High-temperature hydride moderators that enable a compact and higher power density core in a microreactor

Abstract

A core block is disclosed that includes a fuel channel, a heat pipe, a primary moderator matrix configured to surround the fuel channel and the heat pipe, and a secondary moderator channel configured to at least partially surround the fuel channel, the heat pipe, and the primary moderator matrix, wherein the secondary moderator channel contains a metal hydride.

Description

Technical Field

[0001] (Cross - Reference to Related Applications) This application claims the benefit of U.S. Provisional Application No. 62 / 984,591, filed Mar. 3, 2020, the content of which is hereby incorporated by reference in its entirety.

Background Art

[0002] This invention generally relates to nuclear reactors, and more particularly to the arrangement of fuel channels, heat pipes, and moderators within the reactor core.

[0003] The electricity energy market can be classified into a centralized market and a distributed market. The centralized market is based on large (in the range of several hundred MWe) generators and high - capacity high - density power transmission and distribution networks. The distributed market or off - grid market, instead, relies on compact (<15 MWe) generators that are typically connected to localized small - scale distribution networks or microgrids. Currently, examples of the distributed market are remote Arctic communities, remote mines, military bases, and island communities. Currently, the energy in the off - grid market is mainly provided by diesel generators. This leads to high - cost electricity, dependence on fossil fuels, load limitations, complex fuel supply logistics, and aging infrastructure. The strict requirements of the off - grid market include cost reduction, reliability, flexibility, fault recovery, sustainability (clean energy), energy security, and quick installation effort and minimal maintenance effort. Nuclear energy can meet all of these demands.

[0004] A micro - reactor is a nuclear reactor capable of generating less than 10 MWe and deployable for remote applications. These micro - reactors can be packed into relatively small containers, operated without active human intervention, and operated without fuel replenishment / exchange for a longer period than conventional nuclear power plants.

[0005] One such microreactor is the eVinci microreactor system designed by the Westinghouse Electric Company. This eVinci system is a heat pipe cooled reactor power generation system that utilizes fuel, neutron moderator channels, and heat pipes housed within a compact monolithic core block. The heat pipe serves as a passive heat removal device that efficiently transfers thermal energy from the monolithic core to a heat exchanger on the secondary side of the microreactor. The heat pipe is a hermetically sealed tube that contains a small amount of volatile liquid (such as liquid potassium or sodium) that boils at one end of the tube (the evaporator section), and the vapor travels to the other end of the tube (the condenser section), where it condenses and releases its latent heat. The condensed liquid is returned to the other end of the tube by means of a wick that uses capillary forces, and the condensate is drawn back towards the evaporator section. Additional considerations regarding heat pipes are described in U.S. Patent Application Publication No. 2016 / 0027536, published as "MOBILE HEAT PIPE COOLED FAST REACTOR SYSTEM", U.S. Patent Application No. 14 / 773,405, and U.S. Patent No. 3,668,070, entitled "NUCLEAR REACTOR WITH HEAT PIPES FOR HEAT EXTRACTION", all of which are incorporated herein by reference in their entirety.

[0006] The current core in the microreactor utilizes uranium fuel that needs to be enriched to levels far higher than 5 wt% U-235. One such fuel is High Assay Low Enriched Uranium (HALEU), which is uranium fuel enriched up to 19.75 wt% U-235 at most. The industrial-scale amount of uranium enriched above 5 wt% U-235 is limited because there is no ability to manufacture the required scale. This drives up the cost of nuclear fuel and, as a result, the high cost of the microreactor. Consequently, the microreactor has limited accessibility for potential markets and potential customers.

[0007] One such objective of the present disclosure is to provide a lightweight microreactor that is inherently safe, can operate without refueling for several years, can be used with a reduced amount of HALEU fuel or fuel with a low enrichment level comparable to 5 wt% U-235, and can be transported by aircraft, truck, and on conventional roads by meeting strict mass and size limitations. SUMMARY OF THE INVENTION

[0008] In various embodiments, a core block is disclosed that includes a fuel channel, a heat pipe, a primary moderator matrix configured to surround the fuel channel and the heat pipe, and a secondary moderator channel configured to at least partially surround the fuel channel, the heat pipe, and the primary moderator matrix. The secondary moderator channel contains a metal hydride.

[0009] In various embodiments, a core is disclosed that includes a plurality of core blocks. Each core block includes a fuel channel, a heat pipe, a primary moderator matrix surrounding the fuel channel and the heat pipe, and a secondary moderator channel configured to at least partially surround the fuel channel, the heat pipe, and the primary moderator matrix. The secondary moderator channel contains a metal hydride.

[0010] In various embodiments, a core is disclosed that includes a first array, a second array, and a third array positioned between the first array and the second array. The first array includes a first plurality of fuel channels and a first plurality of heat pipes. The first array is configured to alternately repeat fuel channels from the first plurality of fuel channels and heat pipes from the first plurality of heat pipes. The second array includes a second plurality of fuel channels and a second plurality of heat pipes. The second array is configured to alternately repeat fuel channels from the second plurality of fuel channels and heat pipes from the second plurality of heat pipes. The third array includes a first plurality of moderator channels. Each moderator channel from the first plurality of moderator channels contains a metal hydride. The core further includes a moderator matrix. The first array, the second array, and the third array are embedded within the moderator matrix.

[0011] In various embodiments, a core is disclosed that includes a first furnace section, a second furnace section, and a row of moderating channels positioned between the first furnace section and the second furnace section. The first furnace section includes a first row of fuel channels and a first row of heat pipes parallel to the first row of fuel channels. The second furnace section includes a second row of fuel channels and a second row of heat pipes parallel to the second row of fuel channels. The first row of fuel channels forms an interface with the row of moderating channels and defines a first angle therebetween. The second row of fuel channels forms an interface with the row of moderating channels and defines a second angle therebetween. The first row of fuel channels is angled with respect to the second row of fuel channels, and the moderating channels include a metal hydride.

[0012] In various embodiments, a core is disclosed that includes fuel channels, a first heat pipe positioned within a gap between the fuel channels, a second heat pipe positioned within the center of the fuel channels, and moderating channels including a metal hydride. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The various features of the embodiments described herein, together with their advantages, can be understood in accordance with the following description when read in conjunction with the accompanying drawings as follows.

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[0021] Corresponding reference characters indicate corresponding parts throughout the several views. The specific examples described in detail herein illustrate one form of various embodiments of the present invention, and such specific examples should not be construed as limiting the scope of the present invention in any way.

DETAILED DESCRIPTION OF THE INVENTION

[0022] Numerous specific details are set forth in order to provide a thorough understanding of the overall structure, function, manufacture, and use of the embodiments as described in the specification and illustrated in the accompanying drawings. Well-known operations, components, and elements are not described in detail so as not to obscure the embodiments described in the specification. As will be understood by those skilled in the art, the embodiments described and illustrated herein are non-limiting examples, and thus it can be recognized that the specific structural and functional details disclosed herein can be representative and exemplary. Modifications and variations to these can be made without departing from the scope of the claims.

[0023] The terms "comprise" (and any form of "comprise" such as "comprises" and "comprising"), "have" (and any form of "have" such as "has" and "having"), "include" (and any form of "include" such as "includes" and "including"), and in addition, "contain" (and any form of "contain" such as "contains" and "containing") are open-ended conjunctive verbs. As a result, a system that "comprises", "has", "includes", or "contains" one or more elements owns those one or more elements, but is not limited to owning only those one or more elements. Similarly, an element of a system, device, or apparatus that "comprises", "has", "includes", or "contains" one or more features owns those one or more features, but is not limited to owning only those one or more features.

[0024] FIG. 1 illustrates a core block 200 according to at least one aspect of the present disclosure. The core block 200 includes a plurality of fuel sources or fuel channels 202 and a plurality of heat pipes 204. The heat pipes 204 as described above are configured to transfer the heat generated by the fuel channels 202 from the core block 200 to the secondary side of the furnace, and the secondary side can include heat exchange for extracting heat from the heat pipes 204.

[0025] As illustrated in FIG. 1, the fuel channels 202 and the heat pipes 204 can be arranged in a hexagonal pattern. In other embodiments, the fuel channels 202 and the heat pipes 204 can be arranged in other patterns, such as a square pattern, an octagonal pattern, a decagonal pattern, or any other pattern that results in a shape having an even number of sides. In other embodiments, the fuel channels 202 and the heat pipes 204 can be arranged in other patterns, such as, by way of example, a triangular pattern, a pentagonal pattern, or a heptagonal pattern, which result in a shape having an odd number of sides. Other embodiments are contemplated in which the fuel channels 202 and the heat pipes 204 have an asymmetric pattern within the core block 200.

[0026] As shown in FIG. 1, the core block 200 can include twelve fuel channels 202 and seven heat pipes 204. In other words, the core block 200 can include more fuel channels 202 than heat pipes 204. In one embodiment, for each heat pipe 204, there are two fuel channels 202. In another embodiment, for each heat pipe 204, there are more than two fuel channels 202. In another embodiment, there are fuel channels 202 and heat pipes 204 in a 1:1 ratio. Other embodiments are contemplated in which there are more heat pipes 204 than fuel channels 202. In one aspect, the number of fuel channels 202 adjacent to a heat pipe 204 is variable. As shown in FIG. 1, the heat pipe 204 at the center of the core block 200 is adjacent to six fuel channels 202, while the heat pipes 204 along the outer periphery of the core block 200 are adjacent to only four fuel channels 202. Other embodiments are contemplated in which the number of heat pipes 204 adjacent to a fuel channel 202 is the same throughout the core block 200.

[0027] The core block 200 further includes a primary moderator matrix 206 configured to surround the fuel channel 202 and the heat pipe 204 within the core block 200 and to firmly hold the fuel channel 202 and the heat pipe 204. In one embodiment, the primary moderator matrix 206 includes a solid block material having low neutron absorption characteristics and preferably having a small moderation effect. In one such embodiment, the primary moderator matrix can include graphite. In another embodiment, the primary moderator matrix can include silicon carbide. In another embodiment, the primary moderator matrix can include aluminum nitride. In another embodiment, the primary moderator matrix can include stainless steel. In another embodiment, the primary moderator matrix can include, for example, any combination of graphite, silicon carbide, aluminum nitride, and stainless steel.

[0028] The core block 200 can further include a plurality of secondary moderator channels 208. As shown in FIG. 1, the plurality of secondary moderator channels can partially surround the fuel channel 202 and the heat pipe 204 within the primary moderator matrix 206. In another embodiment, the plurality of secondary moderator channels 208 can completely surround the fuel channel 202 and the heat pipe 204. In one embodiment, the core block 200 includes only one continuous secondary moderator channel configured to completely surround the fuel channel 202 and the heat pipe 204. As shown in FIG. 1, the secondary moderator channel 208 can have a cross-sectional shape of a pack. Although the secondary moderator channel 208 is shown having a cross-sectional shape of a pack, other cross-sectional shapes are envisioned, such as a square cross-sectional shape, a hexagonal cross-sectional shape, or any other cross-sectional shape such that the secondary moderator channel 208 partially or completely surrounds the primary moderator matrix 206, the fuel channel 202, and the heat pipe 204.

[0029] As shown in FIG. 1, the secondary moderator channel 208 is configured to overlap with the primary moderator matrix 206 such that the secondary moderator channel 208 surrounds only a portion of the primary moderator matrix 206 while a plurality of portions of the primary moderator matrix 206 are not surrounded by the secondary moderator channel 208. In one embodiment, the core block 200 includes only one continuous secondary moderator configured to completely surround the fuel channel 202, the heat pipe 204, and the primary moderator matrix 206.

[0030] In one aspect, the secondary moderator channel 208 can contain hydrogen atoms in a chemical form that does not dissociate at high operating temperatures within the reactor. In one embodiment, this can be achieved by using a high-temperature metal hydride. In one embodiment, the metal hydride can include metal hydride blocks. In one embodiment, the metal hydride can include metal hydride pellets. In one embodiment, the metal hydride can include metal hydride rods. In one embodiment, the metal hydride can include metal hydride plates. In one embodiment, the metal hydride can include any combination of metal hydride blocks, metal hydride pellets, metal hydride rods, or metal hydride plates.

[0031] In one embodiment, the secondary moderator channel 208 can include yttrium hydride. In one embodiment, the secondary moderator channel 208 can include cerium hydride. In one embodiment, the secondary moderator channel 208 can include yttrium zirconium hydride. In one embodiment, the secondary moderator channel 208 can include any suitable combination of yttrium hydride, cerium hydride, and yttrium zirconium hydride. In one embodiment, the secondary moderator channel 208 can include any suitable material in which hydrogen atoms do not dissociate at high operating temperatures within the reactor.

[0032] The advantage of high-temperature metal hydride moderators, such as the secondary moderator channel 208, is that the metal lattice enables the dissolution of hydrogen within the lattice and the storage of a high concentration of hydrogen within its structure. The high concentration of hydrogen ensures neutron moderation. At the same time, because the storage of hydrogen within the hydride does not involve significant dissociation into hydrogen gas, it is possible to operate at higher temperatures, unlike water, organic compounds, or hydrogen gas at high temperatures. Also, the high-temperature hydride moderator provides a passive method of shutting down the reactor by dissociating hydrogen and removing the hydrogen from the core. At a certain temperature, higher than the operating temperature (higher than 600 °C) and definable by selecting an appropriate moderator and its stoichiometry, hydrogen atoms dissociate and are released from the secondary moderator 208. As a result, neutron moderation is lost and the reactor is passively shut down.

[0033] In addition, by arranging the secondary moderator channel 208 together with the primary moderator matrix 206 and using it in combination with the primary moderator matrix 206, it becomes possible to reduce the amount of fuel required for the operation of the reactor. Using a high-temperature moderator such as yttrium hydride, cerium hydride, zirconium hydride, or a combination thereof together with a low-absorption structural material such as graphite has never been done before in any commercial or experimental microreactor. In one embodiment, the arrangement and combination of the primary moderator matrix 206 and the secondary moderator channel 208 make it possible to reduce the amount of HALEU fuel required for the operation of the reactor. In other embodiments, the arrangement and combination of the primary moderator matrix 206 and the secondary moderator channel 208 enable the use of fuel with a lower enrichment of U-235 than HALEU, such as fuel enriched up to 5 wt% U-235 (low-enriched uranium), which is more readily available than HALEU.

[0034] In addition, the arrangement of the fuel channels, heat pipes, primary moderator, and secondary moderator channels, which will be discussed in more detail below with reference to FIGS. 2-7, provides for a further significant reduction in fuel mass and ensures the inherent safety of the reactor. The combination of the secondary moderator channels 208 with the primary moderator matrix 206, together with the specific arrangement of the fuel channels, heat pipes, primary moderator matrix, and secondary moderator channels, enables the use of other types of low-density fuel sources, such as, by way of example, tri-structural isotropic (TRISO) fuel or U3Si2 fuel enriched up to 5 wt%, in fuel types such as these. The above combination and arrangement of the primary and secondary moderators ensures a negative reactivity coefficient and maintains an appropriate time delay between reactivity feedbacks in different core components, thus enhancing the safety of the microreactor. In addition, due to the above features, the microreactor can operate for a longer period of time than was previously possible, the fuel economy is improved by an order of magnitude, and the levelized cost of electricity (LCOE) of the reactor is improved by at least 50%.

[0035] Referring now to FIG. 2, a reactor core 300 according to at least one aspect of the present disclosure is illustrated. The reactor core 300 includes a plurality of core blocks 200 that are radially repeated within the reactor core 300. The core blocks 200 are housed within a monolithic core housing 302, which can be made of a suitable creep-resistant high-temperature material, such as stainless steel, by way of example. The monolithic core 302 acts as a fission product barrier and as a heat transfer medium between the fuel channels 202 and the heat pipes 204.

[0036] The heat pipe 204 is configured to extend from the core 300 to the secondary side of the reactor so that the heat generated by the fuel channel 202 can be absorbed by the heat exchanger. As discussed above, the heat pipe 204 can include an evaporator section and a condenser section. The evaporator section of the heat pipe 204 can be disposed within the core 300, and the condenser section can be disposed on the secondary side of the reactor configured to extract heat. The heat generated by the fuel channel 202 is absorbed by the evaporator section of the heat pipe 204, and this heat evaporates the working fluid of the heat pipe 204. The evaporated fluid travels to the condenser section and releases its latent heat to the heat exchanger. The working fluid is then returned to the evaporator section (and the core 300) by the capillary action of the wick structure within the heat pipe 204.

[0037] The monolithic core 302 of the core 300 can be surrounded by a plurality of control drums 310, and the plurality of control drums 310 include a neutron absorber section 312 and a neutron reflector section 314. The control drum 310 is configured to rotate between a first position and a second position. In the first position, the neutron absorber section 312 of the control drum 310 can be configured to face the monolithic core 302, restricting or stopping the reactivity within the core 300. In the second position, the neutron reflector section 314 of the control drum 310 can be configured to face the monolithic core 302, thus increasing the reactivity of the core 300 via the Doppler effect.

[0038] In one aspect, the control drum 310 can be the only moving component within the core 300. In one embodiment, all of the control drum 310 is configured to rotate together such that all of the control drum 310 is in either a first position or a second position. In other embodiments, the control drum 310 can be rotatable independently of each other. In other embodiments, the control drum 310 can be rotated to a partially rotated position where a portion of both the neutron absorber section 312 and the neutron reflector section 314 face the monolith core 302. In another embodiment, the control drum 310 is configured to automatically rotate between a first position and a second position depending on various factors such as the temperature within the core 300. In one aspect, when the temperature within the core 300 meets or exceeds a threshold temperature, the control drum 310 can be configured to automatically rotate to the first position, where the neutron absorber section 312 faces the monolith core 302 and limits or stops the reactivity of the core 300. In another aspect, when the temperature within the core 300 drops below the threshold temperature, the control drum 310 can be configured to automatically rotate to the second position, where the neutron reflector section 314 faces the monolith core 302, thus increasing the reactivity of the core 300 via the Doppler effect. In one aspect, in order to increase the reactivity, the space 316 between the control drums 310 can additionally include a neutron reflector. In another embodiment, in order to limit the reactivity, the space 316 can include a neutron absorber. In another embodiment, the space 316 can be a mixture of a neutron absorber and a neutron reflector.

[0039] The core 300 and the control drum 310 can be housed within a containment vessel (not shown), which can include any suitable material configured to house the core 300 and the control drum 310. In one embodiment, the containment vessel can include, by way of example, stainless steel. The containment vessel can be surrounded by additional neutron absorbers, a boron carbide neutron shield, voids for shield cooling, a gamma shield, and a stainless steel outer wall.

[0040] As discussed above, at a certain temperature higher than the operating temperature and definable by choosing an appropriate moderator and its stoichiometry, hydrogen atoms dissociate and are released from the secondary moderator channel 208. As a result, neutron moderation is lost and the core 300 is passively shut down. Referring again to FIG. 2, the core 300 can also include a core shutdown module 350. The core shutdown module 350 provides a secondary passive shutdown system for shutting down the core 300 along with the passive shutdown provided from the secondary moderator 208. In one embodiment, it can be designed such that neutron absorbing material is inserted into the shutdown module 350 at a certain core 300 temperature compared to a predefined threshold.

[0041] As discussed above, the arrangement provided within the core 300 enables a reduction in the amount of HALEU fuel required for the operation of the reactor. Additionally, this arrangement enables the use of other types of fuel other than HALEU, such as, by way of example, fuel enriched up to a maximum of 5 wt% U-235 (low-enriched uranium), tri-structural isotropic (TRISO) fuel, or U3Si2 fuel enriched up to 5 wt%. As an example, for HALEU TRISO, to achieve criticality, it would require 2000 - 4000 kg of TRISO fuel at a 20% U-235 enrichment at a 40% fill rate. Using a metal hydride such as yttrium hydride, the total fuel mass can be reduced to approximately 600 kg of TRISO fuel at a 19.75% U-235 enrichment at a 40% fill rate. The arrangement of FIG. 2 ensures a negative reactivity coefficient and maintains an appropriate time delay between reactivity feedbacks in different core components, thus enhancing the safety of the microreactor. Additionally, with the arrangement of FIG. 2, the core 300 can operate for a longer period of time than was previously possible, with the fuel economy improved by an order of magnitude and the levelized cost of electricity (LCOE) of the reactor improved by at least 50%.

[0042] Referring now to FIG. 3, a core 370, which is another embodiment according to at least one aspect of the present disclosure, is illustrated. The core 370 is similar to the core 300 and the same numbers are used to illustrate similar components. The core 370, unlike the core 300, includes five reactor shutdown modules 350 (whereas the core 300 includes nine reactor shutdown modules 350), and the core 370 does not include either the fuel channels 202 or the heat pipes 204 inserted therein. As can be seen in FIG. 3, the control drum 310, the primary moderator matrix 206, and the secondary moderator channels 208 extend completely along the length of the core 370.

[0043] Next, referring to FIG. 4, a core 420, which is another embodiment according to at least one aspect of the present disclosure, is illustrated. The core 420 includes a plurality of core blocks 400 that, similar to the core 300, include fuel channels 402, heat pipes 404, a primary moderator matrix (not shown), and secondary moderator channels 408. As shown in FIG. 4, the secondary moderator channels 408 have a circular cross-sectional shape. Additionally, the secondary moderator channels 408 are configured such that the core blocks 400 are completely surrounded by the secondary moderator channels 408. In other embodiments, the secondary moderator channels are configured such that the core blocks 400 are only partially surrounded by the secondary moderator 408. Although the secondary moderator channels 408 are shown as having a circular cross-sectional shape, other cross-sectional shapes are contemplated, such as a square cross-sectional shape, a hexagonal cross-sectional shape, or any other cross-sectional shape such that the core blocks 400 are completely surrounded by the secondary moderator channels 408.

[0044] Similar to the core 300, the core blocks 400 are housed within a monolithic core housing 422. The monolithic core housing 422 can also be surrounded by a plurality of control drums 410 that include a neutron absorber section (not shown) and a neutron reflector section 414, and a space 416 positioned between the control drums 410. Different from the core 300, the core 420 includes a single core shutdown module 450 that provides a secondary passive shutdown system for shutting down the core 420, along with passive shutdown provided by the secondary moderator 408. Although only one core shutdown module 450 is illustrated, other embodiments are contemplated in which the core 420 includes a plurality of core shutdown modules 450.

[0045] The arrangement provided in the core 420 enables a reduction in the amount of HALEU fuel required for the operation of the reactor. Additionally, this arrangement enables the use of other types of fuel other than HALEU, such as, for example, fuel enriched up to a maximum of 5 wt% U-235 (low-enriched uranium), tri-structural isotropic (TRISO) fuel, or U3Si2 fuel enriched up to 5 wt%. The arrangement of FIG. 4 ensures a negative reactivity coefficient and maintains an appropriate time delay between reactivity feedbacks in different core components, thus enhancing the safety of the microreactor. Additionally, with the arrangement of FIG. 4, the core 420 can operate for a longer time than was previously possible, with the fuel economy improved by an order of magnitude and the levelized cost of electricity (LCOE) of the reactor improved by at least 50%.

[0046] Next, referring to FIG. 5, a core 500 is illustrated, which is another embodiment according to at least one aspect of the present disclosure. The core 500 encloses a plurality of continuous, circular arrays 530, 540, 550 that extend outwardly from the center of the core 500 towards the monolith core housing 522. As shown in FIG. 5, the core 500 can include a first array 530 that alternately includes fuel channels 502 and heat pipes 504 along its length. The core 500 can also include a second array 540 that includes a plurality of moderator channels 508 that surround or encircle the first array 530. The moderator channels can be similar to the high-temperature metal hydride moderators such as the secondary moderator 208 discussed above. Additionally, the core 500 can include a third array 550 that is similar to the first array 530 and, like the first array 530, alternately includes fuel channels 502 and heat pipes 504 along its length and surrounds or encircles the second array 540. In one aspect, the second array 540 of moderator channels 508 is configured to be positioned between the first array 530 and the third array 550 so as to completely separate the first array 530 from the third array 550. In other aspects, a gap can be defined between the moderator channels 508 of the second array 540 such that the first array 530 and the third array 550 are only partially separated by the second array 540. The core 500 can include any number of arrays until these rows reach the monolith core housing 522 of the core 500 from the center of the core 500.

[0047] The above-described core 500 is advantageous from a manufacturing perspective. At the same time, it also provides the above-mentioned fuel benefits (for example, a smaller amount of HALEU, the ability to use other types of fuel, and enhanced reactor safety). Additionally, although not shown in FIG. 5, the core 500 can include a primary moderator, or a primary moderator matrix similar to the primary moderator matrix 206, configured to firmly hold the fuel channels 502 and heat pipes 504 and having low neutron absorption and preferably a small moderation effect. As discussed above, the primary moderator can include any of graphite, silicon carbide, aluminum nitride, stainless steel, and combinations thereof.

[0048] Columns 530, 540, 550 can be accommodated within the monolithic core housing 522, similar to the above-described cores 300, 420. The monolithic core housing 522 can also be surrounded by a plurality of control drums 510 that include neutron absorber sections (not shown) and neutron reflector sections 514, and a space 516 located between the control drums 510. Although not illustrated, the core 500 can include any number of reactor shutdown modules to provide a secondary passive shutdown system for shutting down the core 500, along with the passive shutdown provided by the secondary moderator 508.

[0049] Referring next to FIG. 6, a core 600 is illustrated, which is another embodiment according to at least one aspect of the present disclosure. The core 600 encloses discontinuous core sections 640, each including a row of fuel channels 602 and heat pipes 604, and the discontinuous core sections 640 are separated by moderator channels 608, 609. The moderator channels 608, 609 can be similar to the high-temperature metal hydride moderators such as the secondary moderator 208 discussed above.

[0050] The columns of fuel channels 602, heat pipes 604, and moderators 608 in one furnace section 640 can be angled with respect to the columns of fuel channels 602, heat pipes 604, and moderators 608 in an adjacent furnace section 604. In one example, referring to FIG. 6, the columns of fuel channels 602, heat pipes 604, and moderator channels 608 in one furnace section 640 form an interface 630 with respect to the rows of moderator channels 609, defining a first angle Θ1 therebetween. Additionally, the rows of fuel channels 602, heat pipes 604, and moderator channels 608 in another furnace section 640 form an interface 632 with respect to the rows of moderator channels 609, defining a second angle Θ2 therebetween. In other words, the angles of the columns of fuel channels 602, heat pipes 604, and moderators 608 are configured to transition from a first angle Θ1 to a second angle Θ2 in the column of moderator channels 609. In other words, the columns of fuel channels 602, heat pipes 604, and moderator channels 608 in one furnace section 640 are angled with respect to the columns of fuel channels 602, heat pipes 604, and moderator channels 608 in another furnace section 640. In one embodiment, Θ1 and Θ2 can be equal. In one embodiment, Θ1 and Θ2 can be different. In one embodiment, the sum of Θ1 and Θ2 can define 90°. In other embodiments, the sum of Θ1 and Θ2 can be greater than 90° or less than 90°. While the above arrangement is advantageous from a manufacturing perspective, it also provides the above fuel benefits (e.g., less amount of HALEU, or the ability to use other types of fuel, increased safety). Additionally, although not shown in FIG. 6, the reactor core 600 can include therein a primary moderator, or a primary moderator matrix similar to the primary moderator matrix 206, configured to firmly hold the fuel channels 602 and heat pipes 604 and having low neutron absorption and preferably a small moderation effect.As discussed above, the primary moderator matrix can include any of graphite, silicon carbide, aluminum nitride, stainless steel, and combinations thereof.

[0051] The core 600 can include, similar to the cores 300, 420, 500 described above, a fuel channel 602, a heat pipe 604, a secondary moderator 608, and a monolithic core housing 622 surrounding other components of the core 600. The monolithic core housing 622 can also be surrounded by a plurality of control drums 610 including neutron absorber sections 612 and neutron reflector sections 614, and a space 616 positioned between the control drums 610. Additionally, the core 600 can include a core shutdown module 650 to provide a secondary passive shutdown system for shutting down the core 600, along with the passive shutdown provided by the secondary moderator 608. Although only one core shutdown module 650 is illustrated, it is contemplated that the core 600 can include a plurality of core shutdown modules 650.

[0052] Next, referring to FIG. 7, a core 700, which is another embodiment according to at least one aspect of the present disclosure, is illustrated. The core 700 encloses an array of annular fuel channels 702 and an array of moderator channels 708. The secondary moderator channels may be similar to the high-temperature metal hydride moderators such as the secondary moderator 208 discussed above. In addition, the core encloses a plurality of heat pipes 704, 710. The heat pipe 704 can be positioned within the gap between the fuel channels 702, while the heat pipe 710 can be positioned at the center of the fuel channel 702. The mesh-type configuration illustrated in FIG. 7 allows an increase in the number of heat pipes 704, 710 per core, resulting in an increase in the electric power output provided by the core 700. In addition, although not shown in FIG. 7, the core 700 can include a primary moderator, or a primary moderator matrix similar to the primary moderator matrix 206 discussed above, configured to firmly hold the fuel cells 702 and the heat pipes 704, 710 and having low neutron absorption and preferably a small moderation effect. As discussed above, the primary moderator can include any of graphite, silicon carbide, aluminum nitride, stainless steel, and combinations thereof.

[0053] Similar to the cores 300, 420, 500, 600 described above, the core 700 can include a monolithic core housing 722 that surrounds the fuel channels 702, the heat pipes 704, 710, the secondary moderator 708, and other components of the core 700. Although not illustrated, the monolithic core housing 722 can also be surrounded by a plurality of control drums including neutron absorber sections and neutron reflector sections and a space positioned between the control drums. In addition, the core 700 can include any number of core shutdown modules to provide a secondary passive shutdown system for shutting down the core 700, along with the passive shutdown provided by the secondary moderator 708.

[0054] The arrangement within the core, in addition to the fuel and safety benefits discussed above, enables a relatively small core to be transported within a standard and available transport system (e.g., a standard ISO transport container), and as a result, by meeting strict mass and size limitations, it can be packed into a low-mass container that can be transported by airplane, truck, and on conventional roads.

[0055] Various aspects of the subject matter described herein are detailed in the following examples.

[0056] Example 1 - A core block comprising a fuel channel, a heat pipe, a primary moderator matrix configured to surround the fuel channel and the heat pipe, and a secondary moderator channel configured to at least partially surround the fuel channel, the heat pipe, and the primary moderator matrix, wherein the secondary moderator channel contains a metal hydride.

[0057] Example 2 - The core block of Example 1, wherein the primary moderator matrix is selected from the group consisting of graphite, silicon carbide, aluminum nitride, stainless steel, and combinations thereof.

[0058] Example 3 - The core block of Example 1 or 2, wherein the metal hydride is selected from the group consisting of yttrium hydride, cerium hydride, zirconium hydride, and combinations thereof.

[0059] Example 4 - The core block of any one of Examples 1 to 3, wherein the secondary moderator channel is selected from the group consisting of blocks, pellets, rods, or plates, and combinations thereof.

[0060] Example 5 - The core block of any one of Examples 1 to 4, wherein the secondary moderator channel is configured to completely surround the fuel channel, the heat pipe, and the primary moderator matrix.

[0061] Example 6 - A reactor core comprising a plurality of reactor core blocks, each reactor core block including a fuel channel, a heat pipe, a primary moderator matrix surrounding the fuel channel and the heat pipe, and a secondary moderator channel configured to at least partially surround the fuel channel, the heat pipe, and the primary moderator matrix, wherein the secondary moderator channel contains a metal hydride.

[0062] Example 7 - The reactor core of Example 6, further comprising a control drum provided with a neutron reflector and a neutron absorber.

[0063] Example 8 - The reactor core of Example 7, wherein the control drum is rotatable between a first position and a second position, and in the first position, the neutron absorber faces the plurality of reactor core blocks, and in the second position, the neutron reflector faces the plurality of reactor core blocks.

[0064] Example 9 - The reactor core according to any one of Examples 6 to 8, wherein the primary moderator matrix is selected from the group consisting of graphite, silicon carbide, aluminum nitride, stainless steel, and combinations thereof.

[0065] Example 10 - The reactor core according to any one of Examples 6 to 9, wherein the metal hydride is selected from the group consisting of yttrium hydride, cerium hydride, zirconium hydride, and combinations thereof.

[0066] Example 11 - The reactor core according to any one of Examples 6 to 10, wherein the secondary moderator channel is selected from the group consisting of blocks, pellets, rods, or plates, and combinations thereof.

[0067] Example 12 - The reactor core according to any one of Examples 6 to 11, wherein the secondary moderator channel is configured to completely surround the fuel channel, the heat pipe, and the primary moderator matrix.

[0068] Example 13 - The core includes a first array, a second array, a third array positioned between the first array and the second array, and a moderator matrix. The first array includes a first plurality of fuel channels and a first plurality of heat pipes. The first array is configured to alternately repeat fuel channels from the first plurality of fuel channels and heat pipes from the first plurality of heat pipes. The second array includes a second plurality of fuel channels and a second plurality of heat pipes. The second array is configured to alternately repeat fuel channels from the second plurality of fuel channels and heat pipes from the second plurality of heat pipes. The third array includes a first plurality of moderator channels. Each moderator channel from the first plurality of moderator channels contains a metal hydride. The first array, the second array, and the third array are embedded in the moderator matrix.

[0069] Example 14 - The core of Example 13 further includes a fourth array including a second plurality of moderator channels.

[0070] Example 15 - The core of Example 13 or 14 further includes a control drum including a neutron reflector and a neutron absorber.

[0071] Example 16 - The control drum is rotatable between a first position and a second position. In the first position, the neutron absorber faces the first array, the second array, and the third array. In the second position, the neutron reflector faces the first array, the second array, and the third array.

[0072] Example 17 - The metal hydride is selected from the group consisting of yttrium hydride, cerium hydride, zirconium hydride, and combinations thereof.

[0073] Example 18 - The core of any one of Examples 13 to 17, wherein the plurality of first moderator channels are selected from the group consisting of blocks, pellets, rods, or plates, and combinations thereof.

[0074] Example 19 - The core of any one of Examples 13 to 18, wherein the moderator matrix is selected from the group consisting of graphite, silicon carbide, aluminum nitride, stainless steel, and combinations thereof.

[0075] Example 20 - A core comprising a first furnace section, a second furnace section, and a row of moderator channels positioned between the first furnace section and the second furnace section. The first furnace section comprises a first row of fuel channels and a first row of heat pipes parallel to the first row of fuel channels. The second furnace section comprises a second row of fuel channels and a second row of heat pipes parallel to the second row of fuel channels. The first row of fuel channels forms an interface with the row of moderator channels, defining a first angle therebetween, and the second row of fuel channels forms an interface with the row of moderator channels, defining a second angle therebetween. The first row of fuel channels is angled with respect to the second row of fuel channels, and the moderator channels contain a metal hydride.

[0076] Example 21 - The core of Example 20, further comprising a control drum provided with a neutron reflector and a neutron absorber.

[0077] Example 22 - The core of Example 21, wherein the control drum is rotatable between a first position and a second position. In the first position, the neutron absorber faces the first furnace section, and in the second position, the neutron reflector faces the first furnace section.

[0078] Example 23 - The core of any one of Examples 20 to 22, wherein the metal hydride is selected from the group consisting of yttrium hydride, cerium hydride, zirconium hydride, and combinations thereof.

[0079] Example 24 - The core of any one of Examples 20 to 23, wherein the moderator channel is selected from the group consisting of blocks, pellets, rods, or plates, and combinations thereof.

[0080] Example 25 - A core comprising a fuel channel, a first heat pipe positioned within a gap between the fuel channels, a second heat pipe positioned within the center of the fuel channel, and a moderator channel containing a metal hydride.

[0081] Example 26 - The core of Example 25, further comprising a control drum provided with a neutron reflector and a neutron absorber.

[0082] Example 27 - The core of Example 26, wherein the control drum is rotatable between a first position and a second position, and in the first position, the neutron absorber faces the fuel channel, and in the second position, the neutron reflector faces the fuel channel.

[0083] Example 28 - The core of any one of Examples 25 to 27, wherein the metal hydride is selected from the group consisting of yttrium hydride, cerium hydride, zirconium hydride, and combinations thereof.

[0084] Example 29 - The core of any one of Examples 25 to 28, wherein each moderator channel of the moderator channels is selected from the group consisting of blocks, pellets, rods, or plates, and combinations thereof.

[0085] Unless specifically stated otherwise as apparent from the foregoing disclosure, it is to be understood that throughout the foregoing disclosure, discussions using terms such as "processing," "computing," "calculating," "determining," or "displaying," etc., refer to actions and processes of a computer system or similar electronic computing device, and that the computer system or similar electronic computing device operates on data represented as physical (electronic) quantities within the registers and memories of the computer system to transform them into other data similarly represented as physical quantities within the memories or registers of the computer system, or other such information storage devices, transmission devices, or display devices.

[0086] As used herein, one or more components may be referred to as "configured to...," "configurable to...," "operable / operating to...," "adapted / adaptable to...," "capable of...," "compliant / compliable to...," etc. As will be recognized by those skilled in the art, "configured to..." generally may include components in an active state, and / or components in a non-active state, and / or components in a standby state, unless the context otherwise requires.

[0087] Those skilled in the art will generally understand that the terms used herein, particularly the terms used in the appended claims (e.g., the body of the appended claims), should generally be construed as "open" terms (e.g., including but not limited to "comprising"), the term "having" should be construed as "having at least", and the term "comprising" should be construed as "comprising but not limited to", etc. Further, if a specific number of recitations in the introduced claims is intended, such intent should be explicitly recited in the claims, and in the absence of such recitation, for example, to aid understanding, the appended claims may include the use of introductory terms such as "at least one" and "one or more" to introduce claim recitations, but the use of such terms should not be construed as follows. The introduction of a claim recitation by an indefinite article "a" or "an" limits the particular claim containing the introduced claim recitation to a claim containing only one, even if the same claim contains indefinite articles such as "one or more" or "at least one or more" and indefinite articles such as "a" or "an" (e.g., "a" and / or "an" should generally be construed as meaning "at least one or more" or "one or more"), and is used to introduce the claim recitation.

[0088] Furthermore, even if a specific number of recited claim limitations are explicitly recited, one of ordinary skill in the art will recognize that such a recitation should typically be construed to mean at least the recited number (e.g., a bare recitation of "two recitations" without other modifiers will typically mean at least two recitations, or two or more recitations). Further, when a convention similar to "at least one of A, B, and C" is used, generally such a construction is intended to be understood by one of ordinary skill in the art (e.g., a "system having at least one of A, B, and C" includes, but is not limited to, systems having A alone, B alone, C alone, A and B together, A and B together, A and C together, A and C together, B and C together, and / or A, B, and C together). When a convention similar to "at least one of A, B, or C" is used, generally such a construction is intended to be understood by one of ordinary skill in the art (e.g., a "system having at least one of A, B, or C" includes, but is not limited to, systems having A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together). Further, one of ordinary skill in the art should understand that, typically, disjunctive words and / or phrases presenting two or more alternative terms in any of the description, claims, or drawings are intended to contemplate the possibility of including one of the terms, any of the terms, or both terms, unless the context indicates otherwise. For example, the phrase "A or B" is typically understood to include the possibilities of "A" or "B" or "A and B".

[0089] Regarding the appended claims, one of ordinary skill in the art will understand that the operations recited therein can generally be performed in any order. Also, while various operation flow diagrams are presented in sequence, it should be understood that the various operations may be performed in an order other than the illustrated order, or may be performed simultaneously. Examples of such alternative orderings can include overlap, interleaving, interruption, rearrangement, increment, preparation, supplementation, simultaneous, reverse, or other modified orderings, unless the context dictates otherwise. Further, terms such as "responsive to," "related to," or other past participles generally do not intend to exclude such variations unless the context dictates otherwise.

[0090] References to "one aspect," "one aspect," "exemplary," "one exemplary," etc. mean that the particular features, structures, or characteristics described in relation to that aspect are included in at least one aspect, and thus it should be noted that the appearances of the phrases "in one aspect," "in one aspect," "in one exemplary," and "in one exemplary" at various places throughout this specification do not necessarily all refer to the same aspect. Further, the particular features, structures, or characteristics can be combined in any suitable manner in one or more aspects.

[0091] Any patent application, patent, non-patent publication, or other disclosure material mentioned in this specification and / or listed in any application data sheet is incorporated herein by reference to the extent that the incorporated material is not inconsistent with this specification. Thus, to the extent necessary, the disclosure explicitly described in this specification supersedes any conflicting material incorporated herein by reference. Although said to be incorporated herein by reference, any material or portion thereof that conflicts with an existing definition, statement, or other disclosure material described in this specification is incorporated only to the extent that there is no conflict between the incorporated material and the existing disclosure material.

[0092] The terms "comprising" (and any formation such as "comprises" and "comprised of"), "having" (and any formation such as "has" and "had"), "including" (and any formation such as "includes" and "included"), and "containing" (and any formation such as "contains") are open-ended conjunctive verbs. As a result, a "comprising", "having", "has", "including", or "containing" one or more elements has, but is not limited to having, only those one or more elements. Similarly, an element of a "comprising", "having", "has", "including", or "containing" system, device, or apparatus "contains" one or more features, but is not limited to having only those one or more features.

[0093] In summary, many advantages resulting from adopting the concepts described herein are described. The foregoing description of one or more forms has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Modifications or variations are possible in light of the above teachings. One or more forms have been selected and described to illustrate the principles and practical applications thereof, thereby enabling one of ordinary skill in the art to utilize various forms and various modifications suitable for the particular use contemplated. The claims presented herein are intended to define the overall scope.

Claims

1. A reactor core, comprising a first array extending around the center of the reactor core, the first array comprising a first plurality of fuel channels, a first plurality of heat pipes, and being configured such that the first array alternately repeats fuel channels from the first plurality of fuel channels and heat pipes from the first plurality of heat pipes, the reactor core further comprising a second array extending around the center of the reactor core, the second array comprising a second plurality of fuel channels, a second plurality of heat pipes, and being configured such that the second array alternately repeats fuel channels from the second plurality of fuel channels and heat pipes from the second plurality of heat pipes, the reactor core further comprising a third array positioned between the first array and the second array, the third array comprising a first plurality of moderator channels, each moderator channel from the first plurality of moderator channels containing a metal hydride, the reactor core further comprising a moderator matrix, wherein the first array, the second array, and the third array are embedded in the moderator matrix.

2. The reactor core according to claim 1, further comprising a fourth array comprising a second plurality of moderator channels.

3. The reactor core according to claim 1 or 2, further comprising a control drum comprising a neutron reflector and a neutron absorber.

4. The reactor core according to claim 3, wherein the control drum is rotatable between a first position and a second position, and in the first position, the neutron absorber faces the first array, the second array, and the third array, and in the second position, the neutron reflector faces the first array, the second array, and the third array.

5. The reactor core according to any one of claims 1 to 4, wherein the metal hydride is selected from the group consisting of yttrium hydride, cerium hydride, zirconium hydride, and combinations thereof.

6. The reactor core according to any one of claims 1 to 5, wherein the first plurality of moderator channels is selected from the group consisting of blocks, pellets, rods, or plates, and combinations thereof.

7. ​ ​ ​ The core according to any one of claims 1 to 6, wherein the deceleration material matrix is selected from the group consisting of graphite, silicon carbide, aluminum nitride, stainless steel, and combinations thereof.

8. Further comprising a monolithic core housing, wherein the first array, the second array, and the third array extend outward from the center of the core to the monolithic core housing. The core according to any one of claims 1 to 7.

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