temperatures below 650°C, a shield (11, 12) defining an internal cavity (160) and limiting the passage of ionizing radiation from said cavity to the environment surrounding said heat transfer cask; a heat transfer path (150) including a heat pipe extending from the inside of the shield to the outside of the shield; a heater (120) for heating the cavity; a convection jacket (110) surrounding the cavity, the convection jacket configured to distribute heat evenly within the cavity, the heater extending into the convection jacket; A heat transfer cask (10).

8. a shield (11, 12) forming an internal cavity (160) and limiting the passage of ionizing radiation from the cavity to the environment surrounding the heat transfer cask (100); a convection jacket (110) surrounding the cavity, configured to melt at 200°C and distribute heat uniformly within the cavity, a heater (120) extending into the convection jacket; and a heat transfer path (150) from inside the shield to outside the shield, the heat transfer path (150) including: a heat transfer cask (100) including a heat transfer path (150) formed in a shape that bends and passes through the interior of the heat transfer path (150) between both ends of the heat transfer path (150) so as to pass through the shields (11, 12), wherein the heat transfer cask (100) is formed only from materials configured to maintain their chemical identity even when exposed to ionizing radiation from spent nuclear fuel, the method comprising: loading fresh fuel (1) from the cask into the reactor; removing spent fuel or nuclear material from the reactor into the cask; A method for storing nuclear fuel in a heat transfer cask (100), comprising:

9. The cask is not closed during the loading or the unloading or between the loading and the unloading, and the method further comprises: The method of claim 8, further comprising activating a heater (120) within the cask to warm the fresh fuel to at least 200°C.

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